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Cylinder groove size tolerance and seal fit

Let's understand how the following cylinder groove size tolerances and seals fit together.

(1) There are many forms of reciprocating motion seals, common L, U, V, and Y, etc., and their shapes are mostly lip seals.

(2) reciprocating lip seals are widely used in reciprocating cylinders of hydraulic systems. The pressure surface of the seal is lip type, and there is a small amount of interference during installation, so that the lip edge is fully in contact with the sealing surface and the sealing effect is generated. When the cylinder is working, the contact force and contact area increase with the increase of pressure, and the sealing performance improves with the increase of pressure. When the cylinder returns, the pressure decreases, the contact area and contact force decrease, and the sealing performance decreases accordingly. This lip operation process is similar to the human breathing process. In addition, this process also plays a role in lubricating the lip.

(3) Seal manufacturers in the world have strict requirements for groove size tolerances and roughness. Therefore, the cylinder manufacturer must produce the cylinder strictly according to the tolerance and roughness requirements.

If the cylinder is not produced as required, three conditions will occur:

Case 1, the trench is too deep, there are two situations:

A. The gap between the seal root and the groove becomes larger, which will cause the seal root to be unfixed.

B. The interference of the seal lip and sealing surface becomes smaller, and the recoil of the seal becomes smaller, so the failure rate of low-pressure oil leakage will increase when the piston rod beats.

Situation two, the trench is too shallow, will also produce two situations:

A, resulting in increased interference between the sealing lip and the sealing surface, increased contact area, resulting in greater friction, in the cylinder return trip seal lip can not be effectively lubricated, increase the heat, add

The damage of the seal lip is accelerated.

B, resulting in a smaller clearance of the seal root, resulting in an increased chance of the seal root being squeezed out when the cylinder is under high pressure.

Case three, the roughness of the cylinder

If the roughness of the hydraulic cylinder exceeds the requirements, it will also lead to two situations:

A. It will lead to increased friction between the inner and outer lips of the seals, and speed up the damage of the lips.


Name: Kevin Li





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