Principle of sealing shaft of mechanical seal

The principle of the sealing shaft of the mechanical seal The mechanical seal is to rely on one or several pairs of end faces that are perpendicular to the shaft to slide relatively under the action of the fluid pressure and the elastic force (or magnetic force) of the compensation mechanism to keep it fit and to be equipped with an auxiliary seal to achieve leakage prevention. Shaft seal device. The commonly used mechanical seal structure consists of a stationary ring (static ring) 1, a rotating ring (moving ring) 2, an elastic element 3, a spring seat 4, a set screw 5, a rotating ring auxiliary sealing ring 6 and a stationary ring auxiliary sealing ring 8 and other components, the anti-rotation pin 7 is fixed on the gland 9 to prevent the stationary ring from rotating. The mechanical seal ring and stationary ring for rotating kettles can often also be called compensation according to whether the mechanical seals for the kettle have axial compensation capabilities. Ring or non-compensation. There are four possible channels for fluid leakage in the mechanical seal: A, B, C, and D. The C and D leakage channels are the seals between the stationary ring and the gland, and the gland and the shell respectively. All of them are static seals. The B channel is the seal between the rotating ring and the shaft. When the end face is frictionally worn, it can only follow the compensation ring for a small amount of movement in the axial direction, and it is still a relatively static seal. Therefore, these Leakage channels are relatively easy to plug. The most commonly used static sealing elements are rubber O-rings or polytetrafluoroethylene V-rings, and the rotating ring or stationary ring as a compensation ring is used as an auxiliary seal, sometimes with the function of an elastic element. The structure of rubber, PTFE or metal bellows. The A channel is a dynamic seal in which the end faces of the rotating ring and the stationary ring are attached to each other and slide relative to each other. It is the main seal in the mechanical seal device and also determines the performance and life of the mechanical seal. Therefore, the processing requirements for the sealing end face are very high, and at the same time, in order to maintain the necessary lubricating liquid film between the sealing end faces, the unit area pressure on the cavity end face must be strictly controlled. If the pressure is too large, it is not easy to form a stable lubricating liquid film. It will accelerate the wear of the end face; if the pressure is too small, the leakage will increase. Therefore, in order to obtain good sealing performance and sufficient life, when designing and installing the mechanical seal, it is necessary to ensure that the pressure value per unit area of u200bu200bthe end face is in the most appropriate range. Compared with the soft packing seal, the seal has the following advantages: ①The seal is reliable. In the long-term operation, the sealing state is very stable and the leakage is small. According to rough statistics, the leakage is generally only 1/100 of the soft packing seal; ② The service life is long in oil and water media, generally up to 1 to 2 years or more, in chemical media, it can usually reach more than half a year; ③The friction power consumption of the mechanical seal is only 10 times that of the soft packing seal. %～50%;