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Performance enhancing actuator-driven pinch valves

Performance enhancing actuator-driven pinch valves
As Guernsey's only water company, Guernsey Water is tasked with supplying high quality drinking water to over 24,000 households and businesses. Nearly 66,000 people rely on the company's daily output of about 12 million litres - a figure which rises significantly during the summer months, when the island's population is boosted by tourists. 

The company's St Saviours water treatment plant was built in the late 1940s, originally using the chemical coagulation and rapid gravity filters. A substantial upgrade in 2004 led to the introduction of ultra-fine membrane filtration. The membrane filter system at St Saviours comprises four banks of filter modules, together with their associated valves and control unit. It operates completely automatically, using compressed air back-pulses to clean the filters every 15 seconds. 

When the system was first installed, it performed much as expected, ensuring a high flow rate of quality drinking water for distribution to Guernsey Water's customers and load-balancing service reservoirs, with minimal maintenance requirements. However, after about 18 months' operation, the system's purging valves began to fail, resulting in much higher maintenance overheads and unacceptable levels of system downtime.

The existing valves were butterfly type units. Festo recommended that they be replaced with actuator-driven pinch valves. The type specified by Festo have a typical operational life of 10 million cycles - equivalent to more than eight years' use with the duty cycle employed at the St Saviours plant.

Festo also recommended using non-contact end-position sensors on all the pinch valves, to eliminate the effect of drive shaft wear, and the installation of a suitable cabinet to help keep the solenoid valves clean and dry. Further refinements included removal of the unnecessary air lubrication system, the addition of a number of Festo quarter-turn actuators and switch boxes, a new 10-inch butterfly valve for water flow control, and an additional high performance silencer to further reduce the sound of exhaust air.
Festo Ltd

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