Mechanical seal is an oil seal device for rotating machinery. Such as centrifugal pumps, centrifuges, reactors and compressors. Because the drive shaft runs through the inside and outside of the device, there is a circumferential gap between the shaft and the device. The medium in the device leaks out through this gap. If the pressure inside the device is lower than atmospheric pressure, air leaks into the device, so there must be Leak-proof shaft seal. There are many types of shaft seals. Because mechanical seals have the advantages of low leakage and long life, mechanical seals are the most important shaft seal method in these devices in the world today. Mechanical seals are also called end face seals. They are defined in relevant national standards: "At least one pair of end faces perpendicular to the axis of rotation is kept in close contact with the fluid pressure and the spring force (or magnetic force) of the compensation mechanism and the auxiliary seal. Device for preventing fluid leakage by sliding relative to each other.