Fixed gas fire extinguishing systems
Quantity of medium need not be more than the largest compartment / space protected.
Simple and safe arrangement is provided to check quantity of extinguishing medium. CO2 cylinders may be weighed without removing them completely from fittings.
Cylinders, piping and pressure arrangements are designed for pressure and ambient temperature.
Medium is stored outside spaces to be protected.
Spare parts are maintained on board.
Pressure relief valves are placed on pipeline. Escaped gas is released on deck in open atmosphere.
Material used for all components shall not melt below 925 deg C.
System is provided with arrangement for testing with AIR.
Control valves are clearly marked indicating space protected.
Arrangement is made to prevent accidental discharge.
Pipes passing thru accommodation are welded (No flanges or gaskets) and no drain plugs or other openings are permitted. Pipes shall not pass thru refrigerated space.
There will be automatic audible and visual warning of release of gas. Audible alarm must be heard clearly in protected space with machinery operating. Alarm should be distinguished from other alarms. Pre-discharge alarm shall be automatically activated on opening of the cabinet door. This alarm shall not last less than 20 s, or may be longer to cover time required for evacuation of protected space. This is not required for local release system like paint locker.
Means of control of fixed gas extinguishing system shall be readily accessible and simple to operate. Instructions to be provided. They should be placed in few locations not likely to be cut off during fire in protected spaces.
Normally AUTOMATIC release is not permitted
CO2 system
For cargo spaces CO2 volume should be 30% of the volume of largest cargo space.
For Ro-Ro ships there shall be at least 45% of the gross volume of the largest compartment. Also need to ensure that at least two thirds of the gas required shall be introduced within 10 minutes.
Carbon dioxide system shall not be used for the protection of special category spaces. (Special category spaces are those enclosed vehicle spaces above and below the bulkhead deck, into and from which vehicles can be driven and to which passengers have access).
For machinery spaces quantity of carbon dioxide carried either 40% of gross volume or 35% of the gross volume of the largest machinery space protected. Then there is some consolation for cargo ships of less than 2000 gross tonnage. For calculation purpose while of free carbon dioxide is calculated at 0.56 m³ per kilo.
For machinery spaces 85% of the gas must be discharged within two minutes.
For container and general cargo spaces at least two third of the gas must be discharge into the space within 10 minutes. For solid but cargo spaces two third of the gas must be discharge within 20 minutes.
Controls to separate controls are provided for releasing carbon dioxide into protected space and to ensure the activation of the alarm. One control is used for opening the valves of the piping which can raise the gas into protected space and second control is used to discharge the gas from its storage containers. Positive means are provided so that they can only be operated in that order.
Two controls are located inside a release box clearly identified for a particular space’ if the box containing controls is to be locked up key to the board shall be in a break glass type enclosure conspicuously located adjacent to the box.
Testing of the installation: there are two tests carried out one is the test of the free air flow in all pipes and nozzles and second is functional test of the alarm equipment.
Low pressure CO2 systems
There is some difference between a high pressure and a low pressure CO2 system.
The system control devices and the refrigerating plants shall be in same location where pressure vessels are stored.
Provision shall be made for
Pressure gauge,
High pressure alarm,
Low pressure alarm
Branch pipe with stop valve for filling
Discharge pipe
CO2 level indicator
Two safety relief valves
Pressure vessel and outgoing pipes shall be insulated.
Vessel will be serviced by TWO automated, completely independent dedicated refrigeration units.
Cooling water shall be supplied by 2 circulating pumps, one being standby.
Audible and visual alarms shall be provided for
Low pressure
High pressure
Failure of refrigeration unit
Lowest CO2 level in tank
If system serves more than 1 space, automatic or manual systems shall control volume released.
(Automatic timer or accurate level indicators)
Steam is no longer used as medium.
Other gas systems need specific approval.