Brief introduction of mechanical seal structure

The mechanical seal is a combined mechanism composed of a series of simple design elements. The sealing function is completed by two main sealing rings with planes to prevent leakage. One of the seal rings is connected with the shaft and rotates, and the other seal ring is fixed on the housing. In order to seal the centrifugal pump shaft, the static seal ring is installed on the gland of the seal cavity. During the rotation of the pump shaft, the sealing surface of the sealing ring mounted on the shaft rubs against the opposite stationary ring sealing surface. The contact action of these two sealed contact surfaces is similar to a bearing and is subject to wear. Any form of system leakage must pass through this sealed contact surface. The force acting in the axial direction keeps the sealing ring always in frictional contact. The source can be mechanical or hydraulic. In many designs, the sum of the two is taken. This stable contact can prevent leakage from the friction surfaces or minimize the amount of leakage.

The gap between the end face of the static ring (Seat) and the dynamic ring (Seal Face) is the main sealing surface, which determines the key to the friction, wear and sealing performance of Jieyi mechanical seal, and also determines the service life of the mechanical seal.

Commonly used mechanical seal structure is composed of static ring (static ring), rotating ring (moving ring), elastic element, spring seat, set screw, rotating ring auxiliary seal ring and static ring auxiliary seal ring, etc., anti-rotation pin 7 is fixed Press on the cover to prevent the stationary ring from rotating. Rotating ring and stationary ring can also be called compensation ring or non-compensation according to whether they have axial compensation capability.

Compared with soft packing seal, mechanical seal has the following advantages:

①Reliable sealing During long-period operation, the sealing state is very stable and the leakage is very small. According to rough statistics, the leakage is generally only 1/100 of the soft packing seal; ②Long service life is generally in oil and water media It can reach 1 to 2 years or more, and it can usually reach more than half a year in chemical media; ③ The friction power consumption is small. The friction power of the mechanical seal is only 10% to 50% of the soft packing seal; ④ The shaft or shaft sleeve is basic It is not subject to friction; ⑤ Long-term maintenance cycle can be automatically compensated after the end face is worn. Generally, no frequent maintenance is required; ⑥ Good vibration resistance does not affect the vibration and deflection of the rotating shaft and the deflection of the shaft to the sealing cavity Sensitive; ⑦ Wide application range Mechanical seals can be used for sealing at low temperature, high temperature, vacuum, high pressure, different speeds, and various corrosive media and media containing abrasive particles.

But its shortcomings are:

① the structure is more complex, and it has high requirements for manufacturing and processing; ② installation and replacement are more troublesome, and it requires workers to have a certain level of installation technology; ③ when accidental accidents occur, it is more difficult to handle; ④ one-time investment is high.