Basic structure, function principle and requirements of mechanical seal

The basic structure, function principle and requirements of mechanical seals. Business Manager of Hebei Innovation Sealing Material Co., Ltd. Tel 0316-8066919 Website:

The mechanical seal is an axial end face sealing device that relies on the elastic element to pre-tighten the sealing pair of the static and moving ring faces and the pressure of the medium pressure and the pressure of the elastic element to form a seal, so it is also called the end face seal.
The basic components that make up the mechanical seal are: face seal pairs (static ring 1 and moving ring 2), elastic elements (such as spring 4), auxiliary seals (such as O-rings 8 and 9), transmission parts (such as drive pin 3 and transmission) Screw 7), anti-rotation member (such as anti-rotation pin 10) and fasteners (such as spring seat 5, push ring 12, gland 11, and set screw 6).
The functions and requirements of the basic components of mechanical seals are as follows:

1) End face seal pair (static and moving ring) The function of the face seal pair is to make the sealing surface fit tightly to prevent media leakage. It requires the static and dynamic rings to have good wear resistance, and the moving ring can move axially and flexibly, automatically compensating for the wear of the sealing surface, so that it fits well with the static ring; the static ring has a floating property and acts as a buffer. For this reason, the sealing surface is required to have good processing quality, and the sealing pair has good bonding performance.

2) The elastic element (spring, bellows, diaphragm) mainly plays the role of pre-tightening, compensating and buffering. It is required to maintain sufficient elasticity at all times to overcome the inertia of the auxiliary seal and the friction and moving ring of the transmission member, and to ensure the end seal pair. Good fit and follow-up of the moving ring, the material requires corrosion resistance and fatigue resistance.

3) Auxiliary seals (O-rings, V-rings, U-rings, wedge rings and profiled rings) which mainly act as a seal between the stationary ring and the moving ring, and also serve as a floating and cushioning function. The sealing element of the static ring is required to ensure the sealing between the static ring and the gland and the floating ring of the static ring. The sealing element of the moving ring can ensure the sealing between the moving ring and the shaft or the sleeve and the moving ring. Floating. Materials are required to be heat resistant, cold resistant and compatible with the media. Type of packing (tetrafluoro-residue, graphite packing, asbestos packing, high water-based packing, aramid packing, cotton packing, ramie packing, ceramic fiber packing, fiberglass packing)

4) Transmission (drive pin, drive ring, drive seat, drive key, transmission lug or jaw coupling) which acts to transmit the torque of the shaft to the moving ring. Materials require wear and corrosion resistance.

5) Fasteners (tightening screws, spring seats, gland, assembly sleeve, bushing) It plays the role of positioning and fastening of static and moving rings. The axial positioning is required to be correct, and a certain amount of spring compression is ensured, so that the sealing surface of the sealing pair is in the correct position and maintains a good fit. At the same time, it is required to be easy to disassemble, easy to place and reuse. Where the sealing ring is matched with the auxiliary seal, the sealing ring should be guided with chamfering and compression amount. Special attention should be paid to the wear-resisting and corrosion resistance of the moving ring auxiliary seal and the bushing. If necessary, the shaft sleeve can be used. Hard cover.

6) Anti-rotation (anti-reverse) It acts to prevent the rotation and release of the stationary ring. It is required to have sufficient length to prevent the static ring from coming out under negative pressure and to require correct positioning to prevent the static ring from rotating. The material is required to be corrosion resistant, and a tetrafluoroethylene sleeve may be added in the middle if necessary to avoid damage to the carbon graphite static ring.

Possible leaks of mechanical seals are as follows

1) Leakage at the sealing sub-sealing surface I This is the main sealing surface, which is the key to determining the mechanical seal friction, wear and sealing performance, and also determines the working life of the mechanical seal. According to statistics, about 80% to 95% of mechanical seal leakage is caused by the seal face seal. Therefore, the contact surfaces are required to be parallel, the surface roughness is required to be high, Ra = 0.05 to 0.20 μm, and the flatness is 2) the leakage at the auxiliary seal II of the static ring and the gland and the auxiliary seal of the moving ring and the shaft (or the bushing) Leakage at III This is the auxiliary sealing surface, which is the key to determine the tightness of the mechanical seal and the follow-up of the moving ring. In particular, the sealing surface of the moving ring and the shaft (or bushing) must first prevent corrosion, scale, coking or chemical reaction materials. Stacking and causing the moving ring can not move.

The above I, II, III are all dynamic seals.

3) The static seal between the gland and the sealed box IV, the sleeve and the shaft static seal V and the dynamic ring inlay structure cooperate with the VI to leak. These three are static seals. Seals or corresponding fits of compatible materials should be selected according to the sealing medium.
Type of packing (tetrafluoro-residue, graphite packing, asbestos packing, high water-based packing, aramid packing, cotton packing, ramie packing, ceramic fiber packing, fiberglass packing)

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