Mechanical seal main components

Moving ring, static ring, cooling device and pressing spring

Auxiliary seal

Seal ring (O shape, X shape, U shape, wedge, rectangular flexible graphite, PTFE coated rubber O ring, etc.)

Elastic compensating mechanism

Spring, push ring.

Spring seat and key or various screws.

Classification of mechanical seals

Divided into single end face, double end face; Balanced type, non-balanced type; Arbitrary spin, fixed spin...

Mechanical seal is a shaft seal device that achieves leakage resistance by a pair or several pairs of relative sliding end faces perpendicular to the shaft under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism to keep sticking and combining with auxiliary sealing. It is also called end face seal. It has reliable performance, small leakage, long service life, low power consumption and no frequent maintenance. And can adapt to the production process automation and high temperature, low temperature, high pressure, vacuum, high speed and a variety of strong corrosive media, containing solid particle media and other harsh conditions of the sealing requirements, such as centrifugal pumps, centrifuges, reactors and compressors and other equipment.

The end clearance between the static ring and the moving ring is the main sealing surface, which determines the friction, wear and sealing performance of the mechanical seal, and also determines the service life of the mechanical seal. The moving ring is loaded axially by the spring and can move freely to maintain contact with the static ring (Seat). Axial mobility allows automatic compensation for wear, eccentricity, and thermal displacement of the shaft. The O-ring plays an auxiliary sealing role, which can play a radial sealing and buffering role, so that the whole seal does not have rigid contact in the radial direction. At rest, the grinding ends of the moving ring and the static ring are in mechanical contact, but when the shaft rotates, complex friction occurs between the end face and the sealed fluid.

Most of the major features of mechanical seals are their automatic interfacial lubrication mechanisms that control seal function, friction, wear, and life. It all depends on the fluid that crosses the interface and establishes a lubricating film so that the seal operates under conditions of actual no contact (usually mixed friction, a state of lubricating friction between dry friction and a full liquid film). Under the pressure of the cavity, the medium passes through the end face of the sealing friction pair. Surface tension and centrifugal force have little effect at this time. As the fluid flows radial across the end face, the fluid pressure continues to fall until it reaches the external back pressure (generally atmospheric pressure), which acts similarly to the bearing function of hydrostatic bearings. The bearing capacity of the seal depends on the change of pressure difference and the shape of the interfacial clearance. The mathematical analysis is more complicated. When the seal rotates, the shear flow in the end face interacts with the change of the remaining height of the end face to produce the hydrodynamic pressure. Under normal conditions, the fluid dynamic pressure field and the hydrostatic pressure field constitute the bearing capacity of the seal during operation. They belong to the opening force part and are used to prevent rigid contact of the seal.

End friction pair (static and moving ring) : In order to keep the friction surface closely fitted to form the sealing surface so as to prevent media leakage, the dynamic ring is required to have good wear resistance. The moving ring can move axially and automatically compensate the wear of the sealing surface, so as to make it fit well with the static ring. The static and moving ring have floating cushioning effect. Elastic element (spring, bellows, diaphragm, etc.) : mainly plays the role of pre-tightening, compensation and buffer, is also an important factor to produce a reasonable specific pressure on the end face of the seal, always maintain the elasticity to overcome the friction and inertia of the auxiliary sealing transmission parts, to ensure that the end face friction pair good fit and the following of the ring, the material requirements of corrosion resistance and fatigue.

Auxiliary sealing (O-ring, V-ring and other sealing rings) : To play the sealing role of static ring and dynamic ring, but also play the role of floating buffer, the auxiliary sealing element of the static ring can ensure the sealing between the static ring and the gland and the static ring has a certain buoyancy, the auxiliary sealing element of the dynamic ring can ensure the sealing between the dynamic ring and the shaft or shaft sleeve and the dynamic ring buoyancy, the material requires heat or cold resistance and can be compatible with the medium. Transmission parts (drive pin electric drive ring, drive seat, drive sleeve, drive key, drive lug or tooth insert connector) : play the role of the shaft torque to the moving ring, the transmission pin, the press ring - drive ring, drive pin - spring seat all play the driving role, the material requirements wear and corrosion resistance. Fasteners (setting screws, spring seat, gland, shaft sleeve) : To play a static, dynamic ring positioning, fastening and dressing role, the requirements of correct positioning, to ensure that the friction pair sealing surface in the correct position and maintain a good fit of the spring specific pressure. At the same time requires convenient disassembly, easy to place, can be reused. When matching with auxiliary sealing, pay attention to the guiding side Angle of the sealing ring and the pressure and elasticity. In particular, attention should be paid to the corrosion resistance and wear resistance of the auxiliary sealing parts of the moving ring and the shaft sleeve, and the hard surface cladding should be used when necessary.

End friction pair (static and moving ring) : In order to keep the friction surface closely fitted to form the sealing surface so as to prevent media leakage, the dynamic ring is required to have good wear resistance. The moving ring can move axially and automatically compensate the wear of the sealing surface, so as to make it fit well with the static ring. The static and moving ring have floating cushioning effect. Elastic element (spring, bellows, diaphragm, etc.) : mainly plays the role of pre-tightening, compensation and buffer, is also an important factor to produce a reasonable specific pressure on the end face of the seal, always maintain the elasticity to overcome the friction and inertia of the auxiliary sealing transmission parts, to ensure that the end face friction pair good fit and the following of the ring, the material requirements of corrosion resistance and fatigue.

Auxiliary sealing (O-ring, V-ring and other sealing rings) : To play the sealing role of static ring and dynamic ring, but also play the role of floating buffer, the auxiliary sealing element of the static ring can ensure the sealing between the static ring and the gland and the static ring has a certain buoyancy, the auxiliary sealing element of the dynamic ring can ensure the sealing between the dynamic ring and the shaft or shaft sleeve and the dynamic ring buoyancy, the material requires heat or cold resistance and can be compatible with the medium. Transmission parts (drive pin electric drive ring, drive seat, drive sleeve, drive key, drive lug or tooth insert connector) : play the role of the shaft torque to the moving ring, the transmission pin, the press ring - drive ring, drive pin - spring seat all play the driving role, the material requirements wear and corrosion resistance. Fasteners (setting screws, spring seat, gland, shaft sleeve) : To play a static, dynamic ring positioning, fastening and dressing role, the requirements of correct positioning, to ensure that the friction pair sealing surface in the correct position and maintain a good fit of the spring specific pressure. At the same time requires convenient disassembly, easy to place, can be reused. When matching with auxiliary sealing, pay attention to the guiding side Angle of the sealing ring and the pressure and elasticity. In particular, attention should be paid to the corrosion resistance and wear resistance of the auxiliary sealing parts of the moving ring and the shaft sleeve, and the hard surface cladding should be used when necessary.