Bitzer OSNA8591-k Oil Defferential problem

[africaguy]

I am in the process of commissioning 6x Blast freezer systems using a Bitzer OSNA8591-K screw compressor on each Blast Freezer.
On one of the units we keep on getting a oil pressure differential alarm over the filter. On changing the filter it runs ok for 7 minutes where after the machine trips again on the same fault. When restarting the compressor with out replacing the filter it will run for only about 1 minute with the old filter in place. Normally this indicates a dirty filter but when I took the filter out for inspection it still looks almost brand new. I have replaced the differential switch as well as the oil stop cover on the filter but the problem still persists. I also changed the electrical cable and plug for the sensor which also did not make a difference.
The pressure difference across the filter on all packs are between 5 and 5.5bar and we have a 8.5Bar differential between HP and LP which is more than enough for the lubrication system to function.
Has any body else ever experienced a similar problem on this type of Bitzer screws and what was the outcome of the problem.
The problem started when the machine had about 1.5Hours running time on it. Also there is no liquid present in the oil.

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[Martin Davies]

Hi out of interest are you using any type of evap pressure regulator?

[RANGER1]

On one occasion solenoid was to small tripping it out on oil flow switch.
Lit was the first one I had worked on & had Danfoss EVRA3 instead of a 10.
Also inperative to have oil separator oil up to temp & oil cooler 3 way thermostat bypass valve installed.
Maybe you have some issues there?