4 replies to this topic

[fahood]

Dear all,

I was wondering if anyone can give me some guidlines for sizing a relief valve against surge pressure. I've looked in API and couldnt find anything except that its not recommended to use conventional valves, thats all. Can you pls point me in the right direction?


Thank you in advance

[ELEMAN]

Hello everybody:

I would suggest you to post this question in the Relief Devices Forum http://www.cheresour...-devices-forum/

Good luck!

[fahood]

I am sorry about that I wasnt aware of such section

[kkala]

Looking into "Waterhammer analysis" by John Parmakian (Prentice Hall, 1955), I have found no information on the subject. If I remember well (not certain) "Hydraulics for engineers" by R.W. Angus (Isaac Pitman, Toronto, 1943) mentions PRVs as a protective measure against waterhammer. I see that the book is still available (e.g. see www.bookfinder.com), but it may not be worth while getting it now.
In my work environment I was informed that the relevant PSVs should have faster response than normall PSVs to be effective. In general we do not design antisurge protection, moreover I have not detected PSVs serving this purpose in the refinery.
Probably best way is to use some software of surge analysis, vary the flow through said PRV and see the results. I suppose surge pressure came from a water hammer analysis using some software.
Note: The question in a more specific form has gone to relief devices forum, under the thread "Back Pressure In Surge Relief Valve", as I can see; but I think my post had better be here, better fitting the original query. Continuation shall be in the other forum.

Edited by kkala, 19 June 2011 - 05:33 AM.

[chemsac2]

fahood,

You are correct in that API 521 suggests that relief valve is not fast enough to respond to peak transient pressures. However, special relief valves are available to take care of this fast transient peak pressure. Refer page 10 in attached file for details.

Moreover, many surge analysis softwares have "Relief valve" module which can help you fix requirements of relief valve i.e. flowrate, response time etc. I am sure AFT Impulse has relief valve module and their help file gives relief valve modeling basis.

Regards,

Sachin

Attached Files

•  30. Piping_Pressure_Surge_Solutions.pdf   326.67KB   277 downloads