There is a vapor return line from LPG storage tank to the loading ship. On this line, two relief valves are installed. (normal operating P is 4 barg, line design P is 22 barg) People on site indicate that these two valves are installed for ESD valves blocking this line. (one ESD valve is at the tank outlet, one is at middle of the line, the other one is near the loading station ) So they call them thermal relief valves. My point of view, TRV only release liquid for thermal expansion. But they say LPG gas also expanses when temperature rises. Based on my calculation, if these valves opens (24.2 barg), it must be the fire case, even higher than material melt down temperature. There is no other case which can lead such high pressure.
The way they size the valves is that taking the normal flow times 1.5, that is the relief load to the valve. To me this is not a meaningful approach.
Is that necessary to have these RV's ? if yes, they have to be sized based on the fire case.
Thanks.
Edited by August, 19 July 2017 - 02:28 AM.