Answer: The lubrication conditions and working environment of screw air compressors are relatively harsh. The lubricating oil must be recycled once every 0.5~1min. At high temperatures and in the presence of catalysts such as steel and copper, the oil is very easy to oxidize and deteriorate, so there are certain requirements for oxidation resistance, which is measured by oxidation stability indicators. In addition, due to the fast circulation speed, the oil is in a state of intense stirring, which is very easy to form foam. Especially at startup, the operating temperature is low, and the oil foam is not easy to destroy. A large amount of oil foam pours into the oil-gas separator, which increases resistance and oil consumption, causing serious overload and overtemperature. Anti-foaming and defoaming measures must be taken. This performance is measured by the oil's anti-foaming property, foam tendency and foam stability. Since the compressor cooler pipes and some parts are made of copper or copper alloy, they are easily corroded and cause the oil to oxidize and deteriorate early, forming oil sludge. Water vapor, dust, etc. in the air will inevitably mix into the oil, which will cause rust and wear on the surface of other parts in contact with the gas. These two performances are measured by the oil's corrosion index and anti-rust test index. When the compressor is running, the oil constantly meets the condensed water in the air and is violently stirred, which is easy to produce emulsification, resulting in poor oil-gas separation and increased oil consumption. The emulsified oil will destroy the oil film and cause aggravated wear, so anti-emulsification is also an important property of the oil.
The lubrication of the air compressor, in addition to reducing the friction, wear and temperature rise of the moving parts, also has the function of sealing the compressed air. The lubricating oil of the screw air compressor is in direct contact with the high-temperature and high-pressure compressed gas, so it is easy to produce lubrication failures that other machines do not have. Therefore, the basic requirements for air compressor oil are: suitable viscosity, good oxidation stability and thermal stability, low carbon deposition tendency and soft and easy to fall off carbon deposition, good rust and corrosion resistance, good oil-water separation, high flash point and low volatility, and good anti-foaming properties.
