york ylcs chiller noisy on shutdown

[koolkatz]

hello guys
i have a ylcs screw chiller that spins backwards on shutdown.i suspect that the discharge check valve is faulty. does anyone have any information regarding the check valve.
can anything else be contributing to this problem?

[NoNickName]

Screw compressors spin backwards when they stop, especially when they have built-in oil separator, which is a reservoir at high pressure. This is normal.
If the two pressures equalise quickly when the compressor stops, then you have a faulty check valve.
On the other hand, if you still have differential pressure, then the check valve is not faulty.

[yorkman_gr]

the backspin is normal in this units once is a for a short time , few sec,if the backspin lasting long and u get fast equalizing pressure then something is wrong with check valve