Timely drainage system upgrades at ENGIE’s Dinorwig Power Station have been expertly delivered by Caulmert’s civil and structural engineering teams.
Situated in in Llanberis, North Wales, Dinorwig is a subterranean pumped storage hydro scheme – one of the largest of its kind in Europe – which provides rapid response power to the national grid during times of peak electricity demand.
The plant is a vital part of Britain’s electricity system, helping to store zero carbon power when it cannot be produced by wind turbines or photovoltaic cells.
Opened in 1984, Dinorwig is in the middle of a mid-life upgrade that started with the replacement of the six main inlet valves (MIVs), which isolate water supply to the turbines. These valves are housed in a huge cavern, the MIV gallery.
The hydraulic control power units to the valves have also been replaced, and that in turn led to a need to install a fire suppression system, which can discharge water at a rate of 40 litres per second.
A potential fire in the valve gallery may be oil-based and, as the density of oil is less than that of water, the burning oil will float and there is a need to prevent this from entering the site drainage system.
Caulmert’s role was to design a drainage system that could be installed in the confined nature of the gallery. In the event of a fire, this system will capture the fire water and drain it to a quarantine tank, as it may be contaminated with products of combustion, oil, and other fire-fighting medium.
Due to the spatial constraints, the use of a conventional ‘trapped’ drainage system was impractical, with Caulmert’s solution focusing on modifying the existing containment bunds for environmental control. The resolution developed was to provide a weir – to confine the discharge of water from a defined location – fitted with a baffle plate to contain the burning oil film.
Caulmert associate David High said: “It is an innovative solution, which we needed to be sure would work as intended.
“We procured a specialist in fluid flow modelling, who created a free surface model that demonstrated that the weir and bund assembly we had designed would behave in the manner intended.
“The concrete channel we designed to contain flows below the gallery floor and stainless steel modifications to the valve bunds look so simple that it is difficult to appreciate the complex design process required to achieve it.”
ENGIE assistant engineer Amy Pritchett said: “Collaboration with Caulmert on this project has been very successful, with an iterative design approach that responded effectively to the constraints of the operational station environment.
