Back pressure valves

[Loafa]

Hi Guys,
been having some fun a new A4AS back pressure valve on a PHE for chilled water, it seems to not want to open and modulate or it opens and wont close off on the set spring.
Seems the only ay to get it operating to some degree is to throttle the down stream suction valve and the liquid feed valve, any advice appreciated
the suction is into the HP side of a two stage system running about 2 bar

[Oregon Jim]

I would guess that you have a small piece of crud stuck in the valve. It doesn't take but just a tiny piece of pipe scale or dirt inside these valves to make them fail. I would order a valve kit and simply rebuild the valve. It is pretty easy to do.

Is it possible that you have the manual opening stem on the bottom of the valve opened? That would prevent the valve from working.

You can find the info on that valve here on line # 23-06; http://www.parker.com/portal/site/PA...vision#results

[Loafa]

Thanks mate, the service manual off that link has it all
cheers

[Segei]

Hi Guys,
been having some fun a new A4AS back pressure valve on a PHE for chilled water, it seems to not want to open and modulate or it opens and wont close off on the set spring.
Seems the only ay to get it operating to some degree is to throttle the down stream suction valve and the liquid feed valve, any advice appreciated
the suction is into the HP side of a two stage system running about 2 bar

Probably, your valve is oversized. Oversized valves have unstable operation. Throttle upstream and downstream of this valve.