Rotork actuators help South West Water make the most of renewable energy

Rotork electric valve actuators are contributing to a noteworthy renewable energy refurbishment programme at a power station owned by South West Water.

Opened in 1932, the plant at Mary Tavy is still England's largest hydro-electric power station, working with smaller stations at nearby Morwellham and Chagford to produce a total of 3,340 kW of electricity from the water resources of Dartmoor.

When the plants were acquired by South West Water in the 1990's, they were still largely operating with their original 70 year old turbines, switchgear and gauges. As such they represent an important piece of industrial archaeology, attracting regular visits from educational, institutional and engineering groups. South West Water has therefore embarked on a refurbishment programme that will improve efficiency without altering the authentic overall appearance of the plant and machinery, panels and gauges. The ?850,000 project entails the installation of new turbine wheels, modern switchgear and valve actuation, and the introduction of automated site control under PLC supervision.

Nine Rotork electric actuators are being retrofitted at Mary Tavy, replacing manually operated equipment to control and govern the flow rate of water into the three Pelton wheel and three Francis wheel turbines on the site, an operation that used to require constant manual attention. Six Rotork IQM modulating actuators will continuously alter the position of the original linear water inlet valves in response to signals received from the PLC. Three Rotork actuators with d.c. motors and Rotork-designed battery control panels are also installed to automatically shut the main inlet gate valves to the turbines in the event of a power failure or similarly important alarm. Actuator installation is an integral part of the turbine refurbishment contract that has been awarded to the turbines original manufacturers, Gilbert Gilkes & Gordon Ltd.

Steve Cryer, South West Water's Hydro Manager, is enthusiastic about the future of hydro-power in the area. He explains: "The programme at Mary Tavy is the first part of a scheme to increase our production of renewable energy at a total of nine existing hydro-electricity sites. In addition, a new station is being built and there are plans for a further four. Most of the work is being carried out by our experienced in-house staff and a centralised workshop is being established at Mary Tavy to service all the plants. Automation will not only improve efficiency but also enable our staff to work with more flexibility at the power stations."