Specially designed test demonstrated thread durability

Contact
  1. Danish Technological Institute
  2. Services
  3. Materials and surface technology
  4. Analysis and testing of metals
  5. Cases and articles about metallic materials
  6. Specially designed test demonstrated thread durability
Otto Lundgren Hejgaard

Your Contact

Contact me

Indtast venligst et validt navn
Or your phone number
?
Thank you for your message
Vi beklager

På grund af en teknisk fejl kan din henvendelse desværre ikke modtages i øjeblikket. Du er velkommen til at skrive en mail til Send e-mail eller ringe til +45 72 20 12 51.

Test af bolt i opspænding

Specially designed test demonstrated thread durability

Case: Functional test of special nut

At the consulting engineering company BIIR, a special nut has been developed for use in assembling tower sections on wind turbines. In this connection, they needed a specially designed test to evaluate the thread’s durability.

As consulting engineers, the Danish company BIIR works on a wide range of different projects – including for the wind turbine industry. In that context, the company developed a special nut – a so‑called nut retainer – which is to be used in the assembly of wind turbine tower sections.

For space‑related reasons, the thread in the nut does not have the same size as normal, and therefore BIIR was uncertain whether the strength of the thread met the specified requirements. The challenge was that, as a consulting company, BIIR found it difficult to make a precise calculation of the thread. They therefore teamed up with the Danish Technological Institute, which has extensive experience with such functional tests and has the facilities needed to create a customized test setup.

Rendering af påspændingsboltSuccessful test of tightening torque

At the Danish Technological Institute, a test was designed to determine whether the thread would withstand the required tightening torque – and more, to be on the safe side.

“The test was carried out by tightening a bolt into the nut retainer and gradually increasing the tightening torque. We started with a torque of 1000 Nm and ended at 3000 Nm, and after each torque increase we measured the distance between the thread turns,” says Otto Lundgren Hejgaard, Product Manager at the Danish Technological Institute and expert in mechanical testing.

Once the test had shown that the thread was strong enough, the same test design was used to assess the thread’s service life – this was done by repeating the test many times at the highest load. The idea is that the nut retainer should be reusable several times.

Together with the consultants from the Danish Technological Institute, we developed a test setup that matched the load we wanted. It was perfect that we could be present during the test, so there was an opportunity to make small adjustments and changes to the load along the way. That gave us the results we wanted, and we feel completely confident about returning the next time we are in a similar situation.

- Esben Eskerod, Chief Technology Officer, BIIR A/S

Reuse of test setup enabled faster tests

With the test reports from the Danish Technological Institute, BIIR had documentation that the nut retainer could withstand the required tightening, as well as an assessment of the expected service life.

Subsequently, it became necessary to change the material of the nut retainer to improve ergonomics when using the tool, and here BIIR had the major advantage that the same test setup could be used to verify the new material – therefore these tests were both faster and cheaper to carry out.