If a safety relief valve discharge through a tee centre piping in two opposite horizontal directions, can we ignore the thrust force, considering them to be balanced ?

regards,

sam

Hi Sam,

The short answer is no.

When the SRV lifts there will be a change of direction of the effluent within the valve itself that will give you a horizontal and a vertical impact. Then when the wave front hits your TEE there will be vertical and horizontal impacts .....and on a good day MAYBE the horizontal components will balance. Keep in mind that the series of impacts is NOT instantaneous. It is best characterized by a time history. Please thoroughly read B31.1 Appendix (Roman number) II for additional information.

Regards, John.

Thank you, Sir John Breen, for your reply. But, I have the following query:

Yes, we can't ignore transient impact of the safety valve during opening up or closing time. But, the verical portion of the load in steady state, gets balanced in the configuration I referred and there remains no horizontal load in steady state. Obviousely, I have assumed same flow rate in steady state all along.

regards

sam

PS- Thanks for B 31.1 App II reference. Now, many of us toy with fluid transients sofware like Pipenet-Transient without knowing the basics.

Well,
I would say that the problem is, in reality, that a pair of relieve valves would never open at the same time. You could model as it will happen but chances, (again, in my opinion), are very slim. I think that in this kind of arrangements, one valve is more sensitive than the other, and whoever is more sensitive is going to pop up before and release the overpressure on the system. If the pressure is not relieved by one valve (which I certainly doubt) then, the second would open, but again the time-force curve will be different.
Since you never know who is the more sensitive one, I would suggest analyzing one at a time. This would be the worst case since the load is totally unbalanced.

Regards,

Pedro Massabié

Where is the pair of safety valves in the theme
"If a safety relief valve discharge through a tee centre piping in two opposite horizontal directions, can we ignore the thrust force, considering them to be balanced ?" ?

My question was regarding two exactly opposite horizontal exit from one safety valve's outlet piping.

regards

sam

Well not to disagree but the answer is yes and no... once steady state flow is reached the reaction forces cancel out, getting to steady state however the forces are unbalanced.

Because the force imbalances in the elbow pairs are short in duration "participation" by the piping system is minimized.

However valve chatter or simmer may still cause serious problems because of the continuous addition of unbalanced pulses.

Upss, sorry I missunderstood your question..., and now I realize that I haven't seen this kind of valves at all.
Regards,