Tag Archives: Explosimeter

MEO Oral Examination Questions on Fire Extinguishers

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:

  1. Fire control stations 
  2. Location of various portable fire extinguishers & FFA.
  3. Fire detecting and alarming system.
  4. Means of escape.
  5. Ventilation system.
  6. 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 ?

  1. First check the condition of fire; it is small oil fire in the bilge well.
  2. Then raise the fire alarm signal.
  3. Remove the combustible material near vicinity.
  4. It is a small fire, extinguish by foam portable extinguisher.
  5. Release the foam direct to the fire by deflecting it from another surface.
  6. Foam is lower specific gravity than oil or water that it will flows across the surface of oil and cover.
  7. 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 ?

  1. Mechanical brake (to prevent accident falling)
  2. Centrifugal brake (to control life boat falling speed between 20 to 40 m/min)
  3. Limit switch (to prevent over tightening of rope) (it is fitted arm of davit just before in limit)
  4. Harbour safety pin (for davit)

What are the windlass safety devices ?

  1. Cable stopper (chain stopper, bow stopper)
  2. Overload trip
  3. Hand brake
  4. 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 ?

  1. If cargo hold (C/H) fire broken out. While the ship is at sea.
  2. Smoke detector will give alarm and signal on the bridge. Duty officer will check which cargo holds is broken out of fire.
  3. Give the fire alarm
  4. To extinguish the fire. Following procedure must be done
  5. Check any person left in the cargo hold (Head count all crew). Totally isolate the cargo hold.
  6. Shut cargo hold ventilation, blower and damper, hatch cover.
  7. 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.
  8. Then go to CO2 room and open master valve for cargo hold.
  9. CO2 alarm will sound in the cargo hold.
  10. Check the required amount of CO2 bottle to use for that cargo hold.
  11. Then release required CO2 to cargo hold by manual actuation of CO2 bottles.
  12. 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%

Reference:

Oral Guide by – MIN ZAR TAR