Access specialist, Harsco Infrastructure (SGB) has erected a 120m high mast climbing work platform (MCWP) through the centre of the tallest electricity pylon in the UK, enabling the Electricity Alliance East, an Alliance between National Grid and Balfour Beatty, to carry out essential electrical and structural maintenance work.
Owned by the National Grid, the pylon carries the power-lines for Harsco Infrastructure to design a safe method of delivering operatives, their tools and materials to a work platform located two-thirds of the way up the 193m high structure.
The exceptional height of the pylon, coupled with its exposed riverside location, ruled out the use of external steps as a safe access method. High winds and the height of the tower meant that it was too dangerous to take materials up the external steps on the pylon, so Harsco Infrastructure designed a suitable access system for the inside of the tower so that workers and equipment could be manoeuvred up to the work platform in safety.
Space within the tower is restricted, especially near the top where it narrows to just 5m x 5m. Harsco Infrastructure therefore proposed a single MCWP with a small platform that could travel up through the narrowing space to the platform.
To support the 120m high slender lattice mast, Harsco Infrastructure designed a special tie to take the weight and transfer the load safely to the pylon. “Our design engineers calculated that we would need to use an unusually large number of ties to ensure the rigidity of the mast” explains Harsco Infrastructure contracts supervisor Simon Hickson. “We therefore designed a bespoke tie with 38 connection holes” he adds
Harsco Infrastructure’s MCWP was erected in February and remained in place until the Alliance finished its mechanical and electrical maintenance work in April.