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Analysis of the causes of hydraulic seal leakage?
- Feb 01, 2019 -

The structural form of the seal, the material of the seal, the design and manufacturing quality of the seal groove, the design and manufacturing quality of the seal surface, the quality of the seal installation, the working environment of the seal and the dirt of the seal. Hydraulic cylinders can cause leakage of common hydraulic seals.


1. Sealed structural form


The structural form of the seal is not properly selected. Extremely easy to cause leakage. In general, the structural form of the hydraulic seal has a very complex effect on the leakage. However, under the same operating conditions, lip seals typically have less leakage than self-sealing compression seals, while lip seals typically minimize leakage of the YX seal.


2. Sealing material


Choosing improper sealing materials can easily cause leaks. If the sealing material is too soft, when the hydraulic cylinder is in operation, the seal can easily penetrate into the sealing gap and be damaged, causing the hydraulic oil to leak. If the sealing material is too hard. Even under the action of a large external force, the deformation of the seal is difficult, and it is apparent that the initial contact stress and the additional contact stress generated on the sealing surface are inevitably lowered, thereby exacerbating the leakage of the hydraulic oil. If the sealing material is incompatible with the hydraulic fluid, the seal will swell, soften, dissolve or embrittle and harden, no longer elastic and lose the sealing effect, causing hydraulic oil to leak.


3. Design and manufacture the quality of the seal groove


1) The size of the sealing groove is unreasonable


If the cross-sectional dimension of the seal groove is too large, the compression deformation generated after the seal is mounted is too small. The seal has low initial contact stress on the sealing surface and is very prone to leakage. On the other hand, if the cross-sectional dimension of the seal groove is too small, although the compression deformation by the seal member is too large, the frictional resistance is large, the temperature is raised, and the seal member is easily prematurely worn to cause leakage.


2) The surface quality of the sealing groove is poor


The seal is installed in the sealing groove, has low dimensional accuracy, rough surface, low positioning accuracy, and is easy to damage the seal and cause leakage.


4. Design and manufacturing quality of the sealing surface


1) The sealing gap is unreasonable


If the sealing gap is too large, the sealing member is easily squeezed into the sealing gap under the action of the pressurized liquid, and the sealing member is liable to be damaged due to frequent operation of the hydraulic cylinder to cause leakage. If the seal gap is too small, the surfaces of the two opposing moving parts are insufficient to form the minimum amount of lubricant film required for relative motion, causing them to be in a semi-dry or dry friction state, thereby accelerating premature wear. Sealing, etc. cause leakage.


2) Poor processing quality of the sealing surface


If the dimensional accuracy is low, the sealing surface of the surface roughness and shape accuracy is often in contact with the seal, which easily damages the seal and causes leakage.


5. Sealed installation quality


The seals are standard parts with high dimensional accuracy and shape positioning accuracy as well as a smooth surface. However, since the assembly is careless or the roughing is liable to cause damage and/or large plastic deformation, etc., it is easy to weaken the sealing effect, resulting in leakage of the hydraulic oil.


6. Sealed working environment


The higher the relative movement speed of the sealing surface, the thicker the oil film formed between the sealing member and the sealing surface. Therefore, its leakage is also very serious.