Moisture is a common contaminant in bearing lubrication, only a small amount of water (for example: 500ppm) can significantly shorten the service life of rolling bearings, and there are plenty of studies or facts that can confirm this. If you work in the bearing industry or frequently install and disassemble and repair bearings, you should also be well aware of the dangers of water on bearings. In fact, at some point, the damaging effects of water on bearings can easily meet or exceed the damage caused by particle contamination. Understanding how water causes bearing damage will help us find appropriate solutions and develop appropriate work objectives, and of course, help analyze bearing failure failures. When water contamination is unavoidable, understanding the failure modes caused by water contamination will help us to optimize the design and selection of lubricants, bearings and seals. Pictures What types of water are included Water in lubricants comes in three forms: dissolved water, emulsified water, and free water. Of these, emulsified water is the most harmful. Dissolved water: Dissolved water is water that has been dissolved in the lubricant. The lubricant is hygroscopic and will absorb moisture from the air, so it will contain a small amount of water. Generally speaking, a small amount of dissolved water will not cause any harm. The maximum dissolved water content that can be allowed in a lubricant is the water absorption saturation point. Before reaching the water absorption saturation point, the lubricant contains water but does not show signs of having water. Emulsified water: After entering water in the lubricant, if it does not separate from the oil, tiny water droplets suspended in the oil become a suspension, and it becomes emulsified water, which is the most harmful. When the lubricating oil emulsifies, first of all, the water content has exceeded the saturation point; when the oil contains emulsified water, the transparency of the lubricating oil will be reduced, cloudy and white in color. Emulsified water is very harmful because they can flow freely and contaminate the oil in the whole lubrication system, in addition, the water will destroy the lubricity of the oil. When emulsified water reaches the pressure-bearing areas where bearings operate, these areas will be poorly lubricated, friction will increase, and thus wear. Free water: When water and lubricant are completely separated, it becomes free water. Free water is relatively harmless, but not without problems. First, free water can also circulate with the lubricant and cause it to emulsify at some point. In addition, water in the oil can weaken some of the lubricant’s properties, such as causing increased foaming and depleting the additives in the lubricant.  

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