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Collett Delivers Redundant Main Inlet Valves for Dinorwig Hydro-Power Station Upgrade

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Collett, a heavy transport and lifting specialist, has completed the delivery of two redundant 147-tonne Main Inlet Valves (MIVs) from Dinorwig Hydro-Power Station to a specialized facility in Bangor. This transport is part of an essential upgrade scheme at the power station, following the earlier delivery of two new MIVs earlier this year to replace existing equipment.

Operating within the challenging mountainous terrain, each valve, measuring 5.3m (L) x 4.7m (W) x 3.7m (H), was loaded from the temporary storage area using an overhead gantry crane. Securely loaded onto two 10-axle flat top trailers, the valves faced a daunting 10% gradient in the long exit tunnel. Collett tackled this challenge with a double-headed approach, using two 8×4 heavy tractor units to pull the valves up the tunnel.


The 11-mile journey to the specialist facility in Bangor was conducted as a convoy, accompanied by a police escort and Collett’s abnormal load escort fleet. The entire journey, covering 12 miles in total, was completed in an impressive 1 hour and 40 minutes.

Prior to transportation, Collett’s Projects Department undertook comprehensive preliminary works, including a route survey, lift plans, method statements, and a risk assessment report. The Heavy Lift Team had also set up the JS-125 500-tonne capacity Jack-Up System during a previous visit to the site.


Upon arrival at the specialist facility, each trailer was reversed under the lifting gantry, allowing the MIVs to be offloaded directly from the trailer. This method proved efficient in a space-limited environment.

Dinorwig Hydro-Electric Power Station, situated near Llanberis in Snowdonia National Park, stands as the largest pumped hydroelectric storage facility in the UK. With a maximum power supply of 1,728MW and a storage capacity of approximately 10GWh, the station effectively manages water between the Marchlyn Mawr reservoir and the Llyn Peris Lake to generate power as needed.

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