Conformity Test in accordance with ISO 3601-5

Significance and Test Method

With the new edition of the ISO 3601-5 standard released in April 2015, there is now an international standard for material formulations and finished part requirements for O-rings.

The Elastomer Institut Richter offers conformity tests for O-rings in accordance with Table 2 and for formulations in accordance with Tables 3 to 9. We inspect both test plates and O-rings. ISO 3601-5 requires the O-ring dimensions d1 x d2 to be 24.99 x 3.53 mm.

The ISO 3601-5 conformity test of an elastomer includes the determination of hardness, tensile strength, elongation at break and compression set. In addition, heat ageing tests and, depending on the elastomer type, different immersion tests in reference media are necessary. The valid test conditions and test methods are listed in the standard’s tables 2 to 9.

ISO 3601-5 specifies requirements for O-ring materials for the following material grades:

  • NBR, cross-linked with sulphur, 70 and 90 IRHD
  • NBR, cross-linked with peroxide, 75 and 90 IRHD
  • HNBR 75 and 90 IRHD
  • FKM 70, 75, 80 and 90 IRHD
  • VMQ 70 IRHD
  • EPDM, cross-linked with sulphur, 70 and 80 IRHD
  • EPDM cross-linked with peroxide, 70 and 80 IRHD
  • ACM 70 IRHD

For more information on ISO 3601-5 and the standard sealing element O-ring, please refer to the technical report “The O-ring as a standard part ”


Further information on ISO 3601-5 and the standard O-ring seal can be found in this technical report: