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What is the reason for the foam of lubricating oil?

- Feb 13, 2018 -

Most of the mechanical lubrication systems are lubricated in a cyclic manner, and the lubricating oil is constantly flowing and circulating under the action of lubrication system oil pump. When the lubricant flows in contact with air and is subjected to intense agitation, it is possible to mix air into the oil to generate foam.

Foaming in lubricating oil can have a series of effects on use. If these bubbles can not be eliminated in time, it will make the cooling effect of lubricating oil drop, pipeline production gas resistance, lubrication oil supply, increase wear, oil tank overflow, and even oil pump and other faults. Therefore, the requirements of lubricating oil has good foam resistance, in the presence of foam should be able to eliminate in time to ensure that lubricants in the lubrication system to work properly.

The formation and harm of bubbles
Foaming is also a common phenomenon in daily life, such as putting soap in the water to stir, it will produce a large regular foam. This is because the soap is foaming agent, when the water is stirred, the air will be mixed in the water, and surrounded by water film, plus soap (also surfactants) on the protection of the water film, so that the water film becomes solid and not easy to rupture, such as resulting in a large number of stable foam.
At atmospheric pressure, the mineral oil dissolved in about 9% of its volume of air. The amount of air dissolved in lubricating oil increases with increasing pressure.
When the pressure is lowered, the excess air is separated from the oil sharply to achieve a new balance. But the separated air is surrounded by oil film, and the oil film is not easy to rupture, it will form a bubble. This is partly the result of bubbles in internal-combustion engine lubricants.
Another source of bubble formation is the mechanical mixing of lubricating oil in contact with air. Lubrication system work, due to intense agitation and splash, the air is stirred into the oil to produce foam, coupled with the oil contains pure dispersed extrusion and other surfactants, it is easy to produce a bubble that is difficult to disappear. In particular, the phenomenon of diesel oil foam is more common.