Two safety valves are fitted  on a manifold which keeps at least one safety valve open to the pressure inside the vessel. In normal condition both the valves are operative.

ADVANTAGES :-

• Added safety :- Higher releasing capacity.
  
  
• No isolation valves required, which give more safety to the pressure vessel with at least one safety valve in operation.
  
  
• Easy maintenance :- One valve can be removed for repairs at any time.
  
  
• The best feature of this valves is that at any given time both the valves can not be isolated, giving positive safety to the plant.