valve leak

[karim14]

Hi , in 1st gas compression plant we have in process out let final stage of compressor one valve to flare ,in shut off position ,we have up stream pressure valve at 340 bar ,but we have in down strem of valve icing on pipe in the morning ,we have sure a leak.
In the 2nd same gas plant we have a same valve to flare ,in shutt of position , with same condition 340 BAR up strean ,and we find in down stream valve icing .
I want to know if i use the optical gun "temperature up stream and down stream to detecte wich valve is leaking more ,to change it before the other in less conditions leaks The type of valve is :ANGLE 90° CCI DRAG VALVES best regards

 

[racookpe1978]

If the leak rate through both valves is so severe that the pipe is icing up downstream of the valve, the temperatures will be nearly identical.

Check instead the amount of icing, the length of the iced section for a better clue.
Listening to the flow "might" give you an idea (higher noise -> more flow from the leaks) but that is very questionable to hear noise levels amid environmental outside noises.