Section 30(3) in The Merchant Shipping (Cargo Ship Construction And Survey) Rules, 1974
(3)(a)In every ship, every pipe connected to any oil fuel storage, settling or daily service tank, not being a double bottom tank, which, if damaged, would permit discharge of contents so as to cause a fire hazard, shall be fitted with a valve or cock which shall be secured to the tank to which it is connected and be capable of being closed from a readily accessible position outside the space in which the tank is situated :Provided that if the inlet pipe is fitted to such a tank a non-return valve similarly secured to the tank may be substituted for the valve or cock required under this sub-rule.(b)Every such pipe connected to an oil fuel deep-tank transversed by any shaft or pipe tunnel, in addition to the valve to be fitted to the tank under the requirements of Cl. (a), a valve or valves may be fitted on the pipe line or lines outside the tunnel or tunnels to enable control to be exercised in the event of fire.
