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Gareth
02-04-2004, 07:47 PM
:confused: I would be very grateful if someone could help me out on a couple of dilemas that I have.
Two seperate Bock AM5 compressors have started leaking on the shaft seal, both systems are around 5 years old and never leaked on the shaft seals before , seems strange both have failed around the same time.
Could it be a coincidence?
Also, has anyone any tips on how to change the shaft seals on these particular units, have already pumped down and closed service valve's etc, but need some advice on the mechanical side of these Bock semi hermetic units?
Cheers Gareth.

chemi-cool
02-04-2004, 08:20 PM
hi gareth.

semi hermetics or open?

no shaft seal on semi hermetics.

first, you have to disconnect the motor from the compressor.
then, take of the coupling from the shaft.
open the ring around the shaft and pull carfuly out.
from the inside, pull out the bottom part of the seal.

insert in back order.

be very carfull on the polished faces of the seal.

that is briefly how its done.
you willneed, before you start, set of seals and a shaft seal.

try to get an exploded view of the compressor so you will know where every thing is located.

I would advice you that for the first time, do it with someone with experiance on that particular job.

on open compressors, leaks will accure when standig still for a long time or lack of lubrication. so clean also the oil filter ad check oil for small particals.

which refrigerant do the units use?

chemi

Gareth
02-04-2004, 09:12 PM
Cheers Chemi

Yes youre right of course open :o

But I cant see any room for a coupling as the motor seems to be attached to the compressor, hence the mistake, open - semi hermetic?

I will have to get an exploded view of the compressor as you suggested.

I will check out the condition of the oil? as the system hasn't been standing still for a long time.

The refrigerant is R22.

I have ordered up the shaft seal @ £104 each, I'm hoping this includes set of seals at that price?

Thank you Gareth.

maco
02-04-2004, 11:27 PM
Hey Gareth, not really familar with the comp you talked about, but i have done shaft seals on york screw and centrif machines. be carefull after you pumped down that the valve is holding and no gas is returning. as already suggested an exploded view would be good for you. this your first seal change? if its a teflon "c" ring try not to touch the teflon as even a finger print could cause it to leak again, make sure you use loads of oil when sliding in the new seal. You say the motor is housed to the comp r you sure its not just the shaft housing. first job is to de-couple the motor and start from there. Shaft seals are actually supposed to leak a little bit off oil as it is actually the oil that creates the seal. But they do wear. how many hours of run time on your machine

shogun7
02-04-2004, 11:28 PM
Gareth,
This may be of some help
http://www.thermagroup.com/index.html
Roger :cool:

Andy
03-04-2004, 11:08 AM
Hi :)
Bock AMR compressors are in essence an open type compressor with a direct coupled motor, making them look much like a semi-hermetic compressor.
To change the seal.
Pumpdown and isolate (already done0
Remove the drive motor
Remove the end cover
Remove the staionary element of the seal
Remove the moving part of the seal, this may be held in place by an allen key type grub screw.
Clean the cover plate and shaft up, looking for excessive wear onthe shaft at the point when the rotary seal is made gas tight to the shaft.
CHECK the compressor thrust, and refer to the manfacturers data for allowable.
Oil up you hands anf the seal assembly, the oil will protect the seal faces during installation.
Fit the seal in reverse order to stripping.
Torque up the cover plate, with a torque spanner.
If you can fill the seal chanber with oil, by a plug on the top or by a hand oil pump, forcing oil into the crankshaft.
Evacuate compressor and run up as normal.

Hope this helps, regards. Andy :)

Gareth
03-04-2004, 11:25 AM
Not sure how many hours run these compressors have done.

Will be caerfull that service valves dont leak, quite critical I should think on this system, as it does not co-orporate a liquid receiver and relies on the condensor to store the refrigerant on pump down.

Thank you for the link to Thermagroup website, very useful will keep this in my favourites.

Changed shaft seals on milk pumps and water pumps in the past but this will be my first refrigeration compressor, so I think I will seek assistance for this installation from a more experienced refrigeration engineer.

I will keep you informed how this job goes and thank you all for the info.
Nice to know this sort of assistance is available, never seen or heard of this in any other trade. :) very re-assuring.

Gareth
03-04-2004, 11:33 AM
Thank you Andy

That info will be very useful I'm sure.

Feeling quite confident now :)

chemi-cool
03-04-2004, 01:54 PM
hi gareth,
]
When I think more about this problem, it doesn look right to me that both seals leak together.

usualy, shaft seals will start leak after a long standing period. once they start working, oil is flowing back inside the compressor and the leak stops.(the same as cars AC compressors).

give it a go before you open the new parts boxes,
let it run for a while and check again.

this may save time and money and maybe not!

chemi

Peter_1
03-04-2004, 04:28 PM
It is a wel known problem with the AM5 compressors, reason why Bock changed to the common semi-hermetic design.
If you see a AM5, then there is always oil under the shaft. (like on a Harley Davidson bike :D )

You will need a special pull-out device (we can borrow it for free at our local Bock supplier)

Frigopol used a similar set-up of compressor motor but that was fully hermetic. It was a vertical standing up compressor with a stainless steel housing around the rotor and the stator was then placed over the SS cover.

So there were no windings inside the compressor (no problems with a burn-out and no heat of the windings inserted in the gas)

Peter.

Gareth
04-04-2004, 06:08 PM
Hi Peter & Chemi

You've got me thinking now :confused: , the reason I thought both compressor shaft seal ware leaking was after seeing a large pool of oil under one of the compressors I inspected the other, and on wiping my hand under the motor i had oil on my hand, immediately thinking it was another faulty shaft seal, but as you said Peter there is always oil under the shaft, this second unit might be ok and as suggested by Chemi I will let it run for a while and check again.

Peter you must be right, It is a wel known problem with the AM5 compressors, as they have embeded some sort of absorbsion material under the motor which is soaked in oil.

The mind bogles

Cheers Gareth.

shogun7
05-04-2004, 09:12 PM
Peter
(like on a Harley Davidson bike ) Must have been an older bike because mine never leaked oil and when the sun was out you needed sunglasses or you would go blind, don't you know?
Roger :cool: :D