Principle and structure of mechanical seal

The principle and structure of mechanical seal The mechanical seal relies on one or several pairs of end faces that are perpendicular to the shaft for relative sliding. Under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism, the mechanical seal is kept attached to the mechanical seal factory and equipped with auxiliary seals. Shaft sealing device to prevent leakage. Common mechanical seal structure is composed of stationary ring (static ring) 1, rotating ring (moving ring) 2, elastic element 3, spring seat 4, set screw 5, rotating ring auxiliary sealing ring 6 and stationary ring auxiliary sealing ring 8 and other elements , The anti-rotation pin 7 is fixed on the gland 9 to prevent the stationary ring from rotating. Rotating rings and stationary rings can often be called compensation rings or non-compensated rings according to whether they have axial compensation capabilities. There are four channels A, B, C, and D for the possible leakage of fluid in the mechanical seal. The leakage passages C and D are the seals between the stationary ring and the gland, and the gland and the shell respectively. The B channel is the seal between the rotating ring and the shaft. After the end face is frictionally worn, it can only follow the compensation ring to make a small amount of movement in the axial direction. In fact, it is still a relatively static seal. Therefore, the leak channels of these seals factories are relatively easy to plug. The most commonly used static sealing elements are rubber O-rings or polytetrafluoroethylene V-rings, while the rotating ring or stationary ring as a compensation ring is used as an auxiliary seal, and sometimes rubber, PTFE or metal bellows that have the function of elastic elements are used. Structure. 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 relatively. It is the main seal in the mechanical seal device, and it is also the key to determining the performance and life of the mechanical seal. Therefore, the processing requirements for the sealing end faces are very high. 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 faces must be strictly controlled. If the pressure is too large, it is not easy to form a stable lubricating liquid film, which will accelerate the end face. The wear and tear; if the pressure is too small, the leakage will increase. Therefore, in order to obtain a good sealing performance and sufficient life, when designing and installing a 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 mechanical 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; ②Long service life, generally up to 1 to 2 years or longer in oil and water media, and more than half a year in chemical media; ③The frictional power of the mechanical seal with low friction power consumption is only that of the soft packing seal 10%～50%. Keywords: seal factory, mechanical seal factory, pump mechanical seal