Economiser & Superfeed Pressure increases

[deepakp]

Hi,
We have a refrigeration system (propane based) with 2 parallel oil injected screw compressors and common evaporator, economiser. There is a 'superfeed' line from the economiser to the compressor.
Recently the superfeed pressure (along with the economiser pressure) goes up and beyond a particular pressure starts affecting the refrigeration. (Temperature goes to -8 deg C from -16 deg C). When compressor is changed over the problem disappears.
Economiser has liquid level through out.

Any ideas on what could be wrong. Will low levels of refrigerant circulating in the system cause such behaviour? Or is it a compressor related issue?

Thanks for your time...

Deepak

[RANGER1]

deepak,
What valves do each compressor have on economizer line.

eg check or non return,stop,pressure control valves,strainers.

Maybe one of these is the problem, either stuck or not fully open, blocked etc.

Suggest that pressures could be checked right at entry point of economizer point on
both machines ,if there is a point that a gauge can be installed to compare.
At the same time observe economizer pressure as well & see what you come up with.

Assuming both compressors are same size & same slide valve position.