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Low pressure CO2 storage for Ship fire protection systems

In some installations, the CO2 is stored in low pressure refrigerated tanks. The cylindrical storage vessels (Figure 14.17) are fabricated to the pressure vessel requirements of the authorities. The tanks are of low temperature steel, fully tested and stress relieved. They are mounted on supports designed to withstand shock from collision. The insulation to limit heat ingress into the CO2/ which is stored at a temperature of 17 deg C, is polyurethane with fire resistant additives, foamed in situ.

Distillers low-pressure refrigerated storage tank
Figure : Distillers low-pressure refrigerated storage tank

 A CO2 fire extinguishing and smoke detector installation (The Walter Kidde Co. Ltd)
Figure : A CO2 fire extinguishing and smoke detector installation (The Walter Kidde Co. Ltd)

Klem valve with pressure actuator (The Walter Kidde Co.Ltd)
Figure : Klem valve with pressure actuator (The Walter Kidde Co. Ltd)

Two refrigeration compressors connected to separate evaporator coils mounted inside the pressure vessels, maintain the CO2 at the required temperature of 17C. One unit is sufficient to deal with heat ingress into the CO2 the other unit is a stand-by. Either water or air cooling can be arranged. The duty from main to stand-by unit can be reversed to equalize running hours, 'The instrument panel contains tank contents gauge, pressure gauge and alarms to indicate CO2 liquid level and pressure and also contains the refrigeration controls,

To ensure that a dangerous high pressure condition does not exist if a serious refrigeration fault develops, pressure relief valves are fitted discharging directly to atmosphere. The valves are mounted on a changeover valve and are set to discharge CO2 gas if the pressure in the vessel rises above the design pressure of 23.8 bar. Each valve can in turn be isolated for removal and periodic testing.

The vessels are fitted with a capacitance type continuous indicator together with a stand-by liquid level indicator which ensures that CO2 liquid level can always be checked approximately by opening the stand-by liquid level indicator valve which will flood the pipe to the same level as the pressure vessel. A frost line will appear due to the low temperature of the liquid CO,. Closing the valve will cause the CO2 to vaporize back into the pressure vessel The filling and balance lines are normally run to the main deck port and starboard sides for hose connections to be made to a road tanker. The balance line is used to equalize pressure with the tanker during the filling operation.



The liquid CO2 discharge is through a 150mm bore pipe fitted with an isolating valve but the quantity of CO2 discharged into the various spaces is controlled by timed opening of a discharge valve. A relief valve is fitted which will, relieve excess pressure in the discharge pipe should the isolating valve be closed with liquid CO2 trapped in the discharge manifold. Automatic or remote operation can be achieved by utilizing CO2 gas pressure from the top ot the tank as the operating medium.

Because of the considerably reduced amount of steel, the storage tank compared with cylinders gives an approximate 50% weight saving and because low pressure CO2 has a greater density than CO2 at ambient temperature, the volume it occupies is considerably less in terms of deck space. Also, low pressure CO usually costs considerably less than CO supplied in cylinders.

A periodical survey of the refrigeration compressors is required by the Classification Societies and this is limited normally to the exchange of pressure relief valves. At intervals of up to 10 years an internal inspection is required via the man-door provided.



Summarized below general cargo ship fire protection equipments & guideline:
  1. Fire main system & related mechanism

  2. The fire main extends to the full length of the ship and from the machinery spaces to the highest levels. Hydrants served by the main, are situated so that with suitable hoses any area on the ship can be reached. .....more

  3. CO2 fire extinguishing installation

  4. Fire extinguishing installations employing CO2 stored under pressure at ambient temperature are extensively used to protect ships' cargo compartments, boiler rooms and machinery spaces. When released the CO2 is distributed throughout the compartment, so diminishing the relative oxygen content and rendering the atmosphere inert. ...... more

  5. Fire fighting equipments

  6. Two independently powered pumps must be provided in all cargo ships of 1000 tons gross and over and in passenger ships of less than 4000 tons gross. Larger passenger vessels and passenger ferries must have three such pumps. The pumps are fitted with non-return valves if they are of the centrifugal type, to prevent loss of water back through open valves when not running. ..... more

  7. Details of fire detectors

  8. A variety of devices are available for detecting fire in unmanned machinery spaces but each has an ability to detect basically only one aspect. Thus, smoke detectors based on the ionization chamber are able to recognize combustion products but will not register radiation from a flame or heat. .....more

  9. Machinery space fire & use of Walter Kidde CO2 system

  10. Walter Kidde CO2 system employs pilot CO2 cylinders to open the distribution system main stop valve and subsequently the valves on the individual CO2 cylinders. .....more

  11. Fire protection system for cargo holds

  12. Holds for general cargo, have been protected against fire by fixed installations which deliver inert gas from an inert gas generator based on combustion of fuel (similar to the system available for inerting oil tankers) and halon systems. .....more

  13. Low pressure CO2 storage

  14. In some installations, the CO2 is stored in low pressure refrigerated tanks. The cylindrical storage vessels are fabricated to the pressure vessel requirements of the authorities. The tanks are of low temperature steel, fully tested and stress relieved. They are mounted on supports designed to withstand shock from collision. ..... more

  15. Halon system

  16. Halon 1301 has the chemical formula CF3 Br being known as bromo-trifluoromethane. It is a colourless, odourless gas with a density five times that of air and extinguishes fire by breaking the combustion chain reaction. .....more

  17. Multi-spray system for the machinery spaces

  18. This system is similar to the sprinkler used in accommodation areas but the spray heads are not operated automatically. The section control valves (Figure 14.20) are opened by hand to supply water to the heads in one or more areas. Ready to use hoses can also be supplied. Fresh water is used for the initial charging and the system is brought to working pressure by means of the compressed air connection. .....more

  19. Automatic sprinkler system

  20. A network of sprinkler heads is arranged throughout the spaces to be protected. Each sprinkler head is normally kept closed by a quartzoid bulb which is almost filled with a liquid having a high expansion ratio. .....more

  21. Details various portable extinguishers & how to use ?

  22. The first line of defence against fire in any area of the ship, is the portable fire extinguisher. Some common portable extinguishers that have been used at sea are described. .....more



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