Sleeve bearing lube oil turned black
Sleeve bearing lube oil turned black
(OP)
Hi guys, in our company we have a FD fan which is supported by two pillow blocks (sleeve bearings). One is 'fixed' while the other is 'free'. I would like to know what is the difference between the two.
Also, quite recently we noticed that the color of bearing lube oil turned black. We tried to flush the oil online several times (meaning draining and filling the oil simultaneously as we cannot stop the FD fan due to operational reasons). But the oil color did not change and is still dark greyish or blackish in color. Later I found that the oil which we have been using was Regal R&O 100 but the recommended one was Regal R&O 68. So, I would also like to know what can cause the color of oil to turn black. There was no apparent metallic debris in the drained oil as well. Also, would this wrong oil or higher viscosity oil that we have been using might have caused bearing damage of some kind and turn the oil black.
Thanks for the help...
Also, quite recently we noticed that the color of bearing lube oil turned black. We tried to flush the oil online several times (meaning draining and filling the oil simultaneously as we cannot stop the FD fan due to operational reasons). But the oil color did not change and is still dark greyish or blackish in color. Later I found that the oil which we have been using was Regal R&O 100 but the recommended one was Regal R&O 68. So, I would also like to know what can cause the color of oil to turn black. There was no apparent metallic debris in the drained oil as well. Also, would this wrong oil or higher viscosity oil that we have been using might have caused bearing damage of some kind and turn the oil black.
Thanks for the help...





RE: Sleeve bearing lube oil turned black
The oil can turn dark from high temperature. For a forced draft fan, this is unlikely. For a very large FD fan, you might have cooling water circulating in a cast-in cooling jacket in the bearing liner. But, none of our FD fans have cooling water in this arrangement. Oil will turn dark if it is exposed to brass particles. Even if you don’t see metallic particles in the oil, if the brass oil rings are rubbing and wearing, the oil will turn dark quickly. You should have view ports to look at the tops of the oil rings. Check to see if they are turning smoothly and delivering a good stream of oil. If the oil ring is jumping around or running hard to one side of the groove, this could be the problem. The oil ring could become unstable if the oil level is too low or too high. Verify that the oil level is at the manufacturer’s recommended level.
I would not expect the one grade heavier oil to cause rapid darkening of the oil. But, you can eliminate this variable by changing the oil to the lighter grade on the run.
The bearing liner may be set in a spherical fit within the housing to allow the liner to align to the shaft. The liner may be locked down in this fit with a jam bolt coming down on the top of the liner. This jam bolt is supposed to be torqued to a certain torque and then locked with a jam nut. You can release this jam bolt and retorque it on the run to be sure that the bearing is properly aligned to the shaft.
Johnny Pellin
RE: Sleeve bearing lube oil turned black
Time for oil analysis.
I would not expect the slightly higher viscosity oil ( 100 ) to cause any problems.
What are the bearing temperatures? How are they being measured?
RE: Sleeve bearing lube oil turned black
Spot on Johnny Pellin, the arrangement we have perfectly matches the description you have provided except that we do have a cooling water jacket. I forgot to mention about the oil level which was quite high. After draining about 4 liters of oil, the level could be seen through the sight glass. I suppose the level should be maintained at 75% of sight glass.
Tmoose, The bearing temperature was 40 degrees C and it is measured using a thermocouple probe and is read on a temperature gauge.
RE: Sleeve bearing lube oil turned black
Johnny Pellin
RE: Sleeve bearing lube oil turned black
Is the temp probe spring loaded to touch the back side of the bearing insert? Or in some less useful location?
Also is the thrust bearing a separate insert, and its temp measured separately and directly?
RE: Sleeve bearing lube oil turned black
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(2B)+(2B)' ?