1. What is ovality of auxiliary engine crank pin?

Combined effect of reduced effectiveness of L.O and directional thrust of the con rod.

This is maximum at around 45 degree ATDC

Uneven loading of units and overloading

Max Allowed: 1/4th of the bearing clearance

Removed By: Insitu Grinding and polishing

Reference: Fillet of crank web

Max. Allowed Grinding: 2mm, because after grinding 2mm or more surface hardness reduces

drastically. Due to this maximum allowable grinding is 2mm.

Bottom bearing damage reason is the ovality, bearing clearance and condition of L.O supply

2. Why are concentric springs fitted for A/E cylinder head valves?

If the frequency of the natural vibration of air or exhaust valve springs is a harmonic of the

camshaft speed, then the spring may vibrate axially and are said to surge. Surge can be

avoided by modifying the sizes of springs by arranging the springs in pairs and fitting one

inside the other.

If one spring fails the valve is held up and is not damaged by striking the piston.

The thickness of individual springs can be reduced as against original thickness.

Normally two springs of different vibration characteristics are chosen.

Moreover, the stiffness requirements and the space congestion at this place warrants a

concentric springs arrangement. The net stiffness is equal to the sum of individual stiffness.

3. What is SQUAT Phenomenon?

It is a venturi effect while vessel is moving on shallow water. A vacuum is created due to

which the draught of the vessel is increased there by increasing the engine load.

Steering ability of the ship is reduced as a result.

4. What is a thermostatic expansion valve?

This is a regulator through which the refrigerant is metered from the high pressure side to

the low pressure side of the system. The pressure drop causes the evaporating temperature

(saturation temp.) of the refrigerant to fall below that of the evaporator.

a. Avoids liquid refrigerant return to the compressor suction.

b. Automatic expansion control and maintain 6 ~ 7 degree superheat.

5. What is the function of an L.P controller?

The LP controller stops the compressor at low suction pressure caused by the closure of all

compartmental solenoids. When the pressure in the compressor suction rises due to solenoid

opening, the LP controller restarts the compressor.

6. What is the function of an L.P cutout?

This is used to protect the compressor against the low suction pressure due to loss of

refrigerant or blockage. If the a/c compressor suction pressure is allowed to fall below

atmospheric pressure then there exists a risk of moisture and air ingress into the system.

7. What is a Coalescer?

A device consisting of a material whose surface provokes coalescence.

The process of combining of larger droplets of a liquid like oil into larger droplets is called

coalescing.

8. Why is there a starting air overlap provided in a diesel engine?

a. To give a positive starting in correct direction.

b. Starting ability from any position.

c. If any one of the valve is malfunctioning. Engine can still be started.

9. What is the significance of firing order?

a. Balancing of primary and secondary inertia forces.

b. To assist the exhaust grouping.

c. For distribution of stress over the length of crankshaft and optimum bearing loading.

d. A firing interval for even turning moment.

10. What are the reasons for foaming in refrigeration compressor crankcase?

Due to rapid boiling out of the refrigerant dissolved in the oil when the pressure is suddenly

reduced.

When the compressor starts operating, if a large quantity of refrigerant has been dissolved,

larger quantity of refrigerant boils out and can be carried through the refrigeration lines.

Reasons:

a. Liquid in the suction line (viz. TEV stuck open, incorrect super heat setting, sensing

bulb not closing, overcharge etc.,)

b. Crankcase heater not working.

c. Compressor capacity too high at the start.

d. Expansion valve giving too small superheat

e. Oil charge is less.

11. Explain the functions of lube oil in refrigeration system

a. Lubrication

b. Seal the clearance spaces between the discharge and suction sides of the compressor.

c. Act as a coolant.

d. Actuate capacity control.

e. Dampen the noise generated by the compressor.

12. What are the various windlass safeties?

ELECTRIC:

a. Electromagnetic brake.

b. Motor overload protection.

c. Short circuit protection.

d. Restart delay timer.

e. A Restart stop.

MANUAL:

a. Manual brake / mech. Brake.

b. Cable stopper.

c. Slipping clutch (torque limiter).

d. Relief valve.

13. What are the steering gear motor safeties?

a. Overload alarm.

b. 200% insulation in motor.

c. High temperature alarm.

d. Self-starting after power failure.

e. Short circuit trip.

f. Phase failure alarm.

g. One of the steering motor is fed from the emergency bus.

Hydraulic side there is two trips

a. Low level cutout

b. High lube oil temperature cutout.

14. What are the overhead crane safeties?

Current to motor’s field coils passes through solenoid coil of a brake which is magnetized and

holds a brake against spring and releases the rotor. Incase of power failure the solenoid is

demagnetized and brake is applied.

SAFETY:

a. Limit switch on the f’wd, aft, port, s’tbd, hoisting and lowering prevents movements

more than the allowed limits.

b. Overload trip.

c. Dead man’s handle.

d. Guards over the pulley.

e. Locking device on the lifting hook.

f. Mechanical locking (to avoid crane movement during heavy weather)

15. What is a critical pressure?

It is the pressure at which gas will just liquefy at its critical temperature.

16. What is a critical temperature?

It is the temperature above which the gas cannot be liquefied under isothermal compression.

17. What are the air bottle safeties?

a. Relief valve

b. Fusible plug

c. Drain

d. Low pressure alarm

18. What happens if fuel pump leaks?

a. Fuel quantity is reduced – loss of power, cylinder liner lubrication is affected.

b. Loss of cylinder power.

c. Late injection.

d. After burning.

e. High exhaust temperatures, smoky exhaust.

f. Power imbalance among units. Compiled by Eswara Arun Kishore

maverickshippy@yahoo.com

19. What are the constant tension winches?

It is a variation of the constant pressure and constant horsepower control for variable

capacity pumps. It is used to achieve constant tension winch system. In this case the pump

control is automatically operative across the neutral such that constant system pressure and

hence a constant motor torque is maintained whilst both drawing in and paying out.

20. What are the causes of turbocharger surging?

a. Rapid variation (reduction) in load.

b. Chocked exhaust and air passage like scavenge ports, valve or air cooler etc.,

c. Abnormal fuel system like a unit misfiring.

d. Chocked air suction filter, fouling of the turbocharger, unbalanced output from the

engine, damaged exhaust valve, scavenge fire.

21. What are the causes of cylinder head cracking?

a. Scale deposits

b. Inefficient cooling water

c. Uneven tightening of bolts and fuel valves

d. Fluctuating cooling water temperature (excessive temperature gradient)

e. Overloading or racing of engine

f. Faulty relief valve

g. Mechanical failure due to gas corrosion, acidic corrosion due to leaky exhaust valves

h. Water side corrosion

22. What is the normal relief valve setting of cylinder head in a diesel engine?

10 ~ 14.5% more than the working pressure about 120 bar (some what higher than

maximum pressure)

23. State the advantages of uniflow scavenging

a. Simple liner construction

b. Long skirt (for piston) not required

c. Stroke length can be increased

d. High scavenging efficiency

e. High thermal efficiency

f. Low grade of fuel can be burnt

g. Uniform wear of piston rings and liner

h. Less thermal stresses

i. Less intermixing of scavenging air with the exhaust gas

j. Exhaust valve can be made to open late – more work, close early – scavenge air is

more utilized.

24. Why cylinder liner wear is more at the top?

a. High temperature exposure due to the combustion gases

b. Loss of liner lubrication in low speed diesels

c. Corrosion, predominantly acidic due to combustion products

d. Fuel impingement, deposits

e. Change of direction of the piston, which causes to a step like formation at the reversal

point

25. What actions do you take incase of stern tube of the ship starts leaking?

a. Maintain low head.

b. Use higher viscous oil.

c. Replenish periodically to counter for the oil loss.

d. Drain off the water periodically.

e. Try to remove foreign particles by changing direction of shaft.

26. How do you test a fresh water generator plant for leaks?

a. Close the outlet of the distillate pump, vacuum breaker valve, bottom blow off valve

and feed water valve

b. Inject air into the evaporator shell

c. Keep the shell pressed up to about 1.0bar gauge

d. Sprinkle soap solution on to the jointings, packings, and suspected areas of the shell

27. What are the reasons for a piston crown to crack?

a. Casting defect

b. Thermal stresses due to cold starting air and scavenging air

c. Scavenge fire

d. Overheated piston(cooling failure, cooling side deposits due to oxidation of the cooling

oil)

e. After burning

f. Faulty fuel injection system (more penetration or loss of atomization)

28. What are the reasons for black smoke from a diesel engine?

a. Poor combustion due to faulty injection system

b. Low compression

c. Insufficient scavenging air

d. Fouled exhaust system

e. Broken piston rings

f. Ineffective lube oil seal

g. After burning, bad fuel and other fuel assisted faults

h. Faulty cylinder lubrication

i. During starting, it is inevitable as the engine maker sets the starting fuel index to a

fixed value. At this index there is insufficient air, low piston speed, cold combustion

chamber, low fuel injection pressure etc., each compounding the cause for black

smoke

29. What are the critical speed effects?

Resonance, torsional vibration, fatigue failure of components

Can be remedied by:

a. Detuners

b. Vibration dampers

c. Electric vibration compensator unit

30. What are the types of vibration in a diesel engine and which is the most

damaging?

Types of vibration:

a. Linear vibration

b. Torsional vibration

c. Resonant vibrations involving any two of the above or may be combinational

Most damaging form of vibration is the torsional vibration mode, affecting crankshaft and

propeller shafting.

31. What is a node?

A node is found where the deflection is zero and the amplitude changes its sign in a vibrating

medium. The more the nodes in a given length the higher the corresponding natural

frequency.

32. What is a forcing frequency?

W.r.t the crank shafts, the forcing frequencies are caused by the firing impulses in the

cylinders.

Firing impulses superimpose on one another and appear as a complex waveform represented

by harmonics –

1x cycle frequency: first order harmonics of firing

2x cycle frequency: second order harmonics

3x cycle frequency: third order harmonics and so on…

33. How can the frequency of resonance, the forcing impulses and the resultant

stresses adjusted?

a. By adjusting shaft sizes

b. Number of propeller blades

c. Firing order

d. Using viscous or other dampers

e. Using balancing weights

f. Detuning coupling

34. What is balancing?

Balancing is a way of controlling vibrations by arranging that the overall summation of the

out of balance forces and couples cancels out, or is reduced to a more acceptable amount.

35. Explain the vibration characteristics of low speed 2-S engines

a. External unbalanced moments

b. Guide force moments

c. Axial vibrations in the shafting system

d. Torsional vibrations in the shafting system

36. What is 1st order moment?

These moments acts in both vertical and horizontal directions. For engines with 5 cylinders

or more, the 1st order moments are of rare significance to the ship but it could be of a

disturbing magnitude in the 4 cylinder engines. Resonance with a 1st order moment may

occur for hull vibrations with two and/or three nodes. 1st order compensator can be

introduced in the chain tightener wheel. It comprises of two counter rotating masses

rotating at the same speed as the crankshaft.

37. What is a second order moment?

The second order moment acts only in the vertical direction and precaution needs only be

considered for 4, 5 and 6 cylinder engines. Resonance with the 2nd order moment may only

occur at hull vibrations with more than 3 nodes. A 2nd order moment compensator

comprises two counter rotating masses running at twice the engine speed.

38. What are the methods to cope up with the second order moments?

a. A compensator mounted on the aft end of the engine driven by the main engine chain

drive mechanism.

b. A compensator mounted on the fore end driven from the crankshaft thus a separate

chain drive.

c. A compensator on both aft and fore end completely eliminating the external 2nd order

moment.

39. What is an electric compensator?

It is electrically driven compensator preferably located in the steering gear compartment,

where deflections are the maximum and the effect of the compensator is maximum. Such a

compensator is synchronized to the correct phase relative to the external force or moment

and can neutralize the excitation. The compensator requires an extra seating to be fitted.

40. What are guide force moments and their types?

The origin of the guide force moment is the angularity of the connecting rod. It is the

vibration of the engine about the foundation bolts.

Guide force moments are caused by the transverse reaction forces acting on the cross head

due to the con rod crankshaft mechanism.

Guide force moments may excite engine vibrations moving the engine top arthwartships

causing a rocking (excited by the H moment) or twisting (excited by X moment) movement

of the engine.

Guide force moments are harmless except when the resonance occurs in the engine double

bottom system. As a precaution, top bracing is installed between the engine’s upper platform

brackets and the casing side for all its 2S models.

41. What are different types of the top bracing for a diesel engine?

a. It comprises of the stiff connections (links) either with friction plates which allows

adjustment to the loading conditions of the ship

b. A hydraulic top bracing – by using the top bracing natural frequency will increase to a

level where resonance will occur above the normal engine speed.

42. How are the axial vibrations caused in the crankshaft? How are they

remedied?

When the crank throw is loaded by the gas pressure through the conrod mechanism, the

arms of the crank throw deflect in the axial direction of the crankshaft, exciting axial

vibrations. These vibrations may be transferred to the ship’s hull through the thrust bearing.

Its remedy is to axially dampen the crankshaft vibrations.

43. How is torsional vibrations generated?

The varying gas pressure in the cylinders during the working cycle and the crankshaft /

conrod mechanism create a varying torque in the crankshaft. It is these variations that cause

the excitation of torsional vibration of the shafting system.

The torsional excitation also comes from the propeller through its interaction with the non

uniform wake field.

Remedy: modify crankshaft natural frequency by adjusting the diameter. Use a torsional

damper.

44. What is under critical running?

The natural frequency of the one node vibration is so adjusted that the resonance with the

main critical order occurs about 35~45% above the engine speed at specified maximum

continuous rating (MCR). The characteristics of an under critical system:

a. Relatively short shafting system

b. Probably no turning wheel

c. Turning wheel with low inertia

d. Large diameter of the shafting

e. Without barred speed range

45. What is overcritical running?

The natural frequency of the one node vibration is so adjusted that the resonance with the

main critical order occurs about 30~70% below the engine speed at the specified MCR. The

characteristics of the system are:

a. Turning wheel may be necessary on the crankshaft

b. Turning wheel with a relatively high inertia

c. Shaft with relatively small diameter (shaft material has to be of high UTS)

d. With a barred speed range of about +/- 10% w.r.t the critical engine speed

46. If resonance occurs, what is the solution?

The following modification(s) have to be carried:

a. Lanchester balancers, either on the engine or electrically driven units usually located

in the steering flat, compensated for ships vibration caused by the 2nd order vertical

moment

b. Counter balancing weights on the crankshaft to be adjusted for compensating the first

order vibrations

c. Combined primary and secondary balancers

d. Adjusting the side stays

47. How to prepare a DB fuel oil tank for a survey/inspection?

a. Empty the oil, strip with portable pumps if required

b. Clean the tank with sea water and pump it through the oily water separator

c. Ventilate the tank(s) with a blower specially provided for the purpose, always cross

ventilate i.e. there should be at least two openings, each for entry and exit for the air

d. Check the space for explosive gases at various points suitably, more sampling should

be carried out at the corners at the bottom most part of the tank

e. Obtain the necessary certificates and get the checklist completed

48. Why are the CO2 bottles provided with dip tubes?

It is to ensure that only liquid is drawn during release. The liquid expands after the nozzles

and assumes the gaseous state. This will prevent co2 freezing and blocking the nozzle

Also it achieves the 85% discharge in 2 Minutes as liquid part represents a large volume of

gas

The materials used in its construction are copper, stainless steel

49. Why a crankcase relief door is not fitted in the refrigeration compressor

crankcase?

a. Possibility of the contamination of the refrigeration system by air by leaks

b. Oxygen is not available in the compressor crankcase

c. The incoming refrigerant temperature is low and chances of hot spots is low

d. Crankcase forms the suction chamber of the compressor and chances exist that the

compressor may draw in air and moisture

50. Why heaters are provided in the crankcase of a refrigeration compressor?

a. To avoid carry over of the lube oil because at low temperature, the separation of the

refrigerant and the oil is difficult

b. To condition the lube oil, by maintaining the viscosity so that the lubrication is

effectively carried out.

c. This prevents the lube oil achieving its floc point which may cause narrowing or

chocking of the passages (flocculation)

51. What are the causes of a centrifugal pump reduced output?

a. Friction and leakage losses, loss of suction head, chocked suction filter, worn out wear

ring, air ingress in the suction side

b. Low voltage is applied to the pump motor

c. Cavitations on the impeller

d. Bad maintenance, incorrect fixing up of the parts after overhaul

52. What are the causes of vibration in the vertical centrifugal pump?

Misalignment of the shaft, worn out bearing, foundation bolts loose, hydraulic clearances -

not proper on the impeller, coupling bolts / seating damaged, bottom bush worn out, heavy

objects/debris deposits, and corrosion/erosion on the rotating parts

53. What is volumetric efficiency of air compressors?

Actual volume of air drawn in / swept volume

54. What is compression ratio?

(Swept volume + clearance volume)/clearance volume

55. What is brake thermal efficiency?

Ratio of the energy developed at the brake to the energy supplied. Amount of heat liberated

during the combustion to the heat equivalent at the brake

56. What is the function of a Solenoid valve in the refrigeration system?

There is an electric signal actuated valve in the liquid line of the refrigeration system just

before the thermostatic expansion valve. This is being actuated by the thermostat in the

refer compartment. The solenoid shuts off the refrigerant supply if the compartment is

sufficiently cooled to the lower set point of the thermostat. Also it connects the supply when

the temperature of the compartment goes high i.e. above the thermostat higher set point

57. What is the function of the back pressure valve in the refrigeration system?

Back pressure valve is fitted just at the exit of the refrigerant from the evaporator coil in a

multi temperature rooms system. This being fitted at the exit of the compartments whose

temperature is set higher (usually at about 4~5 degrees centigrade). The function of the

valve is to maintain equilibrium of the system as the pressure of the gas at the exit of each

compartment differs. More over the back pressure valve creates a back pressure on the

evaporator coil and ensures that most of the liquid refrigerant is made available to the lesser

temperature requirement compartments as their demand for the refrigerant is higher than

the compartments being maintained at a higher temperature. It is spring loaded non return

valve

58. What is the function of a H.P cut out in a refrigeration system?

This is a safety device (trip) provided in the discharge of the compressor. It functions to trip

the compressor if the pressure in the HP side goes high above the working level

59. What is the function of the driers in the refrigeration system?

The filter/drier is installed in the main liquid line of the system to absorb any moisture

present in the refrigerant. It consists of activated alumina or silica gel in a renewable

cartridge. It also accommodates the charging connection

60. What are the usual stern tube bearing clearances?

a. Water cooled stern bearing clearance: 8.0mm (8~12mm)

b. Oil cooled stern tube bearing: 1.87~2.0mm

61. What is a usual volumetric efficiency of a diesel engine?

a. Naturally aspirated engine: 0.85~0.95

b. Supercharged engine: up to 4.0

c. For 2S engine: 0.85~2.5

62. What is a usual propeller drop usual value?

1mm/160mm of the shaft diameter

63. What are the advantages of a thin shell bearing?

a. Increased fatigue resistant properties

b. High load carrying capacities

c. Embed ability

d. Conformability

e. Bedding not required

f. Easy storage, easy fitting, light in weight

g. Increased (enhanced) mechanical properties

h. Better heat transfer due to reduced thickness and uniformity of the contact with the

bearing housing

64. What are the typical bearing failures?

a. Fatigue failure (cracks)

b. Tin oxide encrustation (black SnO2 )

c. Wiping damage of the bearing surface

d. Tearing of the overlay

e. Acidic corrosion

f. Cavitations, erosion

g. Dross inclusion

h. Spark erosion

i. Bacterial attack damage (honey colored deposits on the bearing surface)

65. What are the advantages and disadvantages of the synthetic lube oils?

Advantages:

a. Better low temperature fluidity and pump ability, due to nil wax content

b. Better oil retention at high temperatures

c. Lower friction losses

d. Reduced thickening of the oil in service due to oxidation

e. Lower deposits at higher temperature due to resistance to oxidation properties and

thermal stability

Disadvantages:

a. Increased cost of the lube oil (about 6~12 times)

b. Poor availability

Uses:

a. Air compressors

b. Purifiers

c. Hydraulic units

66. What is the purpose of the lube oil analysis?

a. To determine any deterioration in lube oil properties or additives levels and assess its

suitability for further service

b. To determine the type and level of the contaminants held within the oil which indicate

the rate of contamination and effectiveness of the purification process

c. To predict the internal wear rate on the machinery components

d. To lengthen the time between overhauls or surveys

67. When is the lube oil said have deteriorated?

a. TBN reduces

b. Viscosity reduces

c. Flash point reduces

d. Oxidation increases

e. Water content high

f. Insolubles increase

g. Dispersancy increases

68. What are the problems in cast iron welding?

a. Brittleness (cracks easily)

b. High carbon content in the form of graphite

c. Close grain structure

d. Poor thermal conductivity and differential cooling

e. Possibility of stresses and distortion

69. How is a propeller drop measured?

a. Turn the engine to coincide with the mark on the liner and the stern tube or normal

reference is taken to be that the engine’s unit 1 will be in TDC prior measuring the

propeller drop

This could be also arranged as with a designated blade of the propeller up wards while

measuring this drop. Blades are assigned alphabets A, B, C, D and so on.

b. Take the poker gauge reading and the compare with the previous reading

c. Bearing clearance : 2mm (oil sealed)

: 8mm (sea water lubricated)

Bearing length is about 2xdia of the shaft for oil cooled stern tube bearing

4xdia of the shaft for sea water lubricated stern tube bearing

70. Compare an engine flywheel and its governor

a. A governor maintains the speed of the engine

b. A flywheel controls the cyclic fluctuations of the engine RPM

c. Flywheel works on the virtue of the inertia alone and the governor uses the inertia

principle to actuate the fuel linkages to counter the changes in the engine RPM

71. Why are tie rods provided?

Tie rods are provided to keep the whole engine structure in compression which:

a. Increases the fatigue strength of the engine structure as it is the tensile stress which

causes fatigue

b. Maintain running gear alignment to avoid fretting

The firing forces that press down the bearing saddle also attempt to push up the cylinder

covers, the net effect being to put the whole engine structure into tensile loading. So the tie

rods are tightened such that the engine structure is maintained in compression even during

the peak firing conditions and that the engine is not subjected to the tensile loading.

72. Why tie rods are placed close to the centerline of the crankshaft?

During firing, the transverse girders are subjected to a bending moment as the saddle is

pushed down by the crankshaft acting on the cylinder head. To limit this bending effect and

consequent distortion of the bearing housing the tie rods are positioned as close as possible

to the center-line of the crankshaft.

73. Where is a thrust bearing installed in an auxiliary engine? And why?

Axial location of the crankshaft may be required if the coupling does not incorporate a thrust

housing. This is achieved by forming white metal rings on the sides of one main bearing shell

that allows the shaft to run with a small clearance between running faces on the two

adjacent webs.

In some engines a small collar may be provided at one side of the bearing. It is important to

appreciate that only one such locating bearing should be fitted to any one shaft, otherwise

the differential thermal expansions of frame and the crankshaft may cause problems.

74. What are the environmental problems with the use of CFCs?

a. CFC released into the atmosphere are broken down by pyrolysis to release chlorine

atoms which catalytically destroy ozone layer.(this layer in the stratosphere acts as a

filter to the UV radiation from the sun)

b. Furthermore CFCs along with other greenhouse gases inhibit radiation from the

earth’s surface thereby contributing to the global warming.

75. What is a pH value?

It is the logarithm of the reciprocal of the hydrogen ion concentration expressed in gram ion

per liter.

Pure water at 25 degree centigrade consists of equal concentration of the hydrogen and the

hydroxyl ions and equal to 10

-14

gram ion per liter. If the hydroxyl ion concentration exceeds

the hydrogen ion concentration then the solution is basic and vice versa is acidic in nature.

pH value = log [1/H+]

If the water temperature is increased, the concentration of the hydrogen ion increases and

hence acidity.

76. Why is a man hole door elliptical in shape?

Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole

is lesser in size than the corresponding circular hole. More over it is prime concern to have a

smoothed generous radius at the corners to eliminate stress concentration. Hence other

geometrical shapes like rectangle and square are ruled out.

To compensate for the loss of material in the shell due to opening, a doubler ring has to be

provided around the opening. The thickness of the ring depends on the axis length along the

direction in which the stresses are maximum and the thickness of the shell. It is important to

align the minor axis along the length of the vessel, as the stress in this direction is

maximum.

Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t=

thickness of the shell plating

Circumferential stress: Pd/4t

More over a considerable material and weight saving is achieved as minor is along the

direction of maximum stress.

77. Why is the fridge compressor belt driven?

a. A slight misalignment is a problem or vibration of the electric motor may lead to shaft

seal leakage, leading to loss of the refrigerant. So minimize these the fridge

compressor is belt driven.

b. In case of the liquid entry into the refrigeration compressor, the belt drive gives a

limitation of the damage owing to the slip in the belt and flexibility of the belt

material.

78. Why intercooling is provided in an air compressor? And why is the

compression distributed into stages?

a. By employing the interstage cooling we are trying to achieve an isothermal

compression cycle. So least work is expended in the process.

b. The air outlet temperature after compression is lowered by intercooling. So oxidation

of the lube oil is prevented. Also good lubrication is achieved.

c. Lesser deposits in the air system.

d. Intercooling increases the air density and hence reduced volume of the HP

compression chambers is possible.

e. It facilitates removal of moisture by condensation at the intercoolers.

f. To facilitate intercooling the compression is distributed into stages. Also even load

distribution is achieved over the cycle.

79. What if the compressor motor connections are reversed after overhauling?

a. The lube oil pressure will not be sufficient for lubrication so the compressor may trip

on low lube oil pressure. The moving parts may get damaged due to the failure of the

lubrication.

b. The cooling water pump which is also shafted driven usually does not build up enough

flow/pressure hence the compressor may trip of the cool water non flow or high air

temperature.

80. If viscotherm is absent or damaged how do you maintain the fuel oil

viscosity?

The required viscosity prior injection and the viscosity of the fuel oil at 50°C are provided by

the fuel oil analysis report. Basing on the viscosity nomogram the required fuel oil heating is

determined. The steam inlet to the fuel oil heater is manually adjusted to maintain the

temperature and a close observation has to be maintained on the steam pressure and

temperature of the fuel oil at the outlet of the heater.

81. What are the reasons for the error between the helm order and the angle

shown locally on the steering gear unit?

a. Air in the hydraulic telemotor system

b. Buffer spring too weak or stiff, faulty hunting gear

c. Instrument error/defective

d. Worn out linkages

82. Why are the accumulators used in the hydraulic systems?

a. To absorb shock due to load variation or sudden change in the direction of flow,

impact loading

b. To maintain the circuit pressure by compensating for the loss due to leaks or pressure

increase due to rising temperature

c. To supplement the pump delivery where multiple circuit operations have wide flow

variations with a short term peak demand in excess of the pump capacity.

Accumulator charge can take place during low demand periods to meet maximum

demand later

83. Explain the cross head slipper lubrication

a. The lubricating oil is fed to the guide shoes by a pipe from the main lube oil system

b. The lubricating oil may also be fed from the drilled passages in the pin to the slipper

faces

84. What is the material of the CO2 bottle and its accessories?

CO2 bottle: solid drawn seamless manganese steel

Cable: phosphor bronze

Seal/bursting disc: thickness 0.3mm, phosphor bronze

Pipeline: solid drawn MS galvanized

Siphon tube: copper tube

Cutter: 120° /travel 19mm

85. How will you decide for reentry into the engine room after flooding it with

CO2

Re-entry is determined by

a. Heat build up due to the scale of the fire and the elapsed time after release

b. Has the fire been extinguished or chances of a smoldering fire exists

c. Ship’s position, condition and the prevailing weather (ship may be listing to the angle

of progressive flooding etc.,)

d. The location of the entry point

e. Risk analysis outcome

86. What is the quality of the vapor coming back to the compressor suction in

the refer system? In addition, how will you ensure that the vapor has adequate

degree of superheat?

a. The condition of the vapor coming to the compressor suction line should have

adequate degree of superheat

b. The condition is checked by reading the pressure of the returning vapor and its

corresponding temperature from the P-T chart provided for the specific refrigerant.

This temperature is compared with that of the evaporator outlet and the degree of

super heat is expressed as the difference in the temperature.

87. What is the length of the crank web?

Length of the crank web = stroke length/2

88. What is lignum vita?

In the traditional sea water lubricated stern tubes the bearing material consisted of the

staves of the wood called lignum vitae. This has a property of lubrication in the presence of

sea water. They are fitted with the grains in the axial direction for economy and are shaped

with V or U grooves between them at the surface to allow for access to water. They also act

as a debris collector points. The staves are held in place in the bronze boss by bronze keys

attached to the bush by counter sunk screws. Bearing length is equal to 4times the shaft

diameter.

89. What are the safeties in the fridge system?

a. HP cut out

b. Differential lube oil pressure cutout

c. LP cutout

d. Relief valve in the condenser

e. Belt driven

f. Cylinder head relief valve

g. Cooling water low flow/high temperature alarm

h. Motor overload

i. Oil separator

j. Drier

k. Mech. Seal

l. Unloaders /capacity controllers

m. Non return shut off valves

n. Sensors – temperature, pressure

90. How will you know the presence of air in the refrigeration system? Explain

the procedure for purging air

a. High condenser pressure

b. Small bubbles in the sight glass

c. Compressor discharge pressure high/running hot

d. More superheat

e. Pressure fluctuations

f. Inefficient working

PROCEDURE FOR PURGING AIR

a. In the normal operation of the system, measure the liquid refrigerant pressure,

temperature at the outlet of the condenser/reservoir

b. Check the corresponding saturation temperature for the recorded pressure of the

liquid refrigerant from the P-T chart for the same refrigerant

c. Compare the measured temperature with the determined saturation temperature for

any sub-cooling and adjust the flow of the cooling water through the condenser to

achieve near saturation condition inside the condenser,

Then,

d. With the condenser liquid refrigerant outlet valve closed, circulate cooling water, start

the compressor and pump down the liquid to the condenser/reservoir, checking the

pressure in the suction line. If this pressure is allowed to drop down below the

atmospheric pressure then there could be chances of air ingress into the system

e. Circulate the cooling water till the cooling water outlet and the inlet temperatures

equal, a check to ensure complete pump down operation

f. Check the condenser sea water out let temperature, check the refrigerant pressure

corresponding to its temperature from the P-T chart of same refrigerant

g. Due to the presence of air they don’t agree

h. Release air from the condenser, through the vent cock until the pressure of the

refrigerant in the condenser corresponds to the saturation pressure at the sea water

outlet temperature

91. What is the material of the boiler gauge glass?

The material used in the gauge glass is a special toughened glass containing

a. Silicon oxide or magnesium oxide

b. Borosilicate or lime soda glass

92. What is the material of a boiler tube?

Low carbon alloy steels containing chromium, nickel, molybdenum

93. What is the material of the ship side valve?

BODY: Nickel-Aluminium bronze / cast steel

Stem/Seat/Disc: Monel metal (cupro nickels of varying proportions are used popular being a

Cu:Ni = 2:1)

The cupronickels are known for their great resistance to the sea water corrosion, erosion by

the particles in the sea water, and strength.

94. What is the material of the propeller material?

a. Nickel aluminium bronze (nickalium)

Copper: 55~62%, Aluminium: 0.5~2.2%, Nickel: 0.5%, Manganese:

0.5~1.0%, Iron: 0.4~1.5%, balance is Zinc

b. Manganese bronze

Copper: 58%, Iron: 1%, Aluminium: 1%, Manganese: 1%, Nickel: 0.5%, Zinc:

38%, Tin: 0.5%

95. What is the general composition of the stainless steels?

Chromium: 18%, Nickel: 8%, Carbon: 0.12%

96. What is the material of the 4S engine conrod?

a. Forged steel: Open hearth plain carbon steel

UTS: 432~494 MN/m2

% Elongation: 25~30%

Fatigue limit: 208 MN/m2 (push pull)

b. Nickel steel, 3%Ni

UTS: 695 MN/m2

%Elongation: 20%

Fatigue limit: 309 MN/m2 (push pull)

METHODS OF TIGHTENING:

a. Measuring the extension of the bolts

b. Use of the calibrated torque wrenches

c. Hydraulic tensioning

d. Angle tightening

97. What is the material of the foundation bolts?

High tensile steel

98. What is the material of the tie rod?

High tensile steel

99. What is the material of the double bottom plug?

Silicon steels

100. What is the material of the crankshaft?

Forged low carbon alloy steel. Carbon: 0.12% and less

101. What are the materials used for the diesel engine’s liner and piston rings?

State their principle differences

Generally the materials used for the piston rings are harder than the liner material. This is

due to the fact that the rings are subjected to wear always during their operation but only

the portion of the liner in contact with the rings wears.

Material used for the liner is generally the nodular cast iron, which is tailored to have

expansion along the length and negligible expansion circumferentially. Alloying materials are

added to improve certain characteristics like vanadium and titanium.

Piston rings are cast and machined from graphite grey cast iron. This ring may include

chromium, nickel & copper as alloying substances.

The prime property which distinguishes it from the liner material is that it has to flex

circumferentially.

This is of primary concern for running in and to match the contour of the wearing liner

surface. Also they have to form an effective sealing of the combustion gases.

102. What are the liner wear rates? And how is it achieved?

Old engines: 0.1mm/1000hrs

Modern engines(2S): 0.03mm/1000hrs

Modern engines(4S): 0.12mm/1000hrs

This is achieved by:

a. Highly alkaline lube oil

b. Load dependant jacket cooling water temperature control

c. Good quality of cast iron with a hard face

d. Careful design of the piston ring profile

e. Improvement in lube oil

f. Multilevel cylinder lubrication

g. Condensate separation from the scavenging air

h. By use of the anti-polishing ring or the piston cleaning

103. Explain why stainless steel is resistant to corrosion?

Stainless steel depends on the formation of a protective oxide film, tenacious chromium

oxide for resisting corrosion. This film is formed spontaneously on exposure to air or well

aerated water. Compiled by Eswara Arun Kishore

maverickshippy@yahoo.com

Without this oxide film, their corrosion resistance is only slightly better than other

engineering steels.

104. What is the material of the fuel valve needle and body?

Needle: high speed steel

Body: case hardened steel

105. What is the material of the chain and its tightener arrangement?

High tensile steels

106. Quote some important clearances in the rudder system

Jumping clearance: 6mm

Clearance at raphson slide mechanism: 16~19mm

Propeller drop: 1mm/160mm diameter of the tail shaft

Pintle clearance: 1.1mm~3.3mm

107. What are the usual pressures to which the boilers are tested?

New boilers, if > 6.9bar working pressure, 1.5xdesign pressure

If < 6.9bar working pressure, 2.0xdesign pressure

After major repair, 1.25~1.5x working pressure, duration of the testing: 30Min.

108. Explain the purpose of the hunting gear

a. To put the pump on stroke gradually

b. To stop the pump at the end of the stroke gradually

c. To lock the rudder at desired position till further movement is given at helm

d. To transmit movement of telemotor to pump

e. Spring in the hunting gear store extra control movement to ensure that the pump

operates at the maximum capacity for major part of the turning operation

109. Differentiate between the terms priming and foaming with reference to their

occurrence in a steam boiler

Both refer to the carry over of water into the steam outlet. Priming is due to the

mechanical/physical aspects and the foaming refers to certain insouble/solubles in the boiler

water, which by the principle of increased surface tension cause priming.

The various reasons for priming:

a. High water level in the boiler

b. Rapid changes in the steam demand

c. Safety valve lifting frequently due to its malfunction

d. Rough weather causing heavy rolling/pitching

e. Rapidly raising steam

f. High salinity of the boiler water

Foaming is the formation of unbroken chain of bubbles on the surface of boiler water. A

common cause of the same is the oil contamination.

110. Mention some important mechanical properties of metals

a. Elasticity:

b. Hardness: Resistance to abrasion

c. Plasticity:

d. Toughness: Ability to absorb maximum energy before fracture

e. Ductility: Ability of the metals to deform plastically under tensile force

f. Stiffness: Ability to withstand deformation

g. Malleability: Ability of the materials to deform plastically under compressive force as

in forging or rolling

h. Resilience: Resist shock and impact

i. Brittleness: Tendency of the material towards brittle fracture. Brittle fracture is the

failure of the material without plastic deformation

j. Creep: Plastic flow under constant load application or heat

k. Weld ability:

l. Endurance: Ability to withstand alternating stresses

m. Cast ability:

n. Strength: Ability to withstand rupture

111. What is a tie rod bolt pinch screw? And what is its purpose?

Pinch screw is normally provided at the foot of the engine cylinder jacket to stop the tie rod

from vibrating during the normal service of the engine.

The pinch screw is fitted at the antinodal point of the tie rod to limit its transverse vibration

amplitude, thereby preventing its fracture due to vibrations. These can be arranged as a

group of three screws positioned equilaterally at the antinodal point. Each screw consists of a

stud, which is hand tightened by screwing the outer sleeve and held in place by a lock nut

which is tightened to a torque specified by the manufacturer.

112. What is the course of action after finding that a bottom end bolt is

slackened?

a. Check the length of the bolt

b. Check whether it is within the limits

c. Check for cracks / surface finish. Check the threads

d. The tie rod can be rolled over a flat surface coated with Prussian blue. Any twists in

the rod are revealed by the Prussian blue lines on the tie rod which get adhered along

the twisted plane

e. If found alright, tighten the bolt and check the remaining bolts

113. Define higher calorific value and the lower calorific value

[H2O formed by the hydrogen in the fuel oil cannot exist as water at the high temperatures

in an internal combustion engines. The water formed by the combination of hydrogen and

oxygen absorb the heat from the combustion and forms steam. Therefore, some amount of

available energy is lost in converting water into steam. This energy is not available to the

engine.

Therefore, the calorific value of the fuel reduced by this amount presents the actual calorific

value available to the engine.] -Æ This definition is given by reeds and I feel this has

to be altered after looking into the MANBW manual, which provides a graph to

calculate the Lower calorific value based on the Specific Gravity and Sulfur content.

Therefore, the amount of heat loss due to the inclusion of sulfur, which cannot be separated

by normal fuel oil treatment and its subsequent oxidation to SOx warrants the entire calorific

value to include correction for corresponding fuel content in a specific mass of fuel sample

and the energy loss due to sulfur oxidation. Corrections should also include for ash & water

content.

Therefore, to get the practical scenario two specific calorific values are mentioned Lower

calorific value and the higher calorific value.

Lower calorific value = higher calorific value – the energy loss in converting the mass of the

[water into steam] + sulfur to sulfur oxides + Loss of specific enthalpy due to ash content

present in unit mass of fuel.

114. Explain gear pumps w.r.t the materials used and the clearances

Rotors and shafts are integrally forged of Nitraalloy steel.

Gears are case hardened, medium carbon steel. They are hardened all over and ground

finished after hardening

Casing and bearing housing are close grained grey cast iron

Shafts are supported by white metal bearing or roller bearings or bronze bushes on the free

ends

Liquid being pumped is forced out after being carried around the gear teeth between the

gear teeth and the casing.

Backflow is limited by:

a. Minimizing the radial clearances between the teeth of the gears and the housing

b. Increasing the number of teeth

c. Optimizing the side tolerances /play

Gear pump suitable for operating up to 25bar and can achieve displacement volume of

0.35~1.0 liters/revolution

Clearances between the gear teeth and the housing are of the order 0.02~0.03mm

115. What are the advantages and disadvantages of resin chocks?

ADVANTAGES:

a. 100% contact on uneven surfaces

b. Cheaper to install as no hand fitting is required

c. Don’t corrode and are resistant to most of the chemicals

d. As they achieve good contact, there is little chance of fretting, thus cheaper, shorter,

non resilient bolts can be used. These permit a reduction in the bolt tension by a

factor of 4

e. Avoid vibrations

DISADVANTAGES:

a. Overstressing of the bolts causes the resin to shatter and break

b. Maximum temperature is limited to about 80°C

116. Explain the cavitation in the bearings

Vaporization due to oil pressure falling locally below vapor pressure causes bubbles in the oil,

which when goes to higher pressure region, collapses and shock wave is generated causing

heavy impingement. The causes:

a. High oil temperature

b. Low oil pressure

c. Vibration

d. Oil contamination

117. What are the Nimonic and Stellite coatings?

These are considered to be the hardened materials by the process of metallic cementation

Nimonic: carbon, chromium, Titanium, Aluminium, Cobalt, Molybdenum, Iron, Nickel

There could be other constituents such as Manganese, copper, silicon

Stellite: They are alloys of Cobalt, and Chromium, with the addition of varying amounts of

tungsten and other elements

They are very resistant to corrosion and abrasion. Retain their hardness at a red heat

Since they cannot be forged, they must be cast direct to shape or deposited by welding

118. Why is an equalizing line provided in the refrigeration system?

It is used in the installations where a large drop in pressure occurs in the evaporator. In the

expansion valve, the pressure acting outside (top) of the bellow corresponds to the

saturation pressure plus the degree of superheat of the refrigerant leaving the evaporator.

This pressure is trying to open the valve against the spring force from below the diaphragm.

The external equalizer connection has a saturation pressure of the refrigerant leaving

evaporator, to act below the diaphragm. Therefore the saturation pressure from the external

equalizer connection balances the saturation pressure of the sensing bulb leaving only the

pressure due to degree of super heat only to oppose the spring force. Therefore, this degree

of superheat is supposed to open the expansion valve.

By this method, we are getting a control over only the degree of superheat of the refrigerant

leaving the evaporator coil. This is important to ensure proper utilization of the refrigerant

and that no liquid refrigerant reaches the suction of the compressor.

119. What are the reasons for short cycling of a refrigerant compressor?

a. Refrigerant charge is too low

b. Frosting or clogging of the evaporator

c. Dirty suction strainer

d. Low pressure control differential too small

e. Wrongly adjusted capacity regulator

f. Refrigerant vapor in the liquid line

g. Too much cooling water

h. TEV faulty

i. Too high compressor capacity

120. What is viscosity? Differentiate between the kinematic viscosity and the

dynamic viscosity

Defined as the resistance of fluids to change of shape, being due to the internal molecular

friction of molecule with molecule of the fluid producing the frictional drag effect.

Absolute (Dynamic) viscosity is numerically equal to the force to shear a plane of fluid

surface of area of a unit square meter, over another plane surface at the rate of one meter

per sec, when the distance between the surfaces is one meter.

Kinematic viscosity is the ratio of the absolute viscosity to the density at the temperature of

viscosity measurement.

Viscosity index is a numerical value which measures the ability of the oil to resist the change

in viscosity with the change in temperature. A high viscosity index shows a good resistance

to the change in viscosity with change in temperature.

121. What is an Otto cycle or the constant volume cycle?

This is the constant volume cycle. Although no actual engine cycle operates strictly following

this ideal cycle, the analysis of this cycle provides a tool for comparison of performances of

actual engines under different operating conditions.

The most important noted difference between this ideal cycle and the normal cycle is that

this is a non-flow cycle involving an ideal gas whereas the actual cycle is a flow process and

the gases are real.

This cycle is explained as follows:

At the beginning of the process the cylinder is assumed to be full with a charge of fresh air.

The air is compressed isentropically following the law PV

γ

= constant. Heat is then added to

the same mass of air at constant volume. This point represents the maximum pressure and

temperature in the cycle. From here the air is expanded isentropically to the initial volume

and then the heat is rejected at the constant volume.

122. What is a Diesel cycle?

This thermodynamic cycle is first analyzed by Rudolph Diesel. This is a slight variation of the

above constant volume cycle, the difference being that the heat addition in the cycle takes

place at constant pressure. The other processes during compression, expansion, and heat

rejection remain same as with the constant volume cycle.

123. What actions do you take incase of an EGB Soot fire?

The oxygen levels in the EG Boiler/Economizer is about 14~16%, so this can support

combustion.

The nature of combustible deposits include soot from the combustion of fuel in the plant as

well as some amount of unburnt oil (fuel and lube oil), particularly at low loads.

Ignition of soot may arise at sufficient high temperature of the layer of the soot whose

surface temperature may go up to 300~400˚C, but presence of unburnt oil may lower this

temperature to about 150˚C and under favorable conditions to about 120˚C.

SMALL SOOT FIRES: Mainly occurs during maneuvering with the engine being operated at

prolonged low loads. The situation may arise even at short low load running if the fuel is bad.

Indications:

a. High economizer exhaust gas outlet temperature

b. Sparks from the funnel

c. Engine running parameters showing deviations due to increased exhaust back

pressure

d. High steam pressure or outlet temperature from the super heater section if fitted

How to deal with this situation:

a. Stop the main engine so that the oxygen levels can be brought well below the fire

sustenance levels

b. Carry out the boundary cooling

c. Fire watch to be kept on deck due to the risk of the funnel sparks, fire hoses to be

kept charged

d. Continue running the circulating water pump

e. Never use the soot blowers for fire fighting

f. Stop the auxiliary blowers

g. Ensure that all the exhaust valves are positively closed (check the spring air pressure)

If the soot fire has now turned into metal fire (identified immediately by the loss of the

circulating water of the economizer), stop the circulating water pump. Carry out the

boundary cooling.

If means are provided, deluging the economizer fires with copious amounts of water should

be carried out to the seat of the fire. This is essential because, if lesser amount of water used

the fire is additionally supported by the production of steam sourcing hydrogen for the

situation to get worse.

Hydrogen fire: Occurs because of dissociation of water (steam) into hydrogen and oxygen or

carbon in connection with carbon monoxide and hydrogen

This occurs only above 1000˚C

Iron fire: Oxidation of the iron at high temperature occurs at a rate sufficiently high to make

the amount of hest release from the reactions sustain the process. These reactions may take

place at a temperature in excess of 1100˚C

124. How do you identify the symptoms of a crank case explosion? What action

would you take to minimize the hazard?

a. Engine noise

b. Oil mist detector alarm

c. High bearing temperature (alarm if fitted)

d. In case of minor explosions the crank case relief door releases the pressure

ACTION:

a. Slow down the engine, inform the bridge

b. Take permission from the bridge for stopping the engine

c. Continue running the engine lube oil pumps

d. In severe cases, it is prudent to open the engine room skylights and other vents and

abandoning the engine room. The doors from the engine room to the accommodation

should be kept shut. Return to the engine room only after carrying out risk

assessment

e. Turn the engine by turning gear with the indicator cock opened to prevent seizure of

the hot spots

f. Stay clear of the crank case specially in the region of the relief door to the

turbocharger suction

g. Don’t open the crank case door until sufficient time has elapsed

125. What are the various IG plant alarms and trips?

ALARMS:

a. O2 content high

b. Scrubber tower water level low

c. Deck seal water level high

d. Deck seal water level low

e. IG pressure low

f. IG pressure high

g. IG temperature high

h. Boiler uptake soot level high (Ringlemann)

TRIPS:

a. Scrubber tower water level high

b. Venturi water pressure low

c. Low IG cool sea water pressure

d. Scrubber cool sea water pump abnormal stop

e. Power failure

f. Incorrect mode of the boiler (mode set to NAV, GF.. etc)

g. IG temperature high high (more than alarm level)

h. IG blower abnormal stop

i. Deck seal water low flow

j. IG deck main extreme high pressure

126. Reciprocating pump is getting over heated, what checks should be carried

out?

a. Inlet and outlet valves are to be examined

b. Inspect the seat and lapping should be done if required

c. Valve lift should be checked

d. Inspect piston and piston rings

e. Spring (valves should be checked for tension and springing action)

f. Liner wear down should be checked

g. Driving belt should be checked for wear down or damage

127. Explain the various rudder inspections and testing in the dry dock

a. Visual examination of the rudder plating for cracks and distortion

b. Air plugs and drain plugs are to be opened in the presence of the class surveyor,

repair superintendent and chief officer. Water draining out indicates a breached

rudder and the breach to be located by air pressure testing and applying soap

solution, repairs to be planned

c. Check the rudder drop in the steering gear compartment (trammel gauge)

d. Check the pintle clearances, jumping bar clearance and the palm coupling bolts

tightness to be checked

e. Check the rudder stock for corrosion, erosion and any damage

f. The inspection plates in the way of the upper, the lower pintle to be cut open, and the

pintle nuts checked for proper securing. Later the plates to be welded and tested.

g. Hydraulic test the rudder for a static head of about 2.45m of sea water

h. After draining and re oiling the internals, plug the drain and check the effectiveness

by a vacuum check and cement the plug

i. The rudder stock gland packing has to be checked and renewed

128. What is caustic cracking or embrittlement? What is its cause? Suggest

remedy

This is a form of intercrystalline/intergrannular cracking and occurs when a specific corrodent

and sufficient tensile stress exists. Iron consists of ferritic granules bonded by iron carbide so

this gives a scope of the intergrannular corrosion. This can be found in water tubes, super

heater, reheat tubes, and in stressed components of the water drum. The stress may be due

to thermal, bending or residual stress (due to welding). This usually occurs as a localized

attack in the combination of NaOH, some soluble silica and a tensile stress. The mechanism

begins with the accumulation of the corrodent NaOH due to –

a. DNB (departure from nucleate boiling)

b. Deposition

c. Evaporation at the water line

d. Small leakage

e. High heat flux (rapid evaporation)

f. High pressure

This corrosion below 149˚C or with NaOH concentration below 5% is rare. Increased

susceptibility occurs at about 20~40%. This corrosion is difficult to identify in the beginning

and ND testing has to be carried out at the suspected areas. At some time after the initial

start of the corrosion, this manifests as a whitish highly alkaline deposits or sparkling

magnetite.

COUNTER MEASURES:

a. Applying heat treatment process to relieve stresses after fabrication/repairs (welding

etc)

b. Correct and accurate boiler water treatment

c. Avoid DNB

d. Avoid accumulation of the deposits

e. Prevent leakage of corrodents

f. Prevent carryover

g. Use of rifling in the water tubes

129. A shell & tube type cooler tubes are leaking, what is the procedure to rectify

the leaks?

Before jumping to any conclusions it is prudent to check where the leaks are from. It could

be from the breach on the tube (a hole etc) or from the origination of small gaps between

the tube plate and the expanded portion of the tube. The procedure should to be based on

the findings.

A holed tube should be plugged from both the sides; the plugs can be of cork, wood, rubber,

brass, or copper as supplied by the manufacturer. Care should be taken when plugging with

the metal plugs, not to damage the tube plate.

If the leaks are from the gaps between the tube plate and the tubes, slight flaring of the tube

may help preventing the leaks however this flaring, if excessive will damage the tube plate

and also the tube itself. Alternative methods are available by carrying out surface

preparation and applying metal repair putty, like Devcon’s brush able ceramic repair putty.

In the above process, if the plugging of the tubes is about 10% the tubes have to be

renewed.

130. Explain a tube renewal process

To remove the tube, first remove the flare on the tube by chiseling off the flare flush with the

tube plate and then split the tube taking care not to damage the tube plate. The tube can

then be cut by a tube cutter to drop the tube inside the shell. Fitting of a new tube is carried

out by first positioning the tube in place between the end tube plates and flaring to the

correct amount by a flaring tool after fixing the other end by a brass wedge. It could by

either hand operated, pneumatic or motor operated. The tube should have a protruding part

about 1/4”~1/8” and the flaring should be to about 1/8” + tube diameter at the tip.

131. What is a phosphate reserve? Why is it important in high-pressure boilers?

A reserve of phosphate should be present in the boiler water to neutralize any hardness

salts, which may enter. These salts would deposit as a scale on the heating surface if reserve

were too low while, too high a reserve leads to foaming and possible excess production of

sludge. It also gives alkalinity.

3CaCO3 + 2Na3PO4 ----Æ Ca3 (PO4)2 + Na2CO3

3CaSO4 + 2Na3PO4 ----Æ Ca3 (PO4)2 + Na2SO4

3CaCl2 + 2Na3PO4 ----Æ Ca3 (PO4)2 + 6NaCl

MgSO4 + 2Na3PO4 ----Æ Mg (PO4)2 + 3Na2SO4

Precipitates as Sludge

At high pressure and temperature, reaction from left to right will be more. Therefore, it is

very important in high pressure boilers to keep the reserve level up to required concentration

to avoid excessive caustic alkalinity and thus caustic cracking.

Na2CO3 + H2O Å---Æ 2NaOH + CO2

In high pressure boilers where there is a risk of caustic concentration and subsequent caustic

attack it is common to apply a coordinated or congruent phosphate control programme.

These control methods are based on the hydrolysis of tri-sodium phosphate (TSP) and

disodium Phosphate (DSP) in the boiler water.

Na3PO4 + H2O Å-----Æ Na2HPO4 + NaOH

Na2HPO4 + NaOH Å----Æ Na3PO4 + H2O

The objective is to maintain a desirable pH without the presence of free OH alkalinity. The

desired conditions are obtained by maintaining the relationship of the pH to phosphate

concentration in the boiler water at less than that of the equivalent stochiometric solution of

Na3PO4 (<3:1). This is achieved by the equilibrium reaction above. The congruent phosphate

approach utilizes mixtures of TSP and DSP to further ensure the absence of free OH alkalinity

and usually run with a Na:PO4 ratio of <2.8.

132. What is the routine anchor windlass maintenance?

a. Brake drum should be free of oil, grease and other deposits. The brake drum should

be cleaned periodically with a solvent prescribed by the maker

b. The brake drum and the disk should be checked for wearing out or damage

c. Gear oil should be checked for contaminants and level

d. The direction of tensioning should correspond to the correct operation of the brake. As

the reverse direction for tensioning would render the brake ineffective, check should

be carried out to ensure the same

e. Brake test of the windlass is to be carried out to the pressure mentioned by the

maker on the jack tool. If necessary, the spring tension adjusted. It should be done in

guidance of the instructions and in the tensioning direction. The number of turns on

the drum should also be checked and should be same as to the makers quote

f. The securing device of the tension spring adjust should be checked periodically for

any tamper

g. Anchor windlass testing should be carried out to check the efficiency of the windlass.

The windlass should raise the anchor with chain from 82.5m to 27.5m at a mean

speed of 9m/min

h. The foundation of the windlass should be checked

i. Other routines of the prime mover should also be carried out like for the windlass

electric motor or the hydraulic motor as the case may be

133. What are the cylinder lube oil properties?

a. SAE 50 or higher range oils

b. TBN about 70 for heavy oil burning engines with sulfur content of about 3%

c. Ability to burn completely and leave no deposits

d. Good detergency

e. Good load bearing property

f. Good spread ability

g. Incompressibility for accurate metering and timing the injection

h. High flash point

134. What is a pressure-vacuum valve and why can’t it be used to vent the cargo

vapors during loading?

PV valve is designed to compensate for the variations in the tank pressure conditions due to

variation of temperatures and the vapor quantity. A drop towards vacuum condition because

of condensation of steam will also be handled by this valve. Usual set point of the valve is

about +700mmHg and -350mmHg on the vacuum side.

This valve cannot cope up with the requirements of cargo loading, as its capacity of pressure

venting is small. Moreover it is not designed for this purpose.

The valves displace a weight that vents the tank in case of an overpressure or vacuum

condition. The valves are fitted with velocity vents that make sure that the inert gas is

ejected out of the tank with such a velocity that it clears the deck sufficiently rendering the

deck surface safe.

135. What is a high velocity vent?

Tank vapors can be sent clear of the deck in case of excess pressure or during cargo loading

operation by a high velocity vent. The usual construction of such a valve is incorporated in a

mast riser, which is a long tower for safely venting the excess pressure of the inert gas in the

tanks to the atmosphere. The control is affected through a valve. The height of the mast

riser is arranged to vent outside the hazardous zone, generally 9m or more. The valve

consists of a variable moving orifice held by a counter weight to seal around the batten of a

fixed cone. Pressure build up in the tank causes the moving orifice to lift. The small gap

between the orifice lip and the fixed cone gives high velocity. The escaping gases are made

to pass through a flame arrestor and a flame screen. The valve has a cover that is normally

closed during sailing.

136. Air bottle maintenance and inspection

a. Regularly drain the bottle of water and oil

b. Regular inspection to ensure that the internal condition of the bottle is good

c. Check for corrosion both externally and internally

d. Inside coating, COPAL varnish condition to be checked to ensure that it is unbroken

and no peeling is taking place

e. Welding seam to be checked, carry out dye-penetrant test at suspected areas

f. The tell tale hole between the lap welding seams of the doubler plate / ring to be

checked for leaks in service to ensure that the internal welding is intact

g. Face of the man hole is to be checked for pitting marks

h. Drain should be clear

i. All points of high stress and corrosion are to be thoroughly checked viz. welds,

supports braces, the bottom of the bottle where water/oil is collected. Pay attention

to the zone of water line.

j. Check for leaks at the mounted valve glands/flanges, carry out inspection of the valve

face and seat for wire drawing effect

k. A timing check with the air bottle completely charged and isolated will give a good

idea of the intactness of the pressure vessel

l. The safety/relief valve setting to be inspected as per the class requirement

m. Regularly check the alarms and monitoring equipment for proper functioning

137. Explain the air bottle entry procedure

a. Inspection is to be carried out when the receiver capacity is not required for

maneuvering

b. Receiver properly isolated, depressurized and notice pasted

c. The internal pressure is to be checked by the pressure gauge and by opening the

drain valve

d. Open the manhole door carefully and ventilate the air bottle

e. Obtain an enclosed space permit and comply with it

f. Ventilation is to be maintained during the entire time of enclosed space entry

138. What action should be taken in case of corrosion/wasting observed on air

bottle?

MINOR: clean the site of corrosion, observe the varnish manufacturer instructions for surface

finishing prior applying the coat. Apply new coat of the varnish.

MAJOR: The site has to be cleaned and revarnished as above. The air bottle has to be

derated.

Incase of excessive the entire bottle has to be replaced.

The derating procedure should be carried out as follows:

a. The extent of the derating is determined by the class surveyor to a value which

ensures the safe limit of the hoop stress at this reduced thickness of the shell plating

b. The derating should not violate the starting air requirements for consecutive starts of

the main propulsion engine

c. The setting of the safety/relief valve, should be set not exceeding 10% of the

maximum working pressure after derating

d. The cut in and cut out pressure switches for compressor automation should be

readjusted

For these reasons the air pressure vessels on board ship are fabricated to allow for derating

in future still complying with the consecutive start requirements of the propulsion engine

139. What is a PV breaker? Why is it fitted?

This is a U tube manometer filled with an ethylene glycol solution (as a measure against

freezing). The height of the manometer is manipulated such that the pressure on either side

may displace the solution, into tanks incase of vacuum inside cargo tanks and outside on to

the deck incase of over pressurization inside cargo tanks. Usual set values of PV breaker are

+1800mmHg on high pressure and -700mmHg on vacuum side.

Pressure-Vacuum breaker is fitted to the IG main line on the deck to protect cargo tanks

from the following:

a. Abnormal rise of pressure in the cargo tanks which occurs when cargo is loaded with

specified rate and that all gas outlets are closed

b. Abnormal drop of pressure in cargo tanks which occurs when cargo is unloaded with

the rated capacity of the cargo pumps and the inert gas blower fails

c. Abnormal rise or drop of pressure in cargo tanks which occurs, when the breather

valves fails to operate properly for the fluctuation of the pressure in cargo tanks, due

to variation in atmospheric and sea water temperatures, altering the vapor pressure

inside tanks

140. What is the routine maintenance, checks on the PV breaker?

CHECKS:

a. Check the seal liquid periodically and replenish the liquid in case

• Liquid levels of inner and outer pipes do not coincide

• “0” points of inner and outer pipes do not coincide when the pressure inside

the cargo tanks is atmospheric pressure

b. Clean the flame screen in the cover at the top when the ships makes a dock-in

CHECKING PROCEDURE:

a. Checking the liquid level of the inner pipe (open the vent cock located at most top of

the gauge, close the upper gauge cock and open the lower gauge cock) this is also

termed as “bigger range”

b. Checking the liquid level of the outer pipe (close the vent cock, open the upper gauge

cock also open the lower gauge cock) this is also termed as “smaller range”

Two distinct scales are provided for the liquid gauge one “higher” and other “lower” the

respective readings (as in ‘a’ and ‘b’) should match numerically

MAINTENANCE & INSPECTION IN DRYDOCK:

Disconnect and remove top cover with attached internal stand pipe. Disconnect and remove

Flame Arrestor Assembly. Remove flame screen. Thoroughly clean internal of flame arrestor.

Renew flame screen with shipyard supplied equivalent type mesh. Drain breaker liquid,

thoroughly clean internal breaker body, and stand pipe. Apply two coats of shipyard supplied

tar epoxy by hand brushing to all internal surfaces. Level gauges, cocks and protective

housing to be removed and transported to workshop for cleaning and overhaul. Dismantle

sight glass tubes and cocks for overhauling and cleaning. Upon completion, re-assemble and

re-install onboard with new shipyard supplied approved type jointings, studs, and nuts.

Prove filling and level cocks clear and free. Disconnect and remove PV Breaker valve.

Dismantle and clean surfaces. Lap valve and disc. Set valve to +0.21kg/cm2 and

0.07kg/cm2 in the presence of the attending superintendent. Record and submit calibration

of valve settings. Close on completion with new shipyard supplied approved type jointings

and sealing compound and bolts and nuts.

141. Explain the mounting arrangement of boiler feet

The alignment of boiler should incorporate provisions for thermal expansion at the boiler feet

(saddles) when the boiler is in hot operating condition. Expansion may be in the order of

10mm. Assuming a four-point support; one foot will be bolted down hard to the foundation,

while the other three feet will be bolted down so as to permit the feet to slide.

Holes for the fixed bolts will be reamed in place. The foundation bolts in way of the sliding

feet must be accurately located with respect to the elongated holes in the boiler feet to

enable the feet to slide clear of the bolts. The pipe sleeves prevent the bolts from tightening

down on the sliding feet. A brass liner or a lubricant such as molybdenum disulfide is

normally used to facilitate the sliding action. In some cases, the pipe sleeves are not used.

Instead, the bolts are tightened only slightly so that the boiler foot can slide.

FIXED FOOT

BOLT

ELONGATED

HOLE IN

BOILER FEET

SLIDING FEET

OUTLINE OF

BOILER

Lock Nut

Boiler Feet

Steel Liner

Foundation Bolt

Interference body bolt or fitted bolt

FIXED FOOTCompiled by Eswara Arun Kishore

maverickshippy@yahoo.com

142. What is a fitted bolt?

The answer lies above. This is a closely fitted bolt. The holes are initially drilled to undersize

and are reamed in the assembling place before the bolts are tightened in place. Accuracy is

required in the machining. These bolts could be of two types one having a slight taper of

about 1:100 on diameter and the other having a large taper of about 1:15 on diameter.

However, the holes in either case are reamed in final place.

Some times an oversized bolt is stretched hydraulically reducing the bolt diameter. When

tightened down and the hydraulic pressure is released the final exact fit in the bolt hole is

achieved, like a pilgrim nut on coupling shafts.

These bolts find place in engine / boiler mountings, coupling shafts etc. and form a rigid

fixture. On main engine mounting these are situated aft of the engine in the way of thrust

block. The foundation bolts towards the fore end (either side of the engine ‘P’ ‘S’) are

generally simple foundation bolts which are not fitted bolts. This system of foundation bolts

offers the rigid seating with provision for thermal expansion towards fore end.

143. What is the material of main steam piping and explain how it is supported?

Main steam piping is usually made of seamless low alloy steel. Where temperatures are

above 455˚C, the most widely used alloy contains 0.5% molybdenum, 1.25% chromium.

Gaskets between the flanges are made of thin stainless steel strips spiral wound with

insulating filler between successive layers.

There are three types of supporting to carry the weight of main steam piping.

a. Rod hangers

b. Variable spring hangers

c. Constant force spring hangers

Horizontal sway braces are often used to resist dynamic forces applied to the piping due to

rolling and pitching or due to vibrations transmitted to pipe anchor points. Sway braces could

be of the turnbuckle-rod type, the preloaded spring type or the hydraulically damped type.

At fixed anchor points, the pipe anchor brackets are separated from the anchor foundation

by insulating material to reduce the heat transfer from the steam piping to the hull structure.

144. Soon after complete overhauling a generator engine, its lube oil consumption

increases. What checks do you carry out in this regard?

a. Check that the lube oil system valves are set back to normal, and that the concerned

valves are correctly holding

b. Verify dip stick bottom for any blockage which can give erroneous results

c. Check for normal operation of the purifier

d. Ensure that the piston scraper ring is set correctly, if this ring is boxed back upside

down, the oil scraping action of the ring is lost and uncontrolled lube oil enters the

combustion chamber. This presents a significant oil loss

e. Ensure that the cylinder head valves are correctly boxed back. Misalignment of the

valve spindle with their guide also causes lube oil to enter the combustion chamber

causing oil loss

145. Generator lube oil sump level increases, what are the checks you would

carry out?

a. Check that the generator lube oil systems valves are correctly positioned and that the

sump filling valve is holding

b. Ask the personnel for if they have carried out any transfers just before, related to the

sump oil of the generator

c. Check the purifier for correct operation and that no water is being discharged with the

purified oil

d. Change over the generator concerned, isolate it and check the sump for any

contamination like water. Basing on the findings further inspections can be carried

out, like checking the cylinder liner jacket cooling water sealing O-ring etc.,

146. How do you prepare a boiler for survey?

Before a survey, the boiler must be prepared. The preparation process involves:

I. Water side preparation prior entry into the steam drum for internal inspection

II. Gas side preparation for external tubes inspection also the refractory condition can

be inspected

III. Electrical isolation

Electrical side isolation:

The power supply to the boiler control panel should be isolated. The power supply breakers

for the FD fan; burner pilot fuel oil pump should be switched off and caution tags put.

Gas side/Exhaust side:

a. If the boiler is an exhaust gas boiler, then the main engine should be isolated from

starting positively. The composite boiler should be isolated on the fuel side in addition

by manual isolation of the fuel line by a shut off valve and isolating the power of the

boiler control panel.

b. Oil fired boiler should be isolated on the fuel side by a manual shut off valve and

isolating the power of the boiler control panel

Waterside isolation:

a. The boiler should be taken out of service. With the boiler shut, isolate the boiler on

fuel/exhaust side electrical side and water side by isolating valves, power supply

breakers as the case may be

b. Empty the boiler of water by blowing down, after allowing sufficient time for the boiler

to cool gradually to prevent excessive thermal shock

c. When blowing down to sea, open the overboard valve first then the boiler valve to be

opened gradually. The nearing completion of the blowing down operation can be felt

by falling noise, pressure. At this point, care must be taken not to let the cold

seawater into the boiler. Start closing the boiler blow down valve when the boiler

pressure is low enough, and when it is down to the desired value, the valve must be

closed down tightly and the ships side cock closed. This is to be done to keep out the

seawater ingress positively even though the valves are usually of non-return type.

d. Allow the boiler to cool down further and loose all its pressure, and when the boiler

pressure is at atmospheric pressure open the air cock and gauge glass drains to

ensure the pressure is atmospheric inside the boiler

e. Either the top door or the bottom door can be opened at this stage but not both,

while removing bottom door care must be taken against any hot water if present can

cause injury to the personnel near it

After the boiler has sufficiently cooled the access points can be opened, the spaces well

ventilated, enclosed space entry/steam drum entry procedures should be followed.

The fire/exhaust side should be cleaned after initial examination

a. Open access doors in way of the uptake and front and rear walls and the burner

register and all hand holes

b. Hydro-jet all soot deposits on tubes. Allow for collection and disposal of fresh water

c. Mop up the fireside to dry. Neutralizing chemical can be added in order to avoid

corrosion. Heating lamps can be used to dry out the furnace

d. Scrape hard deposits on all generating and water wall tubes, sweep and remove all

carbon, soot and debris on the furnace floor

The waterside requires a similar approach for cleaning

a. Remove for access to steam drum and water drum manholes and headers

b. Allow for header blanks for water side survey

c. Remove all steam baffle plates in the steam drum

d. Hydro-jet cleaning of the internals of drums and tubes may be required to remove

mill scale and sediments

147. What are oxygen scavengers?

Oxygen scavengers are chemical compounds, which are added to the boiler feed water to

eliminate oxygen residuals and to assist in the passivation of metal surfaces.

There are a number of these chemicals available, and a selection is a function of the amount

of oxygen present, risk, feed system design, economics and any particular limitations

required by the process using the steam.

Some widely used oxygen scavengers are:

a. Sodium sulfite (Na2SO3)

Method of dosage: Dose the feed water continuously to maintain a desired

concentration. Where corrosion in the feed system is experienced, it is used as a

catalyzed form of sodium sulfite. The catalyst (usually a salt of cobalt) is to speed up

the following reaction, so that this is complete before the water gets into the boiler.

How is O2 Scavenged? : 2Na2SO3 + O2 ---------Æ 2Na2SO4

Limitations: The speed of the reaction is influenced by the pH of the feed water

which should be between 8.0~9.5. Sodium sulfite adds some solids to the feed water,

so it should not be overdosed or applied to the cold feed water. Otherwise, this may

lead to increased blow down requirement.

Sodium sulfite can be used in the boilers of pressures up to 62 bars. Above these

pressures, decomposition products such as H2S and SO2 can affect steam purity

b. Hydrazine (N2H4)

Method of dosage: Liquid hydrazine is injected at the earliest possible point in the

feed water system.

How is O2 Scavenged? : N2H4 + O2 --------Æ N2 + 2H2O

Limitations: Excess hydrazine should be controlled to avoid an undue rise in the

ammonia level in the steam; there is a danger of copper corrosion in the condensing

plant. (Ammonia is produced by the decomposition of excess of hydrazine can provide

a suitable alkaline condition in the steam and in the condensate system,

3N2H4 --------Æ 4NH3 + N2). Hydrazine is not permitted in the systems where steam

is in contact with the foodstuffs.

c. Carbohydrazide (Eliminox) (N2H3)2CO)

Carbohydrazide is a combined form of hydrazine. It is superior in performance and is

designed to minimize exposure to hydrazine vapors during handling. Carbohydrazide

reaction products will add no dissolved solids to water. This can be used as an oxygen

scavenger and a metal passivator at both high (230

o

C) and low (60

o

C) temperatures.

Carbohydrazide can be applied to boilers up to 170 bars.

How is O2 Scavenged? : (N2H3)2CO + 2O2 --------Æ 2N2 + 3H2O + CO2

Limitations: in boiler, Carbohydrazide decomposes to hydrazine as one of the

products, so it cannot be used in systems where the steam is used for humidification.

(FDA rules)

d. Tannins

Certain alkaline tannin solutions have good oxygen absorbing capability. A 6ppm of

certain tannins extracts can remove 1ppm of oxygen at a pH of 12. The oxygen

scavenging efficiency is better than that of sodium sulfite.

e. Erythorbic Acid (Sur-Gard) (R1-C(OH)=C(OH)-R2)

This is an effective oxygen scavenger and a metal passivator. This is the only non

volatile scavenger, which can be used for spray attemperation. This does not add

measurable solids to the boiler water; is non-volatile and will not hamper the steam

purity. Erythorbic acid can be used in boilers up to 122 bars. This is considered as a

safe substance by FDA.

How is O2 Scavenged? : R1-C(OH)=C(OH)-R2 + ½O2 --------Æ R1-(C=O)2-R2 + H2O

Limitations: Ammonia is produced in the boiler as a by-product. This is not

recommended for use for boiler lay-up. Good corrosion control requires a high boiler

water pH value since the magnetite film is at its most stable condition when the pH is

10.5~11.5.

147. What are the various control actions?

The basic controller actions can be grouped as

a. Two position or on-off controllers

b. Proportional controllers: It is also called corresponding control. The corrective action

of controller, C, bears a constant ratio to the error θ = ± (Measured Value – Desired

Value), Thus C = -Kθ (where K= constant of proportionality)

c. Integral controllers: It is also called the reset action control. The rate of change of

corrective action is proportional to the error. Mathematically, dC/dt = -Kθ or

C= -K∫θdt + k (where K= constant of proportionality, k= constant of integration, C=

control action)

d. Derivative controllers: It is also called the rate action control. The amount of

corrective action is proportional to the rate of change of error. It is never used alone

and is always used in conjunction with the integral and or proportional controllers. As

with a constant error, the control action being derivate becomes zero. C = -K dθ/dt,

(K= constant, C= control action)

e. Proportional-plus-Integral controllers

f. Proportional-plus-Derivative controllers

g. Proportional-plus-Integral-pus-Derivative controllers

148. How is the chain drive of a main engine inspected?

Chain inspection is to be carried out as follows:

a. Make a general inspection for loose screws and bolts

b. Inspect lube oil pipes for damage, and check oil jet nozzles for possible stoppages or

deformations

c. Examine the rubber track of the guideways for cracks or other damage, replace the

guideway bits if they have started to be plucked out of the rubber stack

d. Check the teeth of the chain wheels. If abnormal wear is found, take a measurement

by placing a straight edge over the wear edges and measure the length of the wear

along the straight edge and the gap between the straight edge and the wear trough

e. Check the chains for cracks on possibly defective rollers and side plates

f. Check that for each chain link, chain rollers can run freely and that the chain links can

freely move on the pin and bushing

g. Check the chain wear by measuring the length of 10 chain links and compare the

result with the value in the data provided by the maker. If the parameter shows

abnormality then adjust the chain tightener

149. Explain the procedure of chain tightening

[Courtesy MANBW]

a. Loosen the nuts A, B, C and D to free the

chain tightener bolt

b. Turn the engine so that the slack part of the

chain is on the same side as the tightener

wheel. If balance weights are mounted, turn

the engine so that the weights hang vertically

downwards

c. With the balance weights in this position,

tighten the nut B on the chain tightener bolt

until there is a clearance of 0.1mm between

the shaft and the nut. then tighten the nut B

to a tightening angle of about 720

o

d. Tighten the nut C hard against the contact face of the shaft. Tighten the nut D, lock

nuts A and B with the tab washer

e. Measure the distance X, if the chain is worn (i.e. X>165mm) repeat the procedure

from ‘a’, but tighten the nut B only to a reduced tightening angle 600

o

.

f. If the distance exceeds the maximum distance 265mm, find and eliminate the cause

of this abnormal chain elongation, like a defective chain, damaged chain wheels or

bearings etc., repeat the procedure from ‘a’.

g. Repeated tightening of the chain will gradually alter the cam angle in relation to the

crankshaft. It is therefore necessary to readjust the camshaft to its initial angular

position after the lead angle has been increased by 2

o

. The camshaft is adjusted by

turning both halves at the coupling joint with the chain wheel

150. Why is a copper gasket annealed?

The essential qualities of a copper gasket are softness and toughness (provision for cold

working without fracture). In its place the copper gasket is subjected to considerable

mechanical stress, resulting from elastic strains internally balanced. These elastic strains are

due to jamming of dislocations, which occurred during cold deformation (during service). If

this cold worked gasket is heated to a sufficiently high temperature the total energy available

to the distorted regions will make possible the movement of atoms into positions of

equilibrium so that the elastic strains diminish and the locked-up energy associated with

them ‘escapes’. Tensile strength and hardness will fall to approximately their original values

and capacity for cold work will have returned.

151. What is the difference between a safety valve and a relief valve?

A safety valve is a pressure relief valve actuated by inlet static pressure and characterized by

rapid opening or pop action.

A relief valve is a pressure-relieving valve actuated by inlet static pressure and opens in

proportion to the increase in pressure over the opening pressure.

The terms ‘safety’ and ‘relief’ are synonymous; the safety valve is generally applied to valves

protecting any vessel, which could explode and endanger life whereas the relief valve is more

appropriate to the valve protecting system containing non-expansible liquid a burst causing

no violent explosion.

Another notable difference between these valves is that the vent of a safety valve is led to a

‘safe’ place (harmless to the working personnel) whereas a relief valve vents just outside the

valve.

152. What are the parameters of a lube oil analysis?

The parameters of a two stroke, heavy fuel oil engine circulating/system lube oil are

a. Specific gravity: Range 0.90~0.98. This is used for identification of the oil. Limits: 5%

of initial value

b. Viscosity: Viscosity increases with oxidation, contamination with cylinder oil, heavy

fuel or water. Diesel fuel contamination decreases viscosity. Limits: Max 40%, Min -

15% of initial value

c. Flash point: Gives an indication of possible dilution with diesel oil. Limits: Minimum:

180˚C

d. TAN (total acid number): Expresses the total content of organic and inorganic acids in

the oil. Organic acids are due to oxidation products. TAN = SAN + weak acid number.

Limits: TAN 2

e. SAN (strong acid number): This expresses the amount of inorganic acids in the lube

oil. Inorganic acids are usually sulfuric acid from the combustion chamber or

hydrochloric acid arising from seawater. This will be stated. SAN makes lube oil

corrosive (especially together with water) and should be zero. Limits: SAN = 0

f. Alkalinity/TBN (total base number): Gives the alkalinity levels in the lube oil

containing acid neutralizing additives. Limits: High = 100%, Low = -30% of initial

value

g. Water: Could be fresh water or sea water, will be stated. Limits: Fresh water: 0.2%

(0.5% for short period), saline water: Traces

h. Conradsen carbon: Residue from incomplete combustion, or cracked lubricating and

cylinder oil. Limits: Max 3%

i. Ash: May be used to indicate the amount of additives in the lube oil. It can also

consist of wear particles, sand and rust. It should always be evaluated by comparison

with the ash content of the unused oil. Limits: Max 2%

j. Insolubles: Stated as pentane/heptane and benzene insolubles. Equal parts of the oil

sample are diluted with benzene and normal pentane or heptane. As oxidized oil

(lacquer and varnish like constituents) is only soluble in benzene, and not in pentane

or heptane, the difference in the amount of insolubles is indicative of the degree of oil

oxidation. Benzene insolubles are the solid contaminants. Limits: Pentane insolubles

Max 2%, Benzene insolubles Max 1%

Apart from the primary parameters as stated above, the insolubles are usually stated as

percentage/ppm of individual constituents such as Vanadium, Sodium, Aluminium, Iron,

Silicon, Tin etc., which shows the engine wear and tear empirically.

153. Explain hot gas defrosting in a/c fridge system

A/C Com pressor

Electric Motor

Condenser

To Other Evaporators

Evaporator Re-evaporator

Suction solenoid v/v

Liquid Solenoid v/v

Hot Gas Solenoid v/v

Expansion v/v

R educing v/v

D rain

Sensing Line

Drain

Defrosting Circuit

From other Evaporators

Two kinds of hot gas defrosting systems by pass line are shown here.

A by pass line hot gas defrosting system as above. This can be carried out for one

evaporator coil when others are in use.

Below is another type of hot gas defrosting system which is also called reverse cycle

defrosting system and is used when all the evaporator coils have to be defrosted.

Condenser

A/C Compressor

Electric Motor

Evaporator

Drain

Expansion v/v

Check v/v

Expansion v/v

Check v/v

Reservoir

Four

way v/v

Defrost circuit

154. What is the difference between coagulation and coalescing?

A Coalescer filter element consists of some pre-filter for particulate removal followed by

compressed inorganic fiber coalescing unit in which water is collected into larger globules

Coalescing action is relatively complex and simply it can be said to be due to the molecular

attraction between the water droplets and the inorganic fibers is greater than that between

the oil and the fibers. When the water globules are large, enough they will move with the

stream out of the coalescing unit.

Coagulation is the process of agglomeration of smaller particles into larger particle due to

intermolecular attraction between similar molecules in preference

155. Why do we carry out boiler water treatment?

The objects of boiler water treatment are:

a. Prevention of scale formation and feed system by

i. Using distilled water

ii. Precipitating all scale forming salts into the form of a non-adherent sludge

b. Prevention of corrosion in the boiler and feed system by maintaining the boiler water

in an alkaline condition and free from dissolved gases

c. Control of the sludge formation and prevention of carry over with the steam

d. Prevention of entry into the boiler of foreign matter such as oil, waste, mill-scale,

iron oxides, copper particles, sand, weld spatter, etc., by careful use of oil heating

arrangements (close watch on the drains), effective pre-commission cleaning and

maintaining the steam and condensate systems in a non-corrosive condition

156. How do you indent a drill bit?

a. Order the drills in consultation with the personnel routinely working with the tools

b. Take the inventory of the drills, estimate the consumption of each drill, analyze to

ensure that excess inventory is not kept

d. Regarding the technical specifications follow the instructions as per the ordering book

viz. IMPA/ISSA

e. Some aspects should be looked into before arriving at a conclusion, these are:

a. Material of the tool and the intended nature of its work, like for light or heavy

duties

b. Industry specification like DIN, JIS, BIS etc.,

b. Length of the drill, normal or extra length

c. Cutting angle, standard angles are 118 & 135 degrees

d. Nature of twist, right handed, left handed, spiral etc.,

e. The shank shape, tapered, straight or ‘S’ cut

f. Number of flutes

g. Drills and counter sinks

h. Reputation of the company and cost

i. Any previous experience with the company’s tools

Most commonly used drills on board are jobber drills (drills without a shank, which are

gripped in the vice) for light duty, tapered shank drills for medium to heavy duty

157. What checks do you make if a compressor trips on low lube oil pressure?

Incase of reciprocating compressor

a. Direction of rotation, in case the motor is overhauled or some maintenance carried on

the motor

b. Suction filter should be cleaned

c. Check the pressure switch

d. Inspect the lube oil pump

e. Check if any lube oil pipe is holed

f. Check for excessive foaming

Incase of rotary compressor,

a. Check whether the lube oil pump is rotating with the compressor

b. Check the condition of vanes and the elliptical casing for scoring damage

c. Check the compressor is free to turn, no seizure of rotor, no wear on the vanes and

the casing

158. What are the reasons of piston seizure in a reciprocating air compressor?

a. Failure of lubrication

b. Failure of cooling water

c. Valve part broken and fell into the chamber

d. Piston ring breakage

159. What are the instructions you would give to the watchkeepers regarding

boiler?

a. Check the water level by gauge glass

b. Keep an eye on the steam pressure

c. Watch the flame pattern

d. Check the vicinity of the oil burning equipment for any traces of oil

e. Maintain the hot well temperature about 85C

f. Check the hot well level and maintain it

g. Atomizing steam pressure should be monitored

h. Fuel oil pressure, temperature, the fuel oil pump its suction pressure

i. Amperage drawn by the related motors like FD fan

160. What is the procedure of conrod removal from a main engine?

[Courtesy MANBW]

a. Turn the engine to BDC.

Dismount the nuts from the

crosshead bearing studs

b. Mount the shackles in the top

of the crankcase in the lifting

brackets, in the athwart ship

direction, and suspend two

tackles

c. Turn the crank to TDC.

Dismount the crankpin

bearing cap, and remove the

bearing cap from the engine

d. Mount the four supports

for guides shoes on the

crosshead guides, turn

the crank towards the

camshaft side, until the

guide shoes rest on the

supports. Adjust the

supports brackets to the

guide so that the weight

of the crosshead is evenly

distributed on the four

supports

e. Mount the lifting

attachments for securing the

connecting rod on the head of the

connecting rod. Fasten tackles to

the lifting brackets A and B on the

box wall, and attach the tackle

hooks to the mentioned lifting

attachments on the connecting rod

head. Haul the tackles tight. Also

mount a lifting attachment on the

lower end of the conrod, on the

exhaust side

f. Turn the crankthrow carefully

towards BDC while following with

the tackles, thus continuously

supporting the connecting rod.

The crosshead now rests on the

four supports. Turn the crankthrow to 90˚ before BDC

g. Shift tackle B from the lifting attachment on one

side of the connecting rod to the lifting attachment

on the other side. Dismount the lifting attachment

on the camshaft side of the connecting rod. Attach

a tackle to the lifting bracket C on the frame box

wall box and connect the tackle hook to the lifting

attachment on the lower end of the connecting rod.

Mount the wire guide on the doorframe. Turn the

crankthrow towards TDC while following with the

tackles thus continuously supporting and guiding

the connecting rod towards the doorway

h. Attach a tackle to the gallery-mounted lifting

bracket E, and hook on to the lifting attachment on

the connecting rod. Shift tackle A from the lifting

attachment on the head of the connecting rod to

the lifting attachment on the head of the connecting

rod to the lifting attachment at the bottom of the

connecting rod. Turn the crank upwards while

following with tackles A, B, C and E, guiding the

head of the connecting rod out of the doorway. Shift

the tackles from one lifting attachment to the other

as necessary

i. Mount a strap around the connecting rod and

suspend the connecting rod from the engine room

crane. Shift tackle B, from the lifting attachment on

the head of the connecting rod to the lifting

attachment at the bottom of the connecting rod.

Remove tackles A and E. continue turning upwards

till about 30˚ after TDC while following with the

tackles and the engine room crane

j. Shift tackle from lifting bracket C to A. lift the

connecting rod out of the engine, using the tackles

and the engine room crane. Remove the tackles by

means of the engine room crane.

161. What is the importance of starting air overlap? What should be the minimum

number of cylinders for a two-stroke engine for air starting? What is the

corresponding number for four-stroke engine?

Some overlap of the timing of starting air valves must be provided so that one cylinder air

start v/v opens as another closes. It is essential that there is no angular position of the

engine crankshaft with insufficient air turning moment to give a positive air start. The usual

minimum overlap provided is 15˚. Starting air is admitted in the working stroke of the

engine and the period of opening is governed by

a. The firing interval of the engine = No. of degrees in engine cycle/No. of cylinders

b. The valves must close before the exhaust commences. It is dangerous and a waste

blowing air to exhaust manifold.

c. The cylinder starting air valve should open after TDC to give a positive turning

moment in the correct direction.

The minimum number of cylinders for a two stroke engines is FOUR and that for a four

stroke engine it is SIX.

This can be concluded as follows:

For a two-stroke engine the air starting valve timing is

Air on 15˚ATDC, Air off 50˚BBDC (exhaust opens at about 40˚BBDC) therefore a net

starting angle of 115˚. At the end of this angle of a unit in power stroke, another unit of the

engine should be 15˚ATDC in the power stroke, for continuity of starting. For this to happen,

the maximum possible crank angle difference can be 115˚ between units.

A two-stroke engine has a complete cycle angle of 360˚, therefore the minimum number of

units ≥ (360˚/115˚) = 3.13….

Minimum possible number of units in a two-stroke engine is therefore FOUR.

Similar approach to four-stroke engines gives the following inference.

Air on 15˚ATDC, Air off 40˚BBDC (exhaust valve opens at 30˚BBDC) therefore a net starting

angle of 125˚. Therefore, maximum possible crank angle difference between units is 125˚.

A four-stroke engine has a complete cycle of 720˚

Therefore, the minimum number of units in a four-stroke engine ≥ (720˚/125˚) = 5.76

Minimum possible number of units in a four-stroke engine is therefore SIX

162. Show how the requirement of carbon dioxide in a ship’s installation is

calculated. How is the number of bottles required calculated?

Regulation stipulates the requirements of CO2 onboard ships as follows

a. For cargo space, 30% of gross volume of largest cargo space

b. CO2 of sufficient amount to give minimum value of free gas equal to larger of

following volumes

I. 40% of gross volume of largest machinery space excluding casing

II. 35% of gross volume of largest machinery space protected including casing

Regulation also states that, for machinery space, piping arrangement should be such that

85% of the gas can be discharged into the space protected including the casing with in 2min.

The following information about CO2 is important

Volume of free CO2 should be taken as 0.56m3/Kg (inverse of density)

CO2 content in a bottle is 45.4Kg (standard)

Water capacity of the bottle = 65.1 liters (standard)

For example, consider a ship in which

a. Engine room gross volume (to upper deck) = 4658m3

b. Engine room gross volume to top casing = 5358m3

c. Volume of the largest cargo hold = 6849m3

Calculation of the CO2 cylinder required as per the regulations for the volume of the air

reservoir = 375m3

Therefore, for engine room the CO2 bottle requirement is calculated as

For gross volume excluding casing,

(4658+375)*0.4/ (45.4x0.56) = 80 cylinders

For gross volume of engine room including casing,

(5358+375)*0.35/ (45.4*0.56) = 79 cylinders

For cargo hold, requirement is calculated as

(6849*0.30)/(45.4*0.56) = 81 cylinders

The requirement is the largest of the above values, which is 81 cylinders

163. What is a compensating ring in a boiler?

If any hole drilled in the boiler shell exceeds the value 2.5t + 75mm, where t = thickness of

boiler shell, the vessel should be compensated for the loss of strength (due to lost material)

by a stiffening ring around the hole (circumferentially). This is called a compensating ring.

164. What is BOD?

In sewage system, the effectiveness of the biological treatment of raw sewage is measured

by BOD, biochemical oxygen demand.

In a biological sewage treatment plant certain bacteria feeds on the raw sewage aerobically

there by rendering the sewage harmless and with reduced suspended solids. After complete

treatment the bacteria has no or little action.

Therefore, by measuring, the amount of oxygen consumed from a sample of treated sewage

the activity of these aerobic bacteria and hence the completeness of the treatment can be

estimated.

In actual check, 1Litre of the sample is collected in a measuring container and stored at

about 20˚C in water, which is well oxygenated and in a container and the amount of oxygen

consumed in a period of five days is measured and is expressed in mg/L or ppm as BOD.

165. What is the difference between a filter and a strainer?

A filter is a fine mesh insert in the pipeline of a fluid for the prime purpose of filtration. It is

normally positioned in the discharge line before the utility (equipment) or in the return line in

some hydraulic systems. The usual size of the mesh is mentioned in microns, which is the

smallest particle that can be filtered by the filter.

A strainer is a coarse mesh inserted usually in the pump suction. It is positioned for the

prime purpose of safeguarding pumps from ingress of heavy debris. In addition, this strainer

helps in preventing chocking of the pipeline in the upstream especially near sharp bends or

narrow passages like coolers. Its objective is not filtration. It is usually mentioned as ‘mesh’

and is the size of the holes of the mesh.

166. What is principle of viscotherm?

The principle of viscotherm is that a drop in pressure of a fluid of laminar flow, across a tube

is directly proportional to its viscosity.

In a viscotherm, a sample of the fuel is pumped at a constant rate through a fine capillary

tube. As the flow through the tube is laminar, pressure drop across the tube is proportional

to its viscosity. Tapping points are provided to enable the pressure difference to be

measured by means of a differential pressure gauge. The gauge is calibrated directly in

terms of viscosity. A differential pressure transmitter provides an analogue of viscosity to a

pneumatic controller, which regulates the supply of fuel heating.

167. What is a bore relief in a bearing?

The bearing sliding surface is machined at the mating faces of the upper and the lower shells

to create bore reliefs. Their main objective is to compensate for the misalignments, which

could result in a protruding edge (step) of the lower shell’s mating face to that of the upper

shell. Such a protruding edge can act as an oil scraper and cause oil starvation

168. What is microbial infestation of lube oil? What are its causes, effects?

Suggest remedies.

Microbial infestation of lube oil is the undesirable growth of bacteria, yeasts and/or moulds in

the oil.

Infestation of the oil can be due to contaminated seawater, hydrocarbon source already

onboard or due to poor housekeeping practices.

The problems are like tank washing with contaminated seawater, water ingress from leaks of

seals (as in a stern tube, CPP etc.,), leaking cooling water, microbe infested fuel oil

contamination, onboard contamination due badly maintained or stagnant tanks (long lay off),

bilge water etc.,

The effects of such microbial infestation can be

a. Slimy appearance of the oil; the slime tends to cling to the crankcase doors

b. Rust films

c. Honey-colored films on the journals, later associated with corrosion pitting

d. Black stains on white metal bearings, pins and journals

e. Brown or grey/black deposits on metallic parts

f. Corrosion of the purifier bowl and newly machined surface

g. Sludge accumulation in crankcase and excessive sludge at the purifier discharge

h. Paint stripping in the crankcase

i. Additive depletion

j. Rancid or sulfitic smells

k. Increase in oil acidity or sudden loss of alkalinity. (BN)

l. Stable water content in the oil, which is not resolved by the purifier

m. Filter plugging in heavy weather

n. Persistent demulsification problems

o. Reduction of heat transfer in coolers

To counter the problems of the microbial infestation, it is necessary to take steps to prevent

such infestation.

The microbial infestation is not possible without the presence of water. Some water in the oil

in inevitable due to leaks, condensation, etc., so it is necessary to constantly purify the oil.

Tanks should be provided with drain cocks at the bottom most part to regularly drain the

tank of water. The tanks should be designed to prevent any pockets where the flow is

minimal or stagnant. The oil should be stored outside the 15~35˚C range. This temperature

zone is very conducive for bacterial growth. Preferably, the tank should be kept at a higher

temperature to facilitate sterilization. Lube oils have a maximum risk of infestation in the

water-cooled pistons engine. Therefore, care must be taken not to allow any scope for water

leakage from the cooling system and the coolers should be kept leak free.

Once the oil is infested, it is necessary to kill the bacteria by physical, chemical or other

means.

PHYSICAL MEANS:

a. Settling: microbes settle the as they have a higher specific gravity (Sp.gr. 1.05)

b. Centrifuges: they can be separated by centrifuging

c. Filtration: microbes can be filtered by suitably staging filters

d. Heat: This is a function of both temperature and time at that temperature. A

temperature of over 70'C for 20 minutes is effective in killing the microbes. However

this is difficult to achieve at the plate surfaces and it may be necessary to sterilize the

tank first say by the use of steam lances before filling with oil for heat treatment

CHEMICAL MEANS:

Killing microbes using microbes is easy and effective, however the selection of chemicals

appropriate for the system application and should be done with care. Such things as

compatibility and hazards should be taken into account. However, if the infestation is acute,

higher concentration of dosage of the chemical is required. This may render the oil unusable

and has to be discharged to shore facilities.

Other means of combating the microbes are available like

a. Irradiation (UV Rays, Gamma Rays or X Rays)

b. By ultrasonic treatment of the infested oil

c. Using microwaves

d. Continuous pasteurization of the infested oil and heat control

169. What are the properties of gear oil?

Properties required for gear case oil:

a. High viscosity. This gives high film strength to prevent metal-to-metal contact. Also a

adhesive of the film to the metal is required to counter the sliding and centrifugal

force

b. It should prevent corrosion

c. It should have high specific heat to be a good coolant

d. High viscosity index

e. Antifoaming

f. Sound damping with good cushioning property to prevent pitting on the gear teeth

faces

g. Oil should be suitable for elasto-hydrodynamic lubrication

170. What is Osmosis? What is Osmotic head?

Osmosis describes the process whereby a fluid will pass from a more dense to a less dense

solution through a semi-permeable membrane. It is very important to the water absorption

processes of plants. Reverse Osmosis is a process, which uses a semi permeable membrane

that retains both salt and impurities from seawater while allowing water molecules to pass.

Filtration of up to 90% is possible thus making the produced water unsuitable for boiler feed

without further conditioning. Improved quality is possible using a two or more pass system.

The fig. shows an experiment to show the effect of Osmosis

(Osmotic head). When the jar is immersed in the

concentrated solution the liquid inside jar increases due to

diffusion of liquid from the concentrated solution to the clean

water inside the jar, which is reflected as an increase in the

water column. This increment in the water column is the

Osmotic head.

171. What are Detergency and Dispersancy properties of lube oil?

Detergency of lube oil is the property of the lubricant to keep engine parts clean. In motor oil

formulations, the most commonly used detergents are metallic soaps, usually of calcium

(metalloid-organic compounds) with a reserve of basicity to neutralize acids formed during

combustion.

Dispersancy of lube oil is the property of the lubricant to keep solid contaminants in a

colloidal suspension, preventing sludge and varnish deposits on engine parts. Usually the

additives used to impart this property are nonmetallic ("achless"), and used in combination

with detergents.

172. Why are air compressors and diesel generator engines not provided with

crankcase oil mist detectors?

Crankcase oil mist monitoring for engine protection are to be provided when:

a. When arrangements are provided to override the automatic stop for excessive

reduction of lubricating oil supply or pressure

b. Power rating is 2250 Kw or more

c. Having cylinders of more than 300mm bore

Air compressors and generator engines in a ship usually do not meet any of the above

criteria and hence are not provided with crankcase oil mist detectors.

173. What is the purpose of steam traps?

Steam traps are automatic valves that release condensed steam (condensate) from a steam

space while preventing the loss of live steam. They also remove air and non-condensable

gases from the steam space. Steam traps are designed to maintain steam energy efficiency

by performing specific tasks such as maintaining heat for process.

Once steam has transferred its energy, it becomes hot water and is removed by the trap

from the steam side as condensate and either returned to the boiler via condensate return

lines or discharged to atmosphere (a wasteful practice).

174. What is the importance of ‘Lip clearance’ in a boiler safety valve?

The boiler safety valves make

use of a special shaped valve

seat and a lip on the valve

which gives increased lift

against the increasing

downward force of the spring.

The action is as shown above.

And this lip value is of

importance and should be

checked during inspection.

Damage to this region can lead

to malfunctioning of the valve.

175. What are the reasons for a lot of deposits in the scavenge space of a marine

engine?

The usual reasons for a lot deposits in the scavenge space of a marine engine are

a. Chocking of the scavenge drains

b. Blow-by due to broken or sticking piston rings

c. Excessive liner wear

d. Faulty injection due to altered timing, bad fuel or incorrect atomization

e. Blow back of exhaust due to increased exhaust back pressure

f. Leaking piston stuffing box

g. Excessive cylinder liner lubrication

176. How does a leaky piston manifests as in an indicator diagram?

As shown above the loss of intactness of the combustion chamber due to leakages, increased

volume or fouling causes the compression pressure and peak pressure to drop.

177. What is the thermal efficiency of the main engine?

Thermal efficiency of a plant = Heat energy converted to work/Heat input

In a main engine heat input = (Fuel consumed x Calorific Value x reference time)

Heat energy converted to work = Brake power x Reference time

178. What is composition of thin shell bearings?

Thin shell bearings are broadly of

a. Tin based White Metal: Tin-based white metal is an alloy with minimum 88% tin (Sn),

the rest of the alloy composition is antimony (Sb), copper (Cu), cadmium (Cd) and

small amounts of other elements that are added to improve the fineness of the grain

structure and homogeneity during the solidification process.

b. Tin-Aluminium (AlSn40): Tin aluminium is a composition of aluminium (Al) and tin

(Sn) where the tin is trapped in a 3-dimensional mesh of aluminium. AlSn40 is a

composition with 40% tin.

179. How do you operate the main engine after a Turbocharger breakdown?

Some points are to be taken into consideration for engine operation with turbocharger out of

operation:

a. Air supply for amount of fuel injected

b. Adequate flow path of the exhaust gas produced

c. Cooling of the turbocharger casing, rotor or bearings

d. Isolation of air/gas/lubricating spaces in the event of no sealing air available

e. Securing damaged parts

The method of turbocharger isolation may be done in a number of ways depending on the

nature of damage.

Bypass arrangement: Turbocharger is bypassed of exhaust gases by a suitable bypass pipe.

Turbine inlet and outlet are isolated by fitting blanks and by pass pipe is fitted to give a

suitable gas path. The compressor side also requires isolation to prevent loss of scavenge air

due to back flow from the receiver. Cooling water and lubricating oil systems may also

require isolation if casing and or seal is damaged.

Rotor removal: If the rotor is damaged it should be removed for repairs. The openings of the

casings should be blanked to prevent internal and external leaks of exhaust gas or air.

Cooling of the casing should be effected as exhaust gases still pass through the casing.

Locking of rotor: If requirement of propulsion is of concern and time is limited, rotor is

locked into position by attaching the appropriate fixtures provided by the maker. An orifice

plate should be inserted on the compressor side to allow a controlled amount of scavenge air

to effect cooling. Cooling water to the casing should also be continued since exhaust gases

pass through the casing. Isolation of the lubrication system may be necessary due to lack of

sealing air.

LIMITATIONS OF OPERATION:

The limits of engine load depend on the actual configuration of the system and how many

turbochargers remain in operation.

A broad consideration of the following points should be made:

a. The actual operating temperatures should be taken into account and limits should not

be exceeded

b. Condition of the exhaust should be monitored to ensure acceptable combustion inside

the cylinder

c. Allowance should be given for rate of change of air supply during acceleration of the

engine

d. Remaining turbochargers should be also monitored for abnormal operation due to

altered gas flow

e. Auxiliary air supply should be provided where possible, but this may be effected by

remaining turbochargers in operation

Internal water leaks: In the event of a holed water jacket it is possible to operate the

turbocharger as an air cooled unit by supplying compressed air as the coolant after isolating

the water supply. Attention must be paid to the operating temperatures of the casing, and

bearings especially turbine end.

Four stroke engines with turbochargers out of service and no alternative air supply may be

operated as a naturally aspirated engine with suitable attention being paid to the operating

temperatures

In any case the engine load is to be limited a value specified by the engine maker for the

conditions of operation and usually for a two-stroke engine its value is about 15%MCR

180. What is the procedure of plugging boiler of boiler tubes?

Procedure of plugging water tubes

a. Clean the face of leaky tube remove all the scales and dirt both in steam and water

drum

b. Plug with brass plug, hammer tight and weld

c. Cover this tube on the furnace side with heat resisting material

Procedure of plugging smoke tubes

a. Brass plug with stud and tightened by nut at both the ends

181. What is the difference between a purifier and a clarifier?

Purifier Clarifier

A centrifuge for separation two liquids of

different densities

A centrifuge for separation of solid particles

from a liquid

Sealing water is added to a purifier to

establish a seal

No sealing water is added

Gravity disc needs to altered with the

changing density of the liquid to be purified

A smallest of the gravity discs provided,

called a clarifier disc is fitted and requires no

alteration

Interface is to be maintained and depends on

process variables viz. density, flow, viscosity

or temperature

Interface is not required but is established if

water is present and moves inwards

Water outlet is normally open Water outlet is normally closed by the

clarifier ring

Provided water seal is maintained particle

separation is also good

Provided no water, particle separation is

good

182. How do you detect a leakage in a bilge pump suction line?

With the main suction of the pump closed, start the pump with discharge open. Monitor the

vacuum in the pump suction, if the vacuum is maintained for sometime the pump is in good

condition.

Proceed for checking the integrity of the suction lines as follows:

With the discharge of the pump opened for delivery,

a. Set the pump to draw bilge from each particular well closing other suction lines valves

b. Start the pump and note the build up of vacuum

c. Repeat the operation for all other suction lines individually, closing other remaining

lines

Now conclusion can be drawn with above observations.

The pump does not achieve good vacuum for any well, in this case

The manifold intactness by opening the sea water valve on the suction side and check it for

the seawater leaking. Repair the line after identifying the location

Identify for the leaks on the suction lines for which the pump does not achieve good vacuum

This can be done by pressure testing the line by opening the seawater valve on the pump

suction. The non-return valve on the line has to be dismantled and the valve put back after

removing the valve disc.

The sealings on the strainers have to be checked, like renewing gaskets.

183. How is an engine lube oil sample collected?

Sampling points for an engine lube oil are clearly mentioned by the maker of the engine. In

any case, the following points are to be adhered to

a. Sample of lube oil should be drawn from the inlet to the engine

b. Before collecting a sample some amount of oil is to be drained from the sampling

point. Later sufficient amount of oil should be collected into a clean container,

decanted and collected in a clean sampling bottle

c. Engine should be in operation as close as possible to the MCR for some time before

collecting a sample

d. The sampling container should be unused one specially produced for lube oil sampling

e. After collecting a sample in the bottle, it should be stored in a cool dry place to let the

oil cool down before securing it with cap/seal. This is essential to prevent slight

condensation in the bottle

f. The sample should be fully identified with the date, vessel name, running hours of the

engine, lube oil running hours, sampling point identification

g. Each time the sample should be drawn from the same point

184. Explain onboard testing of lube oil

Some or all of the testing explained below is done onboard ship.

1. FLASH POINT (Pensky Martin Apparatus)

This method determines the flash point of the lube oil sample in a closed cup. This gives

the lowest possible ignition point of the oil.

A portion of the lube oil sample is slowly heated at a constant rate, whilst continual

stirring is provided. A small flame is directed through an open shutter at regular

temperature intervals, with simultaneous interruption of stirring.

The flash point is the lowest point at which the application of the test flame causes the

vapor above the test point to ignite. For a new oil the flash point should be above 220˚C,

and any reduction would indicate fuel oil contamination.

2. BASE NUMBER

BN tester kits are provided onboard to determine the alkaline properties of the lube oil.

These testers use the chemical reaction of a reagent with the alkaline lube oil additive

(calcium) to produce a pressure rise. 10ml of oil is mixed with equal volume of a reagent.

10ml of another reactive reagent is placed in a plastic cup, which is floated on top of the

oil and reagent. The testing unit is sealed and thoroughly mixed. The resultant pressure

rise is directly read on an calibrated pressure gauge against base number.

3. KINEMATIC VISCOSITY

Onboard testing lube oil for viscosity is by the use of a comparative flow stick. This

measures the relative flow between two oils, usually a sample of the in-use lube oil is

measured against a fresh unused sample of the same grade of lube oil.

The flow stick is filled with 3ml of each oil in each reservoir, once both the oils are at the

same temperature, the flow stick is tilted to cause both oil grades to flow down the

channels. Once the new oil has reached the reference mark, the position of used oil in the

channel is checked. The following inferences can be drawn

a. If the used oil has a low viscosity, due to light fuel dilution. Then oil will have

traveled further down the channel than the new oil.

b. If the used oil has a higher viscosity, due to oxidation or heavy fuel oil

contamination it would not have traveled as far as the new oil.

4. DENSITY

This method uses hydrometer to test the sample oil density. It is important to keep the

oil and the hydrometer at the same temperature and maintained throughout the

experiment.

5. WATER CONTENT

Onboard water content is tested by using a calcium carbide. The tested is carried out by

mixing 5ml of oil with 15ml of a petroleum reagent (paraffin, toluene). The two liquors

are thoroughly mixed and then a measured amount of reagent (calcium carbide) is placed

on floating on the oil/reagent surface. The test unit is sealed and thoroughly mixed to

bring all liquids together. If water is present the carbide will produce acetylene gas, and

the resultant pressure rise will indicate the level of water contamination.

185. What is the material of a boiler valve?

Valve body: Cast Steel

Spindle, valve seat, valve disc and other parts: Monel Metal, Bronze or stainless steel

186. What will be the effect of water in fuel oil?

The effects of water content on fuel oil are

a. Loss of calorific value of the fuel oil

b. Corrosion in the lines, fuel pump (plunger/barrel), injectors

c. Water in oil can lead to vapor lock in the line leading to fluctuating engine RPM,

seizure of fuel pumps

d. In case of seawater contamination, it would lead to high temperature corrosion in the

exhaust system

e. Results in increased cylinder liner wear

f. Cause increased fouling of the exhaust gas ways and turbocharger blades

187. What are actions you would take if a purifier starts overflowing?

Some or all of the following should be checked for in case the purifier overflowing:

a. Sealing water low

b. Excessive fuel back pressure

c. Low pressure, chocked water line (check the water filter)

d. Gravity disc oversized for the density of the fuel oil in question

e. Oil temperature high

f. Excessive sludge deposition inside the purifier bowl

g. Excessive feed rate

h. Sealing ring damaged (between the Bowl and Hood)

i. Check RPM and direction of rotation of bowl

j. Leaking three-way valve

188. How do you calculate the specific fuel oil consumption?

a. Take the fuel oil flow meter readings for a specific time interval usually for an hour

b. Calculate the volume (difference between the above readings)

c. Using the fuel oil sample test results provided by the shore facility, calculate the

density of the fuel oil at the temperature near the flow meter

d. Calculate the mass of the fuel consumed by multiplying the results in b and c

e. Calculate the shaft power of the engine during this interval of time, take an average

value

f. Specific fuel consumption is calculated by mass of fuel consumed/Avg.shaft power

developed by the engine in the time interval.

Express the result in the Units of specific fuel oil consumption: g/Kw-h

189. How do you calculate the shaft power of main engine?

[Procedure for MANBW Engines]

During an interval of time, 1Hour measure engine

a. Fuel index of each unit

b. Engine RPM

c. Scavenge Air temperature

d. Ambient air temperature (Engine Room Temp.)

e. Fuel oil preheating temperature

f. Obtain the specific gravity of the fuel oil at 15˚C, its sulfur content & Lower calorific

value

g. Obtain the cylinder constant (engine data)

Calculate the average fuel pump index, Pθ = sum of all individual fuel index/total number of

cylinders.

Corrected fuel index, Pθ’ = average fuel index x K

Where K = Correction factor for fuel pump index Compiled by Eswara Arun Kishore

maverickshippy@yahoo.com

= K1 X K2 X specific gravity of fuel @ 15˚C

An example of calculation is shown with the following data to calculate K, Hence Pθ’

Lower calorific value of fuel: 9700Kcal/Kg, Specific Gravity @ 15˚C: 0.947, Preheated

Temperature: 104˚C, Engine room temperature: 30˚C, Scavenge air temperature: 32˚C

K1 = 0.953, K2 = 0.926

K = K1 x K2 x Sp.Gr. @ 15˚C = 0.836. Hence Pθ’ = Pθ x K

Mean Effective Pressure Pe = Horizontal coordinate in the above graph

Brake Horse Power (BHP) = C x Pe x Ne

Where C = Cylinder coefficient = 8.811 for 6S60MC MANBW engine

Pe = Mean Effective Pressure

Ne = Engine RPM

OUT PUT OF THE ENGINE (Shaft Power in Kw) = BHP x 0.7355

190. What is P-Alkalinity and T-Alkalinity?

P-Alkalinity: phenolphthalein is less alkaline than hydroxides or carbonates, and when it is

added to a sample containing hydroxides and or carbonates it will first neutralize the

hydroxides forming salts, it will turn pink in color. The acid used after this coloration will first

neutralize the hydroxides forming salts, it will then react with the carbonate molecules

present forming bicarbonate molecules. Bicarbonate molecules are less alkaline than

phenolphthalein, hence, the pink coloration disappears once all the hydroxides and

carbonates have been dealt with by the acid. One bicarbonate molecule is formed from two

carbonate molecules, hence in the test the quantity of acid used is a measure of the

alkalinity due to the hydroxides (caustic) present and half the carbonates.

T-Alkalinity: Methyl-orange indicator is less alkaline than phenolphthalein and bicarbonates.

It can be used initially in place of phenolphthalein or in continuation after the alkalinity to

phenolphthalein test. If no yellow coloration results when the methyl-orange is added to the

alkalinity to phenolphthalein sample no bicarbonates are present. Hence no carbonates are

present. Therefore, the alkalinity as determined in the alkalinity to phenolphthalein test has

been due to hydroxides alone.

191. What is the difference between an over speed governor and a constant speed

governor?

If within a governor, an over speed detection/actuation mechanism is provided to trip the

engine in case of over speeding and or rapid increase of speed then the governor is called an

over speed governor. These were the obsolete governors and commonly had fly or bob

weights restrained by spring. When the engine exceeds a predetermined speed, the weight

moves out to strike some form of fuel cutoff.

Governors designed to maintain the engine speed at the set point are called constant speed

governors. These are also referred to as isochronous governors like the ones usually installed

on COPT and main engine.

192. What are the properties of steering gear lube oil?

a. Satisfactory flow properties

b. High viscosity index

c. Low compressibility

d. Good lubricating properties

e. Low vapor pressure

f. Compatibility with system materials

g. Chemical stability

h. Protection against corrosion

i. Rapid air-release and water separation

j. Good thermal conductivity

k. Fire resistance (desirable)

193. What is the material of connecting rod bolt? What is the importance of

elongation? What is the nature of stresses in this component and why should these

bolts be replaced after some time in service?

The connecting rod bolt in service is subjected to:

a. A dynamic tension loading due to centrifugal force of the mass of connecting rod

rotating with the crank pin

b. A dynamic tension loading owing to inertial forces of the reciprocating mass of the

piston which is fluctuating with angular displacement of the crank and having the

peak value at an instant of 360˚ after the firing TDC in a cycle of operation

c. A dynamic shear stress at the parting of the two halves of the bearing housing

Dowel pins with fitted bolts or serrations at the face or both are used to reduce shear loading

on bolts and possibility of fretting.

Bolts should be constructed of materials having high resilience and should not be stiffer w.r.t

bearing housing.

Pretension of the bolts should be regarded as the single most important factor which

contributes towards the fatigue life of the material of the bolt. Pretension must be kept high

enough, so that the increase in stress owing to dynamic loading remains within the range of

stress already given by pretension.

Some routine checks on this part are (rejection criteria of the bolt)

a. Check for corrosion by acidic lube oil, discard if any present on shanks

b. Check the length of the bolt against a new or bolt tolerances. If longer, yielding of

the material should have taken place. Renew the bolt in this circumstance

c. Check for mechanical damage, especially on shanks

d. Check for fractures by NDT

e. Check the landing faces for uneven tightening

f. Discard the bolt when either designated life, over speed failure or piston seizure has

occurred

194. What are the bunker specifications? What changes would you make in the

event of a bad bunker?

THE INTERNATIONAL STANDARD

In 1982 the working group responsible for the development of the international standard

issued a draft proposal which became ISO 8217 Petroleum products – Fuels (Class F) –

Specification of marine fuels. Another draft proposal was issued at the same time which

became ISO 8216 Petroleum products – Fuels (Class F) – Classification Part 1 – Marine

Fuels. In 1987 the first edition of the international standard was published followed by the

publication of BS MA 100 in 1989, which was identical to the International Standard. The

second edition of ISO 8217 was issued in 1996 and this is denoted as ISO 8217 : 1996.

Distillate Fuels

There are four grades of marine distillate fuels – DMX, DMA, DMB AND DMC. The ‘DM’

denotes ‘Distillate Marine’ and the third letter distinguishes the different grades.

Grade DMX is a pure distillate used for emergency equipment external to the machinery

space. Grade DMA is the equivalent of a gas oil and is also a pure distillate. Grade DMB is

equivalent of a clean diesel, although it may contain some residue giving it a black color.

This means that an appearance test cannot be used on DMB as it is for grades DMX and

DMA. Grade DMC relates to a blended diesel oil which contains a residual component,

normally up to 10 %

Viscosity

Grades DMX and DMA have a specified minimum viscosity to ensure the fuel has sufficient

lubricity.

Flash Point

The flash points for marine fuels is determined by the closed cup method corresponding to

the opening of a previously closed vessel. The minimum flash point is 60°C for all fuels

within the machinery space of a merchant ship classed for unrestricted service, as laid

down by SOLAS national and classification regulations. Grade DMX, used for emergency

equipment external to the machinery space, must have a flash point greater than 43°C. It

should be noted in some countries gas oil and diesel oil are produced for local land based

market to a national specification. A minimum flash point is usually included in such a

specification, however, this value may be below that required by international legislation for

normal marine use.

Pour and Cloud Point

The pour point parameter specifies a winter and summer quality temperature. Normally

vessels burning DMA, DMB, and DMC do not have tank heating. Purchasers should ensure

the pour point is suitable for the equipment on board, particularly if a vessel is operating in

both Northern and Southern hemispheres.

The cloud point is the temperature at which wax begins to crystallize from a clear distillate

fuel. These wax crystals will cause rapid filter blockage. This parameter is only applicable to

grade DMX and is a technical limitation so that emergency equipment can start and operate

at an ambient temperature of –15°C.

Ignition Quality

The Cetane number is the measure of the ease of ignition of a distillate fuel determined by

a special engine test with a variable compression ratio. The higher the number the easier it

is for fuel to ignite in the engine.

The Cetane index is an empirical measure of ignition quality for distillate grades of fuel.

This index is calculated in a number of ways, such as from the mid-boiling point and

density. Bear in mind, these empirical equations do not take account of any cetane index

improver which may have been added in the manufacture of the fuel.

Sediment

The sediment test for the DMB is sediment by extraction which defines the insoluble

residues remaining after extraction of the fuel by toluene. For the blended diesel grade

DMC, the sediment test specified is the Total Existent Sediment. This is the combination of

inorganic and hydrocarbon sediments existing in fuel when delivered. This test is aimed at

limiting the maximum amount of sludge present that could be separated by the filters or

centrifuges.

Catalyst Fines

In distillate fuels the elements vanadium and aluminium, plus silicon for grade DMC, relate

to he residual component of the blend.

RESIDUAL FUELS

From table 2, ISO 8217 : 1996, there are fifteen grades of residual fuel which are

distinguished by three letters and two numbers. The first two letters are common to all

residual grades, ‘RM’ denotes ‘Residual Marine’, and the third letter refers to the

characteristic of the fuel. The two numbers are the viscosity of the fuel at 100°C. Grade

RMA relates to a residual fuel which normally does not require tank heating because of the

defined low pour point. Other residual grades require tank heating as they may have a

considerably higher pour point as defined in the specification.

ISO FUEL STANDARD 8217, 1ST REVISION 1996, FOR MARINE RESIDUAL FUELS

CHARACTERISTIC UNITS LIMITRMA

Density

Grades RMA 10 to RMA 15 have a restricted density so as to give acceptable ignition quality

characteristics when empirically determined from either the Calculated Carbon Aromaticity

Index (CCAI) or Calculated Ignition Index (CII). The density limit of 991 kg/m³ at 15°C is

the technical limit for the efficient removal of water by a centrifuge set up as a purifier

operating with a water seal. Three grades (RMK 35, 45, 55) have a density limit of 1010

kg/m³ which are suitable for vessels with fuel treatment plant capable of receiving such

densities. The two grades with no density limit (RML 45, 55) are intended for machinery

installations where the fuel treatment plant does not include centrifuges, namely a steam

ship.

Viscosity

Carbon residue

The carbon residue of a fuel depends on the refining processes used in the manufacture.

Two grades have no defined carbon residue or density limit (RML 45 and RML 55), a

maximum of 22 per cent m / m applies to Rmh, RMK, 35, 45, and 55, while a limit of 18

per cent m / m applies to RMG 25. The lower limits for viscosity grades 10, 15 and 25

reflect the use of diluents to cut back heavy residual fuel to produce light intermediate fuel.

Ash

In general there is a relationship between the specified ash level in a residual fuel and that

for vanadium. This is because vanadium is the major ash forming component in residual

fuel.

Water

The specification limit for water in residual fuel is based on traditional limits. Excessive

water represents a loss of energy to the fuel purchaser, potential engine operational

problems and possible waste disposable problems.

Sulfur

Sulfur limits in residual fuel provides guidance to lubricant suppliers as to the level of

alkalinity required to neutralize corrosive compounds originating from the combustion of

sulfur.

Vanadium

The level of vanadium in residual fuel depends on the source of crude oil and the refining

process used in manufacture. On a global basis this varies considerably, from 50-100mg /

kg to over 500mg / kg, and the specification differentiates between low and high vanadium

fuels, such as RME 25 and RMF 25.

Catalyst Fines

The purpose of a control for aluminium and silicon is to limit the amount of catalyst fines

delivered with the fuel. Globally, the composition of catalyst fines varies considerably and

can be controlled using limits for aluminium and silicon, considered better than the

historical method of just controlling the level of aluminium.

Sediment

Total Sediment Potential (TSP) provides a measure of the stability of a fuel.

Following are the points to be looked at when using new bunker

a. Start consuming the fuel only after the fuel analysis report from a shore lab with

recommendations is available

b. Bunkers should be stored in the bunker tanks above the minimum transferable

temperature mentioned by the shore lab

c. A watch should be kept on the line filters/strainers soon after changing over. Clean

the filters and ensure no excessive debris

d. Ensure that fuel oil transfer pump is in good operating condition

e. Monitor the purifier / clarifier operation and make adjustments if problems arise like

considering another gravity disc if the purifier starts overflowing

f. Make adjustments like decreasing purifier throughput, preheating temperatures or

operating the purifiers in parallel / series inline with the analysis report

g. Frequently drain the settling and service tanks to asses the amount of water in the

fuel and take further steps in line with the findings like increasing / decreasing

desludging intervals

h. Monitor the line filters/strainers before pumps viz. purifier feed p/p, booster pump

and circulating pump

i. Adjust the back flushing interval of the automatic fuel oil filter based on the findings

j. Adjust the viscotherm to attain the recommended viscosity prior engine inlet

(altered preheating temperature)

k. Adjust VIT/FQS if required

l. Cylinder lubrication, sometimes the scavenge air and JCFW out let temperatures

may be required to be altered if the sulfur content warrants the changes

m. Low load operation of the engine should be limited incase the fuel report shows high

CCAI value

n. Exhaust gas economizer soot blowing & cleaning interval may have to be reduced if

the Conradsen number, CCAI, ash, water content is high. Boiler water circulating

temperature should be monitored so as to ensure that economizer operates above

pinch point

o. Fuel injectors/exhaust valve overhaul intervals may also be altered basing on high

ash, sodium/vanadium, Conradsen number, asphaltenes and CCAI values

p. Soon after the engine is put to consume new bunkers take the performance of the

engine with draw cards to ensure good health of the engine. Further changes in fuel

injection settings may have to be effected if the indicator card diagrams show

deviation

195. How do you select a gravity disc of a purifier?

Makers nomogram is an aid to select a tentative gravity disc in purification, when the

density of the oil at a temperature of 15˚C is known.

The hole diameter of the first gravity disc to be tried appears directly from the nomogram.

However, in practical operation the best result is obtained by using the gravity disc with the

largest hole diameter that will not cause a break of the liquid seal in the bowl or an

emulsification in the water outlet.

The presence of seawater may demand the use of a gravity disc with larger hole than

indicated in the nomogram. (the nomogram is based on the properties of fresh water)

The nomogram consists of two graphs arranged in series, one consists of density of fuel at

15˚C Vs Separating temperature and the other graph is divided into different zones of disc

hole diameters against through put of the purifier.

196. Explain running direction interlock

Running direction interlock is provided to withhold the fuel supply during maneuvering if

the running direction of the engine is not coincident with the setting of the engine telegraph

lever.

At the camshaft, forward end the shaft is coupled to the camshaft and carries round with it,

due to the key, a flanged bush and spring plates which cause an adjustable friction

pressure axially due to the springs and nut. This pressure acts on the coupling disc which

rotates through an angular travel until the stop pin prevents further rotation. This causes

angular rotation of a fork lever and the re-positioning of a control valve plug in a new

position within the sleeve. Oil pressure from the reversing valve can only pass to the valve

block valve (air) and unlock the air start lever and the fuel control if the rotation of the

direction interlock is correct. If the stop pin were to break, the fork lever would swing to

position M and the fuel supply would be blocked.

197. Explain capacity control in a refrigeration system

Automation provided to effect refrigerating compressor operation to meet to the varying

refrigerating load is called capacity control in a refrigeration system. The nature of

automation is dependant on the size, capacity of the refrigeration system.

Capacity control in refrigeration can be achieved by any of the following methods

a. On/off control: if the refrigeration load is absent, capacity control may be effected

by cutting out the compressor motor

b. Variable motor speed: during reduced load, capacity control may be effected by

reducing the throughput of the refrigerant by reducing compressor motor speed.

c. Cylinder unloading: during reduced load condition in a multi cylinder unit

compressor, capacity control may be effected by successively cutting in or out

cylinders or cylinder groups

d. Hot gas bypass: involves passing a portion of the discharge gas from the

compressor directly to the evaporator, bypassing the condenser

e. Hot gas injection to evaporator

f. Evaporator pressure control

198. Explain unloader of a refrigerating compressor, reciprocating type

Large reciprocating compressors are provided with an unloading system which enables the

compressor to start easily with no vapor pressure load in the cylinder, permitting the use of

electric motors with low starting torques. Unloading is effected by holding the suction

valves open, or by opening a by pass valve between the discharge and suction sides during

starting. The unloading mechanism is actuated hydraulically, mechanically or by solenoid

valve.

199. What are the reasons for engine running on air but failing to run on fuel?

a. Fuel pump valves are leaking: valve cages leaking, dirt in fuel, governor gear

jammed and holding valves off seats, faces require grinding

b. Fuel system not properly primed: water in fuel, air left in system, leaky valves,

priming connections left open

c. Fuel oil supply restricted: suction strainers dirty, gravity tank empty, vacuum in

gravity tank, valve in suction line not fully open

d. Fuel injection pressure too low: spill valve jammed, priming valves left open

e. Rotational speed on air too low: starting air pressure too low, starting air restricted,

cylinder head valve leaking, tight bearings

f. Compression pressure too low: piston rings leaking, indicator cocks open, cylinder

head valve leaking

g. Timing of fuel pumps incorrect: fuel pump plungers not functioning properly(spring

return type), incorrect spill valve timing

h. Speed governor jammed: inertial weight jammed, trip pawl not engaging,

connecting mechanism not properly adjusted

200. What are the lube oil properties of a diesel generator engine?

a. Dispersivity or capacity to the cold parts of an engine clean

b. Detergency or capacity to keep hot parts of an engine clean

c. Thermal strength or capacity to withstand temperature changes

d. Anti-oxidant or capacity to resist the action of oxygen

e. Anti-wear or capacity to contain wear

f. Anti-scuffing or capacity to preserve oil film even in the presence of high pressures

g. Alkalinity reserve or capacity to neutralize acids formed during combustion or other

sources thereby preventing corrosive wear

h. Demulsibility or capacity to separate contaminants

i. Resistance to hydrolysis or capacity to withstand the action of water which can affect

additives

j. Pump ability

k. Centrifugibility and filterability or capacity to separate insoluble elements

l. Anti-rust, corrosive and anti-foam are just some of the other properties required

201. Explain a torsion meter on a main engine shafting. How is engine power

calculated from the torsion meter?

Torsion meter is an instrument provided on the engine shafting to measure the torque

developed by the engine.

Torsion meter uses the principle that when a torque is applied to a shaft an angular twist θ is

produced which is dependant on the shaft material torsional rigidity. It is given by

T/r = Gθ/L where r= radius of the shaft, G= torsional rigidity, L= reference length of

the shaft. Where radius, length, and material of the shaft are constant, θ is directly

proportional to the angular twist.

A modern instrument is a contact less all electric instrument. It is as described below:

It based on the magnetic stress sensitivity principle, some ferromagnetic materials

reluctance is less along the plane of stress than across it. Magnetic fields are induced in a

shaft; the distortion of these fields gives an indication of the torque being transmitted.

It consists of three rings fitted on to the shaft each of which carries four electromagnetic

poles. The centre ring acts as a transformer primary with two outer rings acting as secondary

coils arranged at a phase of 45˚ to the primary but are in line with each other.

Poles for inducing currents in the shaft coils are held in a stator frame so that there exists no

contact between this stator and the shaft. A gap of about 3mm is usually maintained

between this stator and the shaft.

An alternating current is fed to the central ring (primary) generating a magnetic field. This

causes an induced currents in the outer secondary coils, which are connected in series such

that when there exists no twist (no torque condition, rpm=0) in the shaft, the induced

currents oppose each other and neutralize. When torque is applied to the shaft stress lines

are inclined to the axis. This distortion causes the induced current in the secondary coils to

increase on one side and decrease on the other side. Thus a resulting induced voltage is

developed in the secondary which is sensed by the secondary poles in the stator. The

magnitude of this induced voltage is proportional to the torque applied.

The signal out put from the instrument is directly calibrated in terms of torque developed by

the engine and read on the display.

Now as torque T is known, power developed by the engine can be calculated from the

following relation,

Shaft Power, P = 2 π NT/60 where N= RPM, π= 22/7 (PI)

202. Explain the procedure of setting a boiler safety valve

The safety valve is the sole safety device, which relieves the boiler of a dangerous excess

pressure. In the majority of designs the oil fired boiler and the exhaust gas boiler have a

common steam circuit, though separate heat input and flue gas paths. The oil fired section of

the oil fired boiler has a fuel cut out which is operated by the steam pressure limiting device,

whereas the exhaust gas boiler has to depend solely on its safety valve to protect it.

In a composite boiler as mentioned above the pair of safety valves can serve to protect the

common steam circuit. An additional pair of safety valves is provided in the outlet header of

the exhaust gas boiler, which has to be set separately.

The setting of the safety valve has to be done when the heat input and the rate of pressure

rise is maximum. The setting of the exhaust gas boiler safety valve to comply with the

above, shall be carried out as follows:

While at sea, with the main engine running at normal service speed and when all systems

are steady, the oil-fired section of the boiler can be fired to augment steam production (all

precautions such as adequate water level in the boiler, operator standing by the burner quick

shut off valve etc. are to be followed). With the safety valve on the steam receiver of the

boiler lightly gagged. The safety valve of the exhaust gas boiler section is set at slightly

higher pressure. In order to ensure that the economizer (or the exhaust gas boiler) operates

under flooded conditions at all times, it is customary to adjust the safety valves of the

economizer to a slightly higher pressure than the safety valves of the boiler steam receiver

of which they are connected.

After setting the safety valve as above to satisfaction locking it to make it tamper proof, the

oil-fired boiler firing is stopped, the steam receiver safety valves gags removed and all the

easing gear properly connected.

The exact lifting pressures are recorded in the logbook authenticated by the CEO and a copy

of the above is to be forwarded to the classification society upon arrival next port.

In the setting of the safety valve of a boiler, three items are of great importance. They are:

1. Setting pressure at which the valve should lift.

2. The accumulation of pressure, which will be above the former due to the valve spring

characteristics

3. “Blow down” which is a drop in pressure below the setting pressure after the valve has

lifted and reseated.

4. For example the following values are relevant:

a. Boiler working pressure: 7 bar.

b. Safety valve setting pressure: 9 bar.

c. Accumulation of pressure: Maximum of 10% of the setting pressure = 9.9 bar.

d. Blow down at 3% of lifting pressure.

FUNCTION 1: Marine Engineering

1. Why is Boiler water treatment required?

2. What is the allowed chloride content?

3. Why is the boiler water circulating pump required for EGB?

4. How does a bourbon pressure gauge work?

5. How do you blow through a boiler gauge glass?

6. Why is a ball given in the gauge glass?

7. How do you tighten a gauge glass after assembly?

8. What is the setting of a boiler safety valve?

9. What is the normally allowed chloride content in a water tube boiler?

10. How do you blow down a boiler and inspect it?

11. Why is pre purging necessary before firing boilers?

12. How does flame failure alarm come?

13. Type of boiler burner on last ship

14. What is the voltage used for the ignitor?

15. How will you know EGB is leaking?

16. How will you stop the leak?

17. What is the purpose of soot blowing?

18. When do you start the circulating pump?

19. What is the temperature of steam in the boiler?

20. What is meant by superheated steam?

21. How is a boiler safety valve set?

22. What is the setting?

23. What is the meaning of accumulation of pressure test?

24. How do you blow down a boiler and inspect?

25. How do you repair leaks?

26. How do you blow through gauge glasses?

27. What is the safety mechanism in case the glass breaks?

28. Which part of a ship's boiler has a higher safety valve setting? EGB or auxiliary?

29. When is the pressure testing of boilers done? How is it done?

30. Why is Fridge compressor belt driven?

31. What is meant by 1 ton of refrigeration?

32. Is there any difference in lub oil pressure readings of fridge compressors when compared to air compressors?

33. How do you read the lub oil pressure of fridge compressors?

34. Some times the pressure gauges used in fridge systems also have temperature readings. What is the use of this?

35. How is the temperature of cold room maintained ?

36. What is the role of the TEV?

37. What is mean effective pressure of diesel engine?

38. What is the cooling water treatment

39. What tests are done on L.O.?

40. What is the correct procedure for L.O. sample collection?

41. Exhaust temp of one unit is high; what could be the reason?

42. How is LO for X head lubrication delivered in (B&W/ SULZER Engines)

43. Why is a bursting disc provided in air compressors?

44. Where is it provided?

45. If a bursting disk ruptures, what will be your action?

46. What are the safeties fitted on air compressors?

47. If the interstage relief valve is lifting, what could be the reason?

48. Why is multistage compression used?

49. How will you test the working of a compressor safety valve?

50. How does the Oil mist detector work?

51. How will you test the opening pressure of a crank case relief door?

52. How many tie rods will be there? Function of tie rods?

53. What is a lantern ring?

54. What is the role of the Thrust block ?

55. Where is the thrust bearing in MC series or RTA engines?

56. Why is the thrust bearing at the aft end of the engine and not at the forward end?

57. Why is the thrust bearing close to the engine and not close to the stern tube?

58. What is the allowed O2 content in IG? How is it controlled?

59. M/E stuffing box components?

60. What is the role of the stuffing box?

61. What is the difference between stuffing box drain oil and scavenge space drain oil?

62. Why are piston rings changed?

63. What is the difference between a PV breaker and PV valve? What are the settings?

64. Why is deck seal used in IG systems?

65. What are the COPT trips?

66. What is the starting procedure for COPT?

67. 4 stroke Valve timing diagram

68. What are the strokes in 2 stroke and four stroke engines

69. Difference between purifier and clarifier

70. What is the separation principle used in purifiers?

71. What is the relation between oil density and gravity disc diameter?

72. Why are telescopic pipes used for oil lubrication?

73. Why is Fuel timing important?

74. How is checked and adjusted? (engine type based on candidate's experience)

75. What is the principle of a diesel engine?

76. Why are 2 springs sometimes used in inlet and exhaust valves?

77. What will you check in springs during o'haul?

78. How does a roto cap work?

79. How is BHP calculation using indicator diagram done?

80. What is MEP and MIP?

80. What is MEP and MIP?

81. What is the difference between the two?

82. Why is cylinder head fitted in engines

83. Are there engines w/o cylhead?

84. Draw 2s timing diagram

85. Why is an expansion tk provided in jcw system?

86. Why do we Blow through' Engines?

87. How is T/C RPM measured?

88. Is there any difference between A/E and M/E Governors

89. Indicator cards why and how are they taken?

90. What is Hydrodynamic lubrication?

91. What is a rolling contact bearing?

92. What is MCR and CSR?

93. What is PS? What is its relation to kW?

94. What was the specific fuel consumption in your last ship?

95. What was the specific Cyl oil consumption?

96. What is the relation between power and rpm of a main diesel engine?

97. What will be the power developed by a main engine if it runs in DD?

98. What is the relation between the ship's speed and engine power?

99. Will the engine develop any power, if it is run when a ship is aground?

100. What is a CPP? How does it function?

101. What is the difference between fuel valve opening pressure and fuel injection pressure?

102. What is an under slung crankshaft?

103. How many crankshafts are there in Vee type engines?

104. How are connecting rods fitted?

105. Do two stroke engines need tappet clearance adjustment?

106. How will you know, without opening anything, that an engine is 2S or 4S?

107. What are the two strokes in 2S engines called?

108. Why does Sulzer use hydraulic jack bolts for main bearings?

109. What is the meaning of TBN in lub oils?

110. Why is LO of different TBN used for M/E cyl oil and Crankcase oil?

111. What are the values of TBN for A/E crankcase oil?

112. What is the difference between "heat" and "temperature" ?

113. If water is found in crank case lo, what could be the cause?

FUNCTION 3: Marine engineering practice

1. Explain how will you o'haul a fuel injector

2. Explain how you will change gland packing of a pump.

3. What is a SDNR valve?

4. How do you o'haul a globe valve?

5. How does a gate valve work?

6. If a gate valve is stuck, what could be the reason?

7. How is a job centered on a chuck in a lathe

8. What safety precautions will you take if working on a lathe?

9. What is a reamer? Where is it used?

10. How does a Quick closing valve work?

11. How do you reset a QC valve after operation?

12. Is there any difference between relief valve and safety valve?

13. Explain how will you prepare for Bunkering?

14. How do you set tappet clearance?

15. What are the steps to take after a blackout at sea?

16. How do you pressure test a fuel vale?

17. How will you replace an exhaust valve seat?

18. How do you install a bearing on a shaft?

19. How do you specify pipe size?

20. What do the numbers on bearings mean?

21. What is the common size between different schedules of a pipe?

22. If an A/E does not start what will be your action?

23. Your action if T/C is surging?

24. Why is a Steam trap used in condensate return lines?

25. How is gas cutting done?

26. How many valves are there on a gas-cutting torch?

27. How do you light a gas-cutting torch and adjust the flame?

28. How do you set up a new pipe for welding?

29. What is GPR/GPO/LH electrodes?

30. How do you select the correct current setting for welding?

31. Crank pin brg clearance

32. Telescopic feeler gauge

33. Piston removal procedure

34. Welding defects?

35. Bridge gauge main brg clearance

36. How does a Stud extractor work?

37. How does a chain block work?

38. What are the safeties on cargo cranes ?

39. What are the safeties on ER crane?

40. How is the load controlled during lowering?

41. How is the E/R crane load tested?

42. Fuel valve not coming out?

43. Setting exhaust valve timing

44. Pumps o'haul?

45. Type of drill bits?

46. Types of threads?

47. Pipe schedule?

48. Important dimensions of flanges? Types of flanges?

49. Indications of scavenge fire? What action will you take?

50. Where are wear rings used? What is their purpose?

51. Boiler gauge glass? Reflex type? Blow through procedure?

52. .ISSA code book?

53. SG hunting gear?

54. Axe blade? How fitted?

55. Load test?

56. SCBA pressure testing

57. Welding surface preparation

58. No water in GG ? What action

59. Flaring tool

60. What is an ermato joint?

61. Why is a copper gasket annealed ?

62. How will you supervise a lub oil Filter cleaning?

63. What precautions have to be taken during cleaning of SW line filters?

64. What is a Dead mans alarm

65. What will be your action if your Reliever appears drunk

66. Your oiler appears drunk. What is your action?

67. Compound gauge?

68. Method of blowing through gauge glass

69. Pump shaft broken? Suggest epairs?

70. What is Gear Back lash?

71. What are different types of gears seen in ship?

72. What is hunting tooth

73. Why is gear oil different others?

74. What are the different types of Taps and Dies?

75. Why do you take Ullages? How do you calculate liquid quantity?

76. What is VRF?

77. What do you check up while opening piston?

78. Q closing valve operation? Why do you shut the valve again before opening?

79. Start airline getting hot - what action?

80. Draw a LS of ball bearing fitted on a shaft.

81. What is a lip seal? Sketch

82. Sketch a mechanical seal.

83. Exhaust bellow sketch?

84. What is a dresser coupling

85. What is Bumping Clearance? How do you measure it?

86. Why is a centrifugal pump started with its discharge valve shut?

87. How will you align a pump to its motor?

88. What checks will you make on a bottom end bearing bolt?

89. How do you measure ovality of a crank pin?

90. How does hydraulic tightening work?

91. Why is the jack turned back a little while slackening?

92. What will you check in UP space inspection?

93. How will you do crankcase inspection?

94. Shipside valve is leaking into E/R. What will you do?

FUNCTION : Electro technology and control engineering

1. What is KVA?

2. What is special about Steering gear Overload safety?

3. Explain the condition for Paralleling of Alternators?

4. What does different position of the synchroscope needle mean; what is the difference between 6 o clock and 12 clock?

5. Why do we close the switch at 11 o'clock and not at 12 o' clock?

6. Why is a Megger used for insulation test and not a multi meter?

7. What are the safeties on MSB?

8. When does Reverse power flow?

9. What is the harm if reverse power flows?

10. How is the protection against reverse power given?

11. How do you test reverse power trip?

12. What is the full form of ACB?

13. If you press the ACB Close button on an idle generator what will happen?

14. What is Under-voltage protection?

15. What is the meaning of preferential trip? Why is it provided?

16. What is the purpose of the earth fault indication on the switch board?

17. If you get an earth fault alarm what will you do?

18. What is Direct Current?

19. What is alternating current?

20. What is meant by phase in AC?

21. Is there phase in DC?

22. Why is DC not much in use now?

23. Where are you likely to see it used?

24. What does three-phase current mean?

25. What is rms value?

26. What is the meaning of power factor?

27. What is the usual value you see onboard?

28. What is the best value possible?

29. What is the benefit of improving power factor?

30. How can it be improved?

31. What is the meaning of saying I and V are in phase?

32. What is the difference between KW, KVA and KVAR?

33. Why are motor ratings given in KW and that of alternator and transformer given in KVA?

34. Where does reactive power go?

35. What is a semi conductor?

36. What is doping?

37. What happens to insulation when temperature rises?

38. What happens to resistance of conductors when temperature rises

39. What is an induction motor?

40. What is "slip"?

41. What is a synchronous motor?

42. Where is it used?

43. How do you use a multimeter?

44. What is an AVO meter?

45. How do you check continuity?

46. What limits the electrical load?

47. What is the voltage used in a meggar?

48. How does current flow during welding?

49. What do we use for welding on ships? AC or DC?

50. What is the voltage?

51. What is the voltage used for ignition in boilers/incinerators etc.?

52. Why is it different from that for welding?

53. Does current flow through hull during welding?

54. If so why don't you get a shock?

55. What is safe voltage to prevent shock?

56. What is the meaning of earthing in a ship?

57. What is the meaning of Star winding/ Delta winding?

58. Is the ship's alternator Star wound or Delta wound?

59. What is the meaning of ACB, MCCB, NFB?

60. What is a magnetic contactor? Where is it used?

61. What is a relay? How is it different from a magnetic contactor?

62. Can you draw a DOL starter circuit?

63. What is the meaning of overload?

64. What is meaning of short circuit?

65. How is protection provided for OL and SC?

66. What is the function of a fuse?

67. What is the normal setting of overload relays?

68. How does a thermal overload relay work?

69. What is single phasing?

70. How can it happen?

71. What is the harm caused by this?

72. What protection is provided against this?

73. Why is it necessary that incoming alternator frequency is more than bus bar?

74. What is dark lamp and bright lamp method for synchronizing? How is the connection made?

75. Apart from renewing bearings is there any reason for opening up motors for maintenance?

76. Why is reverse power protection required?

77. Why is this reverse power used instead of reverse current in alternators?

78. What is the meaning of excitation in an alternator?

79. Is the field current in an alternator AC or DC ?

80. Is the field rotating or stationary?

81. How is it supplied?

82. What is a brush less alternator?

83. How is the excitation achieved in this?

84. What is the meaning of residual magnetism?

85. Why is an air compressor started unloaded?

86. How is the speed of a 3-phase induction motor varied?

87. How is the direction of rotation varied?

88. How does this cause a rotation to change?

89. How is the speed of a DC motor varied?

90. How is the direction varied?

91. What is a diode?

92. What is a zener diode?

93. What is a thyristor? What is an SCR?

94. How does an inverter work?

95. How does a tube light work?

96. What is the function of the starter in a tube light?

97. What is the function of the choke?

98. Where is a slip ring used and where is a commutator used?

99. What is capacitance?

100. Does current flow though a capacitor?

101. What is the unit for capacitance ?

102. What is a neutral?

103. What is the difference between neutral and earth?

104. What is a synchronous condenser?

105. Where and why is it used?

106. If a motor is wound star and you want to change to delta what should you do?

100 If the AVR, is defective, when additional loads come on will the generator be able to take it?

How do you test, reverse power trip, high current trip, preferential trip?

102. What is residual magnetism? Where is it important?

103. Sometimes, when you change the running direction of a E/R blower (from supply to exhaust) it trips. Why?

104. What is the function of the friction clutch mechanism used in purifiers?

105. What is the regular maintenance done on batteries?

106. What safety precautions need to be taken during maintenance on batteries?

107. Why is special lighting used in battery rooms?

108. What is the voltage available from each cell in a lead acid battery?

109. What is the full battery voltage ?

110. How is this voltage achieved?

111. What is the meaning of a normally open contact?

112. How does a Salinometer function?

113. How does the air compressor start and stop automatically?

114. How is the cold room temperature maintained?

115. What is a self-monitoring alarm circuit?

116. Out at sea, if there is a black out during your watch, what action will you take?

117. After a black out the emergency generator comes on; On restoring the main supply we are closing the circuit breaker of the main generator with out bothering about synchronizing. How is this possible?

118. How does the emergency generator start automatically?

119. If all your air bottles are at low pressure and there is a blackout how do you start the generators?

120. What is a shaft generator?

121. Even though the main engine runs at varying speeds, how does the alternator maintain constant frequency?

122. Is the alternator connected star or delta

123. Why is 440 V used for motors and 110/220 V used for lighting?

FUNCTION: OPERATION OF THE VESSEL AND SAFETY OF PERSONNEL ONBOARD

1. Fire main line fittings

2. Purifier room fire

3. Paint locker fire

4. CO2 flooding procedure

5. Uptake fires

6. O2 and C2H2 storage and operation safety

7. EPIRB and SART

8. SOPEP

9. LB brake/ lowering procedure

10. 103.Deck foam system?

11. 104.Where isolation valves given in fire main?

12. What is hydrogen fire?

13. What are the indications of EGB fire?

14. 2.DCP fire extinguisher?

15. Routine checks on FFA

16. Flammability diagram

17. In your kitchen what fuel is used

18. Why is the flame not traveling to the cylinder

19. LEL, UEL

20. Flammability range?

21. Between a log and a small stick which burns faster

22. When you blow on a matchstick the fire goes out. In a stove/or a black smith's hearth blowing air increases the fire.Why?

23. Why is a Relief Valve fitted on fire main?

24. International shore connection; Size? Where fitted? Which part is standard?

25. Enclosed entry procedure

26. ELSA, EEBD

27. 33 Fire main line isolating valves

28. How does a flame screen work? What is the difference between a flame screen and a flame arrestor?

29. What is a flashback arrestor?

30. Why should Acetylene bottles be used in the upright position?

31. What is the correct position for using a portable foam extinguisher?

32. Why is a sand box provided on the boiler flat?

33. What are gas-free conditions for man entry?

34. Should the ventilation blower be running in supply mode or exhaust mode, when the Oxygen check is made?

35. In a tanker, why are bonding straps used on cargo pipelines?

36. What is the rating of the electrical hand glove?

37. What is the important first aid for an electrical shock victim?

38. Is there any protection for a CO2 cylinder in case of a fire in the CO2 room itself?

39. Is the CO2 in the bottle in liquid condition or gas?

40. How does the CO2 alarm ring when the panel door is opened?

41. Can engine room bilges be pumped out in special areas?

42. What will be your action when you discover smoke coming out of

43. During your watch, if you get a under piston temperature high alarm, what will you do?

44. During your night duty on a UMS vessel, there is a fire alarm from E/R. What will be your action in case of

Top

a. Purifier room fire

b. Running generator exh manifold on fire

c. Boiler front on fire

d. Bilges on fire

45. 102.CO2 and DCP difference?

46. Man overboard drill

47. Oil spill drill

48. Life raft floatation

49. Ship's Whistle? How does it work? Where is it fitted?

50. L boat tricing pendant / Bowsing in tackles; Purpose.

51. What is HRU? How does it work? Where is if fitted?

52. What is a Life buoy? Where is it fitted?

53. What is flash point, firepoint and auto ignition temp.

54. What are the tests done before enclosed space entry?

55. What spaces are defined as such?

56. What is the acceptable HC level for man entry?

57. What is TLV? How many types are there?

FUNCTION: SHIP CONSTRUCTION AND STABILITY

1. Deep tank construction

2. Garboard strake, sheer strake

3. Stability and buoyancy

4. Collision bulkhead

5. Camber, margin plate, intercoastal?

6. Free surface effect?

7. Static and dynamic stability?

8. LOLL, GZ,righting lever

9. Pounding effect on rudder

10. What are Skates?

11. Types of floor

12. How ship turns? Rudder function?

13. Why is rudder angle not more than 36 deg?

14. How does the ship move? Propeller function?

15. Why is the thrust bearing fitted aft?

16. What action will you take if there is a thrust bearing high tr alarm?

17. What is a "Torsion Box" in a container ship?

18. Protection/safeties on a generator

19. What is metacentric height? What is its importance?

20. What is dynamic stability? What is its importance?

21. What is a chain stopper?

22. What is a dead man brake?

23. How many brakes are there on a life boat winch?

General Engineering Knowledge (MEO Class 4)

1. What is glide?

2. Describe bunkering procedure?

3. How the tail shaft sealing arrangement is done?

4. What are the measures you will take if the gland packing leaks continuously?

5. Why intermediate shaft is given?

6. How will you take out the valves of air compressor?

7. During dry dock what will you check in seachest valves?

8. What are the safeties of air compressor?

9. What is Heleshaw pump?

10. Define valves and cocks and their functions

11. Which valve is suitable for remote controlled operation and why?

12. What is rudder drop and jumping clearance?

13. Where and why bursting disc is provided in an air compressor?

14. What are reasons of lifting up inter stages safety valves in an air compressor?

15. How to test compressor safety valve?

16. How will you overhaul a globe valve?

17. What are the reasons for a sticking gate valve?

18. What is the theory of density correction?

19. How does quick closing valve function?

20. How do you specify pipe sizes?

21. How do you select correct current setting for welding?

22. What is the common size between different schedules of pipes?

23. Where telescopic feeler gauges are used?

24. What are the safeties of cargo crane?

25. What are the safeties provided on engine room overhead crane?

26. Where are wear rings used?

27. What is hunting gear?

28. Explain welding surface preparation?

29. Draw a lip seal and how it works?

30. Who will you align a pump and its motor?

31. Sketch exhaust bellow?

32. What are the testings carried out on steering gear during a drill?

33. Mention fresh water generator shell temperature, vacuum, and other parameters?

34. What is the significance of stern tube header tank?

35. What are the advantages of four ram steering gear?

36. Describe checks on fresh water generator during watch?

37. What is the significance of greasing steering gear?

MEO Class Exam Questions

1. What is reverse osmosis?

2. What is purifier and clarifier?

3. Discuss purifier operation?

4. What are fuel oil testings done on board ships?

5. What on board tests are done in lube oil?

6. What is the correct procedure to collect lube oil for testing?

7. What is the temperature of fuel oil entering and leaving purifier?

8. What are the safeties of fresh water generator, steering gear and oily water separator?

9. Why purifier overflows?

10. What is viscometer?

11. What is the function of air compressor unloader?

12. What is the function of expansion valve?

13. How the unloader works in an ac compressor?

14. Why fridge compressor is belt driven?

15. How is the temperature of cold rooms maintained?

16. What is he difference between air compressor and ac compressor?

17. What is critical temperature and pressure?

18. What is latent heat?

19. What is meant by short cycling in fridge compressor?

20. Different types of pumps and where they are used?

21. What is the discharge pattern of reciprocating pumps and other pumps?

22. What is jumping clearance?

23. How many types of steering gear are there?

24. Describe arrangement of stern tube?

25. How stern tube cooling is done?

26. How to take crank shaft deflection?

27. Why the suction pressure of refrigeration plant and ac plant are different?

28. What is the function of rudder carrier bearing?

29. How many types of fresh water generator are there?

30. Why centrifugal pump has no relief valve?

31. Arrangements for relieving shocks in the steering gear?

32. What is bell mouth?

33. What is interface of purifier?

34. What are swash plate pumps?

35. Why is oil coming from the water side of purifier?

36. Explain the significance of heat treatment in steels?

37. Hosing down procedure for engine room tank top?

38. What are the precautions before entering inside an air reservoir?

General Engineering Knowledge (MEO Class)

1. Why certain back pressure is maintained for purifier?

2. What is the use of purifier breaks?

3. Explain the functions of purifier centrifugal clutch?

4. What are ALCAP purifiers?

5. Explain the importance of gravity disc in a purifier?

6. How will you manage your air compressor without automatic unloader?

7. How will you confirm that air compressor valves are not leaking after overhauling?

8. Why oil film is coated on a compressor air filter?

9. Effect of air filter mesh size in an air compressor?

10. What is the working principle of an air drier?

11. Name five non metals used on board ships?

12. Routine checks on a fixed foam fire fighting system?

13. How many types of steels and brief their carbon contents?

14. What is the material of safety valve?

15. Define flash point, fire point, viscosity?

16. How many types of propeller?

17. What will you do if emergency alarm raise?

18. What is the function of fire detector?

19. What is saturation temperature?

20. What is humidity?

21. What is the material of cooler tubes?

22. What is specific gravity?

23. What is vacuum?

24. What is meant by critical speed?

25. What do you know about ‘M’ notices?

26. What s the function of poker gauge?

27. What s the function of lubricating oil?

28. What is hydrostatic lubrication?

29. What is inerting, purging and gas freeing in inert gas system?

30. What are fire man’s outfit?

31. What is cetane number and calorific value of a fuel?

32. How will you buy a boiler?

33. What is the formula of stress in longitudinal and circumferential joint?

34. Describe boiler starting procedure from cold?

35. Why boiler water treatment is required?

36. How many types of marine boilers are used on ships?

37. What are the tests carried out for a low pressure boiler water?

38. What is your action on finding high chloride levels in a boiler?

39. What will you do if no water level in the gauge glass?

40. How would you blow down a boiler gauge glass?

41. What are boiler mountings?

42. What will you check while watch on a boiler?

43. What is allowable chloride content in boiler water?

44. If the steam nozzle of the gauge glass is chocked then how will you confirm water level?

45. Why purge a boiler furnace?

46. What is superheated steam?

47. How many types of boiler safety valve?

48. Describe boiler survey procedure?

49. How to check alkalinity, acidity, chloride content in boiler?

50. Draw the lip clearance of safety valve?

51. What is the difference between safety valve and relief valve?

52. What is corrosion, erosion, and abrasion?

53. Comment on materials of boiler construction?

54. Why and how soot blowing is done?

55. Describe automatic combustion system in a boiler?

56. Why flame failure alarm comes and what will be your action?

57. When do you start the boiler circulating water pump?

58. How will you know that EGB is leaking and how to arrest the leak?

59. How boiler safety valve is set?

60. Show the calculation of safety valve area?

61. What do you know about economiser?

62. Describe setting of safety valve?

63. What is steam hammering?

64. What is manometer?

65. What is steam trap?

66. How will you prevent uptake fire?

67. What is dry distillation?

68. What action o be taken if oil is found in the cascade tank?

69. What colour flame indicates efficient or poor combustion?

70. What is Ogee ring?

71. Where the boiler fusible plugs are used?

72. What are the densities of boiler water and seawater?

73. What is the diameter of safety valve?

74. What is the purpose of blow down ring?

75. Is there any arrangement for boiler safety valve draining?

Marine Electro Technology (MEO Class)

1. What is the use of ‘kvar’ meter fitted on the MSB?

2. Where auto transformer starter is used on board ships and why?

3. Explain star delta starter?

4. Why starters are not used for land based installations?

5. Any two applications of zener diode on board ships?

6. How will you come to know whether a fuse is blown out or not, explain two methods?

7. What is meant by intrinsically safe?

8. Name any three intrinsically safe equipments on board other than a torch light and lamp?

9. Explain the working principle of an explosimeter and reasons for false readings?

10. How will you check reverse power and overload relay in the MSB?

11. What are the routine maintenance in an alternator?

12. How will you confirm a solenoid is working or not?

13. What kind of starter could be used for force draught fan for the boiler?

14. How to check the insulation resistance of a DC motor?

15. How to use a voltmeter for synchronization in the absence of synchroscope and synchronizing lamps?

16. How does earth fault detector work?

17. Explain the conditions of paralleling alternators?

18. Draw the synchronizing method?

19. What is he difference between a megger and a multimeter?

20. Comment on air circuit breakers?

21. What are the safeties provided on Main Switch Board?

22. Describe how a self excited generator works?

23. What is the function of AVR?

24. How will you find out earth fault in the system?

25. What is reverse power protection for?

26. What is Wheatstone bridge?

27. Draw the synchroscope system?

28. What do you understand by preferential trip and when they operate?

29. Describe AC and DC? Where DC is used on board ships?

30. What is induction motor?

31. What are star delta windings?

32. What is a short circuit?

33. What is meant by earth fault?

34. What is meant by overload?

35. What is single phasing and how it happens?

36. What is fuse and how many types of fuses have seen before?

37. Why an air compressor is started unloaded?

38. What is the difference between ordinary diode and zener diode?

39. What is the function of starter and choke in a tube light?

40. What is the regular maintenance done on batteries?

41. How does salinometer work?

42. What will be your action on a blackout a sea?

43. How does emergency generator starts on its own?

44. What are the cut out provided on the OWS and checks to be done before putting it into operation?

45. Draw star, delta 3 phase connections?

46. What are the motor safeties, deck crane safeties, and engine room over head safeties to be checked?

47. What is relay? How it is different from a magnetic contactor?

48. What is ohm’s law?

49. What is the expression for resistance in terms of length and area of conductor?

50. What is sequential starting?

51. What is the function of circuit breaker?

52. What essentials are supplied from emergency switchboard?

53. How will you confirm a minimum insulation resistance reading?

54. Describe steering power supply regulations?

55. What is Coulomb’s law?

56. Describe Fleming’s left and right hand rule?

57. Describe lenz’s law?

58. What is the difference between electric and magnetic circuit?

59. Describe and Draw battery charging method?

60. How many types of DC motors are there?

61. How many types of AC motors are there?

62. What is magnetic hysteresis?

63. What is eddy current and how to minimize it?

64. How many types of electric circuits are there?

65. Describe Kirchoff’s laws?

66. How many types of battery used on board ships?

67. What is the constructional difference between AC and DC generators?

68. How to calculate number of poles of a generator?

69. What are the causes of zero voltage in a running generator?

70. What is the difference between an induction motor and synchronous motor?

71. What is the reading of hydrometer reading in full charge and discharge?

72. What is meant by transformer and rectifier?

73. What is he units for voltage, current, power and resistance?

74. Comment on the starting current while using a direct online starter for an induction motor?

75. What is reluctance?

CoC Oral Exam Questions Bank

Maritime Regulations and Survey

• 1. Describe Safety construction survey and items to be surveyed.

  2. Describe Load line survey. Purpose of load line survey. Why do we need load line certificate?

  3. Describe LOAD Line convention.

  4. Why load line mark is at the mid ship/ how to calculate load line for a ship?(details)

  5. Details about Safety equipment survey

  6. How many certificates to be carried on board?

  7. Describe Life boat regulation?

  8. Describe MLC 2006 details

  9. Describe Ballast water regulation.

  10. Describe SOLAS chapters and new amendment

  11. Describe MARPOL ,ALL THE ANNEX OF MARPOL,

  12. All the chapters of annex vi, details of NOx , SOx limit, tyre ,EEOI ,EEDI, SEEMP…….

  13. What is HSSC?

  14. ESP(Enhanced survey program)

  15. Regulation for vent pipe, sounding pipe

  16. Preparation for PSC inspection as C/E?

1. How many annexes in MARPOL?

2. Details of each annex: oil discharge procedure from ER and special area of annex 1. Operation of OWS?

3. What is siphon tube? What is vacuum breaker?

4. What are the data recorded in OWS monitor?

5. How oil and water level sensor works in OWS?

6. How to put entry in ORB? What is action in case of wrong entry? How many people fill up and sign it?

7. What is garbage discharge procedure? How to put entry in GRB?

8. What is annex IV?

9. What is annex VI?

10. What is survey? How many types of survey?

11. Details about the surveys and interval, survey items, validity of the certificates.

12. What is enhanced survey program?

13. What is harmonized system of survey?

14. Describe Safety equipment survey and their items?

15. Describe Safety construction survey and their items?

16. What is under water survey?

17. What is port state, flag state?

18. What is classification society and what is the purpose of it?

19. What is the difference between classification survey and statutory survey?

nstrumentation and Control

1. What is PID control? If PID controller fails what is your action?

2. Cascade control and explanation.

3. Why 2 element control used in boiler water level control

4. Fail safe and fail set with drawing

5. Cascade control and description.

Fire and safety

1. Types of fire and use of fire extinguisher, testing procedure, survey interval, testing pressure and details

2. Describe the Emergency fire pump regulations.

3. What are the Regulations for life boat engine?

4. Describe On load and off load mechanism.

5. Describe Life boat launching procedure.

6. What is HRU? Working principle.

7. Describe the Brakes of life boat davit.

8. Foam system working principle and expansion rates of foam’

9. Sprinkler system and testing procedure

10. Sketch and describe Oxygen analyzer, explosimeter.

11. Exi,Exd,exp,….. How exd and exp constructed.

12. Explain LEL and UFL with graph.

13. State Breathing apparatus regulation and checking system

14. SOLAS regulation for IG system and description of the system

15. State Carbon di oxide flooding regulation, drawing and procedure.

16. What is TLV?

17. What is risk assessment? How to eliminate risk?

Steering Gear:

1. What are Steering gear SOLAS regulations?

2. State Follow up and non follow up steering.

3. What are the Safeties of steering gear?

4. What are the Stops of steering gear

5. What is Rudder carrier bearing?

6. Steering gear sluggish operation

7. What is hunting gear? State the functions.

8. Emergency steering procedure, drill interval.

9. Describe 100% and 50% torque.

10. Describe Steering gear arrangement from bridge to steering flat.

11. Describe Emergency steering procedure?

Shafting and Stern Tube:

1. What is Pilgrim nut? Describe working principle.

2. What is Muff coupling? Describe working principle.

3. Draw and describe Thrust block

4. Describe Tail shaft withdrawal procedure

5. Describe Intermediate shaft with drawl procedure

6. Describe Stern tube drawing, details of drawing .enlarge drawing of each lip seal.

7. What is action in case of oil leakage?

8. Propeller removal and inspection. Propeller caviatation,

9. How much wear down allowed in propeller shaft? Corrosion on the conical part of the propeller shaft what you do at dry dock give your opinion.

10. Purpose of shat grounding?

Bunkering

1. Procedure and calculation. Sampling and reservation procedure as per rule?

2. FO properties and limit of the elements in FO .BDN content. FO handling and purification.

3. What is VCF and WCF. Why they necessary?

4. What is ISO 8217?

5. What is Specific fuel consumption?

6. Definition of : flash point, fire point, pour point, cal value, CCAI value, octane number ,cetene number

Boiler:

1. Difference between boilers

2. Boiler survey types and interval

3. Boiler survey preparation and checks

4. Safety valve types and difference

5. Safety valve setting( both EGB and boiler)

6. Accumulation test ,

7. Back fire, foaming, priming

8. Types of gauge glass and drawing

9. Mountings and boiler safety, alarms and trips

10. Which safety valve set at higher pressure boiler safety valve or EGB safety valve? Why?

11. Different types of boiler tubes and their details?

12. Boiler tube plug/blank

13. How to detect boiler tube is leaking

14. What is pH. What is the range? Why 14 is the maximum pH value?

15. What is leap clearance?

16. What are differences between different types of safety valve?

17. What are the safeties of gauge glass?

18. What is acid corrosion and hydrogen corrosion?

19. What is caustic hide out?

20. What is SIMMERING, CHATTERING, FLUTTER?

21. Scale formation in boiler and treatment.

22. Boiler chemicals used and their limits

23. Boiler water test procedure

24. What is soft water? What is hard water?

25. What is coagulant?

26. Details about Soot fire, uptake fire

Turbocharger

1. Types of turbocharger

2. Function of nozzle ring, labyrinth seals, diffuser, and inducer.

3. Turbocharger vibration and noise. Cause and remedial action.

4. What is T/C surging? State cause and remedial action.

5. Describe T/C cut off procedure. Why u may need to that? What other pre-caution u need to take?

6. Sate Solid wash procedure.

NAVAL ARCHITECTURE & SHIP CONSTRUCTION

1. Details about Principle dimension of ship .

2. How to calculate ship’s cargo carrying capacity?

3. Details of the terms: GRT,NRT,DWT,DISPLACEMENT,

4. Types of bulkhead and their construction.

5. Forward arrangement description and drawing

6. Stern arrangement description and drawing

7. Why load line marking is at the mid ship? Details of load line marking.

8. How u will determine free board of ship?

9. Draw and describe Mid ship section of bulk carrier.

10. What types of stress a ship face?

11. What is 6 degree motion of ship?

12. What are the functions of Bulbous bow?

13. What are the Functions of bow thruster?

14. Construction and position of Collision bulkhead, water tight bulkhead, aft peak bulkhead, fore peak bulkhead.

15. State Stability, Equilibrium, free surface effect.

16. Definitions :Centre of buoyancy ,Centre of flotation , Metacentre , Metancentric height, Righting lever , Angle of loll

17. How many types of rudder? Details of them.

18. Rudder stops and rudder droop.

19. What is rudder stalling?

20. What is jumping clearance?

21. What is pintle clearance?

ELECTRTOTECNOLOGY

1. What is a battery, how and where it supplies current on board a ship?

2. What are the factors for battery & room maintenance?

3. Name the machinery of using 440 V, 220 V, 110 Volt and 24 V current.

4. What is single phasing, why it is occurred, what are the effects and preventive measure

5. What are the Switch Board Safety Devices?

6. What is Synchroscope?

7. How many methods to synchronize?

8. What is stroboscopic effect?

9. Describe Emergency Generator regulation ,starting procedure and its maintenance:

10. Difference between Synchronous Motor and Induction Motor

11. Remedial action when generator fails to excite.

12. What is ur action When Electrical Machine is flooded with SW?

13. Short, open and grounded circuits,

14. What is dash pot, SCR, Transistor, DIODE, Transducer, TRSNSDUCER, Rectifier

15. Describe Brushless alternator and excitation system

16. Describe Static excitation system

17. Describe A/C motor working principle.

18. Describe Motor safeties and their working principle

19. Describe Auto transformer with drawing and details

20. What is Earth fault and detection system

21. Describe Insulated and earthed neutral system, their advantage and disadvantage.

22. DOL and Star-delta system of motor starting.

23. What is word leonard system? Describe with aid of sketch.

E. K. MOTOR

1. Describe the types of crankshaft. Stress on crankshaft. Slippage of crankshaft cause and action to be taken.

2. How to take crank shaft deflection? How u will evaluate the readings?

3. How to extract liner? How u will understand the liner life time is nearing to an end? Name the materials of liner.

4. Describe the Liner lubrication system? What is Alfa lubrication system?

5. Describe x-head lubrication system.

6. How to run engine with one unit cut off?

7. How to run engine with one unit hanging?

8. Chain drives inspection and how to adjust chain elongation. What is the maximum limit of chain elongation?

9. Types of Engine vibration? What are the types of stress on engine? What is critical speed? What is barred range of speed? What is vibration damper? How vibration damper works? What is bracing and why they are fitted?

10. What are forces act on bed plate?

11. Tightness checking procedure of tie rod? How to remove broken tie rod from engine?

12. How timing is adjusted in hydraulic type exhaust valve?

13. How liner is lubricated in 4 stroke and 2 stroke engines?

14. Describe main engine starting and reversing procedure. What is crash manoeuvring? What is lost motion and gain motion?

15. What is speed droop? How to adjust speed droop? What is speed sensing and load sensing governor? What is governor booster?

16. What is isochronous governor? What is load sensing governor?

17. How many types of fuel pump used in ship, draw and describe. How to check fuel pump timing of each type. Working principle of each type fuel pump

18. What is erosion plug of fuel pump? How you will check plunger and barrel during overhauling? What is puncture valve? What is fuel pump lead?

19. What is VIT? Difference between VIT & SUPER VIT?

20. How to take main bearing clearance, big end bearing clearance, cross head bearing clearance?

21. How to take thrust bearing clearance? How thrust bearing lubrication is achieved?

22. Difference between thin sell and thick shell bearing?

23. Hoe to calculate Main engine performance? How many types of indicator cards and how to evaluate?

24. Describe propeller curve.

25. What is your action in case of grounding?

26. What is the cause of scavenge fire? What are the actions to be taken?

27. Describe crankcase fire, cause and action to be taken.

28. Describe starting air line explosion, its cause and action to be taken.

29. What pressure maintained in crankcase?

30. What is your action in case of OMD alarm?

31. What are the safety devices in Crank Case

32. What are the safeties of main engine?

33. Main engine is not starting what is ur action?

34. What is dead spot of engine?

35. During manoeuvring u noticed one of the starting air valve is leaking, what is ur action?

36. During manoeuvring u noticed one of the exhaust valve is badly noisy, what is ur action.

37. Engine turns on air but fails in fuel what are the reasons?

38. Engine fails to turns on air what are the reasons?

39. All unit exhaust temperature high. What may be the reasons?

40. One unit temperature high what may be the reasons?

41. How to take A/E performance?

42. After overhauling A/E leakage is found from shaft seal. What is the reason?

43. A/E LO consumption has been increased, what are the reasons?

LUBRICATION:

1. How many types of lubrication?

2. Definition: TAN, TBN , SAN. Viscosity,

3. What is microbial degradation? What is the remedial action?

4. What is grease?

5. What is the difference between cylinder and crankcase LO?

6. Details about Onboard LO testing procedure

REFRIGERATION:

1. What are GWP and ODP?

2. What is TEV? What is equalizing?

3. How to recharge refrigerant? How to record if needed?

4. How to detect leakage?

5. What is sub cooling .what is super heat.

Metallurgy:

1. Describe normalizing, annealing and nitriding, case hardening, fatigue failure, creep, yield point,

2. What is welding, brazing, soldering

3. What is TIG,MIG

4. What is white metal?

Name the materials and composition of the followings : propeller, hull, rudder , bronze, brass, Monel Metal, Gun Metal, Bell Metal, Bronze, Phosphor Bronze, German Silver , Manganese Bronze, Brass