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Force deformation and thermal deformation of the mechanical seal ring-

by:Lepu Seal     2021-05-11
Force deformation and thermal deformation of the mechanical seal ring
 2017-08-01  
Force deformation and thermal deformation of mechanical seal sealing ring:
The relative rotating sealing surface of the mechanical seal will generate frictional heat. When the relative speed of the moving ring and the static ring is high, the frictional heat is relatively large, and the generated frictional heat is first transferred to the sealing ring, causing the temperature of the sealing ring to rise. After a certain period of time, the heat transferred to the seal ring is equal to the heat lost by the seal ring to the surrounding medium, and a stable heat transfer state is reached. At this time, a stable temperature field is established in the seal ring, and each point in the seal ring It has a different temperature from the initial, so that the sealing ring is thermally deformed. At the same time, the sealing ring is subjected to mechanical forces such as medium pressure, oil film pressure, spring force, centrifugal force, etc., which will also cause surface deformation of the moving ring and the static ring, which is the force deformation of the sealing ring.
The deformation of the sealing ring of the mechanical seal includes force deformation, thermal deformation (Figure 1-16) and residual deformation. Due to the deformation, the end faces of the static and moving seals will be found to wear unevenly in actual use. Some wear more at the inner diameter, and some wear more at the outer diameter. The reason is that this phenomenon is caused by the deformation of the sealing ring due to uneven temperature distribution or uneven pressure acting on the ring. Due to the objective existence of various forces and thermal deformations, it is possible for the gap of the sealed end face to present the five models shown in Figure 1-17: parallel plane gap, convergence gap, diffusion gap, convergence-diffusion gap and diffusion-convergence gap.
Figure 1~16 Deformation of the sealing surface of the mechanical seal ring

Figure 1-17 Gap model of sealing end face

The main factors affecting the change of the shape of the mechanical seal gap are axial force, radial force, axial temperature gradient and radial temperature gradient. For contact mechanical seals, the sealing surfaces should be kept as straight and parallel as possible, and appropriate deformation methods should be used to achieve parallel plane contact to reduce leakage and wear, extend seal life and improve sealing performance. For non-contact mechanical seals, it should be possible to maintain a suitable sealing surface gap after deformation to ensure the stability of the seal, prevent the contact of the sealing surface, and extend the life of the seal.
In addition to the deformation of the mechanical seal seal ring due to force and temperature stress, the main reason for the thermal cracking of the end face due to excessive thermal stress (thermal stress cracking, shown in Figure 1-18) It is because the surface of the sealing ring is heated by friction and the center part of the ring is not heated, causing the surface thermal stress to exceed the allowable stress of the material. Cracks aggravate wear and tear, and crack the seal gap in the balanced seal, causing serious leakage. Therefore, the performance and use conditions of the sealing material should be strictly controlled as much as possible. In the design and use, full consideration and corresponding measures should be taken, and thermal cracking can be avoided.
Figure 1-18 Hot crack on the end face of the sealing ring

Regardless of force deformation or thermal deformation, it will destroy the flatness and parallelism of the end face of the friction pair, produce various fluid dynamic and static pressure effects, and cause the sealing surface to be beaten when the bearing capacity is too large, or the bearing capacity is too small. Severe wear. For this reason, the contact mechanical seal should be kept parallel to the sealing surface as much as possible, while the non-contact mechanical seal has a stable sealing surface gap shape.
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The sealing characteristics of the mechanical seal    the influence of the deformation of the mechanical seal seal ring on the sealing performance
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