What Roles Do the Basic Components of Mechanical Seal Play?

Mechanical seal is an axial end face sealing device that relies on the preloading of the sealing faces of the dynamic and static ring ends by elastic elements, and the compression of the medium pressure and the elastic element pressure to achieve sealing. The end faces of the dynamic ring and the static ring form a pair of friction pairs. The dynamic ring relies on the pressure of the liquid in the sealing chamber to press its end face tightly on the static ring end face, and generates proper differential pressure on the two end faces, maintaining a layer of extremely thin liquid film to achieve sealing. The commonly used mechanical seals parts structure is composed of static ring (static ring), rotating ring (dynamic ring), elastic element, spring seat, fastening device, rotating ring auxiliary sealing ring, and static ring auxiliary sealing ring, and the anti-rotation pin is fixed on the pressure cover to prevent the static ring from rotating. What are the functions of these components?

Dynamic and static ring mechanical seal parts

It is responsible for keeping the sealing surfaces tightly fitting together to prevent medium leakage. The dynamic and static rings are required to have good wear resistance. The dynamic ring can move axially to automatically compensate for the wear of the sealing surface, ensuring good fit with the static ring, and the static ring has floating properties, serving as a buffer.

Elastic element mechanical seal parts

The main function is to generate a certain preloading pressure on the sealing end face, so that the end face can maintain a good fit during start-up, shutdown, and fluctuation of medium pressure. It is also used to overcome the frictional force between the auxiliary sealing ring and the shaft, so that the compensating ring moves along the axial direction to compensate for the clearance formed after the end face wear. In addition, it can also provide a certain buffering effect for the vibration caused by shaft runout. The elastic elements used include cylindrical spiral compression springs, corrugated springs, butterfly springs and bellows. Among them, cylindrical spiral compression spring is widely used. Corrugated springs and butterfly springs have the advantages of small axial size, large rigidity, and compact structure, but small axial displacement and spring force, generally suitable for light mechanical seals with tight axial size requirements. Corrugated tubes are commonly used in special conditions such as high temperature, low temperature, and strong corrosion.

Auxiliary sealing mechanical seal parts

Mainly responsible for the sealing of the static and dynamic rings, and also has the functions of floating and buffering. The auxiliary sealing element of the static ring is required to ensure the sealing between the static ring and the pressure cover, so that the static ring has a certain floating property, and the auxiliary sealing element of the dynamic ring is required to ensure the sealing between the dynamic ring and the shaft or shaft sleeve, with materials that are heat-resistant, cold-resistant and close to the medium.

Transmission mechanical seal parts

The transmission mechanical seal parts include a transmission pin, transmission ring, transmission seat, transmission sleeve, transmission key, transmission protrusion or spline connector, which is responsible for transmitting the torque of the shaft to the dynamic ring, and requires materials that are corrosion-resistant and wear-resistant.

Fastening mechanical seal parts

It includes fixing screws, spring seats, pressure covers, assembling sleeves, and shaft sleeves, and plays a role in positioning and fastening the static and dynamic rings. It is required to be correctly positioned, ensuring that the sealing surface of the friction pair is in the correct position, and maintaining a good fit of the spring preload. At the same time, it should be easy to disassemble and install, easy to position, and can be reused repeatedly. The installation of the Seal Ring Chamfer and the Compression should be noted at the junction with the auxiliary seal, especially the dynamic ring seal ring and the shaft sleeve junction, which require corrosion resistance and wear resistance, and may use hard surface coatings when necessary.

After introducing the basic components of mechanical seal parts, let's take a look at where seal failures occur. The leakage points of mechanical seals are basically manifested in 6 places: the end faces of the dynamic and static rings, the auxiliary sealing of the static ring and the static ring box, the sealing between the static ring cover and the centrifugal pump body, the joint structure of the dynamic ring, the sealing between the sleeve and the pump shaft, and the auxiliary sealing of the dynamic ring.

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