Air Compressor problem...

[ellal]

My compressor has just started doing the following...

When charging up, it gets to just below it's 8 bar limit and then there is a rush of air from the area of the motor until it gets down to about 4 bar and then the air ceases to be expelled..

Any ideas as to what has blown/gone wrong?

 

[Deleted member 174758]

A couple of things spring to mind. Firstly have you drained down the receiver (you should do this after every day's use). Secondly I'd suspect the compressor (receiver) safety pressure relief of blowing off prematurely (these can't be fixed, only replaced - fortunately only £8 to £12 on smaller compressors). If it's neither of those two it may be time to look at the pressure regulator switch box

 

[ellal]

I've drained it, although must admit I don't do it as often as you suggest.

I've narrowed the blowing off down to what I suspect is what you call the safety pressure relief - a small valve with a keyring type attachment.

However, it now appears that the guage is showing the motor is trying to continue past 8bar - maybe it was showing an under pressure previously?

 

[Deleted member 174758]

I've narrowed the blowing off down to what I suspect is what you call the safety pressure relief - a small valve with a keyring type attachment.

Thet sounds right, They're normally brass fittings and reside on top of the receiver (tank)

However, it now appears that the guage is showing the motor is trying to continue past 8bar - maybe it was showing an under pressure previously?

Maybe there's a problem with your control unit, too. Frankly if your safety blow off is playing up then just replace it - no amount of fiddling with it will make it right (and might even result in the compressor exploding) - in any case they aren't designed to be repaired. Once that problem is sorted then you can look at the switch regulator if needs be

Compressors are often set to start automatically if the receiver pressure drops below, say 7 or 8 bar and to stop automatically when the pressure reaches around 10 bar. This is controlled by the switch regulator box. The safety is set to cut in at slightly above the switch regulator maximum, but well below the pressure vessel (receiver) test limit, say about 10.3 bar (not sure, don't have a valve here to check)

PS if you don't drain off your compressor at the end of the session you'll leave water inside which will eventually corrode the area around the drain cock. Best case scenario is that one day you'll start it up and it will wee rusty water all over your trainers - worst case scenario is that it the metal will fail catastrophically under full pressure (often 10 bar/150 psi) which might well not make your day. Rarely happens, but better safe than sorry, I'd say

 

[ellal]

Thanks for the advice...

Is the safety 'blow off' a standard item or manufacturer specific?

 

[Deleted member 174758]

They're not manufacturer specific, but they are preset to a specific pressure. Any compressed air specialist should be able to supply the correct item. In this part of the world we have people like Thorite (Thomas Wright & Co), but there are loads of them out there

 

[ellal]

An update about a problem solved...

I called SIP to get a replacement relief valve, but the guy on the phone said it would be the pressure switch at fault. I duly bought a replacement but that didn't solve the problem..

Called again and got a much more helpful person who suggested adjusting the pressure relief valve..

After fashioning a tool to do so, turning the grooved end by about 10 degrees stopped the blow out and compressor is now working fine...

To be fair SIP said they will refund the cost of the pressure switch, so total cost in the end will hopefully = 0

Thanks for the advice JobandKnock...

 

[Deleted member 174758]

Thanks for the update. Glad you got it all sorted out