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Mechanical seal design requirements for end face seal pair (friction pair)-
by：Lepu Seal
2021-05-10
Mechanical seal design requirements for end face seal pair (friction pair)
2017-08-11
Mechanical seal design requirements for end face seal pair (friction pair):
According to the working characteristics and requirements of mechanical seals, the following issues should be considered:
(1) The material of the end face seal pair should be selected from the material that has the least friction and wear under the given conditions, is corrosion-resistant and allows dry friction (at least allow dry friction in a short time)
(2) When selecting materials, if the specific pressure or pv value exceeds the allowable value, the load factor (area ratio) can be reduced. However, it should also be noted that as the load factor (area ratio) decreases, the reliability of the seal shows a downward trend. This is due to the possibility of failure of the sealing surface under the action of the fluid film pressure in the gap.
(3) During structural design, the average diameter of the sealing surface should be reduced as much as possible to reduce the peripheral speed and the temperature of the friction pair.
(4) The width of the sealing surface of the soft material ring in the sealing pair should be narrower than that of the hard material ring to prevent the hard ring from falling into the soft ring during grinding and causing the sealing ring to peel off or wear strongly. For seals with a shaft diameter of 5~1500mm, the difference in the width of the sealing surface between the soft and hard rings is 1~4mm; while the ring width of the hard-to-hard friction pair can be the same or different.
(5) As the seal width decreases, the friction heat in the friction pair decreases, which improves the heat dissipation performance. In addition, the wear of the sealing surface is also more uniform, and the effective height of the gap is reduced accordingly. It is reasonable to reduce the width of the sealing surface in this way, but the risk of damage to the sealing surface that is too narrow increases, local strength decreases, and the rigidity of the wear-bearing protrusion decreases. When the gas end face is sealed, because the abrasive particles are less likely to damage the sealing face, the end face width can be smaller than the liquid end face seal width. But when the bearing capacity of the gas end face seal is small, the width needs to be larger. The width of the hydrodynamic pressure wiper seal is larger than that of the ordinary mechanical seal because of the groove. The width of the hydrostatic pressure seal is larger than the first two types of seals. This is because it is determined by the force balance and the allowable leakage.
(6) The cross-sectional form and positioning method of the sealing ring should ensure that the deformation of the sealing surface is minimized, and the shape can tend to rectangular and square cross-sections as much as possible. For the brittle material ring, it should be noted that the transition section should be smoothly transitioned, and the fillet radius should be 1~3mm, so that the strength can be twice as large as the sharp transition.
(7) When the friction pair is assembled, the positioning and fixing methods are different. Depending on the working parameters and structure of the seal, it can be inlaid, bonded, hooped, etc.
(8) When selecting dynamic and static rings, consider that the heat supply coefficient of the dynamic ring is larger than that of the static ring, so the material with higher thermal conductivity is required for the dynamic ring. Changing the shape of the friction pair ring is also beneficial to improve the heat supply of the friction pair and reduce the temperature of the friction pair.
(9) The non-vertical seal ring surface of the friction pair will adversely affect its work (such as the effect of installation, manufacturing, amplitude and other adverse factors on the work), so structural and technological measures must be adopted to ensure the smallest error. The error of the moving ring is generally larger than that of the static ring, and the static seal is adopted at high speed.
(10) The radial force on the friction pair seal ring depends on the alignment accuracy, the concentricity of the shaft and the sleeve, and the non-perpendicularity of the sealing surface. The radial force should be reduced as much as possible.
Bergman M481K mechanical seal 551.html,
Basic requirements for mechanical seal design Mechanical seal requirements for elastic components
2017-08-11
Mechanical seal design requirements for end face seal pair (friction pair):
According to the working characteristics and requirements of mechanical seals, the following issues should be considered:
(1) The material of the end face seal pair should be selected from the material that has the least friction and wear under the given conditions, is corrosion-resistant and allows dry friction (at least allow dry friction in a short time)
(2) When selecting materials, if the specific pressure or pv value exceeds the allowable value, the load factor (area ratio) can be reduced. However, it should also be noted that as the load factor (area ratio) decreases, the reliability of the seal shows a downward trend. This is due to the possibility of failure of the sealing surface under the action of the fluid film pressure in the gap.
(3) During structural design, the average diameter of the sealing surface should be reduced as much as possible to reduce the peripheral speed and the temperature of the friction pair.
(4) The width of the sealing surface of the soft material ring in the sealing pair should be narrower than that of the hard material ring to prevent the hard ring from falling into the soft ring during grinding and causing the sealing ring to peel off or wear strongly. For seals with a shaft diameter of 5~1500mm, the difference in the width of the sealing surface between the soft and hard rings is 1~4mm; while the ring width of the hard-to-hard friction pair can be the same or different.
(5) As the seal width decreases, the friction heat in the friction pair decreases, which improves the heat dissipation performance. In addition, the wear of the sealing surface is also more uniform, and the effective height of the gap is reduced accordingly. It is reasonable to reduce the width of the sealing surface in this way, but the risk of damage to the sealing surface that is too narrow increases, local strength decreases, and the rigidity of the wear-bearing protrusion decreases. When the gas end face is sealed, because the abrasive particles are less likely to damage the sealing face, the end face width can be smaller than the liquid end face seal width. But when the bearing capacity of the gas end face seal is small, the width needs to be larger. The width of the hydrodynamic pressure wiper seal is larger than that of the ordinary mechanical seal because of the groove. The width of the hydrostatic pressure seal is larger than the first two types of seals. This is because it is determined by the force balance and the allowable leakage.
(6) The cross-sectional form and positioning method of the sealing ring should ensure that the deformation of the sealing surface is minimized, and the shape can tend to rectangular and square cross-sections as much as possible. For the brittle material ring, it should be noted that the transition section should be smoothly transitioned, and the fillet radius should be 1~3mm, so that the strength can be twice as large as the sharp transition.
(7) When the friction pair is assembled, the positioning and fixing methods are different. Depending on the working parameters and structure of the seal, it can be inlaid, bonded, hooped, etc.
(8) When selecting dynamic and static rings, consider that the heat supply coefficient of the dynamic ring is larger than that of the static ring, so the material with higher thermal conductivity is required for the dynamic ring. Changing the shape of the friction pair ring is also beneficial to improve the heat supply of the friction pair and reduce the temperature of the friction pair.
(9) The non-vertical seal ring surface of the friction pair will adversely affect its work (such as the effect of installation, manufacturing, amplitude and other adverse factors on the work), so structural and technological measures must be adopted to ensure the smallest error. The error of the moving ring is generally larger than that of the static ring, and the static seal is adopted at high speed.
(10) The radial force on the friction pair seal ring depends on the alignment accuracy, the concentricity of the shaft and the sleeve, and the non-perpendicularity of the sealing surface. The radial force should be reduced as much as possible.
Bergman M481K mechanical seal 551.html,
Basic requirements for mechanical seal design Mechanical seal requirements for elastic components
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