Bearing fully submerged in hydraulic oil
Bearing fully submerged in hydraulic oil
(OP)
I was wondering if anybody might have any comments on the possibility of using a cylindrical roller bearing which is completely submerged in a hydraulic oil bath.
The bearing will be used on a test stand, where the inside of the bearing housing will have a circulating oil bath, which will be cooled so that it does not exceed 70˚C (160˚F). The oil would have a pressure of 25 psi maximum.
The bearing is in a stationary housing with a horizontal rotating shaft. A typical cycle will be accelerating the shaft up to a maximum of 3000 rpm (often only up to 1500 rpm max) over a period of about 30 minutes. The speed will be maintained for about 1 minute. Then the shaft will slow down to a complete stop over a period of about 1 hour to 1.5 hours. At most, one of these cycles will be conducted a day.
My primary question is how feasible would this setup be?
I know I would be getting a power loss from this setup due to the extra friction on the bearing, but are there any other concerns I should be worried about?
From what I have gathered, the oil that would be used should be very close to the recommended viscosity for the bearings, but are there any guidelines as far as the filtering that would be needed for the oil?
Thanks for any advise or thoughts you might have.
The bearing will be used on a test stand, where the inside of the bearing housing will have a circulating oil bath, which will be cooled so that it does not exceed 70˚C (160˚F). The oil would have a pressure of 25 psi maximum.
The bearing is in a stationary housing with a horizontal rotating shaft. A typical cycle will be accelerating the shaft up to a maximum of 3000 rpm (often only up to 1500 rpm max) over a period of about 30 minutes. The speed will be maintained for about 1 minute. Then the shaft will slow down to a complete stop over a period of about 1 hour to 1.5 hours. At most, one of these cycles will be conducted a day.
My primary question is how feasible would this setup be?
I know I would be getting a power loss from this setup due to the extra friction on the bearing, but are there any other concerns I should be worried about?
From what I have gathered, the oil that would be used should be very close to the recommended viscosity for the bearings, but are there any guidelines as far as the filtering that would be needed for the oil?
Thanks for any advise or thoughts you might have.





RE: Bearing fully submerged in hydraulic oil
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RE: Bearing fully submerged in hydraulic oil
RE: Bearing fully submerged in hydraulic oil
this will not only lead to powerloss but possibly also to slowing down the acceleration envisaged.
it may also lead to a local temperature rise of the oil in the bearing to such an extend that deposits may be formed on rollers or raceways. if that happens bearing life will be substantially shortened.
if you can't change the oil level, would it be an idea to use a completely sealed grease lubricated bearing?
RE: Bearing fully submerged in hydraulic oil
... or, not. That could make foaming more of a problem.
Mike Halloran
Pembroke Pines, FL, USA
RE: Bearing fully submerged in hydraulic oil
Id suggest using a standard off-the shelf pillow block set-up for oil, such as the SN type or SAF type housing.
Russell Giuliano
RE: Bearing fully submerged in hydraulic oil
Maybe it's not a real issue.
Mike Halloran
Pembroke Pines, FL, USA
RE: Bearing fully submerged in hydraulic oil
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RE: Bearing fully submerged in hydraulic oil
Here is a post from FAG Bearing Lubrication document WL 81 115/4 EA/94/2/00. It is not particularly specirfic... leaves a lot of wiggle room for user judgement:
I know other publications steer toward lower levels for higher D*N (like 1/4 to 1/2 of lowest rolling element while static for 3600rpm 6313).
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RE: Bearing fully submerged in hydraulic oil
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RE: Bearing fully submerged in hydraulic oil
After looking over the thread again, I realized that I gave the wrong size for the bearing. It is actually a 35mm bore, 80mm OD, and 21mm width. Basically the equivalent size of a 6307 bearing, except that it is a cylindrical roller bearing right now. However, it could easily be replaced with a standard ball bearing.
So, after adjusting for my error, that would mean that the highest dN that would be reached would be 105,000 (a max speed of no more than 3000 rpm). So as I understand the guides given by FAG, this might be within the acceptable range of using a higher fill level. The acceleration/power loss resulting from complete immersion are not extremely critical. I guess my main concern would be damage to the bearing due to excess heating. However, I know that I have run across a few publications that specifically mention that vertical shaft applications can run in an immersed state. So if there is fluid circulation and cooling, as well as temperature monitoring of the fluid, maybe it is worth a shot?
I like Romke's idea of a sealed bearing, but since the hydraulic fluid is slightly pressurized (~25 psi) would I need to worry about the oil seeping in or the grease seeping out around the bearing seal over time?
Any other thoughts?
Thanks
RE: Bearing fully submerged in hydraulic oil
Most people use a 10 micron filter but a 5 micron filter would be preferred.