Every pressure vessel or plant in service shall be thoroughly examined by a competent person.

_{A pressure vessel of volume 35 cu. feet having stored air at 150 PSI.}

_{If burst, will release energy equivalent to 227 gm of TNT. This is considered high hazard.}   

PRESSURE VESSEL / PRESSURE PLANT  

If in any factory, any plant or machinery or any part thereof is operated at a pressure above atmospheric pressure, 

effective measures shall be taken to ensure that the safe working pressure of such plant or machinery or part is not exceeded.

Safety valve

Suitable safety valve or other effective pressure relieving device of adequate capacity shall be fitted to ensure that the maximum permissible working pressure to 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 are provided, only one of the devices need be set to operate at the maximum permissible working pressure and the additional device shall be set to discharge at a pressure not more than 5% in excess of the maximum permissible working pressure. 

Some reasons which can increase the pressure 

of pressure vessel -

• Variation in fluid flow rate.

• Failure of pressure reducing device.

• Vessel exposure to heat.

• Heat exchanger tube failure.

• Ambient temperature change.

• Uncontrollable exothermic reactions in chemical plants.