Cascading TRV
Cascading TRV
(OP)
I'm looking for a document or book to purchase that would help me design a cascading thermal relief system for pipes that contain a fluid that is block in by valves.
Thanks for any help,
Thanks for any help,





RE: Cascading TRV
Like a series of plugs made of Cerrobend or other low-melting-point alloys with different melting temperatures?
Mike Halloran
Pembroke Pines, FL, USA
RE: Cascading TRV
It's not too common to have more than one cascade and most times now people don't like the cross connection. Far simpler to include a closed drain system.
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RE: Cascading TRV
A few tips:
a) Actual set pressure on a conventional RVs' is affected by backpressure. For example, a 10% increase in backpressure increases the SP by 10%.
b) Actual set press on a balanced bellows RV is unaffected by backpressure for backpressures up to about 70-80% of set pressure.
You can find this this nugget in the API 521.
Good luck
RE: Cascading TRV
I’m looking at using the C series fixed cracking pressure check valve [10 psi] Swagelok check valve that will vent/relieve pressure back into a vented above ground storage tank. Max pressure in the tank based off fluid height would be 11 psig.
So I guess in a perfect world if the tank were full this would start to relieve once the pressure in the closed pipe reached 21 psi.
RE: Cascading TRV
They are just plain pressure differential valves.
RE: Cascading TRV
I believe you are correct.
This is not really what most people think of as a "cascading relief, nor is a "fixed pressure check valve" seen as a safety valve. the margin on setting pressure is likely to be much higher than a proper spring relief, possibly -50%, + 25%
If the tank level is low, then any pressure >10 psi will flow fluid back to the tank.
Is this what you want?
10 psi is very low - why so low?
This system as described does not make any sense.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.