A wind farm supplying 34MW of energy required lightweight, moveable trough access covers to protect its power cabling.

The UK has set targets to reach net zero carbon emissions in 2050, replacing energy from coal-fired plants with power from nuclear, solar, and on and off-shore wind farms.

A few years ago, Wales’ government identified seven strategic search areas (SSAs) for wind energy development – areas that have characteristics that lend themselves to the accommodation of large wind farms. These locations generally have good wind speeds and a lack of statutory designations. One of these was selected as a site for a large-scale wind farm. This wind farm, which became fully operational in Spring 2017, has an installed capacity of 34MW, capable of providing sufficient renewable electricity to meet the average needs of more than 26,000 homes.

The project consisted of 17 turbines, a control building and a substation to supply power to the grid at the correct voltage and amperage.

Substations require large amounts of cabling and other utilities to be set below the ground while being easily accessible. This substation includes two long precast concrete troughs: one 19m long with a span of 765mm, the other 25m long with a span of 1250mm. The troughs are made by Stanton Bonna, a UK manufacturer of precast concrete pipes, manholes, culverts and linear drainage based in Derbyshire, UK.

Safe trough covers

The troughs, which are set flush into the ground, have an edging created using upright concrete slabs and needed covers that can be easily manually removed for maintenance and monitoring. The covers were also required to perform at a load rating of 40 tonnes, following D400 regulations which includes access covers and gratings. Importantly, the trough covers also needed to provide a safe walking surface for operators, whatever the weather conditions.

The company specified glass fiber reinforced plastic (GRP) composite access covers to meet the required specifications and decided to partner with Fibrelite to create a series of custom GRP trough covers to fit onto their precast concrete troughs.

Fibrelite, based in Skipton, North Yorkshire, UK, also makes GRP composite manhole covers, steam covers and underground containment systems. Its trough covers are customizable and available in a range of load ratings from 1.5 to 90 tonnes for a range of applications and industries including data centres, stadiums, forecourts and many more. They are also available in a range of RAL colours, sizes and configurations.

In this case, Fibrelite designed and manufactured a series of custom GRP trough covers to fit onto the Stanton Bonna precast concrete troughs. The company ‘stepped’ the covers to reduce unit weight and increase the loading capability. They also feature the company’s standard tread pattern to provide improved slip resistance, making them suitable for a safe walking surface. Test reports demonstrate that even when wet, Fibrelite covers have anti-slip properties far exceeding health and safety advisory limits.

As well as this, the D400 load rated 1250mm wide covers can be safely manually removed by two operators without risk of injury. The equivalent size concrete panel would have weighed approximately 400kg, Fibrelite said.

According to Fibrelite, no maintenance of their covers is required, and the GRP composite material has an inherent resistance to corrosion. With regards to structural performance, all covers are independently tested to BS EN124 criteria.