Author Topic: mechanical seal lubrication fluid advice  (Read 3559 times)

Offline picclock

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mechanical seal lubrication fluid advice
« on: September 07, 2012, 04:42:28 AM »
I'm making a part which uses a mechanical seal, the normal carbon/ceramic interface. The seal will be static at near its maximum pressure but operate at a much lower pressure. The seal is in a chamber which will will be filled with a lubricant - the question is which one ? The rotational shaft speed is 500rpm and the seal carbon ring diameter 17.8mm giving a surface speed of 28 M/min, the seal has a rating of 900M/min which is 32+ times more than I need. The seal will only be subject to ambient temperatures. Despite internet searching I have found very little information on the correct kind of lubricant to use.

Any advice / experiences shared most welcome - if all else fails I will just fill it with motor oil.

Best Regards

picclock
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Offline John Rudd

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Re: mechanical seal lubrication fluid advice
« Reply #1 on: September 07, 2012, 06:48:58 AM »
The seal would normally be lubricated with product, a quench lubrication system....

Motor oil is likely to have a damaging effect
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Offline picclock

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Re: mechanical seal lubrication fluid advice
« Reply #2 on: September 07, 2012, 07:20:53 AM »
@ John

The seal is part of a compressed air system, consequently there is no quench lubrication system. This is part of something I am making - not a pre manufactured product. I suspect I could even use water but I figure from what I have read about mechanical seals an oil may be better.  Basically the seal will be immersed in the liquid of choice - the only thing is which is the correct choice  :scratch:

Best regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline John Rudd

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Re: mechanical seal lubrication fluid advice
« Reply #3 on: September 07, 2012, 08:20:41 AM »
Ok,

We run a big gas compressor driven bt a Rolls Royce RB211 jet engine at work here that has a discharge pressure of 99 bar....We use the gas that the compressor is supplied with as a 'lube' for the seals, by directing some of the discharge gas into the mechanical seal...If we didnt do this there is the potential for the seal faces to contact and damage would result...

I dont see why you couldnt do the same using the compressed air as a lubricating medium, but in actual fact it isnt a lubrication per se...Its there to prevent the seal faces contacting...
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Offline crankshafter

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Re: mechanical seal lubrication fluid advice
« Reply #4 on: September 07, 2012, 10:13:00 AM »
Hi picclock
If you  can  use  wather  as lubricant it will  do ok, it's basicly the same seals that  they  use in watherpumps.:-)
Best reg.
CS

Offline AdeV

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Re: mechanical seal lubrication fluid advice
« Reply #5 on: September 07, 2012, 10:32:07 AM »
I happened across this page while googling:  http://www.mcnallyinstitute.com/02-html/2-5.html

It might be of some use in this instance?
Cheers!
Ade.
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Offline picclock

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Re: mechanical seal lubrication fluid advice
« Reply #6 on: September 07, 2012, 11:43:05 AM »
@ Adev

Many thanks, I think I'd already seen that page. As with most info out there it goes into reams of detail about contact faces and elevated temperatures, none of which apply to this application. I am slightly tempted to go for water but one of the sites said that oygen in the water would combine with the carbon and cause face corrosion. At the moment I am thinking a very light clear oil (clear mechanical oil or clock oil perhaps?). I am a little reluctant to use water because of the rusting issues that will occur when the seal leaks (hopefully not for a long long time). As an alternative water with some anti rust ingredient as used in central heating systems may also be a possibility. This is the problem - I just don't know what to use for the best.  As they say ' I used to be indecisive - but now I'm not so sure'  :Doh:

Many Thanks

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline Noitoen

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Re: mechanical seal lubrication fluid advice
« Reply #7 on: September 07, 2012, 05:45:05 PM »
Silicone carbide mechanical seals are more tolerant to running dry.