Hi
I have a pump discharge PSV which is set at 180 psig. The PSV is pilot operated. It is connected to a header which has max operating pressure of 120 psig. So, the backpressure is 120 + built up backpressure. I calculated built up backpressure + backpressure = 125 psig. This is 69% of set pressure. When calculating size of relief valve, we have a backpressure correction factor (Kw). I could not find in API what Kw value to be used? My questions are:
1. Is my backpressure assumption correct
2. How to assume Kw..is it safe to assume 1 for Kw
thanks,
Rs