MEP ORAL QUESTIONS AND ANSWER
1. What is special about steering gear safety.
It has got overload alarm at 150% and short circuit trip.
2. Maintenance of alternator what all to do.
(a) Clean the felt/ air filters.
(b) Remove dust/ dirt from the rotor.
(c) Clean the connections and put some petroleum jelly.
(d) Check the air gap with the plastic feeler gauge.
(e) Check the lub oil level in bearing.
(f) Insulation resistance to take with megger.
(g) Check condition of winding.
(h) Carry out continuity test.
3. Purpose of air gap and how checked.
To avoid the mechanical contact between the stator & rotor and to determine the condition of the bearing. Measured with the help of feeler gauge.
4. Trips on air circuit breaker with values
5. conditions for paralleling alternators
(a) Frequency
(b) Phase
(c) Voltage
6. How to parallel alternators
There are three methods of Paralleling alternators:-
(i) Dark lamp method
(ii) Bright lamp Method
(iii) Synchorscope
7. Why megger is used to test insulation and not multi meter
Megger is used to test insulation because it has higher range say upto 500V.
8. Suppose a motor is not starting what checks u will make
Electrical Checks:
a. Check the connections.
b. Check, if has tripped, then reset and try to start.
c. Check supply is coming from MSB or not.
d. Check single-phasing has not occurred.
Mechanical :
Check the coupling between the motor and driven part is not too tight.
9. Suppose a motor is running hot what checks.
a. Single-phasing
b. Fan is working or not.
c. Overload is occurring.
d. Check condition of bearing.
10. Why insulation resistance checked and how?
A measurement of the insulation resistance gives the best guide to the state of health of the electrical equipment.
a. Disconnect the electrical supply.
b. Refer to the electrical circuit & manufacturer’s instruction before testing.
c. Measure the insulation of the windings to the earth and as soon as possible when the machine is just hot after it has stopped. The minimum value should be
1 MW.
11. Why motor insulation deteriorates
a. Moisture – results in decrease in the measured value of insulation resistance.
b. Dust & dirt deposits – reduces insulation resistance & failure of insulation due to oxidation.
c. Oil & Grease – prevents heat dissipation & causes dirt and dust to settle on the insulation.
d. Ageing – over the period of time the insulation deteriorates due to it getting affected by temperature variation, mechanical stresses, vibrations, moisture and some varnish tend to become hard with age & crack during the operation.
e. Temperature – Excessive temperature dehydrates and oxidizes the insulation, making it brittle & disintegrate under vibration & shock.
12. If water goes to motor what you do.
a. Disconnect the electrical supply.
b. Put MEN AT WORK tag.
c. Remove the coupling bolts.
d. Now, lift the motor using lifting gear & put it on a clean place.
e. remove the cover & fan.
f. Take out bearing & the shaft.
g. The salt contamination must be removed by thoroughly washing with clean fresh water (preferably warm) or if possible , distilled water.
h. De-greasants must be used if it is found that there was ingress of oil.
i. Spirits or alcohol may be used to clean contacts.
j. Dry the motor with dry air & then switch on its heaters or use powerful lamps. During this process , keep its inspection covers open to permits moisture to escape.
k. Put the varnish on the winding & let it dry.
l. Check the insulation resistance. If it is ok then assemble it back & put it for use.
m. The motor must be started on less load & its current monitored for few hours to confirm its satisfactory operation.
13. How do you test that Megger is working Ok
14. What are portable electrical testing instruments used in ER
a. Clampmeter
b. Megger
c. Multimeter
d. Tester
15. What is harm if reverse power flow?
Motoring effect will take place & can damage the prime mover.
16. Why preferential trip provided Purpose?
Preferential trip is provided to safe guard the machineries which are important for safety of ship & safety of personnel onboard.
Preferential trips are designed to disconnect the non-essential services i.e., Breakers controlling Air Conditioning, Galley power, blowers, refrigeration) in the event of partial overload or partial failure of the supply, with the aim of preventing operation of the main breaker trip & loss of power to essential services.
17. How do you test emergency generator?
a. Regular or weekly testing of the emergency generator should include simulation of the loss of normal power.
b. The start up equipment may be provide a push button to interrupt the normal voltage supply to the panel which then triggers the start sequence.
c. Loss of main power supply can easily be simulated by pulling a fuse in the auto-start panel which supplies the under voltage or under frequency relay.
d. This no load running checks should, when practicable, be supplemented occasionally by a proper load test. This requires the disconnection of the normal mains power while the emergency generator is loaded upto near its rated value.
18. How do you check press and temp alarms. What equipment used for same
19. If you get earth fault alarm what you do?
a. Accept the alarm.
b. First of start isolate the breakers one by one.
c. Then, check where the alarm has came & should be eliminated when located.
d. Damaged conductor insulation must be repaired.
e. Dampness or moisture in insulation must be dried out by gentle heat & precautions should be taken to prevent future ingress of moisture.
f. If dirt is the cause, then a thorough cleaning with electro cleaner solvent should be applied & clean.
20. If on starting Generator you find that voltage is not building up what you do?
Residual magnetism is lost. So supply power from outside by connecting battery.
21. What equipment emergency generator supplies.
(a) For a period of 3 Hrs at Emergency lighting at every muster & embarkation station.
(b) For a period of 18 hrs at:-
(i) In all service & accommodation alleyways, stairways & exits, personal lift cars & personnel lift trunks.
(ii) In the machinery spaces & main generating stations including their control positions.
(iii) In all control stations, machinery control rooms, and at each main & emergency switchboard.
(iv) At all stowage positions.
(v) At the steering gear.
(vi) At the fire pump & in all cargo pump rooms.
(vii) The navigational lights.
(viii) VHF & MF Radio installation.
(ix) The ship earth radio station.
(x) At all internal communication equipment
(xi) The fire detection & fire alarm system.
(xii) Intermittent operation of the daylight signalling lamp & all integral signals that are required in an emergency.
22. What is diff between AC and DC?
The difference between AC and DC is that AC is an alternating current (the amount of electrons) that flows in both directions and DC is direct current that flows in only one direction;
The wires outside of our house are connected at two ends to AC generators. DC is found in batteries and solar cells.
alternating current varies with time, sinusoidally... where as DC remains steady.
23. What is rms value?
The RMS value of an alternating current is also known as its heating value, as it is a voltage which is equivalent to the direct current value that would be required to get the same heating effect.
24. What maintenance carried out on Lead acid batteries.
a. Connection to be checked for tightness.
b. Casing surface to be kept clean.
c. Terminals are protected with petroleum jelly or Vaseline.
d. Specific gravity to be check with hydrometer.
1.21 Charged Condition
1.18 Discharged Condition
e. Batteries to be topped up with distilled water.
f. Check & clear vents to ensure H2 gas produced is vented.S
Safeties to be observed while operation & maintenance.
i. Use hand gloves & safety goggles while adding distilled water, shifting of battery, or checking sp. Gravity.
ii. Use insulated spanners to tighten terminals (No Sparking, short-circuiting should take place)
iii. Use plastic bottle or jar to add distilled water.
iv. Should not be left in discharged condition for long period.
v. If adding acid, then first put little Acid, then add water & do the same process.
vi. No naked lights to be taken inside.
vii. No smoking inside battery room.
25. What precautions you will take before entering battery room.
a.Inform the bridge & the engine control room
b.Check the oxygen content.
c. Should be ventilated properly.
d. All PPE to be donned properly & rubber hand gloves to be used.
e. No Naked lamps to be taken inside.
f. .
26. What is meaning of power factor. What is best value. What is normal value onboard. How do you improve?
Power Factor :- The power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power and is a dimensionless number between 0 and 1
The best value is 0.85. The normal value onboard varies in between 0.8 to 0.9.
Power factor can be improved by connecting a Capacitor in parallel.
27. What is meaning of saying current and voltages are in phase
28.What happens to resistance of conductor when temp rises.
Resistance is directly proportional to temperature.
So, resistance will increase if temperature rises.
29. Types of starters in ERoom
a. DOL (Direct On-Line)
b. Star-delta
c. Auto-transformer.
d. Face plate starter
30. Types of Motors in Eroom
a. Induction Motor.
b. Synchronous Speed Motor.
c. DC Motor.
d. Shunt motor
e. Series Motor
31. How do you check continuity.
By using the multimeter, continuity is checked. Continuity is checked between the earth & the motor connection.
32. Meaning of open and short circuit. How checked.
33. Voltage generated in megger.
500 V.
34. What is explosion proof equipment?
It is an equipment:
(a) Having an enclosure capable of withstanding an explosion within it of a specified flammable gas or vapor & preventing the ignition of the specified flammable gas or vapor in the atmosphere surrounding the enclosures by the sparks, flashes or explosion of the gas or vapor within.
(b) That operates at such an external temperature that a surrounding flammable atmosphere will not be ignited.
35. What precautions to take while using megger ion circuits containing Electronic components.
36. What precautions to take before starting a work on electric equipment?
a. Do get to know the electrical circuit or system.
b. Rubber gloves, insulated tools to be used.
c. Portable lamp, if used should be fully insulated without metal guards.
d. Precautions must be observed to isolate and lock off the apparatus. Where, fuses are there, these should also be removed.
e. Before commencing work, it should be confirmed that the system is dead using live line tester.
f. Men at Work signboard to be put.
37. how does tube light work.
38,. Trips on Electric Motor.
Short Circuit trip.
Overload trip.
Reverse power trip.
Reverse current trip
Fuse
39. Overhaul of an Electric Motor.
a. Disconnect the electric circuit.
b. Isolate the system.
c. Remove the fuse & check the electric supply is not coming.
d. Put MEN at Work tag.
e. Remove the coupling bolts.
f. Lift the motor with the help of lifting gear.
g. Open the end cover & remove the fan and clean the fan.
h. Remove the bearing and renew it.
i. Check the condition of winding visually & check the insulation resistance by using megger.
h. If low, then apply varnish on it & dry it with gentle heat.
i. Check the continuity.
j. Assemble the motor.
k. Before putting it into operation, check the load being taken & any noise coming from it.
40. Purpose of AVR
AVR :- Automatic Voltage Regulator
The AVR is used as an exciter. The purpose of AVR is to maintain terminal voltage of an alternator constant on load.
41. What is shaft generator
42 how does air compressor start stop automatically
There is a pressure switch provided which is having a bellow inside which increases & decreases in its size if the pressure rises to reqd. to start the compressor .
43 Main switchboard safeties.
a. Ebonite Rod.
b. Rubber pad infront of switchboard.
c. Dead-front type switchboard.
d. 0.6 meter gap behind the switchboard.
e. Fuse
f. Circuit Breakers.
g. Earth Fault indicators.
h. Panel doors are earthed.
i. No water, steam or oil pipelines to pass in its vicinity.
j. Undervoltage Relay
k. Reverse Power trip.
l. Preferential trip.
m. Overcurrent trip
n. Arc Chute
o. Short-circuit trip.
44. Precautions while connecting shore power?
a. Check terminal box cover screws/nuts to remove(Find out location), lightly greased & ease up.
45 Why load picked by crane does not fall if power goes off
Because Electro-magnetic brakes get operated.
46. How electricity is generated.
47.Maintenance on Alternator?
a. Ventilation passages & air filters to clean.
b. Insulation resistance to check for Stator, rotor winding. If low, then varnish to be done
c. Air gap to check using plastic feeler gauge.
d. Bearing oil to be renewed.
e. Use vaccum cleaner to remove dirt/ dust.
f. Terminal box cover gasket integrity to check.
g. Terminal connections to check for tightness.
h. AVR components, diodes to keep free from oil, moisture or any dirt.
i. Heaters to be checked.
48. What is the function of Diode?
The function of a diode is to allow current in one direction and to block current in the opposite direction.
48. How to carry out Open Circuit & Short circuit test?
Open Circuit Test: The purpose of this test is to determine no load loss or core loss.
One winding of the transformer, usually high voltage side if left open and the other is connected to its supply of normal voltage and frequency. A wattmeter, voltmeter and the ammeter are connected in the low voltage winding.
With the normal voltage applied to the low voltage side, normal flux will be set up in the core, hence normal iron losses will occur which are recorded by the Wattmeter.
The load current on the low voltage winding will be small(2 to 5 % of rated full load current ), the copper loss in the winding will be negligible and will be nil in the high voltage side winding..
So, the wattmeter reading will represent practically the core loss under no load condition.
Short-Circuit Test: This is also known as Impedance test.
In this test, the low voltage winding is short circuited by using a thick conductor (or Ammeter, which serves additional purpose of Indicating Rated load current).
A low voltage at correct frequency is applied to the primary and is cautiously increased till full load current is flowing the high voltage side.
In this test, the applied voltage is small percentage of its rated value, hence flux produced is small with the result that iron losses will be negligible and the Wattmeter reading will represent the full load Cu-loss.
49. Suppose your motor has short-circuited, then how much value will you get on Megger.
51. An example of each.
- Where does magnetic field cuts the conductor?
-where does conductor cuts the magnetic field?
52. How is signal transmitted from Navigational bridge to steering gear?
53. How is the load decided on AC Compressor & how does it works?
54. What is Open-circuit & short-circuit in a control unit ?
55. Safeties in motor?
a. Fuse
b. Overload trip
c. Short-circuit trip
d. Reverse power relay
56. Working principle of Explosimeter?
An explosimeter is a device which is used to measure the amount of combustible gases present in a sample. When a percentage of the lower explosive limit (LEL) of an atmosphere is exceeded, an alarm signal on the instrument is activated. "Explosimeter"
The device, also called a combustible gas detector, operates on the principle of resistance proportional to heat—a wire is heated, and a sample of the gas is introduced to the hot wire. Combustible gases burn in the presence of the hot wire, thus increasing the resistance and disturbing a Wheatstone bridge, which gives the reading.
A flashback arrestor is installed in the device to avoid the explosimeter igniting the sample external to the device.
The combustible gas indicator shown diagrammatically above consists of a Wheatstone bridge with current supplied from a battery. When the bridge resistances are balanced, no current flows through the galvanometer. One resistance is a hot filament in a combustion chamber. An aspirator bulb and flexible tube are used to draw a gas sample into the chamber. The gas will burn in the presence of the red hot filament causing the temperature of the filament to rise. Rise of temperature increases the resistance of the filament and this change of filament unbalances the bridge. The current flow registers on the meter which is scaled in percentage of LFL or ppm.
57. Safeties and precautions on portable electrical equipments?
58. what is the routine maintenance on the starter of main air compressor which is of automatic start stop type?
59. How to test a fuse? -apart from multimeter.
60. Types of Fuses & diagram?
a. Catridge Type.
b. HRC(High Rupturing Capacity)
61. Which is the largest induction motor used onboard?
Alternator
62. Which current is coming out from Alternator?
63. How will know proper working of Megger?
64. Types of Switchboard?
a. Open Type
b. Dead front type.
65. Whats the use of apparent power(kva) & reactive power(kvar)??????
Apparent power consists of active and reactive power. Active power is the share of the apparent power which transmits energy from the source (generator) to the user. Reactive power is the share of the apparent power which represents a useless oscillation of energy from the source to the user and back again
66. What is a Thyristor?
67. Maintenance carried out in Stator.
68. Why Star-Delta starters are used?
69. What all testing equipment is used for testing an electric motor?
70. Basic meaning of Intrinsically safe motor?
An intrinsically safe circuit is one that is designed for a power so low that any spark or thermal effect produced by it whether there is fault or not, is incapable of igniting the surrounding gas or vapor.
71. Difference between Intrisically safe & Explosion proof?
An intrinsically safe circuit is one that is designed for a power so low that any spark or thermal effect produced by it whether there is fault or not, is incapable of igniting the surrounding gas or vapor.
Explosion proof :-
72.Circuit diagram of Megger?
73.What is the function of Commutator?
74.What is the supply given to shipboard general alarm.
24 Volt DC.
75. Maintenance on switchboard?
a. Check contacts of Circuit breaker for damage & dirt.
b. Cleaning of contact using electro-cleaner.
c. Interlocks fitted to check for proper functioning.
How to make sure motor is in good condition? While Running
No noise No vibrations Motor frame temperature normal. Current drawn by the motor is normal. No dirt or dust or no corrosion on fins. Drawing rated current. During Stop condition.
Isloate the system Dismantle the parts Check condition of internal parts, like bearing, fan. No damage to rotor, stator. Insulation resistance to check. No signs of overheating should be there. While starting
Developing correct torque & high starting current. Coming back to its normal rated current in designated time.
76. Draw star, delta 3 phase connections?
77. What are various portable electrical equipment used?
a. Megger
b. Multimeter
c. Clampmeter
d. Live line tester.
78. what is the difference between KW and KVA?
KW means that it is the power deliverd to the load. where as the kva is the power can be meet the load demand. so that kva is not with respect to load.
Procedure for Overhaul of A/E. a. Check whether all tools and spares are available or not.
b. If so, then start the Stand by generator.
c. Check all parameters are normal.
d. Now share the load with the help of synchroscope.
e. Again check all the parameters are within normal range.
f. Put full load on the Stand by generator.
g. Stop the generator on which work has to be carried out.
h. Put MEN AT WORK tag.
i. Shut the air starting valve, fuel oil inlet & outlet valves and isolate the system.
j. Let lube oil priming pump run for half hour after then stop it.
k. Drain the jacket water.
l. Remove the cylinder head cover.
m. Remove high pressure pipe.
n. Take out the injector using its tool.
o. Open the rocker arm bolts & remove it from its place.
p. Remove the Jacket water outlet pipe.
q. Disconnect the scavenge & exhaust manifold from the cylinder head.
r. Open the cylinder head bolts using the Torque spanner or hydraulic jack(As provided on your vessel).
s. Check the lifting gear (Crane & chain block, Eye bolt, etc.)
t. Lift the cylinder head & put it at a suitable place.
u. Open the crankcase door.
v. Bring the piston to TDC position & attach eye-bolt on it and Attach hook of chain block to it.(Before bringing Piston to TDC, the top part of liner needs to be cleaned)
w. Bring the piston to BDC and open the bottom-end bolts & remove bottom end bearing.
x. As load of piston is now on Lifting gear, so take it out & put it on the piston stand.
y. Remove the piston rings using ring extractor.
z. Remove the circlip from the gudgeon pin & take out the gudgeon pin, so connecting rod can be taken out.
How do you decide if piston rings should be changed or not? a. Butt clearance increased then its normal range.
b. Axial clearance increased.
c. Visual condition of piston ring.
How you check lifting gear. a. Check the condition of wire rope & grease it.
b. Check the visual condition of chain.
c. Check the limit switches in the forward, aft, Port & starboard direction are working.
d. Check that emergency button is working.
e. Check the visual condition of the insulated cover is satisfactory.
f. Check overload trip is working satisfactorily.
g. Check the visual condition of chain block, no cracks should be there.
h. Check that safety latch is there on chain block.
What checks on piston and liner. a. Piston:-
i. Check the piston for any cracks.
ii. Check the piston top profile.
iii. Check for any carbon deposits.
iv. Check the butt clearance, axial & radial clearance.
What to do if valve seat damaged?
Checks on crankcase inspection in Main Engine? Safety Precautions:
Inform bridge and Chief Engineer. If in port, take Immobilization certificate. Get propeller clearance from the duty officer. Shut off starting air valve. Put “Men at Work” tag. Stop lube oil pump. Indicator cocks to open. Turning gear should be engaged Wear proper PPE, Shoes & helmet. No naked lamp to be taken inside. Open the crankcase door taking it as a shield. Ventilate the crankcase door properly. No items should be inside the pockets of boiler suit. Inspection:
a. Check the condition of lube oil, for any smell, discoloration, degradation.
b. No paint parts to be there in the sump.
c. Turn the engine to BDC and under stuffing box area for any black oil.
d. Check piston rod for any scoring & roughness.
e. Check piston palm bolts & locking.
f. Check the guide shoes and the area around it.
g. Check guide shoe end cover bolts.
h. Check X-head bearing general condition.
i. Check all bearing for white metal.
j. Check oil pan area of every unit for any sludge formations, bearing metals & foreign particles.
k. Check top & bottom of connecting rod bolts, nuts & locking device.
l. Check the axial movement of bottom end bearing.
m. Check slippage of web & journal by reference marks.
n. Check the teeth of transmission gear.
o. Check the tightness of chain drive.
p. Check c/case relief door spring tension, wire mesh & sealing ring.
q. Check & clear the O.M.D sampling pipes.
r. Start the lube oil pump & check flow .
s. Check c/case door sealing condition & close it c/case door.
t. Make sure no foreign matter or tools should be left inside the c/case.
Tappet clearances why plus how to check. Tappet clearance is taken to ensure positive closing of the valve & for thermal expansion of the valve.
Taking all safety precautions.(See Ans. 1)
Make sure the piston is on TDC.
i. From the marking on the flywheel.
ii. From the fuel cam.
iii. Push rod should be free.
Make sure the engine has cooled down.
Loosen the lock nut of the rocker arm.
Now adjust the tappet clearance between the rocker arm & valve stem by tightening or loosing the nut below the lock nut.
If tappet clearance is less:
i. Valve will open early & close late
ii. Air induced through inlet valve may leak out. So, less air for combustion.
iii. Power will be reduced.
iv. Fuel consumption will increase, engine may become unbalanced, exhaust temp. will be very high.
v. In worst condition, valve may remain open, resulting in loss of compression pressure, burning of exhaust valve, T/C fouling will increase.
If tappet clearance is more:
i. Valve will open late & close early.
ii. Lesser heat energy to T/C, so reduction in scavenge air & hence power.
iii. No proper removal of gases.
iv. Hammering of valve stem-may cause damage to valve stem.
What to check if Engine is not starting on air and fuel Engine not starting on Air:-
a. Low air bottle pressure or air line valve may be shut.
b. Air bottle isolating valve or automatic valve or distributor not functioning.
c. Control air valves faulty or less control air pressure.
d. Start air automatic valve jammed.
e. Turning gear engaged.
f. Reversing has not taken place completely.
g. Control valve for fuel or start is not in it’s end position.
h. Bursting diaphragm on start air line damaged.
i. Fuel lever on maneuvering stand not on remote mode.
j. Auxiliary blower not running or not on ‘auto’ mode.
k. Emergency stop has activated.
l. Interlock is operated.
m. Cylinder air start valve defective or sticky.
n. Piston not in firing mode.
Engine not starting on fuel:
a. Less fuel in service tank.
b. Fuel filter is chocked.
c. Fuel supply pumps not delivering required pressure. Or fuel pump tripped.
d. Fuel level on local maneuvering stand, is not on remote stand.
e. Fuel rack stuck.
f. Fuel pump malfunctioning, jammed plunger.
g. Injector nozzle needle sticking or holes blocked.
h. Compression pressure is too low due to broken piston ring or exhaust valve not closing properly.
i. Fuel pump relief valve leaking.
j. Start air pressure insufficient to turn the engine fast enough.
What to check if Engine is not taking load.
What precautions to take to start A/E After overhaul. a. Water tightness to be checked.
b. Air to be removed from jacket water outlet line.
c. Priming lube oil pump to run before starting the engine.
d. Check the lube oil level.
e. Check the flow of lube oil.
f. Blow through the engine before starting.
How to change purifier to clarifier. Remove the gravity disc.
How to select damn ring for purifier. From the monogram provided with manual, which is drawn with respect to viscosity of oil & which size damn ring to be used.
If monogram not there, then
a. Chief Engineers experience will come into use.
b. Hit & trial method to be used.
i. First use the largest gravity disc and whether oil is overflowing, if so, then use small size gravity disc and follow this process until oil stops overflowing.
What to check if purifier over flowing. a. Size of gravity disc.
b. High throughput.
c. Temperature of the oil.
How to stop Aux Engine if not stopping by stop handle. a. Pull the fuel rack to zero position.
b. Operate any trip.
Charging gas in Dom Fridge? Close the receiver outlet valve and collect the gas in the receiver. Check the liquid level, if it is below L/3, Charging is reqd. Check the weight of the refrigerant bottle & keep it upright. Connect the charging line to the connecting point and keep it loose. Open the bottle valve slightly and purge the line into the collecting cylinder and then tighten the connection. Open the charging valve and fully open the bottle valve. Check the liquid level in the sight glass and make sure no air bubble present in the system. Close the charging valve and the bottle valve. Open the receiver outlet valve & start the compressor. Carry out let detector test.
Charging oil in Domestic fridge. Method 1.
Mostly ships have hand p/p provided which develop more pressure than the inside pressure. Method 2.
Reduce the L.P Cut out setting. Dip the pipe inside the c/case of compressor. Run compressor, vaccum will develop. So, compressor will start sucking the oil. Make sure the pipe is diped fully, because it has got chances of sucking air. If air gets in, then purge it in a separate bottle after charging of oil gets completed.
What to check if Room temp (one room) not coming down? -
What to check if all room temp not coming down? - Room doors not shut properly.
- Room insulation is bad.
- Air in system.
- Room fans not running.
- Evaporators frosted.
- Compressor not working satisfactorily, unloader defective, valve leaky, rings damagd.
- Expansion valves choked/ malfunctioning.
- Evaporator blocked.
What to do if dom. fridge is short cycling/ - L.P Cut out is defective.
- L.P Cut out setting not correct, too low difficult for Cut In.
- Lesser gas flow
Less gas in system. Drier Choked. Expansion valve filter choked or Expansion valve Malfunction. Evaporator Choked. Compressor valves leaking. Actions:-
a. Check L.P. Cut out setting, Cut out pressure OK.
b. Check flow of gas by seeing sight glass which should show full flow of refrigerant.
c. If no full flow- Either less gas or drier chocked, Clean the drier.
d. Check level in receiver, if low, then charge gas.
e. Expansion valve filter choked, then clean it.
f. Expansion valve malfunctioning- Change it.
g. Evaporator choked- Blow-thru evaporator with nitrogen.
Overhaul of centrifugal pump.
Changing pipe join below floor plate without removing pipe.
Can not pump out bilges. What checks? What to do if pipe holed? Check Sounding of bilge tank. Check Bilge tank outlet v/v open or not. Check P/p inlet v/v open or not. Check p/p working properly. If vaccum developing that means hole in pipeline. If pipe is holed:-
Carry out Vaccum test by closing inlet valve & opening outlet /v. If hole is between the inlet v/v and p/p, vaccum will develop, now remove top of v/v and put water. If hole is in between Inlet v/v and bilge tank outlet v/v, then again put S.W
Boiler press coming up and gone above the safety valve lifting pressure. What to do? Use the easing gear to release the excess pressure.
Bridge informs steering not responding. What to do?
Air comp bumping clearance how to check and adjust. Start the Stand by compressor. Stop the compressor whose bumping clearance has to be taken. Isolate the system. Put “Men at Work” tag. Loosen the cylinder head bolts and lift it. Measure the diameter /size of the lead ball. Bring piston to TDC and put lead ball on centre of it. Now, put the cylinder head and tighten it to required torque. Now, again loosen the cylinder head bolt and remove the ball. Measure the size of the ball. The difference between the initial size and final size is the bumping clearance. It can be adjusted by either putting a thinner gasket or putting shim on top half of the bottom end bearing.
Removal of broken stud. First drill the stud little bit & then use Thread extractor which has left hand thread.
Bridge informs lot of smoke from funnel what to do? Reduce load on engine. Check purifier operating alright/ reduce throughput to have better purification. Drain water from settling & service tank. Check scavenge air temperature & adjust if reqd. . Soot blow the economizer. Ensure, fuel oil end heater outlet temperature proper corresponding to attain viscosity at the point of injection. Check, if any particular Exhaust temperature is higher than others, if so, then stop the engine, Change the injector with a spare overhauled injector. Check all fuel pump timings are correct or not. Dismantle and carry out overhaul of T/C. Send fuel oil for Laboratory analysis.
Reasons:
Improper combustion. Burning of carbon particles collected at EGE. Overloading of engine. Inform bridge & Chief engineer. Raise engineers’ call/emergency alarm. Before starting bilge pump note down the position of vessel & time of starting. Other engineers will in between try to locate the hole or burst of pipe and repair. If ingress of water very high, start another pump. Reduce the engine r.p.m. Change over main s.w suction to emergency bilge suction. If level is still coming up try to protect the motor from short-circuiting , if required start emergency bilge suction valve. If situation is not coming in control, prepare lifeboat for lowering. Flooding in Engine Room what to do?
What checks to be made on Aux Engine when running? Checks:
Check scavenge air temperature. Check Exhaust gas temperature. Check r.p.m Check load on A/E. Carry out peak pressure. Check for any abnormal noise or vibration. Check jacket water inlet & outlet temperature. Check Lube oil temperature & pressure.
During running Main Engine stops. What checks? Check whether Emergency stop operated by any personnel. Check level of fuel oil in Service Tank. Check whether purifier working properly. Check whether water is there in Service tank due to improper purification. Low lube oil pressure trip operated, Check L.O P/p developing correct pressure. Control air trip operated, Check control air pressure.
Boiler blow back what to do and reasons?
Reasons:-
Insufficient pre-purging. Blower not working. Accumulation of oil. Leaky solenoid valve. Dripping of burner.
Action:-
Stop the firing. Check the condition of burner, if it is dripping, then overhaul is required. Do the inspection of the furnace. Carry out sufficient pre-purging. Start the boiler on “Auto” mode.
Boiler extinguishes what to do? Accept the alarm. Find out the reason for extinguishing:- if too low water level alarm came, then check pump is developing correct pressure or not , its is working properly. If Tripped on high pressure, let the steam pressure come down. Fuel oil low pressure alarm , then check functioning of fuel pump, oil in service tank. Fuel oil low temp. alarm, then use the heater. Flame failure trip, then clean flame eye, check the furnace & overhaul the burner.
Overhaul of fuel valve? Safety Precautions:-
a. Check whether all tools and spares are available or not.
b. If so, then start the Stand by generator.
c. Check all parameters are normal.
d. Now share the load with the help of synchroscope.
e. Again check all the parameters are within normal range.
f. Put full load on the Stand by generator.
g. Stop the generator on which work has to be carried out.
h. Put MEN AT WORK tag.
i. Shut the air starting valve, fuel oil inlet & outlet valves and isolate the system.
j. Let lube oil priming pump run for half hour after then stop it.
k. Remove the lock nut of the high pressure pipe.
l. Now, remove the high pressure pipe.
m. Take out the fuel injector using it tool.
n. Put it on the testing kit.
o. Check the lifting pressure, atomization, pressure falling steadily, dripping of oil.
p. Now, take out the injector from the testing kit, put in a diesel oil & clean it.
q. Make sure the workshop table should be clean, no rags or jute to be there.
r. Put the injector on the vice and tighten it.
s. Loosen the lock nut of the injector.
t. Now loosen the compression nut to release the spring pressure, then take out the spring.
u. Open the cap nut and take out the needle and guide.
v. Put the parts on the cleaned table.
w. Check the condition of spring by dropping on the floor plate, it should jump and also check it by tightening in the vice and then releasing. The difference in the length,no cracks to be there.
x. Check visually needle, there shouldn’t be any scoring marks because it is made of Nitrite material.
y. Try to insert the needle inside the guide at angle of 45degree, the needle should on its own weight.
z. Check the size of injecting holes by using Go or No go gauge.
i. If go gauge is going then hole size is OK.
ii. If no go gauge going, then it means the size has increased, then nozzle needs to be changed.
iii. Now assemble the injector and do the lifting pressure setting on test kit by adjusting the compression nut.
iv. After this check the injector again for its lifting pressure, atomization, steady fall of pressure and dripping.
How pressure testing of Globe Valve is done? a. Blank one side of valve and put water from the other side, check for any leakage.
Overhaul of a cylinder head & what all to check?
Overhaul of Inlet & exhaust valve of aux.enine?
Function of Roto-Cap in valves & how it is overhauled? a. It helps to rotate the valve during operation with the help of the exhaust gas, so as less wear occurs and stress doesn’t comes only at one point.
What is dye-pentration test, why is it done & how is it done? Dye-Penetration test is a leak test carried out to know about the leakage/ crack in any part.
In it, first the part or unit is cleaned, paint is removed where the crack is suspected, then it marked on the unit. If water is coming, then colour will change, which shows the crack.
How alkalinity test is carried out? Take 200 ml water sample in the stoppered bottle. Add one P.Alkalinity tablet & shake or crush to disintegrate. If P.Alkalinity is present the sample will turn blue. Repeat the tablet addition, one at a time, until the blue colour turns to permanent yellow. Count the number of tablets used and carry out the calculation: P.Alkalinity, ppm CaCO3 = (Number of tablet x 20) -10
f. Record the result obtainied on the log sheet provided, against the date on which result was obtained.
Why water is kept heated in hot-well?
To prevent oxidation To avoid thermal stress on boiler.
Position of Unloader in AC & Ref. compressor ? Unloader in AC & Ref. compressor is located near the suction valve of the compressor.
What all clearances taken in centrifugal pump? The wear ring & impeller. The wear ring & the casing. Shaft and the bush.
Why centrifugal pump is not self –priming? Because of the churning effect it is not be able to remove air positively as mass of air is relatively zero.
What is the position of bearing in centrifugal pump? Near the impeller.
What is the position of piston when taking bearing clearances
- Main Bearing Clearance --B.D.C
- Bottom End bearing clearance—B.D.C
- Cross-head bearing clearance.—B.D.C
How to overhaul gear pump and centrifugal pump? And clearance to take.
How to take out connecting road?
How to test cylinder head relief valve onboard?
During maneuvering Bursting disc of air compressor get damaged, what action to take? Inform the bridge about the problem and to give lesser kicks. Start the stand by compressor. Isolate the compressor whose bursting disc is damaged. Change the bursting disc, if available onboard. If Not available, then let the S.W go into the E/room bilges, otherwise Fresh water cooled , then join a flexible hose and put into the expansion tank.
How will you test the crankcase relief door? The testing of the C/case relief door is done at shore.
Reasons of Purifier overflow? Procedure for doing boiler blow down? Precautions
Ensure nobody is near the ship side blow down valve. Not to be carried out in drydock or alongside. Valve sequence to be followed. Boiler shouldn’t be left unattended during blow down. Monitor the end of blow down. Long blow down to be avoided. Don’t blow down to the E/room bilges.
Procedure
Ship side valve 1 is opened followed by valve 2. Valve 2 is NR which is fully opened to avoid cutting off seat. Rate of blow down controlled by Valve 3. For scum blow down valve 4 & 5 are used.
Action to be taken, if chloride content is excess? Blow down of boiler to be carried out.
How to blow through boiler Gauge Glass? Procedure:
Make sure drain line is clear Close the steam outlet valve. Close the water outlet valve. Open the drain valve. Open the water out valve & let water flow thru it and close the valve after blowing down with water. Open the steam out valve and blow thru with steam. Close steam valve. Close the drain valve. Now, open the water side valve. Let water fill up 3/4th gauge glass. Open the steam valve slowly.
How to tighten boiler gauge glass after overhauling?
Procedure of tightening:
First tighten all the bolts by hand slightly without putting any pressure. Now, tighten bolt 1 & 2 equally. Then 3 & 4. Tighten bolt 5 & 6. then 7 & 8 equally. Tighten bolt 9 & 10. Now again tighten 7 & 8. Then 5 & 6. Tighten bolt 3 & 4. then 1 & 2.
Or you can say we first tighten outward bolts of both side & then inward side.
Then we move in opposite steps. i.e. tight inward bolts & then outward bolts.
AIR COMPRESSOR
Bumping clearance- what is bumping clearance, why it is called so, would it increase with time or
decrease (may increase or decrease),how to adjust in tandem type, why not adjusted by using metal shims
in palm end connection, effects of increased clearance, what was the value of bumping clearance on your
ship( 1% of cyl. Bore, 1.8 mm(CYL bore 180mm ) n 1.4 mm(cyl. Bore 140mm))? Does B/E bearing adjustment
in a/c affect the bumping clearance?
Bumping clearance as the name signifies is a clearance given so that the piston of the marine reciprocating
compressor would not bump into its cylinder head
How to Check Bumping Clearance
1. In case a suitable opening is available the piston can be barred to the top dead centre and then feeler gauges
can be put inside and the clearances checked at two three points.
2. The more convenient method is to take lead wire from the engine store and make a small ball based on the
expected clearance and put it between the piston and the head from the valve opening. Then the piston is
slowly turned to the top dead centre with the help of a Tommy bar. After that the piston is again turned
down and the lead wire ball is extracted and the thickness measured with the help of a micrometer. This
measurement would give the bumping clearance.
The caution which must be observed in these methods is that the clearances of the main and the crank pin
bearing have not been taken into account. The correct method is thus that after turning the piston to top dead
centre the piston connecting rod must be jacked up with the help of a crow bar. It is only after this hidden
clearance has been accounted for, will the correct bumping clearance be found.
How to Adjust the Bumping Clearance
3. The cylinder head gaskets can be changed to a different thickness thus altering the bumping clearance.
4. The shims between the foot of the connecting rod and the bottom end bearing can be changed thus
changing the bumping clearance.
However after adjusting the bumping clearance the clearance should be checked once again to make sure that
there is no error and the clearance is within the range as specified by the manufacturers.
Change in bumping clearance
Wear at the crankpin bearing. The crankpin bearing wears down due to use and this clearance can travel right
up to the piston and an unloaded piston can hit the cylinder head. This type of wear can be recognized when the
compressor makes impact sounds running unloaded at the starting and stopping operations. This type of wear
would also be accompanied by a slow decrease in oil pressure over a period of time.
Opening up of cylinder heads. In certain types of reciprocating compressors the cylinder head have to be
removed for the changing of the first stage suction and discharge valves. When the cylinder head is put back the
correct thickness of the cylinder head gaskets should be used otherwise it would change the bumping clearance. Wear on the main bearings. Over all wear on the main bearings would lower the crank shaft and would thus
lower the piston and increase the bumping clearances.
IMPORTANT….bump clearance or squish is most definitely done with the head gasket installed between
head and cylinder.
Use 2 pieces of lead. Put one piece of lead directly over each end of the wrist pin out near the edge of the
piston but not under a valve. This will give you 2 measurements. 1. piston clearance or squish. 2.
Piston/cylinder angle relative to crank. This angle is important as it shows the cylinders relationship to the
crankshaft. If the pieces of lead are too different in thickness, the piston can run out of available ring
compression and wrist pin end travel and contact the cylinder(scuff) at top and bottom.
differential squish is how the Indians measure and determine the sum of machine errors and the need for
half gaskets under the cylinder base on engines that have alignment issues.
#4 lead shot is perfect for this measurement as it is a uniform size and crushes very consistently. A little
dab of grease or drop of oil will hold them where you put them on top of the piston during the
measurement.
Q. Relief v/v n fusible plug- setting (10% above stage pressure), Reason for lifting of relief v/v of LP
stage and HP stage, where fitted? Why fusible plug is fitted, its material (tin, antimony, bismuth), what
temp blows(121*C)?how to test relief v/v( by normal hydraulic p/p)?
Reasons of LP stage relief v/v lifting- HP stage suction v/v or discharge v/v leaking, 2nd
stage suction n discharge v/v interchanged after over’hl.
Reasons of HP stage relief v/v lifting- delivery v/v shut, setting error of pressure switch,
delivery v/v which is SDNR type is fitted inverted.
Lubrication- how it takes place in main/brg, crankpin bearing, upper n lower cyl. In case of tandem type,
how piston gets cooled? Pressure value n alarm value(2-4 bar, alarm at 2 bar)? Reasons….pressure suddenly
drops, pressure drops slowly (increase in clearance of main brg or crankpin brg), increased oil consumption?
Why Breather is provided in lub. Oil filling line? Is crankcase pressurized during running condition?
For main brg n crankpin brg. Lubrication normally thr is a shaft driven gear p/p.
For lower cyl. In tandem type- it’s by splash. For upper cylinder in tandem type thr is a supply line from the
gear p/p going to suction side of air which supplies small amount of oil mist with air n that mist lubricates the
upper cyl. Sometimes the supply is from drilled hole in con. Rod like we have in A/E.
Reasons oil pressure not rising- motor rotation direction reverse, oil line block due to rag, no oil in sump,
filter clogged, worn metal so increase of clearance.
Increased oil consumption- too much oil in sump( above level H), oil scraper ring wear out, worn piston and
liner.
Breather- it is used so that pressure or vacuum is not created inside crankcase. It has filter so moisture and dirt
don’t go inside and also has metallic plate on the inner side which don’t allow lub. Oil to come out. Cooling line- pressure( 0.2-2 bar), alarms(90*c), why bursting disc, its material( copper), action if it bursts
during maneuvering, at what pressure it bursts, why we prefer bursting disc over relief valve( no chance of
getting reset), purpose of intercooler n aftercooler, What if Main air compressor runs without cooling
water(may cause explosion)? Auto drain trap working?
ANS. If bursting disc bursts during maneuvering- Inform the bridge about the problem and to give lesser kicks,
Start the stand by compressor, Isolate the compressor whose bursting disc is damaged, Change the bursting
disc, if available onboard, If Not available, then let the S.W go into the E/room bilges, otherwise Fresh water
cooled, then join a flexible hose and put into the expansion tank.
Suction n delivery v/v- how u will come to know they r leaking( temp. increase of air, relief v/v lift),
its affects, What would be the consequences of too high valve lift in an air compressor( chances of damage
due to impact, decrease in vol. efficiency)? What would be the consequences of a high spring constant of
spring plates in an air compressor(open late n sit with higher impact which may cause damage)? Can we
interchange spring of suction n delivery v/v( no, delivery v/v spring stiffness is more)? parts of
v/v(remember,the suction n delivery v/v for first stage r in single set but for 2nd stage they r different, the
v/v parts for both suction n discharge of 2nd stage r same but arranged in opposite order)?
Starting- checks before manual starting, current value of air compressor?(Starting
310Amps,full load 30A)
ANS. 1. Lubrication: check the oil level in the sump (b/w H n L)and in the lubricator tank.
2. Unloading: the valves in the unloading lines must be open.
3. Pressure gauge cocks: the cocks must be slightly open to avoid excessive pressure fluctuations
which can damage the pressure gauges.
4. Air filter: check that the air intake filter is clean.
5. Cooling: check that the cooling water pressure is correct(0.2-2bar) and in the case of attached
pumps a visual check of the pump and all the valves in the line must be open.
6. Relief valves: some relief valves have hand testing levers given for testing, the same can be done.
7. Air line piping: check that all the valves in the discharge piping are open and correctly lined up.
8. Final check: the compressor can be turned a few revolutions with a turning bar to check for the free
movement.
Why reciprocating type compressor(pr.ratio is higher )?why two stage, pv diag for you comp.
clearance volume? each stage pressure(4-6 BAR, 25-30 BAR)? Can they vary from normal during
starting? unloader ….purpose, design? What is volumetric efficiency, free air delivery?
ANS. Free air delivery- volume of delivered air is measured at 1 atm and 15*C, it’s called free
air.
If the valve has too much lift then the valve closes late and reduce volumetric efficiency and
also its causes valve to close with greater impact and hence liable to break.
Why 2 stage- first, bcoz we can’t give a pressure of 30 bars in single stage as the lub.oil will
start burning. T2/T1=(P2/P1)^n-1/n where n is around 1.35 for air
Now for p2/p1=30/1
T2=450*C
And at this temp. lub. Oil will start burning. Flash point for lub.oil is 200*C. so we keep the
pressure ratio limited to 5:1.
Secondly, we want to save work by moving towards isothermal line by providing
intercooling b/w stages.
PURIFIER
Why we need to heat oil, purifier formula, why we need disc stack, use of gravity disc,
position of e-line?
ANS. For ans see mcgeorge mar. aux. pg-58-62.
Q. what to do if u want to change DO purifier for HFO purifier?
ANS. adjust temp.(around 95*C),adjust feed rate(reduce), adjust desludge time(increase
desludge time as DO don’t have so much of impurities).NOW FOR GRAVITY DISC,SINCE
DENSITY IN DECREASING, so increase size of gravity disc.
Q. Purifier ……Starting n disludging ? Small fire in purifier trays...wt's ur action?? pairing disc?
(SEE MM,OM2)
. Back Pressure: The back pressure should be adjusted after the purifier is started. The back pressure varies as
the temperature, density, viscosity of feed oil inlet varies. The back pressure ensures that the oil paring disc is
immersed in the clean oil on the way of pumping to the clean oil tank.
Throughput of oil feed: Throughput means the quantity of oil pumped into the purifier/hr. In order to optimize
the purification, the throughput must be minimum.
Pre-checks before starting a Purifier
1. If the Purifier is started after a overhaul, then check all fittings are fiited in right manner. The bowl frame
hood locked with hinges.
2. Check the Oil level in the gear case. Ensure that it is exactly half in the sight glass. Also ensure the sight
glass is in vertical position, as there is a common mistake of fixing it in horizontal position.
3. check the direction of rotation of the seperator, by just starting and stopping the purifier motor. 4. Check
whether the brake is in released position.
• Starting the Purifier
1. Ensure the lines are set and respective valves are open. Usually the lines are set from settling tank to service tank.
2. Start the purifier feed pump with the 3-way re-circulation valve in a position leading to settling tank. 3. Open the steam to the heater slightly ensuring the drains are open so that the condensate drains. close the drains once
steam appears.
4. Start the Purifier. 5. Check for vibrations, check the gear case for noise and abnormal heating.
6. Note the current (amps) during starting. It goes high during starting and then when the purifier bowl picks-up speed and
when it reaches the rated speed, the current drawn drops to normal value.
7. Ensure the feed inlet temperature has reached optimum temperature for separation as stated in the Bunker delivery note
and nomogram (can get the separation temperature and gravity disc size from the nomogram)
8. Now check whether the bowl has reached the rated speed by looking at the revolution counter. The revolution counter
gives the scaled down speed of the bowl. The ratio for calculation can be obtained from the manual.
9. Now, after the bowl reaching the rated RPM, check for the current attaining its normal value.
• De-sludge Procedure
10. Open the bowl closing water/operating water, which closes the bowl. (Ensure sufficient water is present in the
operating water tank)
11. Now after 10 seconds, open the sealing water to the bowl.
12. The sealing water should be kept open till the water comes out of the waste water outlet.
13. Once the water overflows through the waste water outlet, stop the sealing water.
14. Now open the bowl opening water. (This is done to ensure the bowl has closed properly). During de-sludge we can
hear a characteristic sound at the opening of the bowl.
15. Repeat the steps 10, 11 ,12 & 13.
16. Open the 3-way re-circulation valve such that the dirty oil feed is fed into the purifier.
17. Wait for the back pressure to build up.
18. Check for overflowing of dirty-oil through waste water outlet & sludge port.
19. Now adjust the throughput to a value specified in the manual. Correspondingly adjust the back pressure, too.
20. Now the purifier is put into operation. Change over the clean-oil filling valve to service tank.
Q. purifier rpm not coming, reasons, Explain about purifier drive mechanism….how you will
check that ?when you will change it(see MM p4-12,change spiral gear if wear down is more
than 3mm,change friction block lining if wear is 3mm,change pulley if wear is 1mm,change
brake lining if wear is 5 mm). When d motor attains full speed does d horizontal shaft rotates
at d same speed of motor?
Q. why frictional clutch in purifier??
ANS. 1.it gives less staring current for motor, also
2.worm and worm wheel arrangement will break due to high starting torque. REFRIGIRATION SYSTEM
TROUBLE POSSIBLE CAUSE CORRECTIVE MEASURE
HIGH CONDENSING PRESSURE. INLET WATER WARM. INCREASE QUANTITY OF CONDENSING
WATER.
AIR ON NON-CONDENSABLE GAS
IN SYSTEM.
PURGE AIR FROM CONDENSER
INSUFFICIENT WATER FLOWING THROUGH
CONDENSER.
INCREASE QUANTITY OF WATER.
CONDENSER TUBES CLOGGED OR SCALED. CLEAN CONDENSER WATER TUBES.
TOO MUCH LIQUID IN RECEIVER,
CONDENSER TUBES SUBMERGED IN LIQUID
REFRIGERANT.
DRAW OFF LIQUID INTO SERVICE CYLINDER.
LOW CONDENSING PRESSURE. TOO MUCH WATER FLOWING THROUGH
CONDENSER.
REDUCE QUANTITY OF WATER.
WATER TOO COLD. REDUCE QUANTITY OF WATER.
LIQUID REFRIGERANT FLOODING BACK
FROM EVAPORATOR.
CHANGE EXPANSION VALVE ADJUSTMENT,
EXAMINE FASTENING OF THERMAL BULB.
LEAKY DISCHARGE VALVE. REMOVE HEAD, EXAMINE VALVES. REPLACE
ANY FOUND DEFECTIVE.
FROSTING OR SWEATING OF A LIQUID
LINE.
REFRIGERANT LINE RESTRICTION. CHECK FOR PARTIALLY CLOSED STOP VALVE,
OR STUCK SOLENOID VALVE.
SYSTEM LOW ON REFRIGERANT. CHECK FOR LEAKS, ADD REFRIGERANT.
HIGH SUCTION PRESSURE.
COMPRESSOR CRANKCASE SWEATING
OVERFEEDING OF EXPANSION VALVE. REGULATE EXPANSION VALVE, CHECK BULB
ATTACHMENT.
LEAKY SUCTION VALVE. REMOVE HEAD, EXAMINE VALVE AND
REPLACE IF WORN.
LOW SUCTION PRESSURE. RESTRICTED LIQUID LINE AND EXPANSION
VALVE OR SUCTION SCREENS.
RUMP DOWN, REMOVE, EXAMINE AND
CLEAN SCREENS,
INSUFFICIENT REFRIGERANT IN SYSTEM. CHECK FOR REFRIGERANT STORAGE.
TOO MUCH OIL CIRCULATING IN SYSTEM. CHECK FOR TOO MUCH OIL IN
CIRCULATION. REMOVE OIL.
IMPROPER ADJUSTMENT OF EXPANSION
VALVES
ADJUST VALVE TO GIVE MORE FLOW.
EXPANSION VALVE POWER ELEMENT REPLACE EXPANSION VALVE POWER DEAD OR WEAK ELEMENT.
COMPRESSOR SHORT CYCLES ON LOW
PRESSURE CONTROL.
LOW REFRIGERANT CHARGE. LOCATE AND REPAIR LEAKS. CHARGE
REFRIGERANT.
THERMAL EXPANSION VALVE NOT
FEEDING PROPERLY.
a. DIRTY STRAINERS.
b. MOISTURE FROZEN IN ORIFICE
OR ORIFICE PLUGGED WITH DIRT.
c. POWER ELEMENT DEAD OR WEAK
ADJUST, REPAIR OR REPLACE THERMAL
EXPANSION VALVE.
a. CLEAN STRAINERS.
b. REMOVE MOISTURE OR DIRT (USE
SYSTEM DEHYDRATOR).
c. REPLACE POWER ELEMENT.
WATER FLOW THROUGH EVAPORATORS
RESTRICTED OR STOPPED. EVAPORATOR
COILS PLUGGED, DIRTY, OR CLOGGED
WITH FROST.
REMOVE RESTRICTION. CHECK WATER
FLOW. CLEAN COILS OR TUBES.
DEFECTIVE LOW-PRESSURE CONTROL
SWITCH.
REPAIR OR REPLACE LOW-PRESSURE
CONTROL SWITCH.
COMPRESSOR RUNS CONTINUOUSLY. SHORTAGE OF REFRIGERANT. REPAIR LEAK AND RECHARGE SYSTEM.
LEAKING DISCHARGE VALVES. REPLACE DISCHARGE VALVES.
COMPRESSOR SHORT CYCLES ON HIGH
PRESSURE CONTROL SWITCH.
INSUFFICIENT WATER FLOWING THROUGH
CONDENSER, CLOGGED CONDENSER.
DETERMINE IF WATER HAS BEEN TURNED
OFF. CHECK FOR SCALED OR FOULED
CONDENSER.
DEFECTIVE HIGH-PRESSURE CONTROL
SWITCH.
REPAIR OR REPLACE HIGH-PRESSURE
CONTROL SWITCH.
COMPRESSOR WILL NOT RUN. SEIZED COMPRESSOR. REPAIR OR REPLACE COMPRESSOR.
CUT-IN POINT OF LOW-PRESSURE
CONTROL SWITCH TOO HIGH.
SET L. P. CONTROL SWITCH TO CUT-IN AT
CORRECT PRESSURE.
HIGH-PRESSURE CONTROL SWITCH DOES
NOT CUT-IN.
1 .DEFECTIVE SWITCH.
2. ELECTRIC POWER CUT OFF.
3. SERVICE OR DISCONNECT SWITCH
OPEN.
4. FUSES BLOWN.
5. OVER-LOAD RELAYS TRIPPED.
6. LOW VOLTAGE.
7. ELECTRICAL MOTOR IN TROUBLE.
8. TROUBLE IN STARTING SWITCH OR
CHECK DISCHARGE PRESSURE AND RESET P.
H. CONTROL SWITCH.
1. REPAIR OR REPLACE SWITCH.
2. CHECK POWER SUPPLY.
3.CLOSE SWITCHES.
4. TEST FUSES AND RENEW IF NECESSARY.
5. RE-SET RELAYS AND FIND CAUSE OF
OVERLOAD.
6. CHECK VOLTAGE (SHOULD BE WITHIN 10
PERCENT OF NAMEPLATE RATING).
7. REPAIR OR REPLACE MOTOR.
8. CLOSE SWITCH MANUALLY TO TEST
POWER SUPPLY. IF OK, CHECK CONTROL CONTROL CIRCUIT.
9. COMPRESSOR MOTOR STOPPED BY OIL
PRESSURE DIFFERENTIAL SWITCH.
CIRCUIT INCLUDING TEMPERATURE AND
PRESSURE CONTROLS.
9. CHECK OIL LEVEL IN CRANKCASE. CHECK
OIL PUMP PRESSURE.
DECREASED CAPACITY OF THE
COMPRESSOR.
HIGH VAPOR SUPERHEAT. ADJUST OR REPLACE EXPANSION VALVE.
SUDDEN LOSS OF OIL FROM CRANKCASE. LIQUID REFRIGERANT SLUGGING BACK TO
COMPRESSOR CRANK CASE.
ADJUST OR REPLACE EXPANSION VALVE.
CAPACITY REDUCTION SYSTEM FALLS TO
UNLOAD CYLINDERS.
HAND OPERATING STEM OF CAPACITY
CONTROL VALVE NOT TURNED TO
AUTOMATIC POSITION.
SET HAND OPERATING STEM TO
AUTOMATIC POSITION.
COMPRESSOR CONTINUES TO OPERATE
AT FULL OR PARTIAL LOAD.
PRESSURE REGULATING VALVE NOT
OPENING.
ADJUST OR REPAIR PRESSURE REGULATING
VALVE.
CAPACITY REDUCTION SYSTEM FAILS TO
LOAD CYLINDERS.
BROKEN OR LEAKING OIL TUBE BETWEEN
PUMP AND POWER ELEMENT.
REPAIR LEAK.
LOW DISCHARGE PRESSURE WITH HIGH
SUCTION PRESSURE.
DISCHARGE RELIEF VALVE LEAKING BACK
TO THE SUCTION SIDE.
REPLACE RELIEF VALVE.
COMPRESSOR CONTINUES TO OPERATE
UNLOADED.
PRESSURE REGULATING VALVE NOT
CLOSING.
ADJUST OR REPAIR PRESSURE REGULATING
VALVE.
COMPRESSOR OIL BROWNISH IN COLOR COPPER PLATING CAUSED BY MOISTURE
IN THE SYSTEM.
CHANGE FILTER DRIER, OR DEHYDRATOR.
COMPRESSOR OIL GRAY OR METALLIC. COMPRESSOR BEARING WEAR OR PISTON
SCORING.
REPLACE OR OVERHAUL COMPRESSOR.
COMPRESSOR OIL BLACK CARBONIZATION RESULTING FROM AIR IN
THE SYSTEM.
REMOVE AIR FROM SYSTEM.
REFRIGERATION SYSTEM WORKS ON FIRST LAW OF THERMODYNAMICS, REVERSE CARNOT CYCLE.
COP= Q/W
1 TON REFRIGERATION CAPACITY= RATE OF HEAT TRANSFER IN FORMING I TON OF ICE AT 0*C FROM WATER AT 0*C.
ADVANTAGE OF UNDERCOOLING= INCREASE REFRIGERATION EFFECT BY REDUCING AMOUNT OF FLASH OFF AT EXP. V/V.
NAMING OF REFRIGERENT- 1
ST
DIGIT FROM LEFT IS ONE LESS THEN NUMBER OF C ATOMS.
2
ND
IS ONE MORE THEN H ATOM
THIRD IS NUMBER OF F ATOMS. Q.PURPOSE F BACK PRESSURE V/V IN REFER OF REFRIGRENT JUST AFTER EAVPORATER. HOW DIFFERENT ROOM TEMP R MAINTAINED
IN REFRERATION SYSTEM?
ANS. BACK PRESSURE V/V- TO KEEP DIFFERENT TEMP OF DIFFERENT ROOMS. WE USE IT IN VEG. ROOM. WE SET BACK PRESSURE, SO
IT INCREASE THE BACK PRESSURE IN VEG ROOM LINE. AND SO THE SATURATION TEMP. INCREASE. SITUATED AT VEG ROOM DICHARGE.
back pressure valve is fitted at the outlet of veg room. the reason being that the veg room is maintained at a
temperature of +4 -5 degress while fish room is at about -12 to -15 degrees and the flow and amount of
refrigerant at fish room and meat room is greater as compared to that of veg room. hence if back pressure
valve is not fitted then when refrigerants will come at the outlet of all the three rooms then the refrigerant will
tend to flow towards veg room. hence to avoid it a back pressure valve is fitted which will allow refrigerant to
flow out only if the pressure inside the veg room outlet will be greater than the outlet from the main line.
Q: WHAT IS THE DIFFERENCE BETWEEN THE "AUTOMATIC EXPANSION VALVE" AND THE "THERMOSTATIC EXPANSION VALVE"?
THE AUTOMATIC EXPANSION VALVE WAS THE FIRST VALVE DEVELOPED TO PREVENT MANUAL ADJUSTMENT OF THE FLUID METER,
THEN USED AS EXPANSION VALVE. THE VALVE IS DESIGNED TO KEEP CONSTANT PRESSURE IN THE EXPANSION VALVE OUTLET. ON
KEEPING CONSTANT PRESSURE, IT ALSO INDIRECTLY CONTROLS THE TEMPERATURE, HOWEVER, IT DOES NOT ASSURE OVERHEATING,
WHICH WILL PROTECT THE COMPRESSOR.AS THE EVAPORATOR CAPACITY IS REDUCED, THERE IS LESS FLUID EVAPORATION, ON THE
OTHER HAND, BECAUSE THE VALVE MAINTAINS THE PRESSURE, IT ALSO MAINTAINS THE VALUE OF THIS FLOW. ON DOING SO,
HOWEVER, EXCESS REFRIGERANT STILL IN LIQUID STATE IS FED INTO THE EVAPORATOR, WHICH RESULTS IN ITS RETURN TO THE
COMPRESSOR, WITH HUGE MECHANICAL LOSS. ALTERNATIVELY, IF THERE IS INCREASE IN LOAD, THERE WILL BE GREATER
FLUID VAPORIZATION AND IF THE VALVE MAINTAINS THE FLOW, IT WILL INCREASE OVERHEATING OF THE GAS AND LITTLE USE OF THE
HEAT EXCHANGE SURFACE. UNFORTUNATELY, THIS RESULTS IN OPERATION OF THE EVAPORATOR CONTRARY TO THE PRODUCTION OF
COLD, WHEN ITS LOAD IS HIGHER.THESE COUNTERPARTS RESULTED IN REPLACEMENT OF THE AUTOMATIC EXPANSION VALVE BY
THE THERMOSTATIC EXPANSION VALVE IN MOST APPLICATIONS. THE THERMOSTATIC EXPANSION VALVE CORRESPONDS TO THE
OVERHEATING AT THE EVAPORATOR OUTLET AND, AS A RESULT, THIS RESPONDS BETTER TO THE ACTUAL LOAD, RESULTING IN A MORE
EFFICIENT SYSTEM.
Q.REFER COMPRESSOR CHARGING LIQUID AND GAS ? WHERE U CONNECT THE CHARGING CONNECTION? WHY WE TAKE PURGE AIR IN
A SEALED CONTAINER? N HOW U WL COME TO KNOW DAT SYSTEM IS ENOUGH CHARGED WITHOUT WEIGHING BOTTLE(SEE IN GAUGE
GLASS)...
ANS. LIQUID CHARGE- CONNECTION IS B/W CONDENSER AND DRIER. BEFORE DRIER BCOZ MOISTURE MAY ENTER DURING CHARGING,
SO IT WILL BE ABSORBED .AFTER CONDENSER BCOZ BEFORE CONDENSER ALL IS GAS. FOR CHARGING CONNECT CYL. TO A BOTTLE,
PURGE,THEN CONNECT TO CHARGING POINT.
WGAS CHARGING- CONNECTION IS IN SUCTION SIDE, JUST LITTLE BEFORE SUCTION LINE.
REMEMBER, REFRIGERANT COMES TO CRANKCASE FIRST THEN IT GOES TO SUCTION SIDE OF 1ST CYL.
CHARGING CYL. HAS 2 V/V- ONE RED IS CONNECTED TO DIP TUBE AND IS FOR LIQUID CHARGING. AND A BLUE V/V IS FROM TOP AND
DON’T HAVE DIP TUBE AND IT IS FOR GAS CHARING.IN BOTH CONDITION CYL. WE KEEP CYL. UPRIGHT.
IF ONLY ONE V/V THEN WE NORMALLY WE DON’T HAVE DIP TUBE AND IN THIS WHEN LIQUID THEN TURN DOWN BY HEAD.
GAS CHARGING OF REFRIGERATION PLANT:
FOR GAS CHARGING, A SPECIAL T PIECE VALVE BLOCK WITH MOUNTED PRESSURE GAUGE IS PROVIDED
TO COMBINE THREE CONNECTORS INTER-CONNECTING:
FOLLOWING STEPS ARE TO BE TAKEN FOR CHARGING GAS INTO THE REEFER PLANT:
1. CONNECT GAS BOTTLE OR CHARGING CYLINDER, VACUUM PUMP AND CHARGING POINT IN THE REEFER
SYSTEM TO THE VALVE BLOCK. 2. THE DISCHARGE OF THE VACUUM PUMP IS TO BE CONNECTED IN THE EMPTY RECOVERY BOTTLE
3. FIRST OPEN THE VALVE BETWEEN VACUUM PUMP AND CHARGING BOTTLE LOCATED IN THE VALVE
BLOCK WITHOUT OPENING THE MAIN VALVE OF THE CHARGING CYLINDER. THIS WILL REMOVE ALL THE
AIR INSIDE THE PIPE. ONCE VACUUM IS REACHED, CLOSE THE VALVE OF CHARGE CYLINDER IN THE
VALVE BLOCK
4. NOW OPEN THE VALVE OF THE CHARGING POINT PIPE IN THE VALVE BLOCK AND RUN THE VACUUM
PUMP UNTIL THE VACUUM IS REACHED. THIS WILL REMOVE THE TRAPPED AIR FROM THIS PIPE. THEN
SHUT THE VALVE IN THE VALVE BLOCK
5. NOW KEEP THE SYSTEM IDLE FOR 5 MINUTES TO CHECK THERE IS NO PRESSURE DROP. THIS WILL
ENSURE THERE ARE NO LEAKAGES IN THE SYSTEM
6. NOW OPEN CHARGING BOTTLE PIPE VALVE AND THE CHARGING POINT PIPE VALVE LOCATED IN THE
VALVE BLOCK. THIS WILL SET THE LINE FOR CHARGING. ENSURE THAT THE VACUUM PUMP VALVE IS
SHUT
7. NOW OPEN THE MAIN VALVES IN THE CHARGING CYLINDER AND CHARGING POINT OF THE REEFER
SYSTEM
8. DO NOT OVERFILL THE SYSTEM. MAKE SURE THE RECEIVER HAS 5 % SPACE FOR EXPANSION
ENSURE THAT NO REFRIGERANT IS LEAKED OUT IN THE ENVIRONMENT AS THESE EFFECTS THE OZONE
LAYER IN THE ATMOSPHERE.
Q.AIR,MOISTURE,OIL,OVERCHARGING,UNDERCHARGING?INDICATION,HARMS,ACTIONS?
OIL IN THE REFRIGERATION SYSTEM
INDICATION:
• TEMPERATURE IS NOT DROPPING IN THE COLD ROOMS AS NORMAL, DUE TO FACT THAT OIL ACT AS INSULATION IN THE
EVAPORATOR.
• IT MAY CAUSE EXCESSIVE FROST ON THE SUCTION LINE.
• REFRIGERANT COMPRESSOR RUNS FOR THE EXTENDED PERIOD OF TIME.
• LUBRICATING OIL LEVEL IN THE COMPRESSOR WILL DROP.
• REFRIGERANT LEVEL WILL FALL IF OIL HAS CAUSED BLOCKAGE.
CAUSES:
• THIS MAY HAPPEN IF THE OIL SEPARATOR IS NOT WORKING PROPERLY.
• OIL MAY CARRY OVER FROM THE COMPRESSOR AND MAY NOT COME BACK TO THE COMPRESSOR DUE TO BLOCKAGE IN THE
SYSTEM.
• DEFECTIVE PISTON RINGS OR WORN OUT LINER OF THE COMPRESSOR MAY CAUSE THE OIL TO CARRY OVER ALONG WITH THE
REFRIGERANT.
• COMPRESSOR MAY TAKE HIGH CAPACITY CURRENT DURING STARTING.
ACTION:
• CHECK THE OIL SEPARATOR FOR PROPER FUNCTIONING.
• CHECK THE DRIER FOR PROPER CLEANING AND IF ITS REQUIRE CLEANING CLEAN IT
• EVAPORATOR COIL SHOULD BE DRAINED TO REMOVE ANY TRACE OF OIL.
• IF THERE IS OIL IN THE COOLING COILS, INCREASE THE CONDENSER AND EVAPORATOR TEMPERATURE DIFFERENTIALS AND REMOVE
EXCESS FROST ON THE SUCTION PIPE.
• HEAT PIPES WITH BLOW TORCH.
AIR IN THE SYSTEM
INDICATION:
• THIS MAY CAUSE THE REFRIGERATION COMPRESSOR TO OVERHEAT, WITH A HIGH DISCHARGE PRESSURE AND NORMAL
CONDENSING TEMPERATURE. • THERE ARE POSSIBILITIES OF SMALL AIR BUBBLES IN THE LIQUID SIGHT GLASS OF THE CONDENSER.
• CONDENSING PRESSURE OF THE REFRIGERANT IN THE CONDENSER MAY BE HIGH.
• IF THERE IS EXCESSIVE AIR, IT MAY REDUCE THE COOLING CAPACITY OF THE SYSTEM, MAKING THE COMPRESSOR TO RUN FOR THE
EXTENDED PERIOD OF TIME.
• IT MAY CAUSE THE GAUGE POINTER OF THE CONDENSER TO JUMP INDEFINITELY.
CAUSES:
• DURING CHARGING, AIR MAY ENTER IN TO THE SYSTEM.
• IF FREON-12 IS USED AIR MAY LEAKS IN TO THE SUCTION LINE BECAUSE THE WORKING PRESSURE OF THE FREON-12 REFRIGERANT
IS LESS THAN THE ATMOSPHERIC PRESSURE.
ACTION:
• AIR IN THE SYSTEM CAN BE REMOVED BY COLLECTING THE SYSTEM GAS IN THE CONDENSER, LEAVING THE CONDENSER COOLING
WATER ON AND VENTING OUT THE AIR FROM THE TOP OF THE CONDENSER BECAUSE AIR WILL NOT BE CONDENSED IN THE
CONDENSER BUT REMAINS ON TOP OF THE CONDENSER ABOVE THE LIQUID REFRIGERANT.
• CONNECT THE COLLECTING CYLINDER TO THE PURGING LINE OF THE CONDENSER, OPEN THE VALVE, AND COLLECT AIR IN THE
CYLINDER.
• AFTER PURGING THE AIR FROM THE SYSTEM DON’T FORGET TO SHUT THE PURGING VALVE.
• PUMPING DOWN, CLOSE CONDENSER INLET VALVE, COOLING WATER AT FULL FLOW, WHEN CW INLET AND OUTLET TEMP BECOME
EQUAL, SEE WHAT IS THE CONDENSING PRESSURE AND FROM COMPRESSOR SUCTION GAUGE FIND OUT SATURATION TEMP AT
THAT CORRESPONDING CONDENSING PRESSURE, IF IT IS EQUAL TO CW TEMP THEN IT MEANS AIR HAS BEEN REMOVED. RESTART
THE COMPRESSOR WITH ALL SAFETY PRECAUTIONS.
• UNDERCHARGING OF REFRIGERATION SYSTEM
INDICATION:
• COMPRESSOR IS RUNNING HOT AND PERFORMANCE OF THE COMPRESSOR FALLS OFF DUE TO HIGH SUPERHEAT TEMPERATURE AT
THE SUCTION SIDE OF COMPRESSOR.
• SUCTION AND DISCHARGE PRESSURE OF THE COMPRESSOR IS LOW.
• LARGE VAPOR BUBBLES IN THE LIQUID SIGHT GLASS.
• LOW GAUGE READINGS IN THE CONDENSER.
• AMMETER READING FOR THE COMPRESSOR MOTOR IS LOWER THAN NORMAL.
• RISE IN ROOM TEMPERATURE WHICH IS TO BE COOLED.
• COMPRESSOR IS RUNNING FOR EXTENDED PERIOD OF TIME.
CAUSES:
• LEAKAGE OF REFRIGERANT AT THE SHAFT SEAL, FLANGE COUPLINGS, VALVE GLAND ETC.
• EXPANSION VALVE MAY BE BLOCKED AT THE STRAINER.
• PARTIAL BLOCKAGE OF REFRIGERANT AT THE FILTER OR DRIER OR EVAPORATOR MAY CAUSE UNDERCHARGING.
ACTION:
• IDENTIFY AND RECTIFY THE LEAKAGE OF REFRIGERANT FROM THE SYSTEM.
• CLEAN THE FILTER AND DRIER.
• CHARGE THE SYSTEM WITH FRESH REFRIGERANT AS REQUIRED.
• OVERCHARGE OF REFRIGERATION SYSTEM
INDICATION:
• THE LIQUID LEVEL IN THE CONDENSER IS TOO HIGH (HIGH CONDENSER GAUGE READING). THIS WILL REDUCE THE AVAILABLE
CONDENSING SURFACE, WITH CORRESPONDING INCREASE IN THE SATURATION TEMPERATURE AND PRESSURE.
• HIGH PRESSURE SWITCH OF THE REFRIGERANT COMPRESSOR ACTIVATES AND STOPS THE COMPRESSOR.
• THE SUCTION AND THE DISCHARGE PRESSURES ARE HIGH.
CAUSES:
• IT MAY BE DUE TO THE REASON THAT EXCESSIVE REFRIGERANT HAS BEEN CHARGED IN THE SYSTEM.
• AIR IN THE SYSTEM MAY ALSO CAUSE OVER CHARGING INDICATION.
• IT MAY ALSO BE DUE TO THE FORMATION OFFICE ON THE REGULATOR.
ACTION: • REMOVE THE REFRIGERANT FROM THE SYSTEM. THIS IS DONE BY CONNECTING A CYLINDER TO THE LIQUID LINE CHARGING VALVE,
STARTING THE COMPRESSOR, AND THEN OPERATING THE CHARGING VALVE.
• PURGE THE AIR FROM THE SYSTEM AND MAINTAIN EFFECTIVE COOLING.
• REMOVE ICE FROM THE REGULATOR BY USING ANY OF THE DEFROSTING METHODS.
• MOISTURE IN THE SYSTEM
THIS NORMALLY COMES WITH THE INGRESS OF AIR IN THE SYSTEM. MOISTURE MAY FREEZE AT THE
EXPANSION VALVE, GIVING SOME OF THE INDICATION OF UNDER CHARGING. IT WILL CONTRIBUTE TO
THE CORROSION IN THE SYSTEM. IT MAY CAUSE LUBRICATION PROBLEMS AND BREAKDOWN OF THE
LUBRICATING OIL IN THE REFRIGERANT COMPRESSOR.
ACTION:
• RENEW SILICA GEL IN CASE OF MINOR MOISTURE.
• COLLECT REFRIGENANT AND REMOVE ALL AIR AND MOISTURE BY VACUUM PUMP IF THE AMOUNT IS HUGE.
69. recharging LO in refrigerant compressor.
- Collect the refrigerant into the condenser by shutting off the condenser outlet valve.
- Stop the compressor and shut off the inlet and outlet valves of compressor.
- Open the oil filling plug and start filling the oil slowly.
- Start the compressor momentarily(0.5- 0.6 seconds) to facilitate speedy charging.
- After charging to the correct level, tightened up the oil plug.
- Bleed off air in the compressor casing by slightly opening the suction valve and loosening connecting caps from the high
pressure gauge (In case connection fittings for vacuum pump are provided, use the vacuum pump to extract the air from the
compressor crankcase).
Extracting Oil
- i. Pump down the refrigerant into the compressor only. Ensure that refrigerant
- pressure is higher than the atmosphere.
- ii. Loosen the oil drain plug in the compressor crankcase and extract the amount oil.
Precautions:
- 1.) Care to be taken when charging oil so that no air will be trapped in the
- compressor crankcase.
- 2.) Ensure to bleed off air every after charging and extracting refrigeration oil.
Q. bulb in thermostatic exp v/v has come off...what will be the effect??reasons 4 icing on
expansion v/v?
Q.what is short cycling OF REFRIGIRATION, reasons and what u will do? Refrigration system LO
properties. recharging LO in refrigerant compressor? 2.what is the function of condenser..what is
sub cooling..?what will u check to insure that condenser is working properly...what will happen if temp diff
between inlet and outlet of cooling sea water is increasing(cooling water flow is less or chocked) or
decreasing(scaling,) and how will u make sure that it is being restored? Changing of filter drier of ref.
comp?
ANS. For changing filter drier. We can do this when plant is running. Open bypass v/v. close
inlet outlet of drier. Change drier. open inlet outlet n close bypass.
Q. Tev equalising connection. Why?
ANS. We use where evaporator is large. So we have different pressure at inlet and outlet. Act as
second line of defense. That is if bulb comes out then. Q. Did refrgrt’n compressor have relief door?(NO) Why not?(crankcase doesn’t have o2,so
chances of fire is very less.temp. so less bcoz of cool refrigerant .and. also vol. of crankcase is
less so no need as per regulation)
Q. refrigeration oil separator working, type complete...why required?
ANS. Impingement type- fitted in discharge line. Its a closed container fitted with a series of
baffle. As vapour enters the oil separator, there is reduction in velocity due to larger area of
separator. Since oil particles have greater momentum, they impinge on the baffles. And later
gets drained to crankcase through a float valve.
3. What is suc. Press. of refer and AC plant....is thr any diff ..if yes y?
AIR. CONDITIONING
WHAT IS SPECIFIC HUMIDITY, RELATIVE HUMIDITY, SENSIBLE HEAT, WET BULB TEMP, PSYCHOMETRIC CHART,
HOW TEMP. IS CONTROLLED IN AIR CON. SYSTEM, LIGIONILA BACTERIA,
MAIN ENGINE AND AUX. ENGINE FULL FORM
Q. Make and type of a/e and m/e with meanings. Alarms,interlocks, trips on that.
ANS. M/E-MAN B&W 6S46MC-C
MAN-MASCHINEN FABRIK AUGSBERG NURMBERG (DENMARK), BURMEISTER AND WEIN (GERMANY)
6-NO. OF CYLINDERS , S-SUPERLONG STROKE,APRROX. S/B RATIO-3.8 AND ABOVE(OTHER IS L,LONG STROKE-3.2 AND SHORT
STROKE ,K,S/B RATIO-UPTO 2.8)
46-CYLINDER BORE IN cm , M-ENGINE PROGRAMME
C-CAMSHAFT CONTROLLED(OTHER USED IS E-ELECTRONICALLY CONTROLLED)
C-COMPACT, In 1996 and onward the MC-C versions of the small and medium bore engines were added to the
programme. In this case the -C stands for "compact", as the engines were intended to be lighter, cheaper and yet more
powerful. They feature an integrated camshaft housing, simplified cross-head and a variety of other smaller changes to
facilitate the "compact" concept. In exchange the fuel injection system was simplified and the VIT system was made an
option. The small and medium bore MC-C engines are thus best suited to vessels operating for prolonged periods at the
power at which the engines are optimised.
AUXILLARY ENGINE - 5H 21/32
5-NO. OF CYLINDERS, H-HYUNDAI’s HIMSEN(HIMSEN STANDS FOR-Hitouch and Hitech Medium Speed Engine)
21-CYLINDER BORE IN cm , 32-PISTON STROKE IN cm MAIN ENGINE AND A/E
STARTING AIR SYSTEM
How starting air system works, interlocks, function of …..air distributer(to select timing n
sequence), master starting v/v, safeties provided, why bursting disc or flame arrestor….their
working, regulation (for cyl. Bore 230 mm or more+reversing then on all cyl.)and construction,
what action if…..bursting disc bursts during maneuvering, starting air v/v gets stuck, how you
will come to know, what extra precaution if m/e running with one starting v/v isolated, why
negative cam for air distributor, crash maneuvering how, how starting and reversing takes place
in MAN B&W n sulzer, regulations regarding reversing capacity of engine, why air bottle v/v is
slow opening type, regulations regarding size of air bottle, material of….. air bottle(seamless low
carbon manganese steel), starting air line, starting air v/v(cast steel body, stainless steel v/v n
spindle), why overlap is necessary, timing dig. For uniflow, loop, and 4-st naturally n
supercharged engines, how starting air is introduced in ME type engine(starting v/v is solenoid
controlled,no air distributer), is thr a drain line in starting air line (yes, at lowest point in the
pipe), starting difficulties,what starting arrangement on A/E, why not air kick started,
ANS. In cases where the starting air supply has to be cut off to some cylinders, starting in all
crankshaft positions cannot always be expected. If the engine does not turn on starting air in a certain
crankshaft position, it must immediately be started for a short period in the opposite direction, after
which reversal is to be made to the required direction of rotation. Should this not give the desired
result, it will be necessary to turn the engine to a better starting position, by means of the turning
gear. Remember to cut off the starting air before turning, and to open the indicator cocks.
For checking- close master v/v, engage turning gear, open indicator cock, bring that piston to tdc,
open master v/v, if air coming from indicator cock that means leaking.When an engine is in operation leakage of
starting air valves is shown by overheating of the branch pipe connecting the starting air valve to the starting air rail. The heating
occurs due to the leakage of hot gases from the engine cylinder into the starting air line connected to the starting air rail. During
periods of manoeuvring the temperature of each supply pipe from the air rail to the starting air valve should be checked by feeling the
pipe as close to the valve as possible.
WHAT SHOULD I DO IF AN AIR START VALVE JAMS OPEN WHILST MANOEUVRING?
The fuel pump should be lifted (fuel rack zeroed, puncture valve operated or whatever) on the affected unit and the bridge informed.
The load should be kept at a minimum, as one unit is now out of operation. As soon as safe to do so, the engine should be stopped
and the air start valve replaced.
ANS. BODY REQUIREMENTS FOR A REVERSIBLE ENGINE
The main propulsion machinery is to be capable of maintaining in free route astern at least70% of the
ahead MCR revolutions for a period of at least 30 minutes.
The reversing characteristics of the propulsion plant are to be recorded during trails.
The power developed in astern direction should be 60 %of ahead.
SOLAS Requirements: Chapter Two (Reg. 28 & 03)
1. Sufficient power for going astern shall be provided to enable proper control of the ship in all circumstances.
2. Machinery should be able to reverse the direction of thrust of the propeller to bring the ship to rest from
maximum ahead service speed in sufficient time and reasonable distance. This shall be shown and
recorded.11. Crash-Stop
(FPP-Plants and Reversible CPP-Plants)
The procedure is valid for:
! Control Room Control. See Items 8.2, 9.2 and 10.2.
! Control from Engine Side. See Items 8.4, 9.2 and 10.4.
Regarding crash-stop during Bridge Control,see the special instruction book for the Bridge Control System.
1. Acknowledge the telegraph.
2. Give the engine a STOP order.
The engine will continue to rotate (at slowly decreasing speed), because the velocity of the ship through the
water will drive the propeller, and thereby turn the engine.
3. Check that the limiters in the governor are not cancelled.
4. When the engine speed has fallen to the REVERSING-LEVEL (15-30% of MCR-speed, depending on engine
size and type of ship, see Plate 70305):
! Give REVERSING order.
! Give START order.
5. When the START-LEVEL is reached in the opposite direction of rotation (8-12% of MCR-speed)
! Give order to run on fuel.
CRANKCASE EXPLOSION, SCAVENGE FIRE, EGB FIRE
CRANKCASE EXPLOSION -Safeties provided in crankcase, regulations, at what
pressure crankcase door lifts, how many doors, total area of escape in relief door, how do
u test the v/v, OMD alarm , what will u do ? How to check it’s false alarm, What are
different types of oil mist detectors and where are they used and why? How oil mist
formed in crankcase and what safeties provided and maintenance on them? Do all
crankcase doors in A/E have relief v/v? What to conclude if fitted in alternative doors or
only in fwd n aft? Why no crankcase relief v/v in air compressor and reefer compressor.
SCAVENGE FIRE -reasons(give at least 6), indications, action to be taken when passage
through a narrow seaway, what if major fire takes place, what extinguishing arrangements
is there, how to use that? WHAT PRECAUTIONS WHEN ENGINE IS RUNNING on less number of
units?
ANS. MANUAL 704.
Cyl. Oil properties( oilyness is imp.)? After how many cycle alfa lubricator injects fuel?( every 4
th
cycle)
Why exhaust gas temp. is less at exhaust v/v(320*c) but more at entry to turbine(380*c)??pressure of exhaust gas after turbocharger(0.3 bar).
Ans. Its bcoz of intermolecular collision. Also at nozzle the pressure decreses which increases the velocity. Now PV=NRT. As p decreses, t
decreses.
Can you change the fuel injection timing or stop the fuel flow in one of the 3 injectors in a single unit in RT-flex.
Yes, we can stop the fuel through any one injectors at a time. WECS can give signal to any one of the rail valve separately and hence
the particular injection control valve will operate and the particular fuel injector will inject the fuel. This improves the injection pressure at low rpm and loads and
hence improve combustion.
Main brg, x-head brg seizure…action?
How to know that there's an instrumental error from the crankweb deflection readings or we have
not taken reading correctly? to know dat error... We add p+s reading nd f+a reading..nd diff shuldn't vary much...if it vry much den may
be dere s problem in gauge... or we have not taken reading correctly, also the reading on both sides around
bdc shud come zero.
6. How to cut off a fuel pump? Why not cut off by closing fuel inlet valve to that
cylinder? ANS. MANUAL 704 AND VOL 2,909-16.
Q. water cooled piston vs. oil cooled piston adv & disadv. & why oil cooled piston were not used earlier if they
r have so many advantages? Bore cooling? advan.?
ANS. Water- advan- specific heat more than oil so less amount of water is needed, easily available n cheap,
we can keep water temp. as high as 90*C so temp. diff is low whereas in case of oil upper temp. Limit is 65*C
to prevent oxidation.
Disadvan- chances of mixing with crankcase oil, need separate system with p/p etc.
Bore cooling-advan- max. temp at piston surface can be reduced to 400*C from 500*C as in case of cage type
cooling, problems with castings of internal ribs r not thr.in bore system cooling takes place by jet n shaker
effect.
Q. A/E cyl. head has been removed. What all checks to be carried out? what on piston?
ANS. Cracks, distortion, corrosion, cooling water side corrosion n scale etc.
Q.after taking liner calibration f-a readings are more and p-s readings are less.... What is this
phenomenon... And y does it happen?
ANS. Trim is more, ship is moving too much in ballast condition.
Q. How to take cylinder liner calibration for M/E n A/E(both have same method)?consquences
of operating with worn liner? how to calibrate template?max. wear(0.7% of cyl.
bore).honing(gulia244)?running in(done for matching to reduce adhesive wear)(r.sen41)?liner
material(gulia p249), antipolising ring(material is steel, r.sen70)?
Q. is crankshaft able to move axially ,if it does what prevents it, how is thrust taken;full
description? What is axial and torsion vibrations how they are reduced in engine? Moment
compensator everything?
ANS. Axial Damper: The Axial damper is fitted on the crankshaft of the engine to dampen the
shaft generated axial vibration i.e. oscillation of the shaft in forward and aft directions, parallel to the
shaft horizontal line.
It consists of a damping flange integrated to the crankshaft and placed near the last main bearing
girder, inside a cylindrical casing. The casing is filled with system oil on both side of flanges supplied
via small orifice. This oil provides the damping effect.
When the crankshaft vibrates axially, the oil in the sides of damping flange circulates inside the
casing through a throttling valve provided from one side of the flange to the other, which gives a
damping effect.(see r.sen 13.10)
Q .How was your engine piston cooling …line diagram, temp. and pressure, how is the
telescopic pipe arrangement…how will make sure proper cooling .. a very important alarm
on it? Explain crosshead lubrication. What modification ..(SEE 904,708,r.sen26)Why oil is
supplied to shoes, not guide in xhead lubrication?bore relief? tangential
runout?clearance(m/b 0.4-0.6,crankpin0.2-0.4,crshd0.2-0.3? Main engine's main bearing
clearance. BOTTOM END BEARING CLEARANCE? ANS. it will make the system complex bcoz then we will have to make quills like
arrangement at many points. Also we have to make lub. Oil enter crosshead at last so
supplying to shoes is better.
Q.excessive liner lubrication in main engine? EFFECTS? desired properties of cylinder lube
oil(oilyness,viscosity, tbn, viscosity index)? Where r quill. If at bottom what happen, why
thr(p152 r.sen)how lub oil spreads on cylinder....what is clover leafing?
3. Types of indicator cards, purpose if each, draw all diagrams on single ordinate and abscissa with
timing diagram for 2 stroke engine, which diagram suggests error in ir indicator instrument, how to
take atmospheric line, what is 90 deg in phase and 90 deg out of phase, draw power card and draw
card at a situation when you are taking card and engine tripped on some mechanical trip? what will
be the maximum pressure you vil get then..? What is mean effective pressure..how to find
out mip?why we do not use indicator instrument for A/E(see sanyal p309?
Why draw card is called 90 degree out of phase?
In books it is written that ... draw card is taken with indicator drum 90 degree out of phase
with the piston stroke, so it is called out of phase diagram..
My DOUBT...while taking draw card the indicator drum is rotated manually with the help of
string attached to it.So if the rotation of the indicator drum is controlled by us,then how come
it is said to be exactly 90 degree out of phase.
this is purely on experience...nothing else....people took draw cards on experience and after so
many trail and error practices nothing else...
Q. why tappet clearance...what u check before tappet clearance(engine cold, n piston on
firing tdc).... procedure... what is tappet clearance, what is its effect if increased or
decreased? adjustment, tappet on my generators(0.4 in inlet n 0.9 on exhaust), how will u
remove exhaust valve of generator. Tappet adjustment in engine having two inlet and
exhaust v/vs(first balance yoke then adjust tappet)? what checks you will make on inlet and
exh v/vs springs during overhaul(check length,twist). how they held in position? Q.what is viscosity? Types? Viscosity index? SFOC and hw to calculate? cetane no,what if
less? Fire point, ignition point, flash point, pour point,oiliness? Fuel knock and how u
know it(by Fluctuation in rpm, after burn(spark from the funnel, smoke from exhaust). ignition
delay.def.wt governs it?hw it can b minimised?what property of fuel oil is responsible for it?
Q. expansion tank purpose (give six)..why we call it expansion tank? It is also called
compensation tank.
ANS.1. SINCE IT IS SITUATED AT HIGHEST POINT IT MAINTAINS CONSTANT HEAD ON THE SYSTEM AND SO
REDUCE CHANCES OF AIR INGRESS OR STEAM FORMATION. 2.ALLOW FOR EXPANSION. And place for adding
chemical for treatment. 3.PROVIDE A PLACE FOR ADDING MAKE UP FEED,BCOZ OF LEAKAGE AND
EVAPORATION.
1.T/C lubrication(manual708)?what is surging....and hw it occur? and what will u do if
continuous surging takes place? outboard bearing inboard bearing? From main lub oil
system? In case M/E z stopped ….what provision z provided for its lubrication? T/C MAKE
(met type)water n dry washing (see r.sen,tur. Side dry 24-48 hrs n wet every week) kab karte
h. running indications dat it cleaned? pressure of exhaust gas after T/C(0-350mmWC). function
of inducer(guide air smoothly to centre of impeller) and impeller(p181r.sen). P-V diagram of
impeller.,inducer, diffuser, locking of t/c, blade fixing.
Q. Butt clearance will increase or decrease after 8000 hrs? What about stuffing gland rings?
ANS. Butt clearance of piston ring (intial 0.5-1% cyl. Bore)will increase and those of stuffing
box rings( 3 and 4 mm) will decrease with time. When butt clearance of stuffing gland
becomes zero then we change the ring.
Q. Uniflow scavenging, name other 2, which 1 is better and why, which 1 has more power
stroke and why?
ANS.LOOP FLOW and cross flow. Uniflow is better because there is less intermixing of
scavenge air and exhaust gas.BecOz there is no change in the direction of scavenge air in the
cylinder.and when cyl. Length is more than loop n cross scavenging becomes difficult. Uniflow
has more power stroke bcoz of better scavange efficiency and use of super long stroke.
Q. why is a balance weight fitted ? why not in main engine?
ANS. balance weight r fitted only in a/e bcoz during exhaust stroke piston tries to fly out n also
to reduce 1
st
order moment. In m/e 1
st
order moment r compensated by providing idle gear in
chain drive arrangement.2
nd
order moment is also compensated by providing a smaller idle gear
which rotate at double the engine rpm and is fitted at chain drive. Q. what is difference between valve rotocap and spinner and why rotocap on A/E and spinners on M/E, what is
the driving force in both of them..Maintenance and parts of valve rotocap..?no. of cotter and why only
those no. of pieces, purpose of cotter??
ANS.SPINNER ARE JUST VANES,NORMALLLY 6-8 IN NUMBER. M/E EXHAUST V/V IS BIG.AMOUNT OF
EXHAUST IS MUCH MORE SO IT CAN ROTATE THE V/V.BUT IN A/E AMOUNT OF EXHAUST IS LESS SO IT IS
NOT POSSIBLE TO ROTATE SPINNER BY EXHAUST IN A/E SO WE USE ROTOCAP. Cotter is In a/e, it holds
the exhaust v/v spindle, its in 2 pieces held in place by a cir-clip.
Q. why 2stroke engines for propulsion and 4stroke engines for power generation..?CAN WE PUT PROPELLER
IN FWD OF SHIP (propeller efficiency will increase but hull efficiency will decrease)?
ANS. M/E SHUD BE SLOW SPEED ENGINE FOR BETTER HULL EFFICIENCY. N 2ST engine are more efficient at
slow rpm. At high rpm scavenging becomes difficult. GIVE LONG STROKE CONCEPT, TWO ST. MORE POWER
PRODUCED.
Q.LO tests ( all five with name and how pensky martin test carried out ).
83. with respect to A/E Piston what is the name of the top most piston ring? How will one identify which piston
ring goes in which groove if the rings get intermixed????
Top most ring is known as compression ring.Every piston ring has engraved marking....that can be matched with that
given in manual. Also can be compare with the sequence in which the piston ring of other piston of the unit is arranged.
Q. piston ring calibration??
Groove clearences : Necessary because
– to ensure free in and out movement of the ring in the groove to suit the liner bore.
- to allow the gas to pass in the clearance space to press the ring against the liner.
If their is cabon deposits in the groove or the groove clearance is too low then gases may pass directly between liner and
piston ring outer surface and pushing the ring in to the groove causing Ring collapse.
If the Ring clearance is too high then hammering and reduction of piston ring landing surface area in grooves, resulting
breaking of ring and liner crack.
Vertical Groove clearance : around 0.4mm and ring should be renewed if it reaches 0.7mm
Butt clearance : Will allow thermal expansion. If too large -à blow past.
Between 0.5 – 1% of the liner bore.
MAXIMUM ALLOWABLE BUTT CLEARENCE IS NOT USUALLY SPECIFIED AS LIMIT OF 15% WEAR ON THE RADIAL
THICKNESS OF THE PISTON RING AUTOMATICALLY PUTS A LIMIT TO THE BUTT CLEARENCE
Q. why in a/e crankshaft is drilled for lubrication but not in M/E?
ANS. By drilling a hole in crankshaft, its strength is reduced and crack and failure may occur. So
we use it only in a/e and not in m/e.
Q. T/C lub oil. dis-color..reasons... labyrinth sealing..material n how many.?
ANS. Exhaust gas leaking due to leaking labyrinth seal, oxidation, lub. Oil burning due to high
temp. forming deposits, if lub. Oil cooling by water then may be due to water contamination.
Q. thrust bearing ,purpose ,is it fitted in A/E(yes),purpose there ? thrust brg .... working(last
main bearing towards alternator is thrust bearing,it is provided bcoz during power stroke axial opening of web will occur,so thrust will be there.to absord that thrust it is provided,see
r.sen p292) . What is the role of holder bridge in a thrust block and how thrust is transferred
to the ship’s hull.(SEE R.SEN p54).
Q. overhauling of A/E fuel injector and testing, M/E fuel injector overhauling and testing? Did fuel
injectors can be separately injected in both? (YES in ME type) will it increase the combustion
pressure?
Q. stuffing box diagram with rings name,, scrapper ring ,,sealing ring clearances?
1- how quills and lubricator works with diagram,how pressure is developed in lubricator and
how pressur is maintained in quills? liner ovality? why liner wear in f-a part? in 1 unit it is
found to be more than other..y? how to rectify?safeties?tools?
ANS. It is boundry lubrication. Liner wear down is normally more in p-s direction but in tanker
during long ballast passage it is more in frwd- aft direction due to trim. Mainly in aft.
47. what s running direction interlock? hw s d arrangement? hw it s working?(refer arahna)
If the direction of rotation of the engines contrary to the command from the Telegraph, we consider it as
the'wrong' direction. In this situation, the fuel cut out servo must operate to shut-off fuel, in case the engine is already
running. In addition, the starting air is not allowed to be released, thus preventing the re-starting of theengine in the
wrong direction. The Running direction interlock in this engine is connected to the camshaft, and will be operated by the
movement of the camshaft. If the camshaft does not reverse, then oil pressure does not act on the fuel cut-off
servomotor, as can be seen in the sketch below. Thus fuel is cut-off.
Q.black smoke(excess oil,less air), white smoke(excess moisture),blue smoke(lub.oil
burning),yellow(excess sulphur).
2-what are the causes of liner wear down ? when piston rings are stuck or broken what it is
called exactly(engineering term)?
ANS.1. CORROSIVE WEAR( high n low temp. corrosion),ADHESIVE WEAR(DUE TO IMPROPER
LUBRICATION),ABRASIVE WEAR.
Q. crankcase inspection of auxilairy engine, what is pinching of connecting rod(moving
con. Rod with crowbar sideways), elongation gauge's use for measuring bottom end
bearing bolts.
2. NO. OF TIE RODS IN A 6 cyl M/E, purpose? how u will come to know that its slack, how slackness is
measured? What is pinching screw? Action if tie rod is slack (retighten)? How to remove broken tie-rod?
Can we run engine with broken tie-rod (yes, but reduce load)? Can u see any tie rod from above? Are
their tie-rods in A/E(no bcoz single casing type n have underslung crankshaft)?
ANS. (2n+2) n = no. of cylinder. SEE MANUAL VOL 2,912-3
Did your engine can be adjusted for Exhaust valve timings? Why?(YES) ANS. NORMALLY WE DON’T CHANGE but we change if chain slack. here we also take
virtual tappet clearance. Taken in running engine at full load.
Q. resin chocks?how it better than conventional one??where fitted,hw fitted and y
fitted??(SEE ARHANA)
5. Radial T/C vs Axial T/C? Advantages? Emergency lub. Of turbocharger? Why coil spring is
being replaced by spring air in M/E? Can u see ne moving part in exhaust V/V from outside?
What it represents?
ANS. We can see rotation check rod from outside. During working it rotates showing that v/v is
working. We can also check that v/v s closed or not if needed during adjustment.
3.what is SAC vol in injectors..?
The “Sac” is a small volume within the fuel flow path of an electronic fuel injector. In this study, it is defined as the volume between the valve seat (fuel shut off
point) and the entrance to the final metering orifice of the injector. This sac causes fuel injectors to deliver uncalibrated excess fuel .
Q. What is super long stroke and its advantages. Its effects and changes that have been made in engine
design to counter its effects.
ANS. Superlong stroke= stroke/bore ratio is more then 3.8. advantages= cheaper fuel can be burnd as more
time is available for burning, hull efficiency is more when we have slow turning large dia. Propeller but we
can’t increase mean piston speed above certain limit. Now since m.p.s = 2x stroke x rps. So to reduce rpm we
increase stroke.
q. why turning moment is more while running ahead than astern?? Why torque on rudder is more
while running astern??
turning moment is more in running ahead due to neutral point which is about L/6 dist. from fwd and
when running astern it is from aft...........and running astern greater force act at rudder so higher
torque.......
Q. how to calculate SFOC, POWER? How to calculate power if indicator fucked.?( torsiometer)
Q. Difference b/w MIP n MEP?
ANS. MIP=the pressure which when acting on the piston will perform the same work as performed during the
cycle.
MEP= theoretical pressure acting on the engine during power stroke.
Q. overhaul of globe v/v &gate v/v. and inspection in spindle? ANS. globe v/v -Remove the wheel nut and the wheel handle.Open the bonnet bolts and the top portion of the valve
along with the valve seat, stem etc will come out. The bottom portion of the valve will be separate.Hold the bonnet in a
vice and open the gland bolts. Then loosen the gland flange and the gland bush. The valve stem should then be screwed
clockwise and it would come out from below along with the valve disc.bcoz thread Is not in full portion so it will damage.
Remove the set screw that is securing the valve disc to the stem. Remove all the gland packing’s with a gland packing
extractor.
Gate v/v
Open the wheel nut and remove the hand wheel. Open the gland bolts and slacken the gland flange and the gland
bush. Open the bonnet bolts and remove the bonnet along with the bonnet and the valve wedge. Unscrew the valve
stem from beneath the bonnet.
inspection in spindle 1.Check all the threaded parts for damage and if there is any damage on the thread then the
threads must be dressed by a needle file.
2. Check the stem for straightness. The simplest method of checking is by rolling on a flat surface, but the correct
method is to put it on a lathe and center it. Thereafter with the help of a dial gauge put on a magnetic stand at a
suitable point, check the distortion.
3. Check the stem for scratches, as these can damage the gland packing. Any scratches must be removed with an
emery paper or oil stone.
4.The valve and the valve seat must be inspected and if found to be in fairly good condition, they must be ground
together by using a guide for centering and a suitable grade lapping paste. A 1200 grit lapping paste would be suitable
in most conditions (carborandum).
How we knw that lapping is done- 1. Apply Prussian blue on seat. Turn v/v by one turn. If all v/v gets colored then
ok else v/v or seat is not properly even. So more lapping.
2. Mark pencil mark at some places on seat. Put v/v n turn half round. If all mark gone then ok else do more lapping.
SAME LAPPING CHECK MEHTOD FOR EXHAUST V/V.
ELECTRIC ARC WELDING
Q. Procedure and safeties for electric arc welding. Which current source is preferred, AC or DC.(AC bcoz more compact plant, high
efficiency, less initial cost and less maintenance). Butt weld and lap weld? Name various parts where such welds are carried out?
soldering??
ANS. Procedure- in electric arc welding, electric arc is used as a source of heat to melt base metal and if filler metal is used then filler
metal also. Power source has two cables with holders. An electrode is used which has filler metal at the core and a flux coating (of
metal alloy, cellulose etc) outside to protect the molten metal from oxidation. Electrode’s bare part is clamped to electrode holder. The
other holder is connected to base metal. Electrode current= KxD. K= 40-60. D= 5mm dia. for thickness more than 5mm.
Power source- normally we use high voltage and low current system. But for welding we need high current, low voltage system. So
we use transformers for AC and welding generator n rectifier for DC. For DC open ckt voltage is 50V(so DC is more safe).For AC
system, open circuit voltage is around 80V(bcoz voltage shud b high enough to strike an arc and low enough to b safe for welder). Safeties-worn in addition to the personal protective equipment, Welding should not be carried out in hot/humid conditions
which might cause sweat or damp clothing. Under no circumstances whatsoever should a welder work in wet conditions.
Wear welder's goggles or a face shield. Buttweld-the weld is formed by placing two pieces of metal with their edge side by side n
then welding the edges together. Lap weld-made by placing one piece of metal on the other so that they overlap .edge of upper is then
welded to the surface of lower.
Q. What are pms and cms…. What are all the system you had in your ship according to pms ..and cms?
Ans. Class societies allow special status to ships with well implemented PMS. Survey of various machinery components
is performed usually with regular Class surveyor inspection, and it is based on schedule given in Continous Machinery
Survey. Surveyor comes to ship several times per year and inspects various machinery components, determining their
condition. Inspection is scheduled every five years and the system is intended to assure good functionality of ship's
machinery and therefore safety of the ship. As PMS is increasing overall safety and reliability of the ship, Class societies
allow another form of Survey to be performed on the ships with well established PMS. Most of CSM inspections (all
except steering gear and pressure vessels) is carried out by Chief Engineer, based on regular PMS jobs, and Class
surveyor is coming on board the ship only once a year to inspect items Chief Engineer is not entitled to and to check what
items were inspected since last Class inspection.
Q. engine room overhead crane safeties n maintenance ?why lower n upper limit switch is provided? What type of brake n its
working?
Crane takes the load due to the friction b/w the rope windings and the drum. So the number of windings should never go less then
certain number. So we provide lower limit switch.
Upper limit switch is to trip the motor on reaching max. up.
1)electromagnetic brakes are used which are fitted inside the rotating drum. They keep compressing a spring by power n
when power goes, the spring applies the brake.
2) Emergency stop is provided in the remote so that the operator can stop the crane at any time.
3)motor is fitted with distance limit switch in both transverse and longitudinal direction, up and down direction so that the
travel of the trolley and hence crane should not overshoot the rack’s end. Mechanical stoppers are provided for both
directions in case the electrical distance limit trips fail.
4) motor is fitted with thermal protection trip. When the motor windings get overheated, trip will activate saving the motor
winding from burning.Load limit switch is also fitted which will trip the motor if the load to be lifted is above the crane
capacity.
5) Additional tools like i-bolts, shackle, wire sling, belts etc. used for lifting must be checked before use. No one walks or
stand below the crane when it is in the loaded condition.
ACETELENE STORAGE
Q.how acetelene(C2H2)stored in cylinder??why it is stored in form of acetone?? what is pressure and safety? Flashback
arrestor….where placed n working?
ANS. ACETYLENE When burned with oxygen, produces a hot flame, having a temperature around 3000°C. Acetylene
odor that is readily detected even when the gas is highly diluted with air. Pure acetylene is self-explosive if stored in the
free state under a pressure of 2bar.A slight shock is likely to cause it to explode. Acetylene becomes extremely dangerous
if used above 1atm(1 bar).Cylinder Design Acetylene can be safely compressed up to 18 bar when dissolved in acetone
and stored in cylinders filled with porous material, such as charcoal, portland cement or firebrick. These porous filler
materials aid in the prevention of high-pressure gas pockets forming in the cylinder. Acetone is a liquid chemical that
dissolves large portions of acetylene under pressure without changing the nature of the gas. Being a liquid, acetone can
be drawn from an acetylene cylinder when it is not upright. You should not store acetylene cylinders on their side, but if
they are, you must let the cylinder stand upright for a minimum of 2 hours before using. This allows the acetone to settle
to the bottom of the cylinder. NOTE: Acetone contaminates the hoses, regulators, torch, and disrupts the flame.
Q. Where should a Flashback Arrestor be placed? Its Working?
The flashback arrestor should be placed at the closest point to the flame, if due to un-avoidable circumstances the Arrestor cannot be
places close to the cutting nozzle or the flame then it should be placed of the main pipe line, and also on the fuel gas bank, vessel,
cylinder. Flashback arrestor quenches the flame using the following methods
a) By reducing the velocity of the flame, reducing the flame velocity even lower than the minimum flame velocity of the fuel gas
b) Stops the flame propagation into or through a pipe. By placing a flame arrestor at the end of the flammable mixture pipe
feeding a flare or burner, flame can be prevented from moving into the pipe regardless of the mixture velocity. OR By
passing a potentially flammable mixture through a water chamber or some sort of heat sink. This dissipates the heat and
quenches the flashback. OR By blocking the fuel gas path, with a suitable thermal fuse plug, casing the flashback to die out.
OR By blocking the flow of fuel gas in the opposite direction by acting like a non return valve.
Online flame arrestors (passive) – (most commonly used)
Mechanical flame arrestors are filled with metal or ceramic, which absorbs heat from a flashback, quenching it to a temperature below
what is needed for ignition. This stops the flame. With a low enough hydrocarbon/air mixture flow rate, if a flame travels to the face
of the arrestor, it can become stable at that point. Heating of the arrestor body and internals results. Once the arrestor temperatures
increase enough, ignition temperature can be reached on the upstream side of the arrestor and the flashback can proceed. For this
reason, a temperature switch is often installed on the flame side of each arrestor (adding an "active" element).
Q. Type of pump for emergency bilge suction,M/E fuel supply p/p,M/E fuel circulating p/p. lub. oil system of m/e type of pump
.why so? why not c/f p/p? if so then y? where to be fitted? what must b the minimum capacity(MY SHIP capacity 280m3/h at 4
bar)?y that much only?
ANS. M/E LUB. OIL P/P,FUEL SUPPLY P/P,FUEL CIRCULATING P/P- ITS SCREW P/P AND E/M BILGE P/P IS CENTRIFUGAL P/P(see
p367reeds). m/e lub. Oil p/p can be centrifugal p/p but then its impeller is open type and is provided at bottom by increasing the
size of spindle so that there is no problem of priming.
Q. Bilge injection valve dia.?features?
ANS. EM/GNCY BILGE INJECTION V/V- IT’S A SDNR V/V.DIA –ATLEAST 2/3 OF DIA OF MAIN SEA WATER
INLET.VALVE HAND WHEEL OF THIS V/V AND MAIN SEA WATER INLET V/V MUST BE ATLEAST 0.46m ABOVE
FLOOR.E/M BILGE INJECTION V/V IS FIITED TO HIGHEST CAPACITY P/P(MY SHIP 310m3/h).v/v is fitted after p/p
suction v/v so that thr is no need to open suction v/v of p/p. emergency bilge suction pump has no suction filters fitted
before and after the valve. Emergency bilge suction is used only at the time of engine room flooding.
Q.what is proof stress? destructive and non destructive tests?swl?
ans. proof stress can be found by referring to the stress/strain curve at the point where strain is = 0.2%
original volume (the material has grown 0.2% in volume) proof stress will be given as a measurement of
energy (MPa,KPa etc.) as it specifically refers to the amount of energy required to stress the material to
0.2% its original volume. This value approximates to the yield stress in materials not exhibiting a definite
yield point.
SWL is determined by dividing the minimum breaking strength (MBS) of a component by a safety factor
assigned to that type and use of equipment. The safety factor generally ranges from 4 to 6 unless a failure
of the equipment could pose a risk to life; in that instance the safety factor would be a 10.
Q. which all parts to be dye tested during decarb?(crankshaft,piston top surface,piston grooves,Bearings).what is meant by
removing excess dye(dye colour is RED, developr white)?how developer draws it up from crack?
Ans. If excess penetrant is not properly removed, once the developer is applied, it may leave a background in the
developed area that can mask indications or defects. In addition, this may also produce false indications severely
hindering your ability to do a proper inspection. The developer draws penetrant from defects out onto the surface by
reducing surface tension of the dye and by capillary action to form a visible indication, commonly known as bleed-out. Any
areas that bleed-out can indicate the location, orientation and possible types of defects on the surface. [the indication size
is not the actual size of the defect] FRESH WATER GENERATOR
Q. why is necessary to maintain temperature of shell of fwg, if temperature is increasing possible cause and solution. fresh water
gen yield z reduced, possible causes? what was d disch rate of ur ejector pump? fwg principle and wrking?Routine maintenance
on a fresh water generator?With the time the dia. of the nozzle of air ejector enlarged ,how to check (erosion)?Overhaul of fresh
water generator. fwg starting? How 2 make fwg water portable..what is dolomite filter(it increase ph n ad mineral)how it add
minerals 2 water....what r the minerals(K,Ca,Na etc)?
ANS. IF SHELL TEMP. IS LESS-FRESH WATER PRODUCTION WILL REDUCE. IF SHELL TEMP. IS HIGH- ABOVE 80C,THEN FORM HARD
SCALE DEPOSITS OF MAG.HYDROXIDE(MgOH),CALCIUM SULPHATE.AT LOWER TEMP. FORM SOFT DEPOSITS OF CALCIUM
CARBONATE.)
IF TEMP.IS INCREASING THEN CAUSES- 1.SCALE FORMATION IN SHELL ,2. IMPROPER AMOUNT OF FEED WATER SUPPLY. 3. JACKET
WATER TEMP. INCREASING.
Q. CENTRIFUGAL PUMP TROUBLESHOOTING??
TROUBLE CAUSE
Does not deliver any liquid Insufficient priming liquid
Insufficient pump speed
Excessive discharge pressure (such as a partially closed valve or some
other obstruction in the discharge line)
Excessive suction lift Clogged impeller passages
Wrong direction of rotation
Clogged suction screen (if used)
Ruptured suction line
Loss of suction pressure
Insufficient capacity
Crackling noise from the pump
casing
Air leakage into the suction line
Insufficient speed of the pump
Excessive suction lift
Clogged impeller passages
Excessive discharge pressure
Mechanical defects (such as worn wearing rings, impellers, stuffing
box packing,or sleeves)
Does not develop enough
discharge pressure
Insufficient speed of the pump
Air or gas in the liquid being pumped
Mechanical defects (such as worn wearing rings, impellers, leaking
mechanical seals, and sleeves)
Works for a while and then fails
to deliver liquid
Air leakage into the suction line
Air leakage in the stuffing boxes
Clogged water seal passages Insufficient liquid on the suction side
Excessive heat in the liquid being pumped
M/E & A/E AIR COOLER CLEANING (BOTH AIR N WATER SIDE)
Q.how M/E and A/E (see water side n air side in aux. engine folder)air cooler cleaning done.What chemical used (ACC 9,),what is
interval of cleaning, what is manometer normal pr. (160mm aq)and what pr. it should be cleaned ?How will u come 2 know air
cooler needs cleaning?
ANS. SEE VOL 2.910-1. Air cooler cleaning p/p is provided for cooling air side of m/e air cooler. p/p has two suctions.one from a
tank and other from fresh water line.first the tank is filled with fresh water and chemical acc9 is added to it. Then it is circulated from
tank to tank for proper mixing. Then it is pumped to air cooler where we have nozzles on the upper side of cooler. The drain goes to
bilges. After cleaning, fresh water is supplied to nozzles for washing.
FOR BOTH M/E AND A/E, AIR SIDE CLEANING-if pressure drop across air cooler becomes double. WATER SIDE CLEANING-if
temperature of air at cooler outlet increase considerably.
PUNCTURE V/V & VIT FUEL PUMP
Q. puncture valve(see909)? Vit? what is breakpoint? (gulia.p219)
puncture valve is fitted in the top cover of the pump. It consists of a
piston which communicates with the pneumatic/electric system of the engine. In the event of actuation of the shut-down
system, or the "Fuel Oil Leakage Alarm System",or when STOP is activated, compressed air is supplied to the top of the
piston, causing the piston with pin to be pressed downwards and `puncture' the oil flow to the fuel valve. As long as the
puncture valve is activated, the fuel oil is returned through bores
to the pump housing, and no injection takes place.
Vit- in conventional fuel p/p,start of injection is fixed and end of injection i.e the amount of fuel injected in the cyl. Is
controlled by a rack depending on engine load. In vit system two racks are there. one controls the end of injection by
rotating the plunger in the barrel as per engine load. the other one called the vit rack is connected to threaded
barrel(barrel is threaded here) by a threaded sleeve. as the sleeve cannot move axially, and the barrel is prevented from
rotating, then as the sleeve rotates, the barrel moves up and down, thus altering the position of the spill ports relative to
the plunger, and varying the start of injection.
Advantage of vit- Savings in fuel, as SFOC decreases by around 5g/bhp-hr at 90% MCR.the system is set up so that
there is no change in injection timing at low loads(40%MCR).this is to avoid frequent changes of pump lead during
manoeuvring. As the engine load increases above 40%,the start of injection advances i.e. early injection. When the
engine load reached approx.85%MCR at which engine is dsigned to have reached pmax.,retardation of injection timing
takes place so that max. combustion pressure is kept constant between 85% and 100% MCR.vit racks are operated by
pneumatic signal between 0.5bar(min. vit setting) to 5 bar(max. vit setting).vit operation is only active for engine in ahead
direction and control is fron bridge or ECR.when running astern or from local control, the maneuvering system delivers
preset pressure to vit actuators.
Breakpoint- it is the load after which the pmax is maintained constant. So it is normally 85% of MCR in normal vit. But it
can be adjusted in super vit.
Fuel pressure is kept b/w 7-8 bar. Below 7 bar cavitation may occue.above 8 bar shock absorber may not function
properly.
WEAR RING & MECHANICAL SEAL & LANTERN RING Q.what is the function of wear ring in pumps?where fitted?parts of mechanical seal? inspection in mechanical seal during
overhauling, how you will make sure it is usable or not, Mechanical seal.. pms routine.kya dekhoge ki mech. seal change karna hai?
types of c/f p/p? lantern ring fitting??
ANS. Wear rings are typically found on pumps with closed impellers. It decrease the
amount of leakage loss around the impeller. And also as name indicates 'WEAR' which is a
ring can sacrifice its size by taking friction generated between stationary and rotating
elements. The replacement of rings is cheaper than replacing impellers/casing. Wear rings
r fitted to the impeller and/or the pump casing. Parts of Mech. Seal- Rotating and fixed face: The
rotating face is connected to the rotating shaft while the fixed face is connected to the pump housing.
Function of mech.seal- prevent liquid under pressure from leaking out of the pump, or from drawing air into
the pump when under vacuum conditions.
Damage to mech.seal can occur due to- Abrasives- abrasive particles in the liquid being pumped
infiltrates with the liquid between the seal faces and grind away the carbon primary ring. The normal shiny
face of the primary ring and mating ring. Heat Damage-Excessive heat can damage the primary ring and
the elastomer parts. The primary ring is made primarily of carbon. Should the pump be operated without
liquid - even for a very short period of time - the primary and mating ring faces are denied lubricant. This
causes the faces to become very hot. The binder mixed with the carbon breaks down and the face of the
primary ring turns to a dull black powder.
Lantern ring is provided in centrifugal p/p stuffing gland. Located at center of gland and It is a hollow ring which receives liquid from
discharge side of p/p and cool, lubricate the gland. It is provided bcoz the gland may not get proper cooling as p/p may be under
vacuum.
Q. Removal of CENTRIGUGAL Pump for Inspection?
1 Isolate pump electrical circuit breaker on main switch board and attach a warning notice. (Do Not Operate or Men at
Work).
2. Switch off and lock pump supply at its local supply panel. Attach a warning notice to pump local supply panel.
3. Close suction and discharge valves, chain and lock hand wheels.
4. Open pump suction and discharge pipe drain valves to bilge and when water ceases to flow; crack open the pipes /
pump flange joints carefully to ensure that pump has drained off and is safe for opening.
5. Fix a shackle to lifting pad eye above pump and hang chain block; ensuring SWL of block, slings and shackles are
satisfactory.
6. Use a center-punch to mark coupling and casing, then remove the coupling bolts.
7. Disconnect, fixed tag and remove motor supply cables; taping over bare ends with insulating tape.
8. Connect shackle and sling to motor eyebolt and lift motor clear of pump using overhead chain block. Lay motor on its
side out of harm’s way, protecting machined surfaces on both pump and motor coupling halves against damage.
(Cardboard and masking tape is quick and efficient method.)
9. Disconnect all external fittings from pump casing e.g. cooling pipe, pressure gauge, oil reservoirs and air cock.
10. Remove bolting from top cover and remove cover. Scrape off old gasket and check mating surfaces, and renew
gasket on assembly. (Light smear of grease on gasket / faces)
11. The pump shaft with impeller can be lifted out of casing.
12. Dismantle the impeller, and remove the wear ring.
13. Remove the gland packing and disregard; replacing it on rebuild.
Q. Inspection Procedure for CENTRIFUGAL Pump and Motor?
ANS. Pump
1. Impeller, pump shaft and internal volute/casing can now be inspected for erosion, pitting and wear.
2. Rectify pitting or erosion in the impeller and casing with brass putty.
3. Check main drive shaft bearings and thrust bearings for wear and replace if required. 4. Check wear ring clearance using feeler gauges; in my day at sea it was general practice is to replace with new rings at major
overhaul.
5. Check impeller / shaft key and keyways for damage and undue wear, Unscrew impeller shaft securing nut and check threads are in
satisfactory condition; retighten to manufacturers torque settings.
6. Give all parts a good clean removing any dirt/ medium residue
7. Enter date of overhaul and parts renewed in the pump maintenance record card.
Drive Motor
1. Grip motor drive shaft /coupling firmly and check for excess axial and longitudinal movement. Rotate shaft at speed by hand,
allowing it to run to a stop whilst listening for excess noise from bearings. Any doubt on either counts, the bearings should be
replaced.
2. Megger check motor windings to ensure no dampness is present and windings are in good condition. Any suspect readings indicate
a full motor strip to check condition of rotor and stator.
3. If these checks are satisfactory, grease bearings as required. Some bearings are now sealed for life and will not require greasing.
Q. crankcase inspection of aux. eng and m/e(see new folder)?
ANS. before opining door check for leakage, open door then check sealing rings of door, check condition of lub. Oil, tightness of
b.e.bearing bolt locking arrangement, check thr elongation, check sideways movement of piston rod with a crow bar, check b.e.
bearing clearance, check bolt tightness of main bearing bolt and take clearance, move piston to tdc n use torch and check liner for
water leakage, if water leaking from inside then liner crack n if leaking from outside then sealing o-ring leaking, then take gear
drive mechanism backlash, in the end start priming pump n check lubricating nozzles n see if lub. Oil is coming properly from all
points, if lub. Oil is coming more from a bearing then it means that bearing cl. has increased.
SAFETY V/V OF ECONOMISER
Q.why is EGB safety v/v lifting pressure is more than that of boiler safety v/v lifting pressure?
The Exhaust Gas Boiler is circulated with feed water by Boiler Water Circulating pump and the pump
takes its suction from Boiler Steam drum. Hence the pressure of feed water in the EGB, will be the
pressure of steam drum and circulating pump discharge pressure, which will be higher than boiler steam
drum pressure. Hence the Safety valve setting of EGB will be higher than that of its counterpart in
Boiler.
EGB takes suction from the boiler drum and after passing through the economiser tubes the water is fed
back into the same drum. In order to have an efficient heat transfer the economizer tubes need to be
filled with the water completely.Since heat transfer q=mct where m is the mass of the water.If the
economiser tubes are supplied with the water having same pressure then the water in the tubes will be
converted into water and steam. If steam is present in the tubes, then as per the above equation 'm'
decreases finally the amount of heat transfer 'Q' will decrease. So heat taken away from the water
decreases as a result it results in overheating of tubes. So in order to prevent steam formation the
water is supplied at higher pressure ( At higher pressure the boiling point of water will increase).For
increasing the pressure,the return line from the economiser to the boiler drum is provided with a spring
loaded valve which increases the pressure in the line. Because of this the safety valve of egb which is
kept on the return line of the boiler kept at high pressure.The water which is at high pressure when
enters into the steam drum back, its pressure reduces as a result boiling (Vapourisation) of water will
take place inside the drum producing steam.
ACTION IN CASE OF BLACKOUT In case of Blackout following precautions and actions should be taken:-
1. Never panic in such situation, be calm and composed. Emergency generator will restore the power in no time.
2. Inform Officer on bridge briefly about the condition.
3. Call for man power and inform the chief engineer.
4. If the main propulsion plant is running, bring the fuel lever to zero position.
5. Close the feed of the running purifier to avoid overflow and wastage of fuel.
6. If auxiliary boiler was running, shut the main steam stop valve to maintain the steam pressure.
7. Find out the problem and reason for blackout and rectify the same.
8. Before starting the generator set, start the pre- lubrication priming pump if the supply for the same is given from the
emergency generator; if not, then use manual priming handle (provided in some generator).
9. Start the generator and take it on load. Then immediately start the main engine lube oil pump and main engine jacket
water pump.
10. Reset breakers and start all the other required machinery and system. Reset breakers that are included in preferential
tripping sequence. (Non-essential machinery).
Q. what will u do in case of grounding n E/R FLOODING?
Ans. GROUNDING
how we will come to know- Increased load on engine,turbocharger surging,heavy vibration,bridge will come to know from echo
sounder so call bridge.Stop m/e. Change over to high sea chest.
Call engineer’s alarm.
Start taking soundings of all e/r db tanks and bilges. Note down the time and soundings,repeat sounding after 15 min. to check change
in sounding.make sure sounding pipe caps are closed. wait for bridge instruction.they may ask for deballasting or astern kick.
E/R FLOODING
1.Bilge high level alarm will come.
2.Go to bottom platform, find out here flooding is taking place,if any lakage is seen,activate engineer alarm,inform bridge.
Start pumping out bilges using emergency bilge suction.
Lower bilge level. Find out the leakage,isolate the pipe line and rectify.
IF BULKHAED LEAKING-use collision mat, cement bags.
SHOOT BLOWING OF ECONOMISER
Q. HOW TO Shoot BLOW EGB?
ANS. Soot blowing not to be done if there is an indication of soot fire.
SOOT BLOWING IS NOT ALLOWED IN PORT OR PILOTAGE PASSAGE. FOR USA,VESSEL TO BE AT LEAST 50
NM FROM LAND.ENGINE IS TO BE RUNNING AT FULL LOAD.
HOW TO DO-
01. INFORM BRIDGE THAT YOU ARE ABOUT TO START SOOT BLOWING OF THE BOILER SO THAT
CORRECTIVE ACTION BY THE BRIDGE WATCHKEEPER CAN BE TAKEN AND ALL SOOT EXHAUST
SHOULD BE AWAY FROM THE VESSEL. 02. DRAIN THE CONDENSATE FROM THE STEAM INLET AND RETURN LINES OF THE SOOT BLOWER
STEAM PIPING.
03. OPEN STEAM INLET TO SOOT BLOWER SLOWLY AND LET ALL THE CONDENSATE PASS ON TO THE
RETURN LINE BY KEEPING THE LINES OPENED.
04. OPEN THE STEAM INLET FULL ONCE ENSURED THAT THE CONDENSATE IS COMPLETELY
DRAINED.
05. MOVE THE SOOT BLOWERS BY HAND, AND CHECK THE CONTENTS WHICH ARE COMING OUT OF
THE FUNNEL.
CLOSE ALL STEAM INLET AND EXHAUST PIPING TO THE SOOT BLOWER AND CHECK PRESSURE DROP.
WHEN TO DO- 1. IN VERY WATCH
2. WHEN PRESSURE DROP INCREASES BY 15mmWG.
3. WHEN GAS OUTLET TEMP. AFTER EGB IS 15*C HIGHER THEN CLEAN EGB GAS TEMP.
Q. retractable soot blowers working ?
The blower carriage consists of three separate components: the lance hub assembly, the gearbox and the electric motor.The lance
hub housing contains the lance hub, which is supported by two special roller bearings.
Because the lance tube is fully retracted from the furnace and cooled through the blowing medium, the long retractable soot blower
can be used in areas with higher flue gas temperature than any other soot blower type. Retractable property improves the cleaning
effect and reduce erosions due to high temperature flue gases. The blowing medium is supplied through an automated poppet
valve.
Q. Hole in a sea water line how will u repair? If hole is big? Hole is small??If line is not pressuresd
?Material of sea water line??
Ans. If hole is small-
1.use rubber piece and jubilee clip 2.rubber piece and C-clamp
3.use rubber piece and marling rope
4.use pipe repairing kit-it has fiberglass tape and epoxy.
And then weld later.
If hole is big-
1.cement boX 2.change pipe from flange to flange
3.cut that pipe and fit new pipe and weld.
4.take a pipe of little larger dia,cut it from middle and fit it and then weld.
Hole in bulkhead- use cement bags, or collision mat etc.
Material of sea water line-mild steel, galvanized from both sides and painted.Q. Gun metal, where used, composition? Properties? Example of similar
metal?
ANS. Gun metal-10 %tin,88 % copper,2 % zinc.
Strong and corrosion resistant. Used earlier in bearings castings boiler
fittings, sea water pump casing. Originally used chiefly for making guns, gunmetal
was eventually superseded by steel. Gunmetal casts and machines well and is
resistant to corrosion from steam and sea water.
MONEL METAL- CU:NI= 2:1 IT IS RESISTENT TO SEA WATER CORROSION AND EROSION.
STAINLESS STEEL – CHROMIUM=18%, NICKEL- 8%, CARBON- 0.1% and rest iron. Stainless
steel when comes in contact with air or water forms a layer of protective chromium oxide
which prevents it from corrosion.
NIMONIC ALLOY- carbon 0.1%, chromium- 20%, iron -3%, titanium- 2.4% , aluminium- 1.4%,
nickel- 75%.
Resistant to corrosion at high temp., creep resistant, good strength n hardness at high temp.
Q.Definition of suction head and characteristics?
ANS. Npsh available- it is the head that the p/p shud provide by causing drop in preesure to raise liquid from
tank level. The head that a pump must provide by providing pressure drop on the suction side to raise the
liquid from the supply well to the level of the pump. Also known as suction lift.
Q. Safety and relief valve difference??
ANS. Safety Valve - it is characterize by rapid, full opening action.
Relief Valve - liquid applications, opens in proportion to the increase of system pressure over the
opening pressure, so it opens gradually.
Q. advantages of hydrophore system?
ANS. CAN TRANFER water to any height on ship, no need to use tank on top it will move CG
up.
Q. As a duty engg. what to do if hole in rudder(rudder breach )and how u will come to know?
how to take propeller and rudder drop?
ANS. Indications- motor ampere increases, sluggish operation, trim by aft, engine load
increases. Actions- reduce rudder movements, reduce water from aft peak tank. Propeller drop- taken by poker gauge. First the propeller is brought at the reference point. For
some engine this reference point is marked on the propeller and for some engine we have to
bring the piston of cyl. Nearest to fltwheel at TDC. Then remove rope guard at take propeller
drop.(max.2 mm for oil type, n for water type it depends upon dia. Of shaft.for above 305mm
it is 8mm)
Rudder drop- taken by trammel gauge. This takes the form of an 'L' shape bar of suitable construction.
When the vessel is built a distinct centrepunch mark is placed onto the ruder stock and onto a suitable location
on the vessels structure, here given as a girder which is typical. The trammel is manufactured to suit these
marks As the carrier wears the upper pointer will fall below the centrepunch mark by an amount equal to the
wear down.