2 replies to this topic

[sahas]

In sizing of a Safety Relief Valve (SRV) reaction force at the outlet is used by piping engineers to design for the support ( normally supplied by the vendor).
For Steam and vapor applications literature exists which determines reaction forces

I am looking for guidance/standard literature for calculating the reaction force at the discharge for a liquid application where the discharge piping is under a superimposed backpressure of 45 psig and has around 50 feet of 1-1/2" piping .
It eventually vents into an tank. So for all purpose it is a closed discharge system

Does the reaction force for the RV gets affected by superimposed back pressure ?

Any help will be much appreciated.

[ecas]

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In the discharge pipe the force in every direction change is defined by:
F = PA + pAV2/g
P .... pressure
A .... pipe cross-sectional area
p .... fluid density
V .... flow velocity
g .... gravitational constant
During the transient when the valve is opening, the fluid begins to travel trough the pipe displacing the air and the said force acts on every pipe elbow.
When the pipe is completely full of liquid and the flow is continuous, every impact force ( the force produced by the fluid entering the elbow ) is compensated by the corresponding reaction force ( the force produced by the leavig fluid ) and finally only remains the last reactio force.
For example in a valve discharging trough a vertical elbow upward, the only final force will be the reaction vertical down.