Piping Relief Valves back into the system

[homerphish]

How do you size relief lines that are dumped back into the low side suction. IIAR doesn't give a method in it's piping handbook.

I have a 250 lb Surge drum on an evaporator that has a 100 lb relief valve on it. This valve is being piped into a 1.5 in. suction main at 25 psig. How do I size the relief line?

 

[Cooky]

What is this function of the pressure relief valve?.

If it is designed to be part of the control system, and it is EXPECTED that over-pressure occurs in the surge drum as part of the normal cycle of operation, then you can pipe the outlet of the relief valve back into the circuit.

If the purpose of this relief valve is to protect the integrity of the surge drum (stop it from bursting), then you ABSOLUTLY MUST NOT pipe the outlet of the relief valve back into the circuit.

As to the sizing of pipes from the outlet of a relief valve, the valve manufacturer will help you with that.

Cooky