Pneumatic Safety Relief Valve

[morg916]

Hello,
I'm looking to obtain a pneumatic safety relief valve. The specs. are 1/4" inlet 175 psi set pressure (popping pressure) that will be used on a system that is kept at 125 psi under normal operation. The equipment needs to be capable of operating in a temp. range of -40 to 155 F and no leaks up to 150 psi. The current valve we use is a hard seal valve (Stainless Steel ball on Brass), and we are looking to replace this due to minor leaks that were reported and noticed at normal operation. The replacement valve I'm looking for would preferrably be a soft seal, do to less likely to leak. Viton seals do not meet my temp. requirement. Does anyone have any suggestions?
Thanks!

 

[deanc]

Think there is a Code Case and Interps. on this,,,,Will look

 

[israelkk]

What is the gas type? Air? Helium?

 

[morg916]

The gas type is air.

 

[dcasto]

Teflon or PEEK

 

[chicopee]

Is that small leak that you are reporting caused by debris that gets caught when the valve is manually tested?

 

[morg916]

In response to chicopee. The small leaks are seen in new hard seat valves. These leaks are usually only found when a soapy solution is applied, and no audible leaks are noted. The reason these leaks are a problem, in short, is due to one of our customers. They are requesting a better leak proof valve. I was putting this thread out to see if anyone knew of a particular leak proof valve that works well. I purchased 3 and tested them. All 3 didn't hold up as well as the spec's stated. (leaks noticed below normal oper. pressure)
Thanks again!

 

[JoeTank]

Isn't there an ASME Code (Section VIII) requirement that a pressure relief valve be at least 3/4" in diameter? I'm going on memory and do not have a copy of the Code to verify this.

Joe Tank

 

[deanc]

http://www.nationalboard.org/NationalBoard/Publications/NB18/RedBook.aspx

Also Code Case 2211-1 and 2446 for some ideas.

See NBIC Part RE,Appendix D,Appendix E,Appendix F,and Appendix I.

Should find what you need.

 

[chicopee]

Your best bet would be to contact the PRV technical group and discuss your problem. Any safety valve and relief valve that I had dealt over a span of about 15 years would leak primary because of loose debris and mineral build up. Since you have tested 3 new valves, obviously corrosiveness and the two other factors mentioned above are not the issue therefore I am incline to believe that shoddy workmanship may be a problem. Were these valves purchased from an overseas manufacturer?

 

[morg916]

No, these valves where made right here in the U.S.A. I don't want to mention the name of the valves and give them bad press, because besides the small leaks they are very well constructed.

Does anyone have any experience with a CDI soft silicon seat model ST25. In particular, how well it performs in very cold (down to -40F) and very warm (up to 155F) environments?

Thanks again, for everyone's input!

 

[deanc]

Low temp....soft seats...work good until they lift. Then they weep.

Check the NB link.

 

[morg916]

deanc, do you mean that once they pop, they begin to have leakage problems in low temps? Or do you mean that they do not pop correctly, slow air relief escape (low SCFM)?

 

[deanc]

No the valves work as they are designed and rated. I suggest everyone get valves that have the "NB" stamp for this reason.

Just remember there is most likey particles and dirt in your vessel and I have seen the embed on the seat.

Also a soft seat is likey to take a bit of a set and if the valve lifts....things move.