(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,