Mechanical seal is a rotary mechanical seal device. Such as centrifugal pumps, centrifuges, reactors and compressors and other equipment. Because the drive shaft penetrates the inside and outside of the device, there is a circumferential gap between the shaft and the device through which the medium leaks to the outside. If the pressure inside the device is lower than the atmospheric pressure, air leaks into the device. Therefore, there must be one Shaft seal to prevent leakage. Many types of shaft seals, the mechanical seal with less leakage and long life, etc., so the world's mechanical seal is the most important shaft seal in these devices. Mechanical seal, also known as end seal, is defined in the relevant national standards: by at least a pair of end face perpendicular to the axis of rotation in the fluid pressure and the compensation mechanism elastic force (or magnetic force) and the auxiliary seal to maintain fit and relative Slide and form a fluid leakage prevention device.