Relief Valve Installation and Sizing Basis? 1

[byrdo]

I am reviewing the sizing and installation of several RV's and have the following questions:

1. Can a Relief Valve be installed on the outlet piping of the vessel it is protecting? Common sense would say yes, as long as the pressure vessel does not add any addition pressure drop. What if the vessel is a filter or exchanger? Is there anything in the code about this?

2. When sizing a RV for a control valve failure, do you HAVE to ignore the associated piping and look only at the CV of the valve? I have a RV that is too small when looking at the CV of the valve; can I look at the entire system and recalculate the max flow through the valve and piping and see if the RV is okay?

Thanks,

Matt

 

[SooCS]

A RV can be located at the outlet piping of the pressure vessel provided the pressure drop from the vessel to the PV does not exceed 3% of the PV set pressure. Also there should not have any internal that can block the PV e.g. mass pad, valve, etc.

When sizing PV for control valve failed open, I normally ignore the pressure drop through the piping. Usually it is insignificant.

May be I can advise you but need the following information.
1. the design pressure of the vessel,
2. operating pressure of the upstream equipment,
3. do you have any SDV between the pressure vessel and the upstream equipment.
4. What is the application, flamable gas/liquid, toxic,
5. onshore/offshore and where.

 

[Montemayor]

SooCS:

Excellent & concise response!
I believe you meant to write "mesh" instead of mass; but the intent is understood by me and, I hope, byrdo.

byrdo:
You ask about filters and I just want to make sure that you understand the concept that SooCS has pointed out: a clogged or plugged filter (or any internals, for that matter) can present a hazardous overpressure to the vessel where it resides. Therefore, you must protect the vessel upstream of the potential plug and your proposed line PSV. That why SooCs brings up the mesh pad(s) -which are similar potential plugs.

These are very important subjects that should be well-understood and conceived by all design and operating engineers.

Art Montemayor
Spring, TX