Gearbox Oil Foaming

Dear Maha

The problem you describe is very typical in application with Oil with EP additives. These additives, sometimes attack the anti-foam additives. It is not a problem of water or particles in the oil. In this case, you should check the following:

1- When was the last time of oil change? Maybe it is necessary to change the oil.

2- Have you used the same brand of oil for replenishment? I have seen problems with foaming because different brands of oil have been used.

3- Some lubricant suppliers recommend to add silicon additives. These additives will repair the foaming problems, but, it could be negative for other properties of the oil.

I hope my comments could help to you.

Regards,

Dear Cristian Schmid,

Thanks for your useful suggestion. Yes we are planning to do a complete oil change soon. Oil replenishments are done using the same oil and the test sample doesnot indicate any change in oil viscosity.

Initially this gearbox was running with a different oil. But then we changed the oil type to Mobil SHC XMP 32O after complete flushing. This was done more than a year back and we didn't face this foaming problem until recently.

Particle count trend for this gearbox is higher when compared to the other gearbox using the same oil type. I am not sure if this could be a contributing factor for foaming.

Thanks and Regards

Maha

HI MAHA,

I agree with cristian, i recently encountered foaming issues with a customers gear box. Adding a very small amount of anti-foam has helped the issue.

Generally speaking，the proplem has serveal causes such as antifoam agent depletion or shortage, oil level higher than normal, air existing in oil, high water content.

To quote the late James Brown:
'Please, please, please, please...'

Don't add aftermarket anti-foam to your systems. Foam is often only a cosmetic problem. Silicone at the correct treat level will facilitate foam collapse. But if you overtreat, silicone will induce air entrainment. Unlike foam, air entrainment is always a real problem that can cause poor lubrication, pump cavitation, spongy hydraulic response, microdieseling and a host of other effects, all of them bad.

The fact that Jim Min notes that sub-surface air is present in the oil indicates that air entrainment may already be a problem.

That said, involve your supplier. ExxonMobil has a very strong lubricant tech service function. Your foam problem might be caused by contamination that has overwhelmed the AF additive, it may be caused by contamination that has knocked the AF additive out of suspension, or it may be caused by AF drop-out before the oil even got into the system.

AF additives do not dissolve in oil; they are suspended in the oil. Dimethoxysilane (silicone) molecules are much heavier than hydrocarbon base stocks. When air bubbles are above the surface of the oil, the presence of the undissolved silicone molecules creates a local area of higher density, which destabilizes the bubble and causes it to pop more readily. If they were in a true solution, they wouldn't work as intended.

The downside of this is that if you look at silicone's high school yearbook, you'll see that it was voted "Most Likely to Drop Out of the Formulation and Be Found on the Bottom of the Drum". When looking into AF dropout issues, I've found two things:
1 - It is usually associated with some sort of particulate contamination. This is a double problem, as fine particulate contamination can cause foam by itself. One bad actor I've seen in a lot of these cases is diatomaceous earth. This is used as a filter medium in a lot of industrial processes and trace amounts can creep in with additives. For an additive that is truly in solution like a detergent or antioxidant, it's not a problem. But it can knock suspended additives like AF & demulsifiers out of the formulation.
2 - It is more common with PAO-based lubes, since PAO has additive solubility issues in the first place.

Here are some gear oil foaming tests done on name brand oils you may find interesting: http://www.amsoil.com/lit/g2457.pdf

http://www.superoilcentral.com...sor_white_paper7.pdf

I would like to recommend you to use additives in order to power up your lubricants.

And just exactly which additives would you recommend? Top-treating is an art that requires detailed understanding of the lube formulation in question and the application at hand. Randomly treating with some 'magic elixir' is a fool's errand at best.

I would like to recommend an additive (GearMaxx) which can reduce the temperature and improve energy efficiency.

Is it a Flender gear box ? Flender developed a combined air release & foaming test to judge the gear oils. I feel that you should consult the gear box manufacturer's manual.

quote:

Originally posted by Tim Vipond:
Here are some gear oil foaming tests done on name brand oils you may find interesting: http://www.amsoil.com/products...aper.aspx?zo=1181889 .

http://www.superoilcentral.com...sor_white_paper7.pdf

Such a very amazing link!

__________________
Watch Grown Ups Online Free

If you can't find it in the manual, forums like these are a great help. What i usually do if I have auto repair questions is i resort to online DIY resources where real people made real repairs.

Only useful information ... Thanks!