The preload in a bolt can be determined with the help of a specific ultrasonic technique. The measurement is based on accurately monitoring the elongation of the bolt or the changes in sound velocity over a certain length.

We offer 3 types of monitoring:

AT NEWBUILD – starting at zero-load

Bolt preload monitoring can be used to check whether the bolts have been tightened correctly. The measurement is based on accurately monitoring the elongation of the bolt. It is also possible to check what the resulting bolt loads are after a period of time has elapsed, without needing to shut down the installation.

It is a far more reliable method of verifying the applied preload than the conventional torque procedures because the actual elongation and thus the preload is monitored and no correlation is made with the applied torque, which can vary greatly due to friction.

IN-SERVICE – without a known zero-load using our SonicDSC® method

Utilizing a unique combination of mechanical measurements, ultrasonic time of flight determination and a custom computing method the bolt preload can be calculated without having to remove the bolt.

This means in-service preload determination can be conducted with minimal impact and without the requirement of a zero-load baseline measurement.

IN-SERVICE – permanent monitoring

Using either of the two above mentioned techniques we can setup a monitoring system with the ultrasonic probes being permanently attached to (some of) the bolts. Our custom acquisition unit collects the individual time of flight measurements and sends it to our online data center where the information is processed and stored.

By means of our project management tool Qc linQ an online accessible dashboard can be created to exactly show the gathered information in a format you prefer. Allowing you to live monitor and create trend analysis charts if required.