First determine where and when the leakage occurs
Oil escaping from the rod side of the cylinder and internal leakage between the two sides of the piston are not the same problem. Whether leakage occurs during motion, while holding under pressure, immediately after initial installation or after a period of operation helps direct the technical evaluation.
Possible factors to check
Product profile and material
The seal must be designed for its piston, rod or other function and must be compatible with the pressure direction and type of motion. The material must also be evaluated together with the fluid, temperature and mechanical conditions. Different profiles with the same dimensions may not be direct alternatives.
Groove dimensions and clearances
Rod diameter, housing diameter, groove width, groove corners and system operating clearances affect how the product works with the correct preload. An incorrect or out-of-tolerance groove may cause insufficient contact or force the product into a clearance under high pressure.
Rod and cylinder tube surfaces
Surface roughness, scratches, burrs and sharp edges can directly affect seal life. A surface that is too rough may increase wear, while a surface that cannot form a suitable oil film may increase the risk of friction, heat and deformation.
Pressure, temperature, speed and fluid
Product and material selection must meet the actual operating conditions. Sealing performance may be adversely affected when pressure, temperature, motion speed or fluid compatibility falls outside verified product limits. Exact limits must be checked in the relevant product and material table.
Misalignment and guiding
Guiding elements help carry side loads, centre the piston and rod, and limit direct contact between metal surfaces. Worn or insufficient guiding may cause the seal to be compressed in one area and wear unevenly.
Problems that may occur during installation
Passing the seal over a sharp edge, overstretching it with an unsuitable tool, installing it in the wrong direction or assembling it in a dirty environment may cause deformation from the first operation. Before installation, check the groove, chamfers, surfaces and dimensions, and keep components clean.
Leakage Checklist
- Is the leakage internal or external?
- Does the leakage occur during motion or while stationary?
- Are the product code and profile function correct?
- Is the material compatible with the fluid and operating conditions?
- Have the rod, housing and groove dimensions been verified?
- Are there scratches, burrs or damage on the rod or tube?
- Have installation chamfers and sharp edges been checked?
- Was the seal overstretched or cut during installation?
- Are the oil and installation environment clean?
- Are pressure, temperature and speed within the product limits?
- Is there wear or clearance in the guiding elements?
- Are the rod and piston correctly centred?
- Does the removed seal show one-sided wear, cuts, compression or visible deformation?
Frequently Asked Questions
Why does a newly installed hydraulic seal leak?
An incorrect profile or material, groove dimensions, surface damage, sharp edges, contamination or installation deformation are possible factors. The exact cause must be determined by examining the application.
Can scratches on the rod or cylinder tube cause leakage?
Unsuitable surface quality, scratches and burrs may cause the seal to wear or become damaged.
Can contaminated hydraulic oil damage the seal?
Particles may deform the seal and scratch contact surfaces, increasing the risk of leakage.
Should guiding elements and the wiper seal also be checked when replacing a seal?
Yes. Problems with these elements may adversely affect the operating conditions of the primary sealing element.
Related Products
K35 Rod Seal
View product →K29 Pre-Pressure Ring
View product →K73 Piston-Rod Guide Ring
View product →Related Technical Guides
Let us evaluate the possible causes of leakage together.
Send us the product code, dimensions, sample, photographs of the old seal and working surfaces, and the operating conditions.