Screw air compressor wont shut down

[oldman2]

A long shot I know, but hoping someone here works with compressors.

A friend wired in his 2nd hand untested Broom Wade 6010E 7kw 3 phase air compressor. When he test ran it with it connected to a reciever it failed to unload or shut down before reaching the max working set pressure of 8 bar.
I really dont know a great deal about screw comps and could do with a pointer or two as to what can be the problem please.

I found the main pressure differential switch and assumed it may be faulty, as a quick and dirty test I disconnected one of the 2 wires into it, ran the comp then touched the 2 wires together, a solenoid somewhere was heard clicking when I short the pair but the comp didnt unload or shut down.

I'm unsure of the correct method that this model should follow but guess that it loads from once the star delta starter is energised, reaches set max pressure then should unload? the motor should keep running the comp unloaded until a pre set timer times out, if no air is used once the timer times out the comp shuts down, if air is drawn the comp loads up to max pressure again.
Is this the correct operation?

 

[ricicle]

Your understanding of operation sounds correct. Is there a set-up controller that has lost it's parameter settings or is the solenoid faulty. The armature might be moving but is there a faulty diaphragm inside ?
Are the pilot pipes gunked up ?

 

[Zambezi]

Have you checked with the manufacturer to make sure you have all the kit? Sometimes when you buy things second-hand you don't get everything.

 

[oldman2]

I'm pretty sure its all there, the comp was taken as payment for a bad debt so not much chance of getting a history although it does seem that it may have been on its side at some time during delivery so oil may have seeped into somewhere its not normally found.

I didnt want to go stripping it without further info on the control sequence.

Gunked up pilot pipework or stuck diaphram sounds like it could be a pointer, I will get him to have a look, thanks.

 

[ericmark]

It's a long time ago but seem to remember de-load and shut down and once up to pressure they de-load and start a timer and if pressure is held for set time then they shut down my problem is we had two and at end of day I would switch the one running off get in car drive to gate and then second one would start.