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Hydraulic O-rings often fail, leading to oil leaks. Do hydraulic professionals consider this normal? But have you ever considered why these failures occur? What are the types of failure? And how can they be addressed?
I believe many hydraulic professionals haven’t considered this carefully.
Today, let’s explore 12 types of hydraulic O-ring failure and their preventative measures.
1. Installation damage
Description: Partial or complete damage to the seal.
Causes: Sharp edges and corners of grooves and other components. Inappropriate seal size. Low seal hardness or elasticity. Contamination on the seal surface.
Solutions: Remove sharp edges and corners; improve groove design; select a seal of appropriate size; choose a seal with greater elasticity and hardness.
2. Seal curling
Description: The seal is noticeably warped.
Causes: Installation issues, slow speed, material too hard or too inelastic, uneven O-ring surface treatment, uneven groove dimensions, rough groove surface, and insufficient lubrication.
Solution: Ensure proper installation, use highly elastic and self-lubricating materials, ensure proper groove design and surface finish, and utilize backup rings whenever possible.
3. Over-compression
Description: The seal contact surface exhibits planar deformation, possibly accompanied by cracks.
Cause: Improper design: Failure to account for material deformation due to heat and chemical media, or due to excessive pressure.
Solution: The groove design should account for material deformation due to temperature and chemical media.
4. Extrusion
Description: The seal has rough, worn edges, usually on the low pressure side.
Causes: Excessive gap; excessive pressure; material hardness or elasticity too low; groove space too small; irregular gap dimensions; sharp groove corners; inappropriate seal dimensions.
Solution: Reduce gap dimensions, select a material with higher hardness or elasticity, and design the groove appropriately.
5. Permanent compression deformation
Description: The seal contact surface exhibits planar permanent deformation.
Causes: Excessive pressure; Excessive temperature; Incomplete vulcanization of the material; Excessive permanent deformation of the material itself; Excessive expansion of the material in the chemical medium.
Solution: Select a material with low deformation; Design the groove appropriately; Verify compatibility between the material and the medium.
6. Chemical corrosion
Description: Chemical corrosion can cause various defects in seals, such as blistering, cracking, perforation, and discoloration. Sometimes, chemical corrosion can only be detected through instrumental measurements of physical properties.
Cause: Incompatibility between the material and the media or excessive temperature.
Solution: Select a material that is more chemically resistant.
7. Thermal corrosion
Description: Radial cracks appear on the high-temperature contact surface of the seal. Some materials may soften or become glossy due to excessive heat.
Cause: The material cannot withstand high temperatures, the temperature exceeds the expected limit, or the temperature fluctuates too rapidly or frequently.
Solution: Select a material with high-temperature resistance and, if possible, minimize the sealing surface temperature.
8. Wear and tear
Description: Wear occurs in all or part of the sealing area of the seal. Wear particles can be found on the seal surface.
Causes: Inadequate seal surface finish, excessive temperatures, infiltration of abrasive contaminants into the sealing environment, relative movement of the seal, and incomplete seal surface preparation.
Solution: Use the recommended groove finish, self-lubricating materials, and eliminate the components and environment causing the wear.
9. Pressure blasting
Description: Bubbles, pits, and scars appear on the seal surface.
Cause: Rapid pressure changes, low material hardness and elasticity.
Solution: Select a material with high hardness and elasticity to reduce the pressure relief rate.
10. Electrical corrosion
Description: The seal is discolored, with a powdery substance remaining on the surface. Corrosion is evident on the side not in contact with the media.
Cause: Chemical reaction leading to electrolysis, sputtering (material loss caused by ion impact on the surface), and burning.
Solution: Select a material compatible with the media, minimize exposed areas, and review the groove design.
11. Permanent compression set
Description: This defect is often difficult to detect and typically manifests as a reduction in cross-sectional dimensions on seals.
Causes: Improper material curing, high vacuum sealing requirements, low material hardness, or the use of materials containing plasticizers.
Solution: Avoid using materials containing plasticizers and ensure that seals are properly cured to minimize leakage.
12. Pollution
Description: Foreign matter is found in the seal’s cross section.
Cause: Environmental contamination during the production process, corrosion or reaction of materials, and non-semiconductor grade materials.
Solution: Specify cleanliness requirements for production and packaging, and strengthen environmental controls during the production, transportation, and use of seals and raw materials.
★★★Review of previous selected articles:
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- Complete guide to hydraulic cylinder failure repair!
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