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Quality is an integral part of the Superior customer service philosophy.

Total control of all aspects of seal manufacture ensures that we always comply with recognised standards applied by the industry. With our expertise we can closely define and control seal tolerances and surface characteristics. Our continual investment programs enable us to apply the latest control and inspection techniques.

Superior is accredited by ISO 9001:2015 and ISO 14001:2015.

We thoroughly recommend that all quality and specification issues are addressed at the earliest point in the development stage of any new project. This ensures that all customer-critical features and commercial issues are identified from the outset.

O-ring size range standards

At Superior, we pride ourselves on our precision o-ring range which exceeds the cross-sectional tolerances for the following dimensional standards;

  • ISO 3601-1
  • DIN 3771 Part 1
  • BS 4518

The benefit of close tolerances on an o-ring cross section (d2), is the ability to reduce our
customer’s tolerance chain and improve the overall performance of the customer’s product.

In the Superior o-ring size list, the internal diameters conform to ISO 3601-1 tolerances and the cross section diameter has a reduced tolerance. These precision o-ring tolerances apply to NBR 70 compounds. O-rings manufactured in other compounds and hardness’ are produced to conform
ISO 3601-1 tolerances, however dimensions for the internal diameter may be towards the lower end.


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High shrinkage compounds may require dedicated tooling to comply with ISO 3601-1 dimensions and tolerances, but will still allow for the principle of a more accurate cross-section. Superior can also
supply o-rings to customer’s specifications.

Limits of size for surface imperfections for Grade N o-rings


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Quality control: documentation

All documentation for dispatch to the customer conforms to the ISO 9001 standard. The documentation issues and details are continually being revised and updated according to demands from individual customers and the industry in general.

Seal surface inspection levels

All our o-rings are inspected to ISO 3601-3DIN 3771 part 4. The standard level is Grade N.

Environmental compliance

Superior is able to provide materials compliant to current European and Worldwide legislative requirements e.g. ROHS, REACH and IMDS

Please consult our Quality department for specific requirements on sales@superiorltd.com
or call +44 (0)1202 854300.

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If you would like to learn more about how Superior can contribute to your business’ success, we would be pleased to welcome you to meet our people, see our facilities and discuss your needs.
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