Section 18(3) in The Static and Mobile Pressure Vessels (Unfired) Rules, 2016
(3)Shut-off, emergency shut-off valves and excess flow valves-(i)all liquid and vapour connections on vessels, except those for relief valves, plugged openings, and those where the connection is not greater than 1.4 mm diameter opening shall have shut-off valves located as close to the vessel as practicable;(ii)all liquid and vapour connections on vessels, except those for relief valves, and drainage connections of small diameter, shall have an emergency shut off valve such as, an excess flow valve, an automatically operated valve or remotely controlled valve. The emergency shut off valve shall be in addition to the shut-off valve referred to in clause (i) unless the emergency shut off valve is a remotely controlled valve which can be operated from a safe area and shall be of a type which shall not fail:Provided that the emergency shut-off valves is not required in cases where the connection to a vessel is not greater than 3 mm diameter for liquid and 8 mm diameter for vapour, or for vessels meant for storage of noncorrosive, non-flammable or non-toxic gas;(iii)where the emergency shut off valve is of the excess flow type, it shall operate at a designated differential pressure and flow rate for size and service as approved by the Chief Controller and its closing rate of flow shall be below the rate which is likely to result from a fracture of the line it is protecting, calculated under the most adverse weather conditions likely to be experienced. Excess flow valves shall have a rated flow capacity sufficiently above normal flow requirement to prevent valve chatter;(iv)compressed gas road tankers used for flammable, toxic and corrosive compressed gases shall be provided with internal valve having dual function comprising of primary shut off valve and excess flow valve of appropriate rating in liquid and vapour line. Internal valve shall have a spring-loaded fusible link in its actuation lever to shut off in case of fire beneath. Further, the internal valve shall have a shear section and be designed such that in the event of accident, the lower section of the valve is sheared off, the valve seat (soft seat-which ensures zero leakage) remains inside the tank and is closed by self-stored energy (spring).(v)for static vessels, operational fitness examination of excess flow valves shall be carried out during periodic hydraulic test under rule 19 to check physical condition of the parts and its proper operations. For compressed gas tankers operational fitness examination of excess flow valves/internal valves shall be done once in a year. Closing flow rate testing of excess flow valves/internal valves of compressed gas tankers shall be done during the periodic hydraulic test. The excess flow valves/internal valves shall be repaired/replaced by a new ones if found defective on examination or during operation.
