DigiBolt: Digital Bolt Tension Monitoring

Digibolt and SINTEF have together developed a sensor, DigiBolt, that reads the level of tension applied to bolted connection i.e. how much the bolt is physically stretched. The sensor is placed underneath the bolt head or between the nut and the connection face if stud bolts are used. The sensor is primarily used in critical bolt connections. The aim of this project, addition to develop the sensor technology itself, is to develop a system that read the physical load and send this to a cloud solution and thereby be available for our customers. One of the challenges we have worked hard on is to understand the ratio between applied pressure to the sensor combined with change in temperature and how these values influence each other. We now have a solution to this, and more tests are carried out in the SINTEF laboratory. All values are detected by use of ultrasonic which via a handheld reader process the information and send this to a cloud solution. As each bolt connection have their unique tag, our customer will know the condition of each individual bolt. DigiBolt works independently of the choice of tightening tool, whether this is a spanner, torque wrench or hydraulic tensioner etc. DigiBolt's solution has a number of industrial applications and it can be mentioned: Bolts on oil and gas installations, drilling rigs, wind turbines, railings on bridges, road fuses, cranes etc.

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Bolted assemblies constitute a large part of our most critical infrastructure like road constructions, power plants, high-voltage pylons, rock bolts, pipeline joints, large process plants, etc. All these bolts need to have the correct tension for the functionality and integrity of the constructions to be intact. This means that the bolts' axial load or pre-tension must be carefully set during installation and maintained during their lifetime. Insufficient or excessive tension is a major cause of bolted assemblies failures possibly leading to severe malfunction and accidents e.g. bridge collapses, power outages, landslides and chemical spills. In the period 2008-2015, incorrectly tensioned bolts in pipeline joints was the largest cause of hydrocarbon leakages and stop of production. For some bolted assemblies, like pipe flanges with seals, cranes, drill tower etc., regulations require that bolts and nuts need to be re-tightened to the correct tension at regular intervals (minimum every 5th year) to maintain a safe and reliable operation. This requires heavy equipment and is a costly, time-consuming and hazardous task. In this project we propose a novel wireless and cost-saving bolt tension monitoring system, called DigiBolt, which will enable condition-based maintenance, secure assets and prevent major accidents and HSE incidents of bolted constructions.