Ensure a more reliable operation

Bolts are an essential part of most machinery or constructions within many areas, such as wind turbines, bridges, power plants, mining equipment, large road signs and similar. As bolts are essential for the integrity and functionality of the construction, more and more become aware of the importance that central bolt connections of joints are tightened correctly.

One of the most challenging parts of the tightening process is the correlation between the applied torque and the tension that arises when tensioning the bolts. This tension results in an opposing clamping force that holds the two sections of the joint together. If the clamping force is too low, separation and bolt fatigue may occur. On the other hand, excessive stretching may produce damage in structural components of the joint, such as excessive distortion or breakage.

Errors or wear and tear can cause damages or even breakdown, resulting in large financial costs. Achieving the correct bolt pretension is essential in assuring bolted joint integrity. Problems such as bolt fatigue and vibration loosening can usually be prevented by achieving and maintaining the correct clamping force in the joint.

Improve your bolted connections

Correct installation and continuous inspection of critical bolted joints are crucial to the integrity of the assets, but it can also be very expensive. When installing new bolts or evaluating existing bolts, ultrasonic measurement has proven to be a very accurate and cost-effective solution as part of determining the lifespan of wind turbines.

Efficient bolt tensioning

With Bolt-Check, you can calculate the actual correct clamping force, ensuring torque and tension tightening. The system is based on ultrasonic measurement, which is a very accurate solution. It allows you to track the clamping load during the entire tightening process and determine the clamping load without influencing the joint stiffness. In addition, as Bolt-Check provides information about the tension levels, you will have better control of the bolts' tension.

The speed of sound depends on the ambient temperature. If the temperature rises, the speed of sound increases, and if the temperature drops, the speed of sound decreases. Since the stationary target depends on temperature, this variance can affect the accuracy of the measurement. Even minor temperature changes can lead to incorrect results since the measurement of a bolted joint requires accuracy down to the millimeter. The ultrasonic measurement tool uses an integral temperature compensation network to account for changing temperatures. Therefore, you do not depend on measuring the bolted joints under the same environmental conditions, enabling you to use the system at any site.

Streamline processes

Different bolted joints in wind turbines have different levels of accessibility.

For instance, a blade joint can be more difficult to access, control, and repair than a tower flange connection. So far, it has been difficult to measure blind holes, as you have access from only one side of the bolt. Unlike other measurement tools such as a Micrometer or Caliper, ultrasonic measurement does not require access to both sides of the bolt, making it the only tool available to evaluate blind holes.

As a part of the process, a unique Bolt-Tag is added to the bolt. The tag gives you full traceability of your bolts, enabling you to locate each bolt, as well as schedule service and maintenance. With planned service and maintenance, Bolt-Check helps decrease costs and downtime of your constructions.

This is how it works

Bolt-Check can be used when installing new bolts and when evaluating existing bolts as part of determining the lifespan of wind turbines. By using the ultrasonic measurement tool, you can measure the length of a bolted joint. The ultrasonic device measures length similar to how a sonar measures distance from a ship to the sea bed. After a tightening procedure, you can measure a change in length, which can be calculated into a clamping force.

With Bolt-Check, you achieve the right alignment of bolted joints efficiently and in a controlled manner. The tool is suitable for most bolt types and requires no special pre-treatment of the bolts. It can play an important part in maximising the operating time of the turbine and at the same time minimising failure.

Bolt-Check products

Discover our products and services for the measurement of bolted joints


Bolt-Check Standard

When installing new bolts, you can achieve traceability and knowledge of the exact clamping force by using the Bolt-Check standard. When buying or renting the Bolt-Check standard, you will have the tool to ensure smooth tightening and limit human errors when performing service.


Bolt-Check Advanced

With Bolt-Check Advanced, you can calculate the clamping force in already tightened bolts without loosening the bolts, avoiding destructive tests. In order to use Bolt-Check Advanced, both ends must be accessible. After determining the clamping force in each bolt, the data will be logged via our tag system and all data will be available. For subsequent service, the Bolt-Check standard can be used as a tool to follow the development in the clamping force of the bolts.

Approved method for measuring bolt tension

Bolt-Check has received a component certificate from DNV, which means that Bolt-Check can be equated with torque and tension tools for service inspections of wind turbines.

Bolt-Check is, therefore, an approved method that can verify whether the bolt has the correct clamping force. This helps save depreciation of clamping tools, repair, and service of tools. It also contributes to a less time-consuming operation. Compared to the traditional tools, Bolt-Check is physically much smaller and easier to handle. This limits heavy and strenuous work.

How can we help you?

Contact persons
Jens Vestergaard Larsen
Key Account Manager, Bolt-Check
R&D Contact Flemming
Flemming Nielsen
Senior Specialist - Bolt Check
Send us a message