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Mechanical seal structure-
by：Lepu Seal
2021-03-27
Mechanical seal structure
2017-04-11
Mechanical seal is an axial end face sealing device that relies on elastic elements to pre-tighten the static and moving ring end face seal pairs and to compress the medium pressure and elastic element pressure to achieve sealing (Figure 1), so it is also called end face seal.
Basic structure of mechanical seal
The basic elements that constitute a mechanical seal are: end face seal pairs (stationary 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 drive screw 7, anti-rotation parts (such as anti-rotation pin 10 and fasteners (such as spring seat 5, push ring 12, gland 11, set screw 6 and sleeve 13).
Figure 1 Schematic diagram of a typical mechanical seal
The role and requirements of the basic components of mechanical seals
1. End face seal pair (static and dynamic ring)
The function of the end face seal pair is to make the sealing surface fit tightly and prevent the medium from leaking. It requires the static and moving rings to have good wear resistance. The moving ring can move flexibly in the axial direction, automatically compensate for the wear of the sealing surface, and make it fit well with the static ring; the static ring is floating and has a buffering effect. For this reason, the sealing surface is required to have good processing quality to ensure that the sealing pair has a good fit performance.
2, elastic elements (spring, bellows, diaphragm)
It mainly plays the role of pre-tensioning, compensation and buffering. It is required to always maintain sufficient elasticity to overcome the friction of the auxiliary seal and transmission parts and the inertia of the moving ring, so as to ensure the good fit of the end face seal pair and the follow-up of the moving ring. The material requires corrosion resistance and fatigue resistance.
3, auxiliary seal (O-ring, V-ring, U-ring, wedge-shaped ring and special-shaped ring)
It mainly serves as the sealing function of the static ring and the moving ring, and it also plays a role of floating and buffering. The sealing element of the static ring is required to ensure the sealing performance between the static ring and the gland and the static ring has a certain degree of floating. The sealing element of the moving ring can ensure the sealing performance between the moving ring and the shaft or sleeve and the sealing performance of the moving ring. Floatability. The material must be heat-resistant, cold-resistant and compatible with the medium.
4. Transmission parts (transmission pin, transmission ring, transmission seat, transmission key, transmission lug or jaw coupling)
It plays the role of transmitting the torque of the shaft to the moving ring. The material requires wear and corrosion resistance.
5. Fasteners (set screws, spring seats, glands, assembly sleeves, shaft sleeves)
It plays the role of positioning and fastening the static and moving rings. The axial positioning is required to be correct, to ensure a certain amount of spring compression, 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 reusable. Where it is fitted with the auxiliary seal, the installation of the seal ring must have a guiding chamfer and a crushing amount. Special attention should be paid to the wear resistance and corrosion resistance of the auxiliary seal of the moving ring and the shaft sleeve. If necessary, it can be used in the joint with the shaft sleeve. Hard surface cladding.
6, anti-rotation parts (anti-rotation pin)
It plays a role in preventing the static ring from rotating and falling out. It is required to have sufficient length to prevent the static ring from falling out under negative pressure, and to be correctly positioned to prevent the static ring from rotating with the moving ring. Corrosion resistance is required on the material, and a tetrafluoroethylene sleeve can be added in the middle when necessary to avoid damaging the carbon graphite static ring.
The possible leakage path of mechanical seal
1. Leakage at the sealing surface I of the sealing pair
This is the main sealing surface, which determines the friction, wear and sealing performance of the mechanical seal, and also determines the working life of the mechanical seal. According to statistics, about 80%-95% of the leakage of mechanical seals is caused by the seal pair of the seal end face. Therefore, the contact surface is required to be parallel, and the surface roughness is required to be high, Ru003d0.05~0.2um, and flatness <0.9um. For different media, it is required to use a suitable combination of sealing materials, pay attention to wear resistance and corrosion resistance, and select appropriate geometric parameters (area ratio and width to diameter ratio, etc.) and performance parameters (specific pressure, spring load, etc.).
2. Leakage at the auxiliary seal II of the stationary ring and gland and leakage at the auxiliary seal III of the moving ring and shaft (or sleeve) This is the auxiliary sealing surface, which determines the sealing performance of the mechanical seal and the followability of the moving ring The key, especially the sealing surface of the moving ring and the shaft (or sleeve), must first prevent the moving ring from being unable to move due to rust, scale, coking or accumulation of chemical reaction materials.
Above I, II, and III are all dynamic seals.
3, the static seal IV between the gland and the sealed box, the static seal between the shaft sleeve and the shaft V, and the leakage at the moving ring inlay structure VI are static seals. According to the sealing medium, the gasket of compatible material or the corresponding matching should be selected.
The basic structure, principle of action and requirements of mechanical seals are first published on the Vacuum Technology Network. For reprinting, please indicate the initial website of this article in the form of a link. 389.html,
Mechanical seal principle diagram Mechanical seal standard
2017-04-11
Mechanical seal is an axial end face sealing device that relies on elastic elements to pre-tighten the static and moving ring end face seal pairs and to compress the medium pressure and elastic element pressure to achieve sealing (Figure 1), so it is also called end face seal.
Basic structure of mechanical seal
The basic elements that constitute a mechanical seal are: end face seal pairs (stationary 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 drive screw 7, anti-rotation parts (such as anti-rotation pin 10 and fasteners (such as spring seat 5, push ring 12, gland 11, set screw 6 and sleeve 13).
Figure 1 Schematic diagram of a typical mechanical seal
The role and requirements of the basic components of mechanical seals
1. End face seal pair (static and dynamic ring)
The function of the end face seal pair is to make the sealing surface fit tightly and prevent the medium from leaking. It requires the static and moving rings to have good wear resistance. The moving ring can move flexibly in the axial direction, automatically compensate for the wear of the sealing surface, and make it fit well with the static ring; the static ring is floating and has a buffering effect. For this reason, the sealing surface is required to have good processing quality to ensure that the sealing pair has a good fit performance.
2, elastic elements (spring, bellows, diaphragm)
It mainly plays the role of pre-tensioning, compensation and buffering. It is required to always maintain sufficient elasticity to overcome the friction of the auxiliary seal and transmission parts and the inertia of the moving ring, so as to ensure the good fit of the end face seal pair and the follow-up of the moving ring. The material requires corrosion resistance and fatigue resistance.
3, auxiliary seal (O-ring, V-ring, U-ring, wedge-shaped ring and special-shaped ring)
It mainly serves as the sealing function of the static ring and the moving ring, and it also plays a role of floating and buffering. The sealing element of the static ring is required to ensure the sealing performance between the static ring and the gland and the static ring has a certain degree of floating. The sealing element of the moving ring can ensure the sealing performance between the moving ring and the shaft or sleeve and the sealing performance of the moving ring. Floatability. The material must be heat-resistant, cold-resistant and compatible with the medium.
4. Transmission parts (transmission pin, transmission ring, transmission seat, transmission key, transmission lug or jaw coupling)
It plays the role of transmitting the torque of the shaft to the moving ring. The material requires wear and corrosion resistance.
5. Fasteners (set screws, spring seats, glands, assembly sleeves, shaft sleeves)
It plays the role of positioning and fastening the static and moving rings. The axial positioning is required to be correct, to ensure a certain amount of spring compression, 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 reusable. Where it is fitted with the auxiliary seal, the installation of the seal ring must have a guiding chamfer and a crushing amount. Special attention should be paid to the wear resistance and corrosion resistance of the auxiliary seal of the moving ring and the shaft sleeve. If necessary, it can be used in the joint with the shaft sleeve. Hard surface cladding.
6, anti-rotation parts (anti-rotation pin)
It plays a role in preventing the static ring from rotating and falling out. It is required to have sufficient length to prevent the static ring from falling out under negative pressure, and to be correctly positioned to prevent the static ring from rotating with the moving ring. Corrosion resistance is required on the material, and a tetrafluoroethylene sleeve can be added in the middle when necessary to avoid damaging the carbon graphite static ring.
The possible leakage path of mechanical seal
1. Leakage at the sealing surface I of the sealing pair
This is the main sealing surface, which determines the friction, wear and sealing performance of the mechanical seal, and also determines the working life of the mechanical seal. According to statistics, about 80%-95% of the leakage of mechanical seals is caused by the seal pair of the seal end face. Therefore, the contact surface is required to be parallel, and the surface roughness is required to be high, Ru003d0.05~0.2um, and flatness <0.9um. For different media, it is required to use a suitable combination of sealing materials, pay attention to wear resistance and corrosion resistance, and select appropriate geometric parameters (area ratio and width to diameter ratio, etc.) and performance parameters (specific pressure, spring load, etc.).
2. Leakage at the auxiliary seal II of the stationary ring and gland and leakage at the auxiliary seal III of the moving ring and shaft (or sleeve) This is the auxiliary sealing surface, which determines the sealing performance of the mechanical seal and the followability of the moving ring The key, especially the sealing surface of the moving ring and the shaft (or sleeve), must first prevent the moving ring from being unable to move due to rust, scale, coking or accumulation of chemical reaction materials.
Above I, II, and III are all dynamic seals.
3, the static seal IV between the gland and the sealed box, the static seal between the shaft sleeve and the shaft V, and the leakage at the moving ring inlay structure VI are static seals. According to the sealing medium, the gasket of compatible material or the corresponding matching should be selected.
The basic structure, principle of action and requirements of mechanical seals are first published on the Vacuum Technology Network. For reprinting, please indicate the initial website of this article in the form of a link. 389.html,
Mechanical seal principle diagram Mechanical seal standard
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