“We have recently noticed a significant increase in foam in one of our lube systems. A supplier recommended adding an after-market anti-foam agent. Is this a good idea?”
While in some circumstances adding an anti-foaming agent may resolve the issue, it generally is not a good idea to add any after-market additive to a lube system. If foam has traditionally never been a problem but has suddenly started, think about treating not the symptom (the foam), but the cause.
If nothing has changed with the design of the lube system or reservoir, it is likely that this sudden increase in foaming tendency is caused by contamination. Because foam suppression in a lubricating oil is closely related to the air/oil surface tension, any contamination that can result in either an increase in air entrainment, such as solid particles, or a decrease in surface tension can cause this type of effect. Common contaminants that can decrease the surface tension include water, grease and surfactants, such as soaps and detergents used during machine wash-down.
To diagnose the root cause of your problem, try looking for significant increases in water or particle contamination or the appearance of unexpected elements in your spectrometric analysis data, such as lithium, calcium, aluminum or barium that may signal some other ingested grease or chemical contaminant.