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Need Spare PSV

Need Spare PSV

Need Spare PSV

I'm evaluating the need of installed spare PSV for many PSVs for a plant under design development.
Does anyone have experience in cases where installed PSV is provided to allow maintenance work of the other PSV?

Any experience is more than welcome


RE: Need Spare PSV


What you are proposing is (and has historically been) done on conventional steam boilers and LPG storage tanks and vessels - for many years.  It is common practice to spare relief valves on these type of continuous and critical service for doing inspection and maintenance work.

Many of us on this forum have that experience, having installed CSO, separate, block valves on the relief valves as well as special 3-way block valves.  (CSO = car sealed, Open)

What, specifically, are the fluids and process conditions involved?  

RE: Need Spare PSV

I'm trying to have general guidelines in which spare PSV is not required as the PSV can be taken off with no safety or operability concern.
I will give some examples:
- Thermal relief
- Spare equipment
- PCs provided in the system and can take the rated flow relief if some PSVs taken off service

I think, from experience, above cases should not have installed spare PSVs


RE: Need Spare PSV


You specifically asked: “Does anyone have experience in cases where installed PSV is provided to allow maintenance work of the other PSV?”  The answer was yes.

As a Chemical Engineer you should know that we need specific identification of the fluids and process conditions – as I’ve requested and you’ve failed to supply.  You should also know that by specifics, what is meant is: pressures, temperatures, fluid identities and compositions, equipment or vessels protected, etc., etc.

To give general comments and advice on general information regarding safety relief devices is something I regard as dangerous – especially when given to non-experienced or neophyte engineers who can easily interpret the application in a wrong manner.  I’m not saying you’re inexperienced; but you are asking the question(s) and we don’t know you personally or your engineering background.  Decisions or advice on pressure relief devices is serious business and we need specifics to specifically address the subject raised.

The quality and accuracy of the responses you receive are directly proportional to the quality of the basic data supplied.

RE: Need Spare PSV

With regards to spare equipment then i would say that the requirements for spare psv would depend on how you use this equipment.

If the equipment is allways just sitting there - not on a sort of "hot standby" and the spare capacity is not critical then it would be double jeporady to spare the PSV - on the other hand if the equipment is critical or maybe you "swap" units so that the spare unit becomes the main unit on a rotational basis then maybe a spare PSV is required.

Best regards


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