Excessive Pressure Drop in Pressure Reducing Valve
Excessive Pressure Drop in Pressure Reducing Valve
(OP)
I have a Fisher 627WH pressure regulator, used in anhydrous ammonia service. This valve was originally going to see up to ~750 psig and drop it down to 300 psig, but now is only seeing about 150 psig. I am seeing excessive pressure drop across it, ~100 psig! It doesn't make any sense, the valve should be wide open and only see minimal pressure drop (<5 psig). We took it out and inspected the internals and found no trash or debris in it. Any clue what could be causing the pressure drop?





RE: Excessive Pressure Drop in Pressure Reducing Valve
To answer your question a full set of conditions (original and current) is required.
RE: Excessive Pressure Drop in Pressure Reducing Valve
RE: Excessive Pressure Drop in Pressure Reducing Valve
Original conditions:
Max inlet pressure - 730 psig
Outlet pressure - 600 psig
Temperature - 93 F
Max Flow - 16.2 gpm
Current conditions:
Inlet pressure - 170 psig
Outlet pressure - 30 psig
Temperature - 50 F
Flow - 625 lb/hr ~ 2 gpm
This valve (regulator) has a 1/4" orfice in it with a 1" body, could the diameter of the orifice be restricting flow? Is this a possibility? Or the liquid ammonia could be flashing as it goes through the valve, but this is a low flow rate, so I'd be surprised if cavitation is the problem.
RE: Excessive Pressure Drop in Pressure Reducing Valve
htt
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Excessive Pressure Drop in Pressure Reducing Valve
RE: Excessive Pressure Drop in Pressure Reducing Valve
RE: Excessive Pressure Drop in Pressure Reducing Valve
Or run my $2000 process simulator.
RE: Excessive Pressure Drop in Pressure Reducing Valve
The regulator has spring to keep the valve closed with 730 psig and 600 psig outlet. At the lower outlet pressure a spring with a lower spring coefficient is needed. The fisher book says you need a 627W with a low pressure spring. You should be able to get the parts to modify and not replace the whole valve.