E.ON switches valves at UK power plant
26 Jul 2010
Northwich, UK – E.ON has recently applied Emerson’s Fisher Control-Disk valve to improve backwash flow control within the water-treatment system at E.ON’s combined heat and power (CHP) plant in Northwich, Cheshire, UK.
The resulting elimination of filter media losses and subsequent downtime has enabled E.ON to reduce costs and improve availability as it provides steam for two local soda-ash plants.
The E.ON CHP facility is one of the largest of its type in the UK, generating 130MW of electricity for local residents and capable of supplying around 500 tonnes of steam every hour for two nearby soda-ash production plants in Winnington and Lostock.
Make-up boiler feed water from the River Dane is cooled and pre-treated to remove any algae or silt, then passed through one of six filters before being sent to a holding tank. The filters are cleaned by air scouring and backwashing to remove any material blinding the filter.
The original butterfly valve used in the backwash process could not provide a steady flow rate, causing media to be lost through the filters. Filter media had, therefore, to be replaced or refilled at an average cost of £3,500 a year. The downtime for this maintenance also affected the plant’s ability to meet its steam requirements.
E.ON installed an eight-inch Fisher Control-Disk rotary valve to replace the original butterfly valve. The new valve has dramatically improved backwash flow control without compromising capacity at peak demand. Since it was installed, the plant has not lost any filter media or experienced any downtime due to water filter problems.
Neil Price, improvement and performance coordinator at E.ON, said the new valve also delivers, when 100% open, a flow rate adequate to meet the water plant demands, without restrictions. “Its performance and reliability led to savings of £3,500 a year and enabled us to improve our customer service.”
According to Emerson, the Fisher Control-Disk valve’s disk profile and equal-percentage characteristics that enable it to adapt to changing process conditions and to provide control over a wide range. The valve is said to provide between 15% and 70% travel without compromising capacity, whereas standard butterfly valve designs offer only 25% to 50% of travel.
