The task of manufacturing the steel structures for the T pylon test line has been awarded to Mabey Bridge. Pylons are part of the South Wales-based company’s heritage: it helped construct the traditional lattice structures when the high voltage grid was built in the 1950s. David Raynor, Mabey Bridge’s project director, explains the challenges of making the new 21st century design.
In its state-of-the-art factory at Chepstow, Mabey Bridge is putting the final coats of paint to the steel work structures that will form the test line of T pylons.
The company is manufacturing all six of the new T pylon designs, with 40 of its staff working across two shifts to meet the tight deadline required by National Grid. The pylons will then be making their way to the training academy at Eakring in North Nottinghamshire to be erected in early Spring.
David Raynor has played a central role in developing the new pylons. From advice on steel procurement to recommendations for metal coatings and fixtures, he’s brought together the technical team and shop floor engineers to answers questions that are being asked for the very first time.
It’s been a contract with both big and small challenges. One challenge is that the T pylon design is much smaller than the wind turbines usually built by the company, so some of Mabey Bridge’s workforce has needed training on working in confined spaces.
“Apart from the much smaller scale though, there hasn’t been much difference in the approach,” said David. “It’s using the rolling, cutting and welding techniques that we know well. “
A bigger challenge has been bringing together all the manufacturers involved, as some of the other iron and steel castings were made elsewhere. Putting together the T pylons structures with this in mind has been a test of Mabey Bridge’s technical and design skills.
“There are five designs of pylon in the T pylon family, and they’re all different,” added David. “There is a tight timescale for having them ready, but it’s been fantastic to see how all the manufacturers have pulled together to hit the deadline.”
Highly specialised equipment
All the T pylons start as raw steel sheets, shot-blasted to remove any rust or imperfections. Each piece of plate is specifically identified, marked with key information about its size and weight and then cut to specified sizes. The plates are then rolled using highly specialised equipment which creates circular cans. The can sections are then welded and joined together. Once welded, Mabey Bridge carries out a full ultra-violet check for any imperfections.
As well as the main monopoles of the T pylon, other fittings are made to hold the arms. Mabey Bridge then bolts together the components and carries out a trial erection on the factory floor to ensure that the structures all fit together.
Three coats of paint are sprayed manually onto the pylons – a metal spray paint, a primer coat and a final grey-coloured top coat. Then they’re ready for a final inspection, before being taken by road to the location of the test line.
“The whole process takes roughly a week from start to finish and we’ve been able to work on several pylons at the same time,” said David. “There’s been a real sense of pride about working on such a new and important development.
“For me, I’ve grown up looking at steel lattice pylons and have seen what a change wind turbines have made to the landscape. The old pylons have served us well but at some point new technology and new designs come long. I can’t wait to see what the new pylons will finally look like.”
So it’s full circle for the company who were building the first high voltage grid back in the 1950s, and are now once again at the forefront of new technology.