Smarter bolt operations for offshore wind turbines

Find a way to deliver a cost-effective alternative to traditional methods of checking and tightening bolts and a method to identify loss of tension or failure of a bolt or series of bolts for SSER.


Scottish & Southern Electricity Renewables (SSER) is a leading developer and operator of renewable energy across the UK and Ireland, with a portfolio of around 4GW of onshore wind, offshore wind and hydro. SSER has the largest offshore wind development pipeline in the UK and Ireland at over 6GW and has an onshore wind pipeline across both markets in excess of 1GW.

During installation of an offshore wind turbine, upwards of 1000 bolts are used to secure its components in place. On operational wind turbines, approximately 10% of bolts at key bolted connections are checked annually to monitor for loss of tension.

These checks require hydraulic tensioning/torque tools which are heavy and cumbersome to use, posing manual handling risks for personnel. Work locations also have access challenges including the need for marine transfers, working at height, and working in confined spaces.

Bolt failures are not automatically detected on offshore wind turbines at SSER sites. In the event of a bolt failure, all wind turbines affected by the bolt batch may have to be shut down until bolt checks can be completed or a root cause analysis is completed, this can also result in significant downtime.

The challenge

The challenge is to deliver a cost-effective alternative to traditional methods to checking and tightening bolts and a method to identify loss of tension or failure of a bolt or series of bolts. The method must be suitable for use at operational offshore wind farms, without the need for widespread bolt disturbance.

Proposals are welcome for cost-effective solutions in a variety of forms, including:

  • Online tension/torque monitoring systems which eliminate the need for physical bolt checks or enable better planned tightening campaigns. 
  • Quicker and safer methods of checking bolt tension.
  • Methods to detect bolt failure or to detect bolt defects prior to failure.
  • Data-driven methods to target bolt checks most effectively, allowing for condition-based monitoring of bolts, rather than periodic monitoring
  • Solutions which can integrate with electronic data collection

Proposals are welcome for:

  • Existing market-ready technologies
  • Development proposals to improve on market-ready capability

While not limiting the technologies from solution providers, it is expected that solutions would consider innovations from some of the following areas: 

  • Data analytics
  • Internet of Things
  • Aerospace engineering and manufacturing
  • Automotive assembly and manufacture
  • Heavy engineering and manufacturing
  • Artificial intelligence

SSER is primarily interested in solutions which can be applied to existing bolts, however solution requiring retrofitting of hardware may be considered if a clear case for cost and operational benefit can be made.

Rewards and benefits 

Successful applicants will be given an opportunity to pitch to SSER representatives.
Successful solutions may be trialled at SSER sites.

The package may also include:

  • Support from KTN
  • Technical support
  • Invitation to attend or present at KTN events
  • Support if any Innovate or similar competitions are relevant.

Functional requirements

Each WTG has approximately 600-1000 bolts that require torque or tensioning during construction and maintenance activities, these are currently subjected to periodic checks visually and or by use of a torque or tension tool.

Under the stresses of an operational environment, each bolt can suffer from a failure, loosening or relaxation effect. This places a requirement on the wind farm operator to send a technician to check the bolts individually to measure whether each bolt is set at the correct tension. Each bolt may need to be re- tightened. Due to the elastic response of the bolted connection, the tightening of a single bolt can influence the tension levels in the other bolts. Therefore, all bolts need to be checked on each occasion, resulting in a long and laborious process.

The bolts are tightened in defined sequences, which are determined at the design stage. This sequence must be followed when tightening the bolts.

Current approaches include technicians checking and or tightening the bolts with heavy, hydraulic or battery powered torque or tension tools, often with more than one machine in use at a time. During the tightening of the bolts, an ultrasonic measurement device (secured to the bolt head or tip) can be used to check the tension. While the final tension levels in the bolts are fixed by the designer of the connection, the bolts themselves, the technology used to tighten and measure the bolts, as well as the bolt tightening sequence, could be changed by the solution provider.

The process is slowed by a lack of efficiency in the operation of the tightening tools and the measurement device, where data must manually be gathered on the spot by an engineer and then analysed before further action (e.g. re-tightening bolts) is taken.

The current process involves large heavy tools with hydraulic hoses and electrical cables, which can lead to an untidy workplace. The tools themselves also present risk from the high-pressure hydraulics and electricity. New solutions should seek to overcome these issues.

Currently checks are predominantly conducted visually or with the use of a torque or tension machine which have both hardware and software solutions for an individual bolt but do not consider readings from a sequence of bolts. A new solution should seek to understand the whole process, connect this data in a more intelligent way, looking at a component-to-component connection holistically, speed up the measurement and analysis process and feed it back to the technicians for them to infer new actions.

The proposed solutions for this challenge must be deployable without requiring major changes to existing manufacturing and design of offshore wind turbines. Major changes would result in significant cost or time to install offshore, which is unlikely to be recovered by the savings from the new solution.

The final solution could be adapted for use in both new build sites and operational sites, and therefore will need to be applicable to different types and makes of turbines. 

Remote monitoring of the tensions in the bolted connections is optimal to reduce cost, time and risks associated with visiting offshore wind turbines. A remote solution will have to include data connectivity back to shore via the site communications network, satellite or 4G etc.

Technical requirements

The following bolt types and locations should be considered by solution providers:

Bolted connections include:

  • Blade to blade bearing
  • Hub to blade bearing
  • Hub to main shaft
  • Main shaft to gearbox /Generator
  • Gearbox to generator
  • Nacelle to bedframe
  • Nacelle to tower
  • Tower to Tower sections
  • Tower to TP
  • Component to bedframe

Solutions should enable data to be recorded via an internet connection and viewed remotely. This should aim to allow the user to map and assess a ring of bolts and provide an ongoing monitoring capability by keeping records of each bolt.

Either torque or tension should be applied to tighten the bolts depending on the type of connection, bolt type.

A solution should be able to record and build up maintenance and historical data for the turbines tested and ideally provide analytical tools to help predict future campaigns.

Torque wrenches currently in use are mechanical with no digital input, however some hydraulic pumps that drive these tools have the ability for a serial input.

Currently, multiple measurement tools are used to gather data, and these are manually collected onto a single device before being analysed in Excel (CSV file). New solutions should seek to automate this process using wireless connections to multiple measurement devices.

Solutions should be heavy duty and highly dirt and humidity resistant.

The ability for technicians to operate any solutions using gloves is an essential and ideally hands free. It must be capable of operating inverted. It should be small and light enough to prevent operator fatigue and not present pinch points or put the operator in the line of fire.

Closing date

Launch of the Competition: 17/06/22
Deadline for applications: 02/08/22
Selection and notification of finalists: 30/08/22
Date of Pitch day: TBC

Solutions should be Fully deployable commercially within 12 months of competition win.

How to get involved

For more details about this challenge and to apply, visit the KTN Innovation Exchange website.