Dear All,
I am working on Relief Rate estimation for Fuel Gas Control Valve failure case with HP / LP interface (High Pressure 600# upstream of Control Valve and Low Pressure 300# downstream of Control Valve). There are two Slam Shut valve provided to protect against over pressure scenario downstream of Control Valve.
My questions are
1) Do we take credit of Slam Shut Valve in Relief Rate estimation for Control Valve failure case?
2) If yes, how to estimate the relief rate (by taking credit of Slam Shut Valve)?
e.g. for reverse flow scenario with two dissimilar check valves API allows credit by considering 1/10th of pipe diameter as orifice size and calculate the relief rate. Is there such credit for Slam Shut Valve?
For easy understanding I have attached system schematic.
Look forward to expert opinion in this regards.