Understanding the new fastener testing standard DIN 25201

Article originally published in FastenerEurAsia, October/November 2012 – part 1 of 4 of Morten Schiff’s series on the new DIN 25201.

Demanding new test requirements could result in existing fastener product ranges becoming obsolete as they drop from specification lists. In a series of four articles, Vibrationmaster CEO Morten Schiff explains the important differences between conducting Junker Testing of fasteners for self-loosening behavior under the old standard, DIN 65151, and the new DIN 25201.

Updating a forty-year legacy of Junker Testing’s architect, Gerhard Junker

When it was first introduced in 1969 by engineer Gerhard Junker, the Junker Test, as it became known, represented a huge step forward for fastener testing. Junker Testing became the recognized global standard for testing the self-loosening behavior of fasteners under transverse loading conditions by vibration testing. Junker Test benches are the mainstay of fastener product testing as prescribed by the original DIN 65151, which is an internationally recognized symbol of quality, safety and security in the fastener industry.

Following the publication in 2010 of the new DIN 25201, that has all changed. Certainly, the new DIN builds on the original DIN 65151 defined by Junker, but it takes things much further in setting out exactly how to conduct the vibration testing of fasteners. For the first time, the new DIN allows researchers, test engineers and clients worldwide to conduct fastener vibration tests that genuinely compare like with like. This also gives greater confidence to engineers specifying components, because the testing standards of critical fasteners are so much tougher than under DIN 65151.

Awareness of the new DIN 25201 in the fastener industry is poor

But there are still manufacturers and customers in the fastener industry who are unaware that the old standard, DIN 65151, has been superseded, and that a much tougher new test regime is in place. They are in danger of losing competitive advantage, and their products could simply drop out of the market. That’s because, unless a re-testing program is initiated, many fastener products lacking test certification to DIN 25201 will begin to disappear from engineers’ specifications.

Whilst the original DIN 65151 only specified that vibration testing must be conducted using a Junker Test Bench, the new DIN 25201 sets out exactly how the testing must be completed. It introduces new mandatory requirements to conduct reference and verification tests that compare the self-loosening behavior of bolted joints; requires the use of a washer during testing; and sets out strict test reporting procedures.

Many international standards evolve incrementally, so although deviation from the latest standard is not ideal, the impact on component safety and reliability can remain within acceptable tolerances. However, the new standard for testing the self-loosening behavior of fasteners using vibration testing is so advanced and substantially different compared to the previous standard, that not testing fasteners to the new standard could immediately impact negatively on product safety and reliability.

Next in the series – Part 2: Equipment requirements to conduct vibration testing according to the new DIN 25201.

References

• DIN 65151: 2002-08 Dynamic testing of the locking characteristics of fasteners under transverse loading conditions (vibration test), Deutsches Institut für Normung e.V., Berlin 2002
• DIN 25201-4: 2010-03 Annex B Test specification for demonstrating the resistance to self-loosening of secured bolted joints, Deutsches Institut für Normung e.V., Berlin 2010