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How to Find Out if the O-Ring is Vulcanized Properly?

A lot of times vulcanized O-Rings come apart and fail while being used in an equipment or assembly line. This causes a lot of trouble and delay as the failure of the O-Ring results in stopping the assembly line. The method of testing vulcanized bonds should be a serious consideration to avoid disruption and for the smooth running of your assembly line. The bond strength varies due to the different specifications of the cross-section. Transfer and injection bonds are stronger than butt bonds.

Apart from sourcing your vulcanized O-Rings from a trusted partner, there is a method you can use to inspect the quality of vulcanized O-Ring bond. This method will make sure that the vulcanized O-Ring can be put into the application without any problem.

This technique involves pulling the vulcanized o-ring bond perpendicular to the plane. This is sufficient to determine if a corner bond is of good quality. Make sure to clamp the gasket in such a way that the pull is evenly distributed over the bond and does not have the most stress on the inside of the corner. If the O-Ring stays put, it is good enough to be used, and it can be installed in your equipment.

Refer to figures (a) and (b) for injection bond and corner bond, respectively.

Injection Bond Vulcanized Bond Testing

Figure (a)
Pull Test in direction of arrows. Pull rate of 500mm/min. (20 in./min) is generally acceptable.

Corner Bond Testing Vulcanized O-Rings

Figure (b)
Pull test for 45º Corners.
Pull in direction of arrow.

Bad Bonded Vulcanized O-Ring EPDM. How to inspect Vulcanized Bond

Bad Vulcanized Bond

Properly (strong) Bonded Vulcanized O-ring Buna Cross Section COR Manufacturing

Good Vulcanized Bond

Important things to note:

  • The method of testing vulcanized bonds by pinching, doubling over or twisting, as described by some, is not a proper way to test the bond quality as every material has a different thickness at the cross-section and is used in different types of applications. These methods of testing are very generic and not suitable for accurate testing. 
  • Do not exert a lot of force on the joint to ascertain that the joint of vulcanized O-Ring is strong enough. It will only result in breaking off the bond between the cord.
  • Don't bend or fold the o-ring at the joint, or the joint will break.
  • Also, inspect the o-ring thoroughly to check if there is any crack or pinhole at the joint. If there is one, discard the O-Rings as it is not suitable to be put under application, and it will fail if you use it.

For more information or further clarification, please feel free to contact COR Manufacturing. Our experienced team can answer all your questions.

You can read our blog on Vulcanized O-Rings to learn more about them.

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