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Comment on this..

Comment on this..

Comment on this..

(OP)
Say i have a PSV provided for a system in which the rated flowrate of the PSV is 10 times bigger than the required sizing flow rate.Ultimately my inlet and outlet pressure drop are not within the code limits.In this case is there any possible solution available other than going for a smaller size PSV or modification of PSV including Bellows,pilot,remote pilot.can i comply for codes with the available system ???

Remember my pressure drops are very high of order say 70-80% of the set pressure.So changing pipe size is not helping me that much and my valve is full lift type.

please help me out..................

RE: Comment on this..

liquid or vapor service?

RE: Comment on this..

Just put in a smaller one or a modulating pilot operated.

RE: Comment on this..

The relieving capacity with backpressure below typical limits may be 10 times bigger than required; however, the relieving capacity with 80% backpressure will be much less.

I2I

RE: Comment on this..

Agree with dcasto...

I still don't understand why you have large PSV with small relief load... there are so many practical problems associate with this arrangement... Code compliance is just on paper...

JoeWong
Chemical & Process Technology

RE: Comment on this..

Rig the PSV with a custom orifice or install one upstream to split the load.

RE: Comment on this..

(OP)
@ Lizking.Its a vapour service device...........

RE: Comment on this..

(OP)
@ insult to injury - no i face inlet pressure drop problem here..............

RE: Comment on this..

(OP)
@ maddocks

on 1st option - is it possible to fix a custom made orifice in a existing device(PSV)???

2nd option - what do you mean by split load ???the problem i am facing here is the sizing flowrate is very less when compared to device rated flow.

RE: Comment on this..

Has the vendor been consulted regarding the application?

I2I

RE: Comment on this..

You may have been able to work something out if it was liquid service.  But if this is truly an ASME Code application & vapor service, you are what is commonly known as "screwed."

RE: Comment on this..

If your inlet line losses are so high then the PSV is probably not even gonna open (fully) meaning that your equipment won't be prtected.  

RE: Comment on this..

(OP)
@ Lizking

great reply..........Yeah i know i am screwed and if it is a liquid service we can apply square law.i escpaed by this on couple of devices.

cheers...........

RE: Comment on this..

(OP)
@ Homayun...

yes i agree with you.....My system is not safe.

RE: Comment on this..

Guys...
Is partial modification of exisiting PSV acceptable from code and authority viewpoints ?

Who dare to certify correct Kd factor for a modified PSV ?
If answer is vendor, check with vendor if they are willing to...also check the cost...

After modification, is the PSV API or ASME compliance ?

Is the modification cost is lower than replace a small PSV ?

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JoeWong
Chemical & Process Technology

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