All about CO2 Systems: Requirements, System and Procedures!

All about CO2 Systems: Requirements, System and Procedures!

Carbon Dioxide

Carbon dioxide is an effective fire suppression agent applicable to a wide range of fire hazards.  It has a high rate of expansion which allows it to work fast. When applied to a fire, CO2 provides a heavy blanket of gas that reduces the oxygen level to a point where combustion cannot occur. Since carbon dioxide is a gas, there is no clean-up associated with a system discharge which means minimal business interruption.

CO2 Critical Temp/Press

The critical temperature/pressure of a substance is the press/temp at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied.

For CO2, Critical Temp= 31.2 deg C; Critical Pressure= 73 bar

Co2 System Requirements

• Discharge Req:

1. At Least 50% discharge @ 1 min.
2. At Least 85% discharge @ 2 min.

• Capacity Req:

1. 30% of gross vol @ THE LARGEST PROTECTED cargo space
2. 40% gross vol @ machinery space EXCLUDING CASINGS
3. 35% gross vol for vessels GT < 20000 (WHEN CASINGS ARE INCLUDED)
4. Total no of CO2 cylinders depend upon the highest gross vol out of points 1,2,3 in a particular ship

Major Other Requirements

• Safety procedures against unauthorized use of the system
• Machinery Space valve to be fitted with alarm (audio+visual) and blower trip
• Alarm must trigger well before operation
• Permanent piping arrangements
• Distribution Manifold+ piping, pressure test @ 122 bar
• Pipe D > 19mm
• Cu and flex pipes allowed between cylinder outlet and Manifold
• Pipes to Cargo Spaces, not to pass through E/R
• Hydraulic Pressure Testing for bottles after 20 years from date of installation and thereafter every 5 years
• Quantity of CO2 to check every 4 years which can be distributed as 25% of bottles annually, this must ensure checking of each bottle every 4 years
• All Stop valves to check monthly to ensure their position and working
• The installation must be checked monthly for leakages
• All connection to cable operating system to inspect for tightness every 3 month
• All control valves to inspect annually
• Air blow through annually

CO2 Calculation Requirement

• For cargo space: CO₂ quantity shall be sufficient to give a minimum volume of free gas, equal to 30% of gross volume of largest cargo space so protected.
• For machinery space: CO₂ quantity shall be sufficient to give a minimum volume of free gas, equal to 40% of gross volume of machinery space so protected excluding the casing.
So, if weight of CO₂ / bottle  = 45 kg / bottle and Free gas volume of CO₂ = 0.56 m³/ kg.     then, Required CO₂ bottles for cargo space   = (0.3 x Largest cargo space gross volume) / (0.56 X 45)
and
Required CO₂ bottles for machinery space  = ( 0.4  x  Machinery space gross volume) / (0.56 X 45)

CO2 Precautions and Points to Remember

• It is recommended that in the event of any fire breaking out on-board, including one that requires the fixed CO2 system to be activated, the nearest Coastguard to your position is informed as soon as practicable.
• Carbon dioxide (CO2), a compound of carbon and oxygen, is a colorless gas with a slightly astringent smell causing coughing to occur when inhaled; at high concentrations it is acutely toxic. As it is about 50% heavier than air, it will form a blanket over a fire and smother it.
• To obtain “total flooding” of an engine room, a CO2 concentration of about 35% by volume or more is required to be obtained within 2 minutes. This will reduce the oxygen content of the air in the space to less than 15% to extinguish the fire. At this CO2 concentration human life cannot be supported.
• It is therefore essential that personnel leave the space as soon as the CO2 warning alarm sounds. CO2 should not be discharged into a space until all those within have left and a full head count has been taken.
• Before a space is filled with CO2 it is essential that the compartment ventilation flaps are properly closed and sealed, ventilation fan emergency stops and all fuel and hydraulic oil remote quick closing valves are operated.
• Masters, skippers and crew should be fully competent with the remote and local operation of the fixed CO2 fire extinguishing system for the isolation of fuel oil, hydraulic oil and ventilation systems from the space.
• Typically, it takes about 15–20 seconds after release of CO2 before the concentration within the space reaches a dangerous level.

SAFETY PRECAUTION BEFORE CO2 RELEASE

• Inform Bridge which intern inform nearest Coast Guard
• All personnel evacuated and head count done
• Ventilators & Fans Auto Stop upon opening the CO2 release cabinet
• Dampers, Skylight & All Entry Doors Closed
• M/E and other machinery stopped
• All QCVs operated
• All pumps stopped
• Emergency Generator Run for using Emergency Fire Pump for boundry cooling (if required)
• Fire mains Isolating Valve to be closed so that pressure is not lost by supplying water to deck line

SAFETY PRECAUTIONS AFTER CO2 RELEASE

• It is strongly recommended that expert advice should be obtained from ashore before ventilation of the space or any attempt at re-entry is made. The nearest Coastguard to your position may be contacted who will assist in trying to obtain this advice. Unless specifically requested, this will not be interpreted by the Coastguard as a request for on-scene fire-fighting assistance.
• Immediately after activation of the CO2 system checks should be carried out to ensure that the gas has been correctly released from the cylinders. This can be achieved by feeling the CO2 cylinders which should be cold to the touch and visually checking the individual cylinder release valves to ensure they are in the open position.
• Crew should keep well clear of the ventilation flaps to prevent the inhalation of noxious gases.
• Ventilation of the space should not be resumed until it has been definitely established that the fire has been extinguished. This is likely to take several hours. 
• Entry into a space that has contained CO2 should only be attempted by trained personnel wearing breathing apparatus with safety lines attached and sufficient back-up immediately available should difficulties arise.
• An attendant should be detailed to remain at the entrance to the space whilst it is occupied.
• An agreed and tested system of communication should be established between any person entering the space and the attendant at the entrance.
• Should an emergency occur to the personnel within the space, under no circumstances should the attendant enter the space before help has arrived and the situation has been evaluated to ensure the safety of those entering the space to undertake the rescue.
• In the event that the ventilation system fails any personnel in the space should leave immediately.

CO2 Fixed Installation Explanation+Procedure 

[Uni-tor Example Used: All Rights Reserved to Uni-tor]

Uni-tor CO2 System is designed as total flooding system

co2 ffs high pressure system

Uni-tor CO2 System consists of a high pressure cylinder bank with either manual or pressure operated cylinder top valves, with one or more pressured CO2 cylinders connected via a common manifold.

Wilhelm-sen Technical Solutions has a type of pressure operated cylinder valve, which only requires a small quantity of gas to release the system and therefore it is fast operating and applicable to operate in big series. Automatically closes when evacuating the pilot gas.

The cylinder bank and unique manifold will be stored in a well-ventilated and insulated room, and the pressure operated valves are connected to the manifold using flexible high pressure hoses.

From the main manifold, CO2 is led through the distribution valves to the protected spaces.

From main distribution valves, a piping system is used to distribute the gas to the discharge nozzles which are places uniformly throughout the protected spaces.

Machinery Space (Engine Room) CO2 Flooding Procedure:

CO2 System operation in Machinery Spaces:
A Co2 system of machinery spaces consists of a bank of Co2 bottles that can be operated from a remote place located away from the machinery spaces. The system also consists of pilot Co2 cylinders which control the activation of the bank of Co2 bottles. The Pilot cylinders are contained in a control box and are normally kept disconnected. The system is connected to the pilot cylinders and the control box with the help of steel wires or flexible pipes. All these pipes are fitted with a quick action coupling.

• When the system is to be activated, the coupling in plugged into the corresponding socket. The valves of the pilot cylinders will be opened with the help of the levers in the main CO2 control system.
• The CO2 from the pilot cylinders will open the system’s main stop valve.
• The main stop valve has a piston which gets depressed due to the Co2 gas pressure and allows the pilot gas to flow to the bank of CO2 cylinders.
• This pilot gas operates the cylinders’ valves. All these valves have an actuator which gets operated by the pilot pressure.
• The detection of fire is done by various sensors installed in the machinery spaces.Though the opening of control box operates an alarm, the main decision for CO2 flooding is taken by the Chief engineer, after due consultation with the master of the ship.
• Before releasing Co2 into the fire affected space, it should be made sure that everybody is out of the place and total head should be counted.
• The place is fully enclosed i.e all skylights & ventilators are closed air-tight and pumps supplying fuel oil should also be stopped in order to prevent re-ignition.
• Separate levers for each and every space are present inside the main controlling cabinet. The operating of a particular lever activates the pilot bottles, which helps in releasing the complete bank of bottles designated for that place.
• With the opening of the master valve, Co2 is flooded inside the fire affected space, which then smothers the fire with the help of blanket effect.
• Boundary cooling should be carried out.

Machinery space minimum requirement:

1. Two nos. of fire hydrants with hoses, minimum.
2. 10 ft³ of sand and sawdust with scoops.
3. One fixed installation of CO₂ or foam or Halon.
4. Portable extinguishers of at least 2 nos. of 2 ½ gallon (11.37 litres) foam or CO₂, depending on BHP.
5. Semi-portable extinguishers of 45 kgs of CO₂.
6. Drip pans and trays for every F.O. and L.O. tanks.
7. Monitoring, detection and alarm system.
8. Emergency fire pump.
9. 2 nos: of main fire pumps.
10. International shore connection.
11. Inert gas system.

Machinery space fire fighting: by CO₂ flooding system:

1. CO₂ flooding to machinery space must be done by master’s order.
2. CO₂ must be released by competent engineer, CE.
3. When cabinet door is opened alarm will sound and all ER fans will be stopped.
4. Before releasing, all ER crew to be counted.
5. All openings must be shut [ventilator flaps, fire damper].
6. All fuel pumps and quick closing valves of fuel tanks and fuel transfer line must be shut from remote control position.
7. After opening the cabinet door, master valve must be opened first.
8. Pull the operating handle of pilot cylinders.
9. CO₂ , released from pilot cylinder, operate the gang release bar so that all CO₂ from quick release or total flooding cylinders will be released to machinery space.
10. By regulation, 85% of the capacity must be able to be released within 2 minutes.

Cargo Hold CO2 Flooding System :

• The release mechanism of CO2 system in cargo spaces is same as that of the machinery spaces. The only difference is that the cargo spaces have a different type of fire detection system.
• For detection of fire in cargo hold, a sample of air is drawn from all the cargo holds by an extractor fan.
• This sample of air is passed through a cabinet wherein a set of smoke sensitive sensors analyze the sample.
• The sensors will detect any presence of smoke in the sample. As soon as the sensor detects smoke in the sample, it activates the CO2 alarm system of the ship.
• A part of the sample is also discharged to the wheelhouse in order to cross-check the presence of smoke in the sample. This can be done by smelling the smoke. The sample is later vented to the air.
• In order to check whether the extractor is extracting samples from the holds, a small indicator propeller is fitted, which ensures that the samples are taken.

Cargo hold fire fighting: by CO₂ flooding system:

1. Remote detector fitted at the bridge can detect concerned cargo space.
2. This operation must be done by master’s order.
3. After ensuring no person left in cargo space, seal off the cargo space [closing of ventilation fan, fire damper, hatch cover].
4. Before discharging, change 3-way valve to CO₂ discharge line so that connection to smoke detector is isolated.
5. Open the quick opening valve so that alarm will automatically initiated.
6. Manual operation procedure and amount of CO₂ bottle to be released is stated in CO₂ room.
7. By master’s order, release the correct amount to concerned cargo space.
8. Topping up procedure must be followed at port arrival.

Safety devices on CO2 flooding system:

1. Master valve with alarm switch.
2. Relief valves at manifold.
3. Stop valve and pull handle are in lock release cabinet and alarm switch.
4. Safety bursting disc at each CO2 bottle.
5. Leakage detecting pressure switch on manifold.
6. Non return discharge valves after CO2 bottles.

   General inspections in CO2 room:

   1. Check emergency light and all other lights.
   2. Check exhaust fan / ventilation.
   3. Check all bottles overall condition, clamps, valves etc.
   4. Check operating wire condition.
   5. Check CO2 alarms.
   6. CO2 room key should be in position.
   7. Check the operating instructions.
   8. Inspection to be recorded in log book and Saturday safety routine book.
   Survey on CO2 flooding system:
   1. Check CO2 weight every 2 years
   2. Testing of cylinder at 228 bars
   3. Blow through the lines
   4. General inspection on Instructions, Key, Emergency lights, Ventilation, Alarms etc.

   Advantages:

   1. Can permeate throughout the space.
   2. After discharging, it leaves no residues and no damage to other parts.
   3. No hazard for electrical equipment.

   Disadvantages:

   1. Only suitable for confined space, and needs total sealing of the space.
   2. Fatal to life.
   3. Re-ignition can occurs after fire is completely died out.
   4. No cooling effects, only extinguished by smothering and inhibition.

   CO₂ room safety arrangement:

   1. Exhaust fan, and suction duct is provided at the bottom of the room. Any accumulated CO₂ from leakage at the bottom can be exhausted to atmosphere.
   2. Cable operated Safety Valve is fitted on Pilot Cylinder discharge line.
   It prevents accidental discharge of CO₂ from Quick Release Cylinders due to action of
   leakage gas from Pilot Cylinder.
   3. Relief Valves are fitted on each discharge line from cylinders so that leakage gas can safely dispose to atmosphere.
   4. Check Valve is fitted in connection pipe between each cylinder discharge valve and manifold, so that leakage of one cylinder cannot effect other cylinder.
   5. Each bottle has a combined Bursting Disc, which will rupture spontaneously at a pressure of 177 bar at 63΄C.
   6. Pressure Gauge and pressure Alarm in the manifold.

   Maintenance of CO₂ flooding system:

   1. Weekly inspection for alarm system.
   2. Bottles should be weighed yearly; level checked by ultrasonic or radio active isotope detector. Level reference mark should be provided. If 10% loss of weight, recharge them.
   3. All the pulley, wire, rope and toggle must be free from dirt, scales and well lubricated.
   4. CO₂ branch pipe and discharge nozzle should be cleared with compress air at two year interval.
   5. Bottles should not be exposed to temperature of 60΄C.

   Weighing of CO₂ bottle:
   1. Bottles should be weighed yearly by special weighing device designed for this purpose.
   2. It has a reference mark to determine 10% loss of weight.