(1)Every plant or machinery used in a factory and operated at a pressure greater than atmospheric pressure shall be-(a)of good construction, sound material, adequate strength and free from any patent defect;(b)properly maintained in a safe condition;(c)fitted with-(i)a suitable safety valve or other effective device to ensure that a maximum permissible working pressure of the vessel shall not be exceeded;(ii)a suitable pressure gauge easily visible and designed to show at all times the correct internal pressure in lbs. per square inch, or in kilogram per square centimetre, and marked with a prominent red mark at the safe working pressure of the vessel:(iii)a suitable stop valve or valves by which the vessel may be isolated from other vessels or source of supply of pressure; and(iv)a suitable drain cock or valves at the lowest part of the vessel for the discharge of collected liquid,(d)thoroughly examined by a competent person:-(i)externally once in every period of six months;(ii)internally, once in every period of twelve months:Provided that if by reason of design, construction and use of the vessel a thorough internal examination is not possible, this examination may be replaced by a hydraulic test which shall be carried out once in every two years in case of vessels not in continuous processes and once in every four years in case of vessels in continuous processes; and(iii)Hydraulically tested at intervals of not more than four years:Provided that in respect of pressure vessels with thin walls such as, sizing cylinders made of copper or any other non-ferrous metal periodic hydraulic test may be dispensed with on condition that the requirements laid down in sub-rule (5) are fulfilled:Provided further that it shall be sufficient for the purposes of clause (c) of this rule if the safety valve, pressure gauge and stop valve are mounted on a pipe line immediately adjacent to the vessel and where there is a range of two or more similar vessels in a plant served by the same pressure lead, only one set of such mountings need be fitted in case they cannot be isolated.
