Section 56(4) in The West Bengal Factories Rules, 1958
(4)Every pressure vessel shall be fitted with-(a)a suitable safety valve or other effective pressure relieving device of adequate capacity to ensure that the maximum permissible working pressure of the pressure vessel shall not be exceeded. It shall be set to operate at a pressure not exceeding the maximum permissible working pressure and when more than one protective device is provided, only one of the devices used be set to operate at the maximum permissible working pressure and the additional device shall be set to discharge at a pressure not more that 5 per cent in excess of the maximum permissible working pressure;(b)a suitable pressure gauge with a dial range not less than 1.5 times the maximum permissible working pressure, easily visible and designed to show at all time the correct internal pressure and marked with a prominent red mark at the maximum permissible working pressure of the pressure vessel;(c)a suitable attachment for fixing a standard test pressure gauge for checking the accuracy of the pressure gauge referred to in clause (b) of this sub-rule;(d)a suitable stop valve or valves by which the pressure vessel may be isolated from other pressure vessels of plant or source of supply of pressure. Such a stop valve or valves shall be located as close to the pressure vessel as possible and shall be easily accessible; and(e)a suitable drain cock or valve at the lowest part of the pressure vessel for the discharge of the liquid or other substances that may collect in the pressure vessel;Provided that it shall be sufficient for the purpose of this sub-rule if the safety valve or pressure device, the pressure gauge and the stop valve are mounted on a pipeline immediately adjacent to the pressure vessel and where there is a range of two or more similar pressure vessels served by the same pressure lead, only one set of such mountings need to be fitted on the pressure lead immediately adjacent to the range of pressure vessels provided they cannot be isolated:Provided further that in case where owing to the nature of the process or the action of the contents of the vessels a pressure gauge or safety valve or both cannot work reliably, a tested and reliable working thermometer with a sufficient large scale, on which shall be clearly marked the maximum permissible temperature in the vessel or pyrometers or rupture discs in addition to the pressure gauge and safety valve may be fitted as may be directed by the Chief Inspector.
