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Principle Of Mechanical Seal
- Feb 02, 2018 -

The clearance between the static ring and the moving ring is the main sealing surface. It determines the key to the friction, wear and sealing performance of the mechanical seal, and also determines the service life of the mechanical seal.

The movable ring can be freely moved by the loading of the spring, so as to keep the contact with the static ring. Axial mobility allows automatic compensation for heat displacement of wear, eccentricity and shaft. O shaped ring auxiliary seal, can play a radial sealing and buffering effect of the sealing in the radial direction without rigid contact. In the case of static, dynamic and static ring end face grinding ring in mechanical contact, but when the shaft rotates, the friction effect of complex occurred in the end and sealed fluid.

Most of the main characteristics of mechanical seals are its automatic interface lubrication mechanism that controls sealing function, friction, wear and life. It all depends on the liquid passing through the interface and establishing the lubricant film, so that the seal can be operated under the condition of the actual frictional friction, which is usually between the dry friction and the complete liquid film.

Under the pressure of the cavity, the medium passes through the end face of the seal friction pair, and the surface tension and the centrifugal force have little influence at this time. As the fluid flows through the end face, the fluid pressure continues to decrease until it reaches the external back pressure (usually atmospheric pressure), which is similar to the bearing function of hydrostatic bearing. The bearing capacity of seal depends on the shape change of pressure difference and interface gap. The mathematical analysis is rather complicated. It can refer to books related to mechanical seals, such as Gu Yongquan, Cai Renliang and others.

When the seal is rotated, the shear flow in the end faces with the change of the remaining height of the end face to produce hydrodynamic pressure. The pressure field has a similar bearing function for the hydrodynamic bearing, and it depends on the viscosity, rotation speed and the change of the end clearance.

Under normal conditions, hydrodynamic fluid pressure and fluid pressure field of the bearing capacity of sealing operation, which belongs to the part of the opening force, to prevent the rigid contact seal. When the opening force and the closing force deviate from the balance, the end face is automatically adapted