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Relieving capacity of PRV

Relieving capacity of PRV

Relieving capacity of PRV

(OP)
Hi

In the following equation
A=(13160W?TZ) / CKP1Kb?M

A =    Minium effective discharge area,square millimters                                    
C=     Coefficent determined from an expression of the specific heats of gas or vapour at standard condtions (if not known use 315)                                        
K=    Effective coefficent of discharge K= 0.975                                        
Kb=     Capacity correction factor due to back pressure = 1 for atmospheric                                        
M=     Molecular weight of the gas or vapour from standard tables                                         
P1=     Reliveing pressure, KiloPascals absolute. This is the set pressure (kPa) + overpressure (kPa) + atmospheric pressure (kPaa)                                        
T=    Absolute temperature at the valve inlet, degrees Kelvin (C + 273)                                        
W=     Relieving capacity, Kilograms per hour                                        
Z=     Compressablity factor. Use Z = 1.0 if value unknown                                        
What would W relate to ? a % of tank volume?

Thanks

RE: Relieving capacity of PRV

W is the required relieving flowrate (at relief conditions) established from an overpressure scenario analysis.

RE: Relieving capacity of PRV

(OP)
Thanks I have just found that myself.

Is A - Minimum effective discharge area,square millimeters                                    

The area of the flange on tank or exit erea of PRV?

RE: Relieving capacity of PRV

A is in mm's.  It is the relief valve orifice area.  Check out API 526 for relief valve body sizes vis-a-vis orifice size.

RE: Relieving capacity of PRV

About A

The way i understood it A is actually more like a nominal area that makes it possible to compare valves from different makers. Ther actual free area may differ but the manufactor will then know how to compensate.

Best regards

Morten

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