CHAPTER XI | FIRE PROTECTION
11.3 WATER SPRAY SYSTEM
11.3.1 On ships carrying flammable or toxic products, a water spray system for cooling, fire prevention and crew protection should be installed to cover:
a. exposed cargo tank domes and any exposed parts of cargo tanks;
b. exposed on-deck storage vessels for flammable or toxic products;
c. cargo liquid and vapour discharge and loading manifolds and the area of their control valves and any other areas where essential control valves are situated and which should be at least equal to the area of the drip trays provided; and
d. Boundaries of superstructures and deckhouses normally manned, cargo compressor rooms, cargo pump rooms, store-rooms containing high fire risk items and cargo control rooms all facing the cargo area. Boundaries of unmanned forecastle structures not containing high fire risk items or equipment do not require water spray protection.
11.3.2 The system should be capable of covering all areas mentions 11.3.1 with a uniformly distributed water spray of at least 10 l/m2 per minutes for horizontal projected surfaces and 4 l/m2 per minutes for vertical surfaces. For structures having not clearly defined horizontal or vertical surface, the capacity of the water spray system should be determined by the greater of the following:
a. Projected horizontal surface multiplied by 10 l/m2 per minute; or
b. Actual surface multiplied by 4 l/m2 per minute.
On vertical surfaces, spacing of nozzles protecting lower areas may take account of anticipated rundown from higher areas .stop values should be fitted at intervals in the spray main for the purpose of isolating damaged sections. Alternatively, the system may be divided into two or more sections which may be operated independently provided the necessary controls are located together, aft of the cargo area. A section protecting any area included in 11.3.1 (a) and (b) should cover the whole of the athwart ship tank grouping which includes that area.
11.3.3 The capacity of the water spray pumps should be sufficient to deliver the required amount of water to all areas simultaneously or, where the system is divided into sections, the arrangements and capacity should be such as to simultaneously supply water to any one section and the surfaces specified in 11.3.1(c) and (d). Alternatively, the main fire pumps may be used for this service provided that their total capacity is increased by the amount needed for the spray system. In either case, a connection, through a stop valve, should be made between the fire main and water spray main outside the cargo area
11.3.4 Subject to the approval of the Administration, water pumps normally used for other services may be arranged to supply the water spray main.
11.3.5 All pipes, valves, nozzles and other fittings in the water spray systems should be resistant to corrosion by sea-water, for example by galvanized pipe, and to the effect of fire.
Read More: GC CODE 1983