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Key Points To Check When O-ring Leaks
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Oil Seal Technical Information
Main Reason Failure Mode Reason Countermeasures
Twist Twist The O-ring is twisted and deformed.

① Faster movement speed.

② Eccentric movement.

③ Uneven sliding surface roughness.

④ Twisted installation.

①Change to D-ring, X-ring, lip seal.

②Eliminate eccentric motion.

③Improve the roughness of the sliding surface

④Pay attention to installation. (Grease application, etc.)
Hardening Hardening Hardening, twisting, cracking, etc.

The operating temperature exceeds the heat resistance limit of rubber.

Reduce the ambient temperature.

Change to a material with excellent heat resistance.
Swelling (softening) Swelling (softening) The whole body becomes soft and swollen.

①Rubber materials are not suitable for sealing objects.

②This problem may be caused by the cleaning agent remaining in the machine after cleaning with light oil, gasoline, etc.

①Change the rubber material.

②Remove the cleaning agent.
Permanent deformation Permanent deformation The cross-sectional shape of the O-ring becomes the same as the groove.

This is more common when there is a synergistic effect of excessive compression, high temperature, and the object being sealed.

Reselect groove dimensions and materials.

Cool the seal.
Extrusion Extrusion The outer or inner surface of the O-ring is completely (or partially) cracked.

Affected by pressure, clearance and swelling above the limit.

Ensure proper clearance or use retaining ring.

Change rubber material.
Bite Bite Cut off the excess part of the outer or inner surface of the O-ring, or dig out a part.

① The chamfering of the cylindrical end face or shaft end face is insufficient and the O-ring is installed from the front.

② The O-ring groove is shallower than the specified value compared to the cross-sectional diameter of the O-ring and is barely installed.

③ During installation, the hole, threaded part, end, etc. are damaged.

① Make appropriate chamfers.

② Modify the groove size.

③ Pay attention to the chamfers at the ends.

Use a mounting fixture when installing.
Ozone crack Ozone crack The entire surface of the O-ring has cracks like cracks.

Since the O-ring was placed in the air in an extended state, it was affected by ozone and cracks appeared on the surface.

Do not place in the air in the stretched state.

Apply grease or oil to the surface of the O-ring to prevent it from coming into direct contact with the air.
Scars Scars The outer or inner surface of the O-ring is scratched.

When installing the O-ring, the threads etc. will scratch the inner (outer) surface of the O-ring.

Use a protective clamp during installation to prevent threads from directly contacting the O-ring.
Wear Wear The O-ring contact part is worn.

① When the surface roughness of the surface in contact with the O-ring is too rough, wear occurs due to pressure fluctuations.

② Insufficient lubrication.

③ Foreign matter such as dust and metal powder enters.

① Make the roughness of the corresponding surface in contact with the O-ring meet the requirements.

② Improve lubrication.

③ Remove foreign matter and use a filter or dust ring.