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Hydrovane Compressor Blows A Main Seal

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awemawson:
For the past eleven years my 2.2 kW Hydrovane compressor has given loyal service, rewarded by the occasional oil and filter change. Although it is on 24/7 it doesn't get heavy use - in fact in those eleven years it has only run for 268 hours. It wasn't new when I got it and I fitted the hours meter pretty soon after I got it.

Recently I've noticed that it is pumping up rather more often than it has  been, and a splurge of oil has been dripping out of the oil cooler onto the tank. Speaking to the chap I bought it from (amazingly he is still in business!) it should pump it's 50 litre tank up from discharged in two and a half minutes. I tried it yesterday and it took three and a half minutes, and today it wouldn't ever get there poor thing.

Received wisdom it that it's probably the rear air / oil seal. So today I dismantled to check and order parts.

The air vane compressor hangs off the motor, so, a bit of dismantling and sure enough lots of evidence that indeed this is the problem (or certainly A problem!)

awemawson:
This is where the fun started - just need to remove two counter sink 6 mm x 20 mm  socket cap screws and pull the old seal out. One was fine, but the other had rounded off faces to it's hex socket, and no way would an allen key turn it.

I tried all the tricks I know:

 - grind the end of the key to raise a burr
 - peen the socket with a pin punch to close it up
 - heat the screw cap with a red hot bar

etc etc and nothing worked - nothing for it but to drill it out  :bang:

Now due to the nature of the beast this meant using a hand held drill - not nice in a situation where precision is called for. Now M6 tapping drill is 5 mm so theoretically if I can manage to drill 5 mm then I can re-tap which should dislodge the remains of the thread. Fortunately the screw was not high tensile - which is probably why it had been rounded in the first place, and also fortunately with socket cap screws you have a good chance of getting a  pretty well centred drill to start with.

I selected a drill that just fitted inside the rounded hex, drilled all the way through, then worked up in 0.1 mm steps until I got to 5 mm at which point the top of the countersink came off releasing the oil seal.

A careful clean up, and an M6 tap produced an acceptable if not perfect thread.  :thumbup:

OK pull the oil seal, but first clean up the shaft as there is a bit of surface rust. Now we can order parts.

The seal itself is actually a double seal with lips facing both ways, as not only does it seal against air pressure and oil, under some circumstances it has to seal against vacuum or 'suck'

20 mm shaft - the seal is £80  :bugeye: :bugeye: I was advised that the best way to buy it was as part of a 'Top Up' kit that had the seal, all the oil rings and gaskets, and various shims and bits. What with the Top Up kit and a filter / oil change kit I have no change out of £140  :bugeye:


Bits on order - should arrive later in the week, meanwhile no air to any of the workshops  :(

. . . it's amazing how often today I've reached for a blow off gun, forgetting there is no air !!

Spurry:
Very neat job, managing to get that reluctant screw out. 
Now you've shown how to do it, my excuses are rapidly diminishing for ignoring the noises my Hydrovane is making.
Pete

awemawson:
It ain't fixed yet Pete, this may not be the only problem - but the only way to find out is to pack it with expensive  bits and put it back together  :med:

NormanV:
This is going off topic but is still to do with repairs.
On Sunday I sold my Raglan Mk 1 lathe, I felt it was worth £200 but I only got £125. None the less I was happy to get that money. In the meantime my Land Rover blew a top hose. It cost me £157 to be fixed. How the f**k do I make any progress in this world? I know that if I had not sold the lathe I would be in deep ****, but for a short time I was dreaming of what I could do with my new found riches. Ah, such is life!
 

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