VALVE POSITION FOR STANDARD PSV

[TrustedDesire]

Hello house,
Please, i want to know the position of valves on standby PSV.
I know that the downstream manual valve should always be locked open, and if it is a single valve upstream, it should be locked close. But in a situation of double-block upstream what should be the position of each valve upstream the PSV.

 

[EmmanuelTop]

Both isolation valves upstream of the standby PSV should be locked closed (see attached).


Dejan IVANOVIC
Process Engineer, MSChE

 

[EmmanuelTop]

It is like any DB&B arrangement - normally both valves are kept in closed position.

Dejan IVANOVIC
Process Engineer, MSChE

 

[pennpiper]

NO! NO! NO! You are misreading the attached sketch. Any Block Valves upstream or down stream of a PSV should be Car Sealed Open (CSO) or locked OPEN not Closed.
If the block valves are car sealed Closed then there is no reason to have a PSV. A Blocked in PSV is rendered non-functional.

Sometimes its possible to do all the right things and still get bad results

 

[EmmanuelTop]

The OP was referring to a standby PSV (isolated).

Dejan IVANOVIC
Process Engineer, MSChE

 

[pennpiper]

However, in the case where you have parallel PSVs then you can have one set of block valves CSO (Open) and one set of Block valves CSC (Closed).

Sometimes its possible to do all the right things and still get bad results

 

[EmmanuelTop]

This was the question. You probably scared the OP

Dejan IVANOVIC
Process Engineer, MSChE