Section 56(6)(b) in The West Bengal Factories Rules, 1958
(b)No pressure vessel or plant shall be used in a factory unless there has been obtained from the maker of the pressure vessel or plant or from a competent person a certificate specifying the design pressure or maximum permissible working pressure thereof, and starting the nature of tests to which the pressure vessel or plant and its fitting (if any) have been subjected, and every pressure vessel or plant so used in a factory shall be conspicuously marked so as to enable it to be identified as to be the pressure vessel or plant to which the certificate relates and the certificate shall be kept available for perusal by the Inspector.