The Hazard Of Small Bubbles in Lubricating Oil

It is very important that keep lubricating oil clean without contamination of moisture, solid impurities, and particles. People who have worked in the field of Industrial lubricants understand this point. But we should also pay special attention to the air bubbles in lubricating oil - whether it is foam on the surface of the oil or the bubbles in the oil.

The reasons for mixing air in lubricating oil are complex, and sometimes it is not necessarily the problem of oil itself, so adding anti-foaming agent and changing oil can not solve the fundamental problem. Below, let's understand the invisible killer in lubricating oil - "bubbles".

First of all, what are the hazards of bubbles to lubricating oil and the machinery?

1. The air bubbles accelerates oxidation and deterioration speed of the lubricant.

Bubbles will accelerate the oxidation and deterioration speed of lubricating oil, accelerate the consumption of additives, affect heat dissipation, the lube cannot form a complete oil film on the metal surface, and this may cause wear to equipment.
2. Local high temperature.

Bubbles in the high pressure system will also cause local high temperature, so that the oil quickly metamorphism.Due to the air is easy to compress, there is air bubbles in the lubricating oil, the thickness of the oil film will become thinner and even the oil film will break, the lubrication between the mechanical parts was not sufficient, and this caused direct friction and parts sufrace wearing.
3. The formation of cavitation damage bubbles under pressure rupture, the metal surface will also form cavitation damage. In addition, bubbles can cause unstable operation of equipment. For the problem of bubbles in lubricating oil, oil detection experts and lubricating oil technicians have carried out a series of studies. Let's understand the relevant situation of bubbles generation:
(1)  Pure oil itself will not produce foam, if you add other things, such as impurities, and additives, such as anti-wear agents, extreme pressure agents, dispersants, etc., the more polar additives, the easier it is to generate foam, such as anti-wear additives and extreme pressure additives are polar additives.
(2) The size of the bubbles in the oil is related to the interfacial tension of the oil. If the tension is small, the bubbles formed will be small. The smaller the bubbles, the easier the oil to form more stable foam, not easy to burst and disappear.
(3) The entry of water into lubricating oil will reduce the interfacial tension of the oil, so that the oil is more prone to foam. For most oils, as long as there is 1000ppm of water content, the oil will continue to foam.
(4) The higher the viscosity of the lubricating oil, the smaller the bubbles contained in the oil, the slower the speed of the bubbles released, which will cause the oil contains more bubbles. The bigger the bubble, the shorter the time it takes for it to escape, which makes sense, because the bigger the bubble, the easier it is to get to the surface of the oil.
(5) The volume of bubbles is inversely proportional to the viscosity of lubricating oil, low viscosity oil is easy to produce large bubbles, high viscosity oil is easy to produce small bubbles. The larger the bubble, the easier it is to break, and the small bubble is relatively "tenacious", not easy to break, so it is relatively stable after generation, and it takes a long time to disappear.