Fire Fighting
How water extinguishes fire ?
Mainly by cooling the material on fire.
Steam generation is useful for smothering.
Water is more suitable against fire in wood, paper and textiles.
How foam extinguishes fire ?
The extinguishing effect of the foam is a combination of smothering and cooling.
Foam is used against fire in oil surfaces.
How dry chemical powder extinguishes fire ?
The extinguishing effect of the powder is mainly by inhibition (chain reaction breaking) and effective mainly against fires in flammable liquid, gases and electrical equipment.
How CO2 extinguishes fire ?
The extinguishing effect is smothering and inhibiting.
CO2 is heavier than air, the best condition for extinguishing is in closed spaces.
CO2 give no secondary damage.
It is electrically non-conductor and therefore suitable against electrical equipment fire.
How halon extinguishes fire ?
Extinguishing effect is nearly exclusively inhibition.
Halons are suitable against fires in liquid and electrical equipment.
All Halons are consider to be toxic to some degree because with hot surfaces and flame causes them to break down yielding toxic substances.
How many kinds of extinguishers are there in E/R ?
There are 3-kinds of extinguishers in E/R.
There are foam, CO2 and dry power types.
How to operate chemical foam extinguisher ?
It can be operated by releasing the cap by means of operating handle and turning it up side down.
Aim to near the fire (base or wall).
Shake the bottle and foam will come out.
How to operate and extinguish the CO2 extinguisher ?
Remove the safety pin and then the valve-operating lever is squeezed to pierce the disc.
The liquid CO2 leaves into the discharge horn and emerge as a cloud of CO2.
What are the portable fire extinguisher used for ? Where are they located ?
Portable fire extinguishers are the first line of defence.
It can be deal with an emergency as prompt action
All extinguishers should be located in an easily accessible position
The correct type to deal with the class of fire expected in that area
Painted in the appropriate color code.
Regularly inspected and tested.
How to extinguish small control room electrical fire ?
When E/R control room electrical fire breaks out, we must use CO2 portable fire extinguisher, because CO2 is electrical non-conductor.
First give the fire alarm signal.
Check the condition of fire and cut out the power if is possible.
Shut off E/R ventilator and close the E/R entrance door but one exit door must be opened behind me.
Take CO2 portable extinguisher and fight the fire by staying up stream of air and the distance about 3-4 ft from fire.
Move back to the exit door.
Leave the extinguisher and close the exit door.
What are the effects of chemical foam ?
The extinguishing effect of the foam is a combination of smothering and cooling.
When burning surface is covered with foam, it will insulate the flame from the liquid surface, there by the heat radiation against the liquid is decreased and the gas generation decreased and fire stops.
Foam is used against fires in oil surface.
What is chemical foam safety device ? Its function ?
Small radial hole at cap
Atmosphere valve
The cap has small holes in the threads or also has in the middle of bottle thread so that any internal pressure must be released before the cap is fully removed.
Firstly, unscrew slowly foam will emit, so it cannot injure.
What is fixed installation ?
It is a fixed fire extinguishing equipment fitted for engine room and cargo hold to extinguish the immerse fire controlled by remote station, (Eg. usually mechanical foam or CO2 )
How to take action for cabin fire on ships ?
Give the fire alarm signal.
Check the condition of fire and remove the combustible material near vicinity.
Isolate electrical supply to that cabin.
Take the nearest portable extinguisher.
Remove the safety guard and strike the knob smartly.
Then release the extinguishing media to the fire spaces.
Give the boundary cooling to it adjacent spaces, if the fire is great.
The fire will stop by cooling effect.
Where do you use a CO2 fire extinguisher ?
CO2 fire extinguisher is used in electrical equipment fires.
It is electrically nonconductor.
CO2 is heavier than air but it can be carried away by combustion gases and flame, if it is used out door.
The best condition for extinguishing is in enclosed space.
CO2 is a clean medium and give no residue, therefore it has no secondary damages.
What is the fire control plan ?
It is a general arrangement plan which shall be permanently exhibited on board for the guidance of ship personal and also exhibited outside the deck house with water tight enclosure for the guidance of shore fire brigade.
It consists of details of:
Fire control stations
Location of various portable fire extinguishers & FFA.
Fire detecting and alarming system.
Means of escape.
Ventilation system.
Fixed fire fighting instillation system.
What is the principle of fire fighting ?
Cooling to reduce the temperature.
Smothering to reduce emission of vapour.
Cutting off combustion material.
Cutting off oxygen.
Interrupting chain reaction by chemical.
What is the difference between mechanical foam and chemical foam ?
Mechanical Foam
Bubble filled with air.
Foam produced by mechanically mixing of foam concentrate , water & air (Special nozzle required).
Expansion ratio is higher 30:1, 200:1
Mostly used fixed installation & non portable fire extinguisher.
Chemical Foam
Bubble filled with CO2.
Foam produced chemical reaction of Al2(SO4)3 ,Na2HCO3 and foam stabilizer
Lower expansion ratio
Mostly Used as portable fire extinguisher.
What are the properties of mechanical foam ?
Mechanical foam is smothering agent.
The production of this foam is mainly a process of agitation of a mixture of water, air and single foam compound, resulting in which is a vast and continuous bubble formation.
Foam compound is an aqueous solution of partially hydrolyzed keratin, stabilized with iron salts.
With modern foam making nozzles, the mechanical foam constituency can be varied from sloppy to stiff.
Stiff foam has only blanketing quality.
Sloppy foam has smothering and additional cooling properties.
The expansion ratio is 30:1 water to foam compound, producing 200:1 foam to compound.
Quantity of the foam to give about six inches depth over the areas to be protected.
The duration for the whole capacity discharge should be less than 5 minutes.
The foam should not be disturbed too early since reignition may occur from the residual heat.
What is Davy’s safety lamp ?
Employed for detection of the tank atmosphere whether explosive or containing fatal gases.
If the flame in the lamp burn clearly, the tank atmosphere is free from any fatal or explosive gases.
If it is develops a faint blue cap above, it is the sign of an explosive gas present.
If the lamp burns black or goes out, foul gas such as carbon dioxide is present.
The lamp will not burn in an atmosphere containing less than 16% of oxygen.
How will you test smoke detecting system for cargo holds ?
Smoke test- by applying smoke to the detector head, alarm will activate and light up the indicator lamp.
Check the line cleanliness between cargo hold and smoke detector.
Any blockage can be clear by using compressed air.
Open the 3-ways valve fully, it will contact the CO main and cargo hold line and blow with compressed air.
How to extinguish E/R bilge fire ?
First check the condition of fire; it is small oil fire in the bilge well.
Then raise the fire alarm signal.
Remove the combustible material near vicinity.
It is a small fire, extinguish by foam portable extinguisher.
Release the foam direct to the fire by deflecting it from another surface.
Foam is lower specific gravity than oil or water that it will flows across the surface of oil and cover.
The fire will stop by blanking with foam.
Differentiate between explosimeter and Davy’s safety lamp ?
Explosimeter
To measure the consideration of inflammable gas and vapour in the atmosphere
Quickly and accurately.
It can measure remote from required tank.
It is necessary to skill full for operation.
Based on Wheatstone bridge principle.
No need to handle with care.
Davy’s safety lamp
To detect the tank atmospheres, whether it is explosive gas or fatal gas.
It can get verify roughly the tank is gas free or not.
It is required to apply directly into the required tank.
Based on the ordinary fire process.
No need to highly skill.
But it required careful handling.
What are LFL and HFL ?
Lower flammable limit (LFL)
The concentration of hydrocarbon gas, 1% by volume in air below which there is insufficient hydrocarbon gas to support and propagate combustion is Lower Flammable Limit.
Higher flammable limit (HFL)
The concentration of hydrocarbon gas in air 10% by volume, above which there is insufficient air to support and propagate combustion.
It is a highest concentration of hydrocarbon gas in air for explosion.
What are the E/R fire fighting / detecting equipments ?
2 number of fire hydrants at each floor.
3 types of portable extinguisher.(CO2, foam, Dry powder) located in easily accessible position (2 nos. of within 10 m) and correct type to deal with expected class of fire in that area.
Non-portable fire extinguisher (136 Liters foam extinguisher for boiler space.)
Sand box with shovel.
Smoke detector and alarm system.
Fixed fire fighting installation system.
What are the safety devices on life boat ?
Mechanical brake (to prevent accident falling)
Centrifugal brake (to control life boat falling speed between 20 to 40 m/min)
Limit switch (to prevent over tightening of rope) (it is fitted arm of davit just before in limit)
Harbour safety pin (for davit)
What are the windlass safety devices ?
Cable stopper (chain stopper, bow stopper)
Overload trip
Hand brake
Slipping clutch for overload prevents any undesirable damage such hull damage due to anchor and rope broke out.
What will you do for cargo hold fire ?
If cargo hold (C/H) fire broken out. While the ship is at sea.
Smoke detector will give alarm and signal on the bridge. Duty officer will check which cargo holds is broken out of fire.
Give the fire alarm
To extinguish the fire. Following procedure must be done
Check any person left in the cargo hold (Head count all crew). Totally isolate the cargo hold.
Shut cargo hold ventilation, blower and damper, hatch cover.
Fully open the three way valve to that cargo hold, the line to smoke detector is closed and connect the CO2 main line and cargo hold.
Then go to CO2 room and open master valve for cargo hold.
CO2 alarm will sound in the cargo hold.
Check the required amount of CO2 bottle to use for that cargo hold.
Then release required CO2 to cargo hold by manual actuation of CO2 bottles.
Fire will stop because room atmosphere is smothering by CO2 gas.
What is the composition of inert gas in ships ?
N2 – 85%
CO2 – 14%
O2 – 1%
The classification of fire helps in selecting the appropriate extinguishing media according to the nature of the material undergoing combustion. The four classes of fire are given below.
Class A
Fires in ordinary combustible materials such as wood, cloth, paper, rubber and many plastics are classified under this. In general fires involving solid materials, usually of an organic nature, in which combustion normally takes place with the formation of glowing embers.
Water is the best extinguishing medium for Class A fires. Some Dry Chemical Powder (DCP) are also used.
Class B
Include fires involving liquids or liquefiable solids. Fires in flammable liquids, oils, greases, tars, oil based paints, lacquers, etc.
Foam is the best extinguishing medium for Class B fires. But its reactivity should be ensured in case of Chemical fires.
Class C
Fires involving gases. Flammable gases such as methane, natural gas, acetylene, etc.
Dry Chemical Powder is widely used for extinguishing gaseous fires. Its ability to cut the chain reaction in the combustion process makes it suitable for the purpose.
Class D
Fires involving metals, including magnesium, zirconium, sodium, lithium, potassium, etc.
Steam, Dry Chemical Powder can be used against meal fires.
The classification of fire tells us which fire extinguisher to be used for efficient extinction of fire.
Since fire on board is very dangerous and Shore Professional Fire Brigade can not be call at sea, fire prevention is vital on ships. Fire fighting arrangement to be well maintained on ships. Fire prevention included regular fire drills on board with proper training.
Prevention of Fire on Ships
Cleanliness
No oils, oily rags and wastes should allow in the vicinity of the heat source such as the places of (Boiler, Heaters and M/E exhaust system). They are liable to ignite spontaneously.
No oil leak should be tolerated such as from oil tank’s trays and drip pan, fuel and lube oil separator’s trays, fuel and lube oil valves, oil burners and piping connection.
Tank top and bilges should be cleaned and hose down frequently. Cleaning could be done with some chemical if oil is accumulated considerably.
Tank tops and bilges should be painted white and these place illuminations to be provided.
Heat Sources
No naked lights and smoking should be allowed inside the engine room and near the bunker.
Paint should be stored in special well ventilated stored away from machinery space or heat source and automatic water sprinkler system to be provided as per regulation.
Welding practice should be done only in workshop and away from combustible material storing spaces carefully, then all the protective cloths to be put on and earthing should be ensured.
Fire Fighting Appliances
Should be kept in working order:
All portable extinguishers and semi portable one to be ensured in good working order and properly placed inside the machinery space and always made handy.
Fixed fire fighting installation should be test once a week and it’s maintenance to be done periodically such as compress air blowing of lines and discharge nozzle and alarm testing and function testing. The contents inside the unit to be weighed or checked periodically.
Emergency fire pump should be kept in good working order and test run to be done weekly without any failure.
Fire detection, monitoring alarm system to be tested to weekly without any failure.
All fire hydrants and their connection should be kept in very good order also to the sandboxes and scoop.
Fire men outfits two numbers should be also kept in good order and handy at all time.
International shore connection should be placed at proper location and to be in good order.
All engine room members should be properly educated about fire fighting appliances and their operation.
Fire drill should be carried out at least once a month.
Action When Fire Break Out on Ships
Small Fire
Find the origin of fire, inform to chief engineer and all engine room member, restrict fire to prevent spread out if possible and extinct it on the spot with portable extinguisher or by another means. (In practice, as soon as, noticing of the break out of fire, the fire alarm or emergency alarm must be activated before taking any action.)
Big Fire
Sound fire alarm system.
Evacuate all ship crew, count them and assign as per muster list.
Remote stopping of all fuel pump to be done.
Remote closing of all quick closing valves to be done.
Remote closing of skylight door and engine all watertight door to be done.
Remote closing of all engine room ventilation damper to be done.
Prime mover and all machinery to be stopped.
All engine room entry and exit door to be closed perfectly.
All ventilation fan in engine room to be stopped manually.
Fixed fire fighting installation system to be operated by C/E or 2/E in a very proper manner. See Operation of CO2 Flooding System.
November 22, 2015 10:53 pm | Leave a Comment | Frozee
Since fire on board is very dangerous and Shore Professional Fire Brigade can not be call at sea, fire prevention is vital on ships. Fire fighting arrangement to be well maintained on ships. Fire prevention included regular fire drills on board with proper training.
Prevention of Fire on Ships
Cleanliness
No oils, oily rags and wastes should allow in the vicinity of the heat source such as the places of (Boiler, Heaters and M/E exhaust system). They are liable to ignite spontaneously.
No oil leak should be tolerated such as from oil tank’s trays and drip pan, fuel and lube oil separator’s trays, fuel and lube oil valves, oil burners and piping connection.
Tank top and bilges should be cleaned and hose down frequently. Cleaning could be done with some chemical if oil is accumulated considerably.
Tank tops and bilges should be painted white and these place illuminations to be provided.
Heat Sources
No naked lights and smoking should be allowed inside the engine room and near the bunker.
Paint should be stored in special well ventilated stored away from machinery space or heat source and automatic water sprinkler system to be provided as per regulation.
Welding practice should be done only in workshop and away from combustible material storing spaces carefully, then all the protective cloths to be put on and earthing should be ensured.
Fire Fighting Appliances
Should be kept in working order:
All portable extinguishers and semi portable one to be ensured in good working order and properly placed inside the machinery space and always made handy.
Fixed fire fighting installation should be test once a week and it’s maintenance to be done periodically such as compress air blowing of lines and discharge nozzle and alarm testing and function testing. The contents inside the unit to be weighed or checked periodically.
Emergency fire pump should be kept in good working order and test run to be done weekly without any failure.
Fire detection, monitoring alarm system to be tested to weekly without any failure.
All fire hydrants and their connection should be kept in very good order also to the sandboxes and scoop.
Fire men outfits two numbers should be also kept in good order and handy at all time.
International shore connection should be placed at proper location and to be in good order.
All engine room members should be properly educated about fire fighting appliances and their operation.
Fire drill should be carried out at least once a month.
Action When Fire Break Out on Ships
Small Fire
Find the origin of fire, inform to chief engineer and all engine room member, restrict fire to prevent spread out if possible and extinct it on the spot with portable extinguisher or by another means. (In practice, as soon as, noticing of the break out of fire, the fire alarm or emergency alarm must be activated before taking any action.)
Big Fire
Sound fire alarm system.
Evacuate all ship crew, count them and assign as per muster list.
Remote stopping of all fuel pump to be done.
Remote closing of all quick closing valves to be done.
Remote closing of skylight door and engine all watertight door to be done.
Remote closing of all engine room ventilation damper to be done.
Prime mover and all machinery to be stopped.
All engine room entry and exit door to be closed perfectly.
All ventilation fan in engine room to be stopped manually.
Fixed fire fighting installation system to be operated by C/E or 2/E in a very proper manner. See Operation of CO2 Flooding System.
The automatic water sprinkler system is an automatic fire detecting, alarm and extinguishing system which can deal quickly and effectively with any outbreak of fire that may occur in accommodation or other spaces on ships.
The system consists of several sections comprising a number of sprinkler heads mounted on the pipes, each section being connected through a section control valve to a sprinkler main which in turn is connected to a pressure tank and a pump. Number of sprinkler heads per section to be not more than 200. Each section has an alarm system.
The entire system is initially charged with fresh water at a pressure of about 8 bar by a tank (tank is half filled with fresh water), maintained under pressure by compressed air. This should be such that the pressure at the highest sprinkler head in the system is not less than 4.8 bar. It is also connected to an independent sea water pump with its own sea water suction. Each sprinkler head has a quartzoid bulb which retains a diaphragm seal in the outlet of the water pipe. This bulb is partially filled with a special fluid so arranged that a rise in temperature in the compartment concerned will cause the liquid to expand and entirely filled the space, the bulb burst, the water pressure forces the diaphragm out and water flow out from the sprinkler. Under the specific pressure maintained in the tank by air pressure, the water from the sprinkler is deflected outwards and broken into a fine spray by the serrated edge of the sprinkler base and will adequately cover a floor area of about 16 square meters at a rate of 5 L / m2 / minute.
When the sprinkler head comes into operation, the non return alarm valve for the section opens and water flows to the sprinkler head. This non return valve also uncovers the small bore alarm pipe lead and water passes through this small bore alarm pipe to a rubber diaphragm. The water pressure acts on this diaphragm and this operates a switch which causes a break in the continuously live circuit. Alarms both visible and audible, fitted in engine room, bridge and crew space are then automatically operated.
Thus the pressure drop at the release of the water causes an alarm to sound on the bridge and indicates on the board, the zone in which the ruptured sprinkler heads are situated. When the system pressure dropped to 5 bar, the sea water pump will start automatically and continue supply with sea water. A hose connection is also provided so that water can be supplied to the system from shore when ship is in dry dock. The sprinkler heads are spaced not more than 4 meters apart and 2 meter from any bulkhead or part of the ship’s side which forms a boundary of the protected space.
Stop valves ‘A’ and ‘B’ are locked open and if either of these valves are inadvertently closed, a switch will be operated that brings the alarms into operation. The alarm system can be tried by opening valve ‘C’ which follows delivery of water similar to that of one sprinkler head to flow to drain. At least two sources of power must be provided to operate the sea water pump and automatic alarms. The component should be tested weekly.
What are the requirements of automatic water sprinkler system on ships ?
Each sprinkler head must be capable of delivering water at a rate of 5 L / m2 / minute.
Each sprinkler head is sufficient to cover the area of about 16 square meters.
One section is permitted to contain maximum 200 heads.
The pressure at the highest sprinkler head in the system is not less than 4.8 bar.
Sprinkler heads are spaced not more than 4 meter apart and 2 meter from the vertical wall.
There must be at least two powers source for the sea water pump, alarm system and FW pump.
This system consists of independent sea water pump with its own sea water suction.
Section alarm can be tested individually by test cock on each section.
What is the principle of shattering quartzoid bulb in sprinkler head ?
Principle is ‘Boiling Liquid Expanding Vapor Explosion’ (BLEVE). It is an explosion caused by the rupture of a vessel containing a pressurized liquid above its boiling point.
How the sprinkler head operates in automatic water sprinkler system on ships ?
Each sprinkler head is made up of steel cage fitted with a water deflector. A quartzoid bulb, which contains a highly expansible liquid, is retained by the cage. The upper end of the bulb presses against a valve assembly which incorporates a soft metal seal. Refer to the diagram below.
When quartzoid bulbs are manufactured, a small gas space is left inside the bulb so that, if the bulb is subjected to heat, the liquid expands and the gas space diminishes. This will generate pressure inside the bulb and the bulb will shatter once a predetermined temperature is reached.
Once the bulb shatters the valve assembly falls permitting water to be discharged from the head which strikes the deflector plate and sprays over a considerable area.
Generally the operating temperature range of quartzoid bulbs is 68 °C to 93 °C but the upper limit of temperature can be increased. Quartzoid bulbs are manufactured in different colours which indicate the temperature rating of the bulb.
RATING
COLOUR
68 °C
RED
80 °C
YELLOW
93 °C
GREEN
141 °C
BLUE
182 °C
VIOLET
What is emergency fire pump ?
It is a fixed emergency fire pump independently driven by self cooled compression ignition engine or an electric motor which power is supply from emergency generator.
When all the fire pumps are out of action either by disabling the pumps or their source of power, emergency fire pump can still be used.
Where emergency fire pump is fitted in your ship ?
It is fitted at steering flat, shaft tunnel, forward part of the ship.
The pump to be located remote from machinery space.
Why emergency fire pump on board ship ?
It is fitted as alternative means of providing water for fire fighting if a fire in any one compartment could put all the fire pumps out of action either by disabling the pumps of their source of power.
What are the requirements / regulations for emergency fire pump ?
Passenger ships of 1000 grt and upwards and in cargo ships of 2000 grt and upwards must have fixed emergency fire pump independently driven by a self cooled compression ignition engine or an electric motor driven by electric power from emergency generator.
It must be located outside the E/R room, in the steering flat, shaft tunnel or in forward part of the ship.
It must have own suction, total suction head should not exceed 4.5 meters under all conditions of list or trim.
Pump capacity must not less than 25m3/hr and must be able to deliver two ½ inches bore jet of water having a horizontal throw not less than 40 ft.
Fuel tank for engine shall contain sufficient fuel to run on full load for at least 3 hrs and reserve fuel for 15hrs, store outside the machinery space.
The prime mover engine at that unit must be hand started and able to start by one man.
If the pump is fitted above the water level, priming arrangement must be fitted.
If diesel engine driven, (a) Easily started in cold condition (zero degree C by hand cranking ), (b) Fuel tank for engine shall contain sufficient to run on full load for at least 3 hrs and (c) Sufficient reserve fuel for 15 hrs, store outside the machinery space.
If motor driven: emergency power supply heating arrangement to be provided.
What are the requirements / regulations for number of fire pumps on ships ?
Passenger ship of 4000 GRT and upward at least 3 pumps.
Passenger ship of < 4000 GRT at least 2.
Cargo ship of 1000 GRT & above at least 2.
Cargo ship of < 1000 GRT according to administration.
Operation Test
Operation test is carried out on water mist fire fighting system onboard ships for the verification of pump condition and pump discharge pressure.
The testing procedure is as follows.
All section solenoid valves must be in closed position and water supply valve to be kept open.
Open the pump drain valve.
Turn the select switch to manual in pump starter panel.
Start the pump.
Check the pump and discharge pressure.
Stop the pump.
Drain out the water from pump unit.
Automatic Release Test (Without Flooding)
Close water supply valve.
Disconnect motor power cables.
Open air valve at the pump discharge. (For providing air to the nozzles instead of water).
Actuate both flame and smoke detectors in the relevant area.
Check the alarm at the control panel and repeater panel.
Check visual and audible alarm in the protected space (Engine Room).
Check the release of air from nozzles at the relevant area.
Push stop button from control panel.
Follow same testing for other sections.
Manual Release Test (Without Flooding)
Close water supply valve.
Disconnect motor power cables.
Open air valve at the pump discharge. (For providing air to the nozzles instead of water).
Press start button from control panel for the area to be tested.
Check the alarm at the control panel and repeater panel.
Check visual and audible alarm in the protected space (Engine Room).
Check the release of air from nozzles at the relevant area.
Push stop button from control panel.
Follow same testing for other sections.
Alarm Test
Freshwater tank low level alarm can be tried out by manually lowering the float.
Electric source failure can be tested by removing fuse from the control panel.
Air Blow Test
The whole piping system to be blown through with compressed air at a pressure of 7 to 8 bar.
Check the free passage of air from the nozzles.
Treatment after Testing
Drain out the water from all piping and make sure piping, wiring, and equipment is installed properly and ready for service.
Rules and Regulations
Water mist discharge of 30 seconds is to be carried out for at least one section (as per DNV).
Pressure testing of water piping system to be done for at least 1.5 times maximum working pressure (as per DNV and KR).
Cleanliness, Vigilance and Common sense are the principal weapons to prevent fire. Tank top should be kept clean and well lighted, it is recommended that the tank top be painted white so that any oil leakages from drip trays, pipes, joints, filters and valves may be easily spotted and leakage dealt with promptly before any dangerous accumulation of oil arises.
Bilges must be kept clean and the pumps and strainers for the bilges maintained in good working order.
International shore connection shown above is a standard sized flange with nuts, bolts and washers and a coupling for ship’s fittings. The dimensions are shown. The fitting and joining must be suitable for a working pressure of 10.5 bar. Four bolts are required of 16mm diameter and 50mm length, also eight washers.
Water is the chief fire fighting medium on a ship and the fire main is the basic installation for fighting fires. The system shown below has two independently powered pumps which are also used for general service and ballast. These pumps supply two engine room hydrants and the deck main through the isolating valve.
The later is required in the fire main system to prevent loss of water through damaged pipe work in the engine room if, to maintain the deck supply, the emergency fire pumps has to be used. The emergency fire pump is shown as being situated in the tunnel, with a supply to deck fire main through tunnel escape and also to both hydrants in the shaft tunnel by engine room water tight door. The deck main has a drain at the lowest position so that the pipe can be emptied (particularly of freshwater) in cold weather. If this is not done, the pipe can be damaged by water freezing, but more important he pipe will be blocked by the ice and not stable.
Automatic Foam Compound Induction System
A flexible automatic foam compound induction system used in many tankers used to supply deck foam monitor equipment is shown in figure below. The automatic inductor on the suction side of the pump maintains the appropriate foam liquid quantity in the water stream. Water pressure of foam liquid suction ports are provided at the side of the automatic foam inductor unit. Water under pressure from the discharge side of the pump enters the pressure port inducing foam liquid from the tank through the foam liquid suction port.
A swing paddle fitted in the body of the inductor, in the main water flow, moves backward and forward, according to the rate of flow. The paddle rotates a water metering vane in the water pressure port, bypassing water into the foam liquid port, thus diluting the foam liquid entering the water stream at the correct concentration to meet all flow conditions. The atmospheric type foam liquid tank enables the system to be replenished during operation.
Portable fire extinguishers are very much helpful in dealing with small fires. They can prevent fire from spreading, which prevents an uncontrolled fire. Different types of fire extinguishers are used in ships. It may be water, foam, dry chemical powder, carbon dioxide, etc. They are kept in a place from where it can be easily taken out and used if necessary. Portable fire extinguishers are normally painted with red colour. In additional they have a colour band around them, which represent the type of extinguisher or its content inside, thereby anybody can identify the type of extinguisher from far away. Also there must be clear instructions posted on them including its quantity, name and year of manufacture, details of approval, classes of fire where it can be applied, last service date, test pressure details, temperature range of effective use, etc.
Water Fire Extinguisher
Water fire extinguishers are of the most simplest design. A 9 liter capacity portable water fire extinguisher is shown above. This extinguisher can be used for class A fires (or in other words, fires on solid materials such as wood, plastics, furniture, paper, cloth, etc.). The extinguisher contains fresh water with added salts to reduce freezing point and a CO2 bottle inside. The extinguisher is not pressurized when not in use. It must be stowed and operated in upright position.
For operating the extinguisher, remove the safety pin, un-clip the hose, point the hose towards seat of the fire, and squeeze the handle. While squeezing the CO2 bottle top seal is pierced and releasing CO2which can pressurize the container to expel the water out through the hose with high pressure. This pressurized water comes out through the nozzle and extinguishes fire. For stopping water discharge, handle can be released. Once used, depressurize the container and extinguisher to be recharged.
Characteristics of Portable Water Extinguisher
Simple extinguisher where extinguishing medium is water with added salts to reduce freezing point.
Expellent used is carbon dioxide bottle which is used as a cartridge. It can be easily replaced with the spare while recharging. Used bottles can be recharged from shore.
Since discharge contains only fresh water, no cleaning up is required.
Water extinguisher extinguishes fire in two ways. One is by cooling property of the water, by which it takes away the heat. Second is by covering the material on fire with a blanket of steam, formed by evaporation of the water, which helps to cut the oxygen supply for firing (Smothering)
It cannot be used on live electric equipment since water is a good conductor of electricity.
Do not to keep the extinguisher in high temperature areas, since increase in temperature causes pressure of carbon dioxide gas to increase and it may result in accidental release of the gas to the container.