Dirty Torque

Whilst nuts and bolts are simplistic components, they are often safety and performance critical, i.e. failure could lead to the asset being non-operational or a catastrophic accident. We only have to be reminded of the Potters Bar rail derailment which claimed the lives of five passengers, or the Sayono-Shushenskaya hydropower plant disaster which cost almost one billion pounds to rebuild to see the impact that bolted connections can have. 

Bolts are prone to loosening during operation of assets due to settling and embedding losses as well as vibration induced loosening. To prevent catastrophic failures, bolts need to be regularly inspected to check that they are tight. For remote assets or those in hazardous environments, this presents a significant operations challenge which can lead to asset downtime, high maintenance costs and health & safety risks for technicians. A prime example of this is an offshore wind farm. Around 10% of wind turbine bolts need to be checked on an annual basis and this will cost the Operator up to £10M per turbine over the full operational life of the asset. On top of this, the turbine has to be shutdown for 24-48hrs which means no energy is produced at a time of record high prices.   

There is a new type of bolt, which incorporates the latest low power wireless technology, which is proving to be a real gamechanger. 

Sedwell have developed InterBolt™ - an intelligent bolt which embeds a bolt load sensor to measure the tightness of the joint. InterBolt communicates with the outside world using a LoRa radio.

When technicians are on-site, the bolt load measurements are transmitted over a LoRa wireless link to a ruggedised tablet where they are received and displayed.

This provides the data to enable technicians to accurately tighten bolts on site and inspect bolts without the need for heavy and cumbersome torquing equipment.

When technicians leave the asset, InterBolt™ then sends the bolt load data over a separate LoRa wireless link to a cloud service via a local gateway. This enables fully autonomous and remote monitoring of bolts, eliminating the need for technicians to go offshore.

The two wireless links formed by InterBolt are quite different in their requirements and characteristics. They therefore offer significant scope to be optimised to maximise wireless range whilst minimising energy usage to ensure long battery life.

The LoRa MAC/PHY layers found in commercial-off-the-shelf transceivers enable the transmission power, coding rate, bandwidth and spreading factor to be tuned to meet the characteristics of a specific wireless channel. 

Sedwell’s CTO, Jack Hughleigh, researched low power wireless links as part of his PhD studies at the University of Huddersfield and has leveraged that previous experience to develop and implement transmission power and data rate control protocols into InterBolt™. This essentially enables InterBolt to dynamically select the optimum speed and volume to speak at in order to achieve the minimum energy consumption. Deployments on wind turbines have confirmed the effectiveness of these protocols with communication distances of over 1km being regularly achieved, whilst still achieving a battery life of 15 years. 

These wireless bolts are designed to survive some of the harshest conditions on earth for extended periods of time. From hurricane force gales to the deepest mines, the InterBolt™ will continue to function normally.

In addition to the bolt’s ruggedness, it has been future-proofed for a generation. This is essential for heavy industries, which cannot be constantly upgrading components. The computer technology is tried and tested, which should result in lower maintenance costs. 

The bolt also has a battery life of around 15 years, and can be replaced independently. This further increases efficiency for customers and reduces waste considerably.

At present, InterBolt™ is primarily aimed at the Offshore Wind industry and is currently undergoing operational field trials with the major OEMs and Operators. Over the next few months, further deployments in the mining, construction and rail industries are planned to address some of the biggest bolting challenges that maintenance teams are facing today. 

 Perhaps what makes InterBolt particularly impressive is that the wireless communications functionality was clearly not an afterthought of InterBolt™, but instead an integral part which has been highly refined to meet the application requirements. After all, I think we should expect dynamic start-ups to be implementing dynamic wireless communications protocols.