SCA Hygiene achieves three times valve payback in six months 26 January 2011

Branded tissues manufacturer SCA Hygiene in Prudhoe, Northumberland, says it has eliminated unscheduled boiler shutdowns costing up to £20,000 each in lost production.

Neil Carroll, area engineering leader, says that the plant replaced single isolation valves, fitted to the gauge glasses on its boiler, with Spirax SafeBloc double block and bleed valves.

He explains that, since it is company policy only to carry out maintenance on live steam systems behind double block and bleed isolation, even relatively minor problems had meant shutting down and depressurising the boiler – so halving production output for up to 10 hours.

"We replaced the existing single isolation valves with four SafeBloc valves on each of our boilers, so that any future maintenance work on our gauge levels can be done without having to shut down a boiler," explains Carroll.

"Previously a boiler shutdown could cost us up to £20,000 in production downtime. The last four valves paid for themselves three times over within the first six months."

Double block and bleed (DBB) – achieved by closing two isolation valves, with the intermediate bleed valve being left open to provide a sealing integrity check – is the industry's best practice for double isolation for safe maintenance.

Carroll says that Spirax SafeBloc incorporates two isolation valves and a bleed port in a compact assembly, making it easy to install into the space left by an existing single isolation valve.

"SafeBloc is basically two valves with a bleed port in the space left by one valve, giving it the face-to-face dimensions of a single valve," he says.

"We would never have been able to install a DBB system in the past, as other designs take up too much space, often sticking two to three feet out from the boiler," he adds.

He also says that a retrofit can be undertaken quickly, without the time-consuming and expensive pipe cutting, welding and pressure testing needed to engineer a conventional double block and bleed arrangement from separate isolation and bleed valves.

Brian Tniham

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