Lubricating oil is known as the blood of the equipment. It flows inside the equipment and plays the role of lubrication, friction reduction, cooling, cleaning and rust prevention. If the lubricating oil is contaminated, it will cause lubrication failure, equipment wear and tear, and then cause equipment failure and shorten the service life of the equipment.
Lubricating oil contamination is a complex problem. Sometimes it can be found in daily inspections, but in some cases it cannot be found. Some pollution cannot be observed by the naked eye. Moreover, for all pollution, when it can be found by the naked eye, it means that it is already very serious. In short, lubricating oil contamination should be discovered and treated early, especially for more sensitive and critical equipment. Oil testing can accurately analyze the contaminants in the lubricating oil by testing the oil, just like detecting abnormal conditions in the human body through blood testing.
1. Particles
Particles are the most harmful pollutants. They enter the lubrication system and cause abrasive wear, metal crushing and scratching, and metal fatigue. Particles generally have a certain hardness. Many particles are very small in size and can pass through the gaps between parts and circulate inside the equipment, causing wear. Common particulate matter includes dust, grit, fine metal particles generated during equipment operation, rust residue, etc.
Particle pollution not only harms the equipment itself, but also shortens the service life of lubricants. Abrasive wear increases the metal powder content in the oil. These fine metal particles not only further wear the equipment, but also accelerate the oxidation and deterioration of the lubricant, because metal powder catalyzes the oxidation rate of the oil. Given that the harm of these particulates is chain-like, it is important to monitor and deal with them early.
Oil testing can detect fine particles in the oil and early wear of the equipment. By detecting the particle count in the oil, we can understand the cleanliness of the oil and whether particulate contaminants have entered.
If particulate matter is found to have entered the lubricant, general remedial measures include: finding where the particles come from, then blocking the source, and removing the particles by filtering - but this approach may not always be effective. Sometimes it is difficult to completely remove the particles by filtering the oil, and the oil must be replaced.
2. Water
Water is a common pollutant. Although it is not as harmful as particulate matter, it can destroy the lubrication effect, deteriorate the oil, cause equipment wear, and cause metal corrosion. There are three forms of water in lubricating oil: dissolved water, emulsified water, and free water. Among them, emulsified water is the most harmful.
Dissolved water is water that has been dissolved in the lubricating oil. Lubricating oil is hygroscopic and will absorb moisture in the air, so it will contain a small amount of water. Generally speaking, a small amount of dissolved water will not cause any harm, unless some circumstances require the water content of the lubricating oil to be particularly strict. The maximum allowable dissolved water content of the 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, or turbidity, reduced transparency, etc.
After water enters the lubricating oil, if it is not separated from the oil, tiny water droplets are suspended in the oil to become a suspension, which becomes 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 lubricating oil will decrease, become turbid, and the color will turn white or even milky white. Emulsified water is very harmful because it can flow freely and contaminate the oil in the entire lubrication system. In addition, water will destroy the lubricity of the oil. When the emulsified water reaches the pressure-bearing area where the equipment is operating, these areas will be poorly lubricated, friction will increase, and wear will occur.
When water and lubricating oil are completely separated, they become free water. The harm of free water is relatively small, but it can also cause problems. First, free water may also circulate with the lubricating oil and cause oil emulsification. In addition, the water in the oil will weaken the demulsification of the lubricating oil, leading to increased foam, consumption of additives in the lubricating oil, shortening the service life of the lubricating oil, and easily breeding bacteria and stinking.
In addition to causing poor lubrication, the harm of water to equipment also includes hydrogen embrittlement and rust. Lubricating oil can prevent metal rust. If water enters the oil, it is easy to cause metal rust.
Water will shorten the service life of the lubricating oil. In addition, water will cause the loss and consumption of antioxidants in the lubricating oil, causing the lubricating oil to oxidize and deteriorate. Lubricating oil oxidation will form acidic substances, sludge and paint film, increase the viscosity of the oil, affect the effect of splash lubrication, etc.
When it is found that the lubricating oil has water in it, the correct way to deal with it is to first find the source of water, cut off the source, and then take measures to remove water. In serious cases, it is best to change the oil, and it is best to determine it through oil testing.
3. Mixing with other lubricants
When using lubricating oil, it should be avoided to mix with other oils. However, in some cases, such as leakage, using the wrong lubricating oil when refueling (wrong lubricating oil viscosity selection or wrong additive type selection), too much residual oil, etc., will cause different lubricating oils to mix.
For example, mineral oil and conventional PAG synthetic oil (non-oil-soluble PAG) are incompatible. If these two oils are mixed, the viscosity of the mixed oil will increase and sludge will be formed. Other phenomena include increased acid value and clogging of the filter element by sludge. At the same time, due to the mixing, poor lubrication will occur, and equipment wear will also occur.
When other oils are mixed in the lubricating oil, the solution is to change the oil and flush the lubrication system. It cannot be removed by filtering.
Using the wrong type of lubricant is also a common problem. It may be that the wrong oil is added accidentally when changing the oil, or the wrong oil is selected directly. For example, if the equipment requires extreme pressure lubricant (EP) or anti-wear lubricant (AW), and the user mistakenly adds general anti-oxidation and anti-rust oil, it will cause wear during the operation of the equipment.
If the equipment with high requirements for the anti-emulsification of lubricants is mixed with oil products with detergent dispersants, the anti-emulsification/oil-water separation of the oil will be weakened. For example, if engine oil is mixed with turbine oil, 1 liter of engine oil mixed with 7000 liters of turbine oil can destroy the anti-emulsification of turbine oil, so lubricant mixing must be avoided. In this case, all oils need to be changed and the lubrication system flushed.