Sometimes one can observe lub oil foaming at a sightglass of a sleeve bearing. Never paid much attention to it as it does not seem to harm the reliability of the bearing, vib, temps and uptime usually are okay. I just wonder: what causes this foaming? Or any disadvantages known?
Regards,
Arie Mol, NL

arie mol, I noticed this issue in some of the high speed, vertical pumps. I beleive type of the oil and oil reservoir temperature has significant impact on foaming. Try synthetic lubricant and little higher oil temperatures..

As you said, never noticed a problem. Air entrainment isn't unusual and its commonality is more than one would think if one observed more. Of course generating air bubbles in the load area is very bad. Look at the bottom of the oil and middle; also, how long does it take to disipate?

Can adding anti-foaming agent help?

Has your system got oil cooling? Although it may well be just air entrapment, take a sample and test for water as this will also lead to foaming in a system.

Foaming can be caused or increased by contaminants or by charactistics of the oil (foaming tendency).

You don't need a lab to check this. Take a liter sample bottle half full and shake it vigorously for 5 minutes to create bubbles). If it's impossible to get bubbles, you don't have a foaming tendency problem. If you get bubbles, let it sit for 2 hours. Bubbles should be all gone. If you suspect contamination, do the test on sample from the equipment/sump and sample of new oil and compare how long it takes for bubbles to go away.

Along with the characteristics of the oil, the type and turbulence of the air/oil interface makes a difference. Oil level higher or lower than normal can level change the way the equipment tends to whip the air into the oil.

It seems that oil rings running erratically might possibly cause foaming.... usually can be inspected in a viewing port.

Foaming lubricants are quite common,in fact virtually every lubricant has the capability to foam. The amount of foam depends on the amount of agitation and the amount of aeration present in the system.The presence of some detergent and dispersant additives tends to promote foam formation. Foaming also increases oxidation and reduces the flow or oil to the bearings. In addition, foaming may cause abnormal loss of oil through orifices. If the foaming is excessive then there may be a need to either add an anti foaming agent (usually a Silicon derivative) or check the level of Silicon in the next sample to ascertain if there is already a silicon deficiency.

hi,
can somebody know of testing the oil to determine what is the % contamination of additives, say silicon or other chemicals that are not present in the original(new oil) test sample.
we have some little knowledge on the tribology structure. Wear, Contamination,Chemistry.
for wear you need to test some particles by particle counter. for contamination only for water. for chemistry the software just say additives so how do you determine what kind of additives and what % to really eliminate or prevent this.

thanks for any info. also using csi.
ianski