Safety valve discharge loads

Dear all,

I am looking for any book, paper or code to know a bit more how to calculate the transient loads during the discharge of safety valves, specially in closed discharge systems. Could you recommend m any?

Thanks in advance

I would like to recommend following;
1) Analysis of Power Plant Safety and Relief Valve Vent Stacks, Transaction of the ASME, 1975, G.S.Liao
2) ASME B31.1 Appendix II
3) Time-Dependent Pipe Forces Caused by Blowdown and Flow Stoppage, F.J.Moody, Transaction of the ASME 1973
4) Transient Analysis of water Slug Discharge in PWR safety/Relief Valve Piping, D.A.Van Duyne, ASME 1981
5) Flow of Fluids through Valves, Fittings, and Pipe, CRANE, 1985

Other member may give better idea.

Hello Carletes,

Sun Wee has it covered. I can only add American Petroleum Institute Standard RP-520.

If you want to really get serious about the topic seek out the DIERS publications:
http://www.aiche.org/diers/

Regards, John.

I would like to add one more to the list:

Steam Flow through safety valve vent pipes by Brandmaier and Knebel- Journal of Fluids engineering-June 1976.

Regards

Thank you all.

I think I have got all the papers you have suggested (except Transient Analysis of water Slug Discharge in PWR safety/Relief Valve Piping), but I still don't see it clear how to get the transient forces in the discharge of my closed system. I would desire a document with any "example" about how to apply all those hard differential equations to a real system (perhaps I am dreaming..) Do you know any?

regards,

Look in the back of the piping codes at the
section marked 'how to guess your way through common analytical problems'
You'll probably find out there how to do trunnions and pipe attachments as well.

:p

(only joking)

So, there is not any book, paper, etc where these problems are discussed from a more "peactical" point of view? Something like "differential equations applied to the real world"?

Regards

Carletes, the formula in ASME B31.1 Appendix II is very straight forward and practical.
I normally get the force from the RV supplier, when available.
Dynamic analysis is described in detail in the Caesar Application Manual.

RS,

The problem is that the B31.1 formula is valid for steady discharge but there are transient forces that must be evaluated for those systems whose discharge is not straight forward to the atmosphere. I suppose that a software of compressible flow transients will make it quite esay but when you don't have that...That/s my problem...

regards,

anyone want to volunteer writing up a method for inclusion in the code, attend all the meetings, resolve all comments etc.? I thought not...

But in all seriousness this is a topic that should be covered but nobody has "volunteered" so we all are left wanting....

Yes Carletes, that is why we have Caesar and time history analysis. The time history analysis is suggested in the ASME B31.1 for the closed systems.
You should use Caesar's Time History analysis to calculate stresses and forces in the piping system due to a short duration precalculated dynamic force.

Another analysis is the calculation of dynamic force due to a dynamic event. This is science in itself for which we "pipers" use approximate methods as one referenced in ASME Code. Dynamic piping stress analysis does not involve analysis of the fluido-dynamic phenomena induced by the process fluids flow. The phenomena is to be analysed and relevant dynamic loads are to be provided by the Process Department if approximate methods are not sufficient. There are specialised software packages for calculations of transients in fluids used by process guys.

You can read the following article . http://www.pipingdesign.com/articles/piping_surges.pdf

But, unless you have some knowledge about transient analysis, you will not be able to run the softwares viz. pipenet-transient, AFT-Impulse in public domain correctly.

Many in the nuclear industry have dedicated their whole life in this field just to ensure plant safety. It is better not to trivialize this field. If you are really interested, go back to your engineering school once more for learning the same.

regards,

sam

Engineering design is about safety without waste of too much money.

The easiest solution for this problem is using the reaction force supplied by the safety valve manufacturer and taking 2 as DLF to run static analysis. The reason for this is that most of safety valve piping systems can be considered as one degree freedom system, in which the greatest DLF is 2.

Jack

How about the fact that some huge companies consider POP forces while here in this forum nobody mention it?

Regards,

"We are but warriors for the working day..."

With the time I am given to do most analysis, I follow Jackdliu's method. However, many times I do not have the manufacturer's information, so I calculate a thrust load from the formula in API 520, put it in the model as a static load, and get on to the next job. Don't forget to double it, like he said.

The problem, of course, is that although you didn't have time to do anything more sophisticated, if something goes wrong the company that sues you will have plenty of money to pay some engineer who's never been outside the walls of a university to do some unbelievably impressive dynamic analysis that shows that the failure could have been anticipated if you had spent ten times the man-hours analyzing it.

If anyone has a better practical method I would love to hear it.

Many engineers seems to be atracted by the dynamic analysis, but from my experience is quite unusual to be really required.

Regards,

P.S. And yes, at a rate of few hours per line, is anyone expecting full analysis?

http://www.aft.com/products/impulse/

Carletes,

I have a similar concern regarding relief valve loading. From the instruction, it looks like the software AFT Impulse has this fuction. I have used AFT Fathom and others from AFT. They are good and easy to use.

Carter