The knowledge of refrigeration oils

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Although refrigeration oil is just a minor component, using inferior quality products for it can even cause the machine to burn down. I believe many of my colleagues have also encountered this issue: using low-quality refrigerant oil can cause corrosion of the compressor, even if it doesn’t lead to direct damage to the machine; as a result, noise levels increase and the cooling efficiency drops significantly. The technical parameters related to \"refrigeration oil\" are also quite extensive and complex; Engineer xxx will help us sort them out. 　　Author: Hello! I’ve learned that many users encounter various problems when using refrigerant oil, so I hope to get some technical assistance from you. Engineer: It’s an honor. 　　Author: I heard that if there is a problem with the refrigeration oil, it can cause the machine to overheat. What is the reason for this? 　　Engineer: What we call “compressor burnout” is actually the destruction of the compressor. There are various reasons for this phenomenon, and insufficient viscosity of the refrigerant oil is one of them. As we all know, refrigeration oil must have a certain viscosity in order to maintain good lubrication of the friction surfaces of moving parts, thereby allowing it to remove some heat from the compressor and serve a sealing function. Generally, refrigeration oil must operate under two extreme temperature conditions: the temperature of the compressor discharge valve can reach up to 150 degrees, while the temperatures of the expansion valve and evaporator can drop as low as -40 degrees. Such a working environment requires it to have excellent adhesion-temperature properties. If the viscosity of the refrigeration oil is insufficient, it will lead to increased wear on the compressor bearings and cylinder block, higher noise levels, reduced cooling efficiency, and a shortened lifespan of the compressor; in extreme cases, it may even cause what is commonly referred to as \"compressor burnout\". 　　Author: I see. 　　Engineer: It’s not just viscosity issues; the pour point is also an indicator that can lead to \"machine burnout\". As mentioned earlier, the operating temperature of compressors varies widely; therefore, to ensure that the lubricant can perform its functions properly, it is required to maintain good fluidity even at low temperatures. Therefore, the pour point should generally be 10 degrees lower than the freezing temperature, and the viscosity-temperature characteristics must also be good, so as to ensure that the refrigeration oil can return smoothly from the evaporator to the compressor in low-temperature conditions. If the pour point of the cooling oil is too high, it will result in slow oil return, which can easily lead to engine damage. In addition, a low flash point of the refrigerant oil can also pose certain risks. 　　Since conventional refrigeration oils have a high degree of volatility, a low flash point leads to an increased amount of oil in the refrigeration cycle, which not only increases losses and costs but also, more seriously, raises the risk of combustion during the compression and heating process. Therefore, it is required that the flash point of refrigeration oils be at least 30 degrees higher than the temperature of the refrigeration exhaust gas. 　　Author: It seems that there are indeed many technical specifications related to refrigeration oil; without knowing these, it’s really difficult to make a choice. I often hear a word from some users: “corrosion”. I would like to know how the phenomenon known as \"corrosion of compressors\" occurs in everyday life, and how we can avoid it 　　Engineer: The process of corrosion is quite complex, involving many chemical reactions; I’ll give a brief introduction to it. Since ice formation in the evaporator affects cooling efficiency, it accelerates the decomposition of the refrigerant once it comes into contact with it and corrodes the equipment. Therefore, if the moisture content in the refrigeration oil is too high, under the catalytic action of metals, the moisture in the refrigeration system will react with the refrigerant, producing hydrochloric acid and hydrofluoric acid, which in turn causes corrosion to the compressor. Corrosion can **reduce the lifespan of the compressor**, even leading to its premature failure, causing significant losses for the user. 　　Author: It seems that the harm caused by “corrosion” is no less severe than that caused by “overheating”. Are there any other reasons that can cause corrosion? 　　Engineer: Yes, for example, insufficient chemical stability of the refrigerant oil, or too low thermal stability. As we mentioned earlier, the maximum compression temperature of a compressor is quite high, reaching 130–160 degrees. At such high temperatures, the refrigeration oil decomposes due to heat, forming carbon deposits that cause wear on the compressor. Oil decomposition products react chemically with the refrigerant, reducing its cooling efficiency; meanwhile, the acidic substances produced cause severe corrosion to the compressor. 　　Author: Well, it seems it’s all principles that we need to understand. These technical specifications should all serve as benchmarks to help us assess the quality of a refrigeration oil. Besides what was mentioned earlier, are there any other technical indicators that need attention? 　　Engineer: Well... the wax content also needs to be taken into account. During use, the mixture of the refrigerant and mineral oil-based refrigeration oil leads to the precipitation of insoluble substances such as paraffin, which precipitate at temperatures above the freezing point. If the paraffin content in the refrigeration oil is too high, it can cause blockages in the cooling system and the refrigeration pipelines, which is very dangerous. 　　Author: Therefore, we need to pay attention to these technical indicators, and use them to evaluate and select refrigeration oil. 　　Engineer: Indeed, analyzing various principles can seem quite technical, so ordinary consumers can make decisions when making purchases by considering several key indicators, in order to avoid unnecessary losses as much as possible. 　　Through this consultation, it was easy for us to identify several key issues: insufficient viscosity of the refrigerant oil, excessive moisture content, high paraffin content, inadequate chemical and thermal stability, too low flash point, and too high pour point. Deviations in these parameters are the main factors that commonly lead to operational failures. Regardless of the process of using refrigeration oil, any mistakes made during the selection phase can lead to significant losses. It seems that refrigeration oil may seem like a minor issue, but it actually cannot be taken lightly; it is indeed a detail that cannot be ignored.