clarke industrial compressor

[1.8T]

I have a large clarke industrial compressor, i think the model number is SE19C200ND, bought new from machine mart 4 years ago but not used it a lot as i use my smaller compressor normally, one day i went to switch it on and it wouldnt start, turning the compressor over by hand then trying the switch again and it will start however, i left it running for a bit and switched it off and tried to start it again and the same thing happens, anyone any ideas? its wired into its own power supply and isnt tripping the mcb

 

[shenion]

Could be the start capacitor is getting weak.

 

[tigler]

Does the motor hum as it's trying to start ? What conditions has it been kept in ?

 

[1.8T]

Does hum yes i remembered that after posting, been stored indoors, well in a shed out of the rain anyway

 

[tigler]

Reason I asked about how it's been stored is because I have known motors on compressors tighten up and eventually seize through internal corrosion. Occasionally I've known the varnish in the windings flow into the rotor and seize it.
So, first thing to determine is if this problem is mechanical or electrical. Remove the belt and see if the motor is free to turn, it should be totally free and move at the slightest touch, if not it's suspect. Try the air end (pump) too, that should be fairly easy to turn, if it becomes very stiff there is a problem.
If all is well with the mechanical side then try the motor without the belt on by just turning on as normal, it should spin up immediately. If it's sluggish or weak then there is the problem. Could be a cap or a winding.

 

[1.8T]

Will have a look as soon as i get a chance

 

[1.8T]

Finally got round to having a look at this, with the belt removed the motor will start instantly, turned it on and off half a dozen times and same every time, turning the compressor over with a single hand it seems to turn alright, some resistance but i put that down to compression? not sure how it should feel really, odd really as if i can turn it one handed i would think a 4hp motor would manage it ok, only thing of note really was the belt was very tight so im wondering if that could do it and maybe i should try it with the belt back on set a bit looser, remember though i have had this since new and never touched the belt before now

 

[tigler]

There will be slight resistance when turning the compressor, so thats normal. If the motor turns without any resistance, at the slightest touch, then any problem it may have will be electrical.
If there is reluctance to start up again with the belt back on it is more than likely the motor run capacitor. They are available from Maplin and quite easy to replace.

 

[mike 109444]

Could be the unloader valve. The fact that you got it to run up (your first post) then it would not restart (tank now full of air?) means the compressor pump may be trying to push against the full tank of air. The unloader is that short hiss of air you would hear when the compressor has reached pressure and turns off. It dumps the air in the pipe going from the pump to the tank, so the pump "sees" very low pressure in that bit of pipe when it goes to fire up again. You could try emptying the air then switch on. If it fires streight up suspect the unloader.

 

[1.8T]

Mike tank is empty, refitted the belt tensioning to the same as before and it wont run up, im going to slacken the belt off a little and see if it makes a difference as i said belt seemed very tight to me, tigler how can i test the start cap?

 

[tigler]

Without appropriate test equipment it's not really possible. They aren't very costly from Maplin though, caps that is.

 

[1.8T]

What test equipment is needed?

 

[tigler]

A capacitance tester that applies the working voltage to the cap under test.
Have you tried gripping the motor pulley with gloved hands to determine if it's developing power ? If you're careful it's a good indicator of a problem with the motor.

 

[Shox Dr]

WARNING

Do not do the above with the belt fitted fingers/limbs may be removed


sorry Tigler, just thought it needed to be said.

 

[brightspark]

use a piece of 2x2 inch wood 3 foot long. gently lever it against the pulley to determine if theres any power its either the starting windings or the start capacitor thats knacked keep hands away belt or no belt

 

[tigler]

Please excuse my flippancy there guys, I think nothing of doing stuff like that myself !
Yes, do be very careful and remove the belt first !

 

[eil]

Capacitors would be my first to check as has already been said, they don't make them like they used to thats for sure, get some new ones in you will need them sooner than later.

 

[tigler]

Problem with modern caps is that the oil that was used to fill them and act as an insulator is now an illegal substance. They now rely on plastic materials which break down much more quickly and often suddenly fail, and this can happen even when the cap isn't being used ! Look carefully at the cap or caps if it has start and run caps, any bulges or splits in the casing and they are dead or dying.
The ones from Maplin are UK made and good quality, definitely better than most imported stuff.
To give an example of how much longer old caps last, I have a couple of single phase compressors with their original caps, going back to at least the 70's and some the 60's, and they still work. Yet I expect to replace the caps on modern compressor motors when they have done as little as 3-4 years !