The second common pollutant of air compressor lubricating oil and its detection!
Air compressor lubricating oil is the most common pollutant - water
Water is a common pollutant, although the harm is not as serious as particulate matter, but water will destroy the lubrication effect, make the oil deteriorates, cause equipment wear, water will also cause metal rust. There are three forms of water in lubricating oil: dissolved water, emulsified water, free water, among which, emulsified water is the most harmful.
Dissolved water is the water that has been dissolved in lubricating oil. Lubricating oil is hygroscopic and absorbs moisture from the air, so it contains a small amount of water. In general, small amounts of dissolved water do little harm, except in some cases where the water content of the lubricating oil is particularly strict. The maximum allowable dissolved water content of lubricating oil is the water absorption saturation point. Before reaching the water absorption saturation point, although the lubricating oil contains water, it will not show signs of water, such as emulsification, turbidity and reduced transparency.
Lubricating oil into the water, if there is no oil and leave, tiny water droplets suspended in the oil to become suspension, become emulsified water, emulsified water is the most harmful. When the lubricating oil is emulsified, the water content has exceeded the saturation point. When the oil contains emulsified water, the transparency of the oil will be reduced, and the color will be white or even become milky white. Emulsified water is very harmful because it can flow freely and contaminate the oil throughout the lubrication system. In addition, the moisture will destroy the lubrication of the oil. After emulsifying water reaches the pressurized area where the equipment is operating, these areas will be poorly lubricated and wear due to increased friction.
When water and lubricating oil are completely separated, it becomes free water. Free water is less harmful, but it can cause problems. First, free water may also circulate with lubricating oil, causing oil emulsification. In addition, the water in the oil will weaken the emulsification of the lubricating oil, lead to the increase of foam, consume the additives in the lubricating oil, shorten the service life of the lubricating oil, and easy to breed bacteria.
Moisture damage to equipment in addition to poor lubrication, and hydrogen embrittlement, rust. Lubricating oil can prevent metal corrosion, if water in the oil, easy to cause metal corrosion.
Hydrogen embrittlement, also known as hydrogen damage, can cause bearing damage. Water breaks down into hydrogen and oxygen, and hydrogen is also produced by electrolysis and corrosion, which water promotes. High-strength steel is particularly vulnerable to this problem. In addition, additives added to lubricating oil and grease contain sulfur (extreme pressure additives, anti-wear agents, etc.). Mineral oil itself also contains certain sulfur impurities, which will promote the corrosion and cracking of metals. Both moist atmosphere and free moisture may cause hydrogen embrittlement of metals.
Moisture will destroy the strength of the oil film and the integrity of the oil film. Lubrication depends on oil forming a layer of oil film between the metal contact surface. The oil film separates the direct friction between the metals and prevents direct contact of the metals. If water enters the metal contact force area of the bearing, it will destroy the integrity of the oil film, reduce the strength of the oil film, lead to poor lubrication or direct friction between metals, cause metal fatigue damage, metal scraping and fragmentation.
Water will shorten the service life of lubricating oil. In addition, water will cause the loss and consumption of antioxidants in lubricating oil, leading to oxidation and deterioration of lubricating oil. Oxidation of lubricating oil will form acid substances, mud and paint film, increase the viscosity of oil, affect the effect of spray lubrication and so on.
In the field, you can observe the appearance of the lubricating oil. If the transparency of the lubricating oil is reduced, white, cloudy or emulsified, it means that the oil is in water. In addition, the heating method is also simple and easy. This method can be used for the most basic judgment, simple operation, use a piece of iron, heated to 130℃ on the fire, drop a drop of lubricating oil on the iron, if there is water will be observed bubbles, because the water in the oil is heated and evaporated caused by bubbles, the larger the number of bubbles, the more water content. If you see bubbles and hear crackling sounds, it means that the water content is relatively high, probably more than 2000ppm. However, the heating method is only suitable for the determination of emulsified water and free water.
Karl Fischer moisture detection is the most accurate moisture detection method, free water, emulsified water, dissolved water can be detected, under the condition of proper operation, the moisture detection can be quantified to 10ppm (0.001%) level, general industrial monitoring and precision industrial monitoring can be used.
When the lubricating oil water is found, the correct treatment method is to first find the water source, cut off the source, and then take water measures, serious when the best oil change, it is best to determine by oil detection.
