Compressor oil change index

Compressor oil change index The general indicators for determining whether the refrigeration oil can continue to be used are: appearance, viscosity, acid value, moisture, pour point, flash point, compressive strength, copper corrosion, mechanical impurities and insolubles. Exterior 　　The quality of the frozen oil should be determined by certain chemical and physical analysis. During normal use, the quality of the oil can be intuitively judged from the appearance color of the oil. High-quality frozen oil should be colorless and transparent, and it will become light yellow after a period of use. With the extension of use time, the color of the oil will gradually become darker and the transparency will become worse. If the freezing oil becomes orange-red or red-brown, it should be replaced. 　　 viscosity 　　The kinematic viscosity value of frozen oil is the main index reflecting the lubricating performance of oil products, and it is also the basis for many countries in the world to formulate the brand of frozen oil. If the viscosity is too high, the low temperature performance of the oil is not guaranteed, which is not conducive to heat transfer, and it will reduce the power of the machine. Failure such as "bonding". 　　Acid value 　　 acid value is an important index of refrigeration oil, and the corresponding test method is GB/T4945 or GB/T7304. The acid value in frozen oil reflects the degree of oil refining and oxidation to a certain extent. 　　Moisture 　　In the refrigeration cycle system, even if only a small amount of water is present, ice plug phenomenon will occur in the low-temperature throttling device and lead to the premature generation of flocculants in the freezing oil. At high temperatures, moisture also reduces the stability of the oil. On the other hand, the closed refrigeration oil is in direct contact with the motor coil. The presence of water will destroy the insulation and even cause motor breakdown. 　　 pour point 　　 The minimum temperature at which the oil can flow is called the pour point of the oil. When the refrigerant is compressed, part of the oil mist often enters the pipeline. Even after passing through the oil-gas separator, the two cannot be separated cleanly. This requires the oil to have good low-temperature fluidity (low pour point) in the refrigeration system. In order to avoid blocking the throttling parts, the chiller will stop working or attached to the evaporator heat exchange tube to reduce the heat transfer efficiency. Flash point 　　 The flash point of the frozen oil refers to the lowest temperature at which the flash fire occurs when the oil vapor generated during heating is mixed with the air and comes into contact with the flame. If the flash point of the frozen oil is reduced, it means that the oil is mixed with light oil or part of the oil has been decomposed to generate low-boiling decomposition products. Generally speaking, the flash point of refrigeration oil is 15-30℃ higher than the compressor outlet temperature. 　　 Compressive strength The compressive strength, also known as breakdown voltage or dielectric strength, refers to placing the freezing oil in a container equipped with an electrode to apply a voltage. When the voltage gradually increases to a certain value, the resistance of the oil suddenly drops to zero, a strong The current flows through the oil in the form of sparks or arcs, and the critical voltage value at this time is called the dielectric strength. The main factors that affect the breakdown voltage of refrigeration oil are moisture, impurities, and temperature. 　　Copper sheet corrosion Copper corrosion test is currently the most important method for measuring the corrosion of industrial lubricating oils. It is a test under the specified conditions that the oil product and the metal surface in contact with it have a tendency to corrode. The corrosion resistance of the oil product is certain. The degree can reflect the refining depth and deterioration degree of oil products. 　　 Mechanical impurities and insolubles 　　Mechanical impurities are one of the routine monitoring items for the lubrication management of chiller compressors, because the mechanical impurities in the oil will accelerate the abnormal wear of the compressor, and will also block the oil circuit and the filter, resulting in lubrication failure of the compressor. Mechanical impurities are one of the indicators to determine whether the refrigeration oil needs to be changed. Generally, mechanical impurities below 0.005% are considered to be free of mechanical impurities. If it exceeds 0.005%, it contains mechanical impurities and the freezing oil is judged to be unqualified.