Views: 2493 Author: Site Editor Publish Time: 2020-08-29 Origin: Site
Bellows mechanical seal is widely used. The bellow mechanical seals can be divided into rubber bellows mechanical seals, elastomer bellows mechanical seals, plastic bellows mechanical seals and metal bellows mechanical seals. In addition to bellows seal, there are also spring seal, non contacting mechanical seal, pump seal and gland packing which are often used in industry.
The metal bellows should have large elasticity, strength and rigidity. It can be used for pressure up to 7MPa, and is suitable for high and low temperature operation. Bellows are a kind of sealing element which integrates elastic element, auxiliary seal and torque transmission mechanism. Their torque mode is unique to bellows mechanical seal. The specific pressure on the end face of the bellows is uniform, and they have the characteristics of high temperature resistance and good tracking performance. There are two kinds of bellows commonly used: compression bellows and welding bellows. The compression bellows are made on the press by the method of thin-walled pipe stretching and forming, while the welding bellows are made by welding the inner and outer circles of the film sheet.
In order to keep the sealing surfaces fit each other all the time, the spring plays a constant regulating role between the mechanical seal and the movable spindle. When the elastomer bellows mechanical seal is used between the rotating surface and the main axis, the elastomer will move back and forth on the main axis. This kind of repeated friction will wear the anti-corrosion materials on the main axis, make the protective coating of the oxide film on the main axis fall off, and finally form the wear groove on the friction surface of the main axis, resulting in the leakage of liquid from the main axis. In order to solve this problem, the replaceable sleeve is usually installed in the stuffing box. However, the only permanent solution to corrosion and wear is to remove the dynamic seal. Today, most seal manufacturers produce non corrosive wear seals to prevent corrosive wear on pump parts. The sealing pressure of the contact surface depends on the effective cross section of the seal itself and the pressure inside the stuffing box. The cross section on the other side of the rotating surface of the unbalanced seal is completely exposed to the pressure range of the stuffing box. This creates a higher seal pressure between the sealing surfaces, increasing the operating temperature and increasing the wear rate. Under high temperature working condition or when the liquid has strong corrosiveness, the service life of mechanical seal will be greatly shortened. Balanced mechanical seal can reduce seal pressure and prolong seal life.
Metal bellows mechanical seal uses several small springs to produce relatively uniform load pressure on the sealing surface, so it is more sensitive to blockage. The bellows are welded by a series of metal plates to form a bellows seal to prevent leakage. With this device, the sealing pressure between sealing surfaces can be more uniform, and the secondary seal of sealing surfaces does not need to be increased, so there will be no corrosion and wear.