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CO2 fire extinguishing installation for the cargo holds- Ship fire protection systems

Fire protection on ships is provided by detection and fire-fighting equipment together with structural features which are intended to contain an outbreak of fire and the employment when required of non-combustible materials to prevent its spread.

Dry cargo holds

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. The sea-water fire main is also designed to be used in such spaces if necessary. Fire detection heads like those described for engine rooms have also been used. The type of installation described below, however, is typically used. It provides detection and the means to extinguish a fire.

CO2 cargo space system with smoke detection

The CO2 fire extinguishing installation for the cargo holds normally incorporates a smoke sampling system so that fire can be detected in the early stage at the smoke detecting cabinet, which is situated in the wheelhouse. Each cargo compartment is individually connected to the smoke detecting cabinet by a small bore pipe through which a continuous sample of the air in each space is continually drawn by a fan.

CO2 fire extinguishing installation
Figure : CO2 fire extinguishing installation

Part of the sample can be discharged into the wheelhouse to check for the smell of smoke otherwise it vents to atmosphere. Because the ends of pipes in holds could become blocked, an indicator is fitted at the ends in the cabinet to demonstrate air flow. This telltale is usually in the form of a light propeller which is rotated by the air flow. Any smoke issuing from the pipes in the cabinet, is emphasized by the diffused lighting and should be visible, but a photo-cell detector will automatically operate an alarm.

A three-way valve is fitted on each pipeline below the smoke detector cabinet. This is normally set so that the pipe between the dry cargo space and the smoke detecting cabinet is open. When smoke is detected, the valve for the particular space is operated thus isolating the smoke detecting cabinet from the space and opening the pipe to the CO2 cylinder battery, ready for discharge of gas to the cargo space on fire. The system of pipes for smoke detection are also used for fire extinguishing.

The CO2 is stored in liquefied form in 45 kg solid drawn steel cylinders under pressure, or at low temperature and moderate pressure in large bulk storage tanks. In systems designed for cargo space and machinery space protection, the cylinders will be arranged for a ganged total discharge to the machinery space and limited discharge of one or more cylinders (usually by manual release) to individual cargo spaces, depending on the volume of each space. Instructions on how many cylinders are to be released for each cargo space will be displayed at the control station.

The cylinders are stored vertically, with their discharge valves at the top and internal syphon tubes are arranged so that discharge is always from the bottom of the liquid. Liquid is thus discharged into the pipe system with vapour being formed only as the liquid leaves the nozzles. Without a syphon tube, CO2 would evaporate from the liquid surface and pass through the pipe system as a gas, to give a very slow discharge.

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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