Gearbox Oil Foaming - How to Remove

[eeinmeworld]

I have an existing gearbox system being fed Dextron III oil. The system is 5.9:1, max speed of about 21000 RPM on the high side. It appears that my reservoir is not big enough to allow the oil to settle out all of the foam being generated at higher speeds. This problem is causing my gearbox to heat up quickly and my heat exchangers to lose their capability. Anyone have any ideas on how to speed up the de-foaming process. I am looking at ultrasonic cleaning devices as a possible solution. They help remove bubbles out of liquid. Any suggestions would be appreciated.

 

[butelja]

Does the gearbox operate at atmospheric pressure or at a slight vacuum? The high speed gearbox on some centrifugal compressors that I'm familiar with uses an air ejector to operate the sump at a partial vacuum. I'm told that this reduces foaming tendencies, as well as eliminating oil leaks.

 

[eeinmeworld]

The gearbox is operating at atmospheric pressure. One of the problems that I know that we have is that the gearbox currently does not have a breather on top of it. This will help, but I still think I have a bigger issue to deal with here. I wondered if it was possible to ultrasonically vibrate the return pipes as well. Did not know if this would be a structural issue though.

 

[nickelkid]

Check with Royal Purple or another, reputable, synthetic oil producer. If a simple oil change may be able to get it done, but the oil manufacture will know best if he can help.

 

[rkarthik]

Based on my experience a breather in the reservoir would be better in solving the problem and also a good synthetic lubricant may be mobil would be better.Is there any ingress of water in the oil which is being used, it is better to check the same through ferrographic analysis - which would give amount of water in the oil and wear in the gearbox also.
It is also better to check the diameter of the return line to the gear box also.

 

[jabonet]

I had the same problem using Dextron III, I fixit changing oils for a more fancy one... I wonder if you can buy an antifoaming agent and do the same.

if you have any 21000RPM moving parts coming in contact with the oil in your carter, you will allways have foam. if you have space you can increase the carter volume to give more time to the bubles to disapear, or have an external tank to increase the amount of oil without running out of space.

hope this helps.

 

[automatic2]

In some cases excessive oil quantity will compound foaming. Typically a high speed requirement will have oil fall with gravity through the fit, then disperse without resistance from pooling fluid. Teeth in a box will typically be sprayed with pumped lubricant as opposed to dip feed. Make sure drain lines are clean and not allow fluids to backup and cause churning.

 

[helphelp1]

The first thing to do is make sure the pump is not "sucking" air on any of the suction piping or its casing.

What oil does the manufacture recommend ?

Have the oil analysised, contact your oil supplier, they often will do this for you. The oil compinies have engineering staff that should be able to assist you.

Also, there are special additives that can help with foaming, again check with your lubrication company.

A breather is a definate need.