Gas fire-extinguishing systems in machinery spaces
The use of a fire-extinguishing medium which, either by itself or under expected conditions of use, gives off toxic gases in such quantities as to endanger persons is not permitted. New installations that use fire-extinguishing media, which have ozone-depleting properties under the Montreal Protocol, are not permitted.
The necessary pipes for conveying a fire- extinguishing medium into protected spaces are to be provided with control valves which are to be so placed that they will be easily accessible and not readily cut off from use by an outbreak of fire. The control valves are to be so marked as to indicate clearly the spaces to which the pipes are led.
Suitable provision is to be made to prevent inadvertent admission of the medium to any space. Where pipes pass through accommodation spaces they are to be seamless and the number of pipe joints are to be kept to a minimum and made by welding only.
The piping for the distribution of fire-extinguishing medium is to be of adequate size and so arranged, and discharge nozzles so positioned that a uniform distribution of medium is obtained.
All joints are to be made by suitable barrel couplings, cone connections or flanges. Screwed and running couplings are not allowed except that threaded sleeve joints may be allowed where connecting the nozzles to the distribution piping in the protected spaces.
All pipes are to be arranged to be self-draining and where led through any refrigerated spaces, the arrangement will be specially considered. A means whereby the individual pipes to all protected spaces can be tested using compressed air is to be provided. Distribution pipes are to extend at least 50 mm beyond the last nozzle.
Steel pipes fitted in spaces where corrosion is likely to occur are to be galvanized, at least internally. Means are to be provided to close all openings which may admit air into, or allow gas to escape from, a protected space.
Where the volume of free air contained in air receivers in any space is such that, if released in such a space in the event of fire, such release of air within that space would seriously affect the efficiency of the fixed fire-extinguishing system, an additional quantity of fire-extinguishing medium is to be provided.
Means are to be provided for automatically giving audible warning of the release of fire-extinguishing medium into any space in which personnel normally work or to which they have access. The alarm is to operate for a suitable period before the medium is released.
Where pneumatically-operated alarms are fitted which require periodic testing, carbon dioxide is not to be used as an operating medium. Air-operated alarms may be used provided that the air supply is clean and dry.
Where electrically-operated alarms are used, the arrangements are to be such that the electric operating mechanism is located outside the pump room,
The means of control of any fixed gas fire- extinguishing system are to be readily accessible and simple to operate and are to be grouped together in as few locations as possible at positions not likely to be cut off by a fire in a protected space. At each location, there are to be clear instructions relating to the operation of the system having regard to the safety of personnel.
Automatic release of fire-extinguishing medium is not permitted.
Where the quantity of extinguishing medium is required to protect more than one space, the quantity of medium available need not be more than the largest quantity required for any one space so protected.
Means are to be provided for the crew to safely check the quantity of medium in the containers.
Containers for the storage of fire-extinguishing media and associated pressure components are to be designed and tested to Codes of Practice recognized by LR, having regard to their locations and the maximum ambient temperatures expected in service.
The fire-extinguishing medium is to be stored outside a protected space, in a room which is situated in a safe and readily accessible position and effectively ventilated. Any entrance to such a storage room is to preferably be from the open deck and in any case be independent of the protected space.
Access doors are to open outwards, and bulkheads and decks including doors and other means of closing any opening therein, which form the boundaries between such rooms and adjoining enclosed spaces are to be gastight.
In systems where containers discharge into a common manifold, non-return valves are to be provided at the connections of the container discharge pipes to the manifold to allow any container to be disconnected without preventing the use of other containers in the system and to prevent the discharge of extinguishing medium into the container storage room in the event of the system being operated.
Manifolds are to be tested by hydraulic pressure to 1,5 times the design pressure. The design pressure is the maximum gauge pressure to which the system may be subjected and is not to be less than the gauge pressure corresponding to the maximum ambient temperature expected in service. After the hydraulic test, manifolds are to be carefully cleaned and dried before the non-return valves are finally fitted.
For ships on unrestricted service, spare parts for the system are to be stored on board. As a minimum, these are to consist of:
- 1 actuator;
- 1 flexible hose (cylinder to manifold); and
- the cylinder bursting discs and sealing washers for all cylinders.
Carbon dioxide systems
The volume of free carbon dioxide is to be calculated at 0,56 m3/kg.
For machinery spaces:
- The quantity of carbon dioxide carried is to be sufficient to give a minimum volume of free gas equal to the larger of: 30 per cent of the gross volume of the largest machinery space protected, including the casing;
- The fixed piping system is to be such that 85 per cent of the gas can be discharged into the space within two minutes; and
- The distribution arrangements are to be such that approximately 15 per cent of the required quantity of carbon dioxide is led to the bilge areas.
Two separate controls are to be provided for releasing carbon dioxide into a protected space and each is to ensure the activation of the alarm. One control is to be used to discharge the gas from its storage cylinder(s).
A second control is to be used for opening the valve of the piping which conveys the gas into the protected space. The two controls are to be located inside a release box clearly identified for the particular space. If the box containing the controls is to be locked, a key to the box is to be in a break-glass type enclosure conspicuously located adjacent to the box. There is to be a dedicated release box for each protected space, in which personnel normally work or to which they have access, see also 7.1.7. The space served is to be identified at the release box.
Distribution pipes for carbon dioxide are not to be smaller than 20 mm bore.
High-expansion foam systems
Any required fixed high-expansion foam system in machinery spaces is to be capable of rapidly discharging through fixed discharge outlets a quantity of foam sufficient to fill the greatest space to be protected at a rate of at least 1 m in depth per minute. The quantity of foam-forming liquid available is to be sufficient to produce a volume of foam equal to five times the volume of the largest space to be protected.
The expansion ratio of the foam is not to exceed 1000 to 1.
Alternative arrangements and discharge rates will be permitted provided that equivalent protection is achieved.
Supply ducts for delivering foam, air intakes to the foam generator and the number of foam-generating units are to be such as will provide effective foam production and distribution.
The arrangement of the foam generator delivery ducting is to be such that a fire in the protected space will not affect the foam-generating equipment.
The foam generator, its sources of power supply, foam-forming liquid and means of controlling the system are to be readily accessible and simple to operate and are to be grouped in as few locations as possible at positions not likely to be cut off by fire in the protected space.
Foam concentrates carried for use in fixed foam fire-extinguishing systems are to be of an approved type. They are to be tested at least twice during each five year period to verify that they remain fit for service. Evidence in the form of a report from the foam manufacturer or an independent laboratory will be accepted.
Pressure water-spraying systems
Any required fixed pressure water-spraying fire-extinguishing system in machinery spaces is to be provided with spraying nozzles of an approved type.
The number and arrangement of the nozzles is to be such as to ensure an effective average distribution of water of at least five litres per square metre per minute in the spaces to be protected. Where increased application rates are considered necessary, these will be specially considered. Nozzles are to be fitted above bilges, tank tops and other areas over which oil fuel is liable to spread and also above other specific fire hazards in the machinery spaces.
The system may be divided into sections, the distribution valves of which are to be operated from easily accessible positions outside the spaces to be protected and which are not to be readily cut off by fire in the protected space.
The system is to be kept charged at the necessary pressure, and the pump supplying the water for the system is to be put automatically into action by a pressure drop in the system.
The pump is to be capable of simultaneously supplying, at the necessary pressure, all sections of the system in any one compartment to be protected. The pump and its controls are to be installed outside the space(s) to be protected. It is not to be possible for a fire in the space(s) protected by the water-spraying system to put the system out of action.
The pump may be driven by independent internal combustion type machinery, but if it is dependent upon power being supplied from the emergency generator, that generator is to be arranged to start automatically in case of main power failure so that power for the pump required by 7.4.5 is immediately available. When the pump is driven by independent internal combustion machinery, it is to be so situated that a fire in the protected space will not affect the air supply to the machinery.
Precautions are to be taken to prevent the nozzles from becoming clogged by impurities in the water or corrosion of the piping, nozzles, valves and pump.