Check valve noise - heat-pump

[desA]

Hi everyone,

We have a heat-pump with a Copeland zr scroll compressor, with a 1/2" flare Castel check valve installed in the discharge line.

The piping restrictions mean that the check valve lies on approximately 15 degree incline.

At high temp operation, it seems like the check valve may be vibrating. The line is sized at discharge nozzle diameter - too small, in my view. My thoughts are that there may be excessive gas velocity through the check valve.

It's not a serious noise, but enough of a rattle to bother my ear.

Could anyone shed light on what is going on. Thanks so much.

[narkom]

Hi!
I know that Danfoss uses special check valves in discharge lines to avoid resonance problem:
"In refrigeration plants with compressors
connected in parallel, it is advantageous to use
NRVH, since the spring is stronger than the one
utilised in NRV. Also, resonance problems can be
avoided at partial load in the refrigerant plant."
Because the stronger is the spring the higher is system's resonance frequencies.

[desA]

Hi Narkom,

Thanks very much for your comment. This makes sense in terms of resonance. Using the stronger spring would make sense here.

I'll look into the Danfoss range & bring one in. Now that you mention the NRVH, I remember seeing that in their catalog.

Excellent - thanks again for your wise advice.