Smart valve solves E.On CHP water flow control problems 18 June 2010

Backwash flow controls on the water-treatment system at E.On's CHP (combined heat and power) plant in Northwich, Cheshire, have been improved, thanks to the installation of a Fisher Control-Disk valve.

The unit, from Emerson Process Management, has eliminated filter media losses and downtime, so enabling E.On to reduce costs and improve availability as it provides steam for two local soda-ash plants.

Neil Price, improvement and performance coordinator at E.On, explains that this CHP plant is one of the largest of its type in the UK, generating 130MW of electricity and capable of supplying 500 tonnes of steam every hour to the soda-ash plants in Winnington and Lostock.

Make-up boiler feed water comes from the River Dane, is cooled and pre-treated to remove algae and silt, then passed through one of six filters before being sent to a holding tank. The filters are cleaned by air scouring and backwashing.

Until recently, this aspect was problematic, with difficulties being experienced in controlling the backwash flow. Its original butterfly valve could not provide a steady flow rate, causing media to be lost through the filters. As a result the filter media had to be replaced or refilled at an average cost of £3,500 a year. The downtime also affected the plant's ability to meet its steam requirements.

E.On replaced the butterfly with an eight-inch Fisher Control-Disk rotary valve and Price reports dramatically improved backwash flow control, without compromising capacity at peak demand. Indeed, since it was installed, the plant has not lost any filter media or experienced any downtime due to water filter problems, he says.

"The Fisher Control-Disk valve not only controls the backwash flow rate more accurately, but also it delivers, when 100% open, a flow rate adequate to meet the water plant demands, without restrictions," comments Price. "Its performance and reliability led to savings of £3,500 a year and enabled us to improve our customer service."

The improved performance reflects 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 an unusually wide range. The valve provides between 15% and 70% travel without compromising capacity – compared to standard butterfly valves' 25% to 50%.

Brian Tinham

Related Companies
Emerson Process Management

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