SCA's comfort zone

Tissue-paper manufacturer SCA Hygiene Products UK, based in Prudhoe, has eliminated unscheduled boiler shutdowns costing up to £20,000 each in lost production by installing double block and bleed (DBB) valves.

SCA’s Northumberland mill operates 24/7, producing branded tissue and only carries out maintenance work on its live steam system behind DBB isolation.

The company suffered minor, though frequent, problems with blocked level gauge glasses on its boilers. As only single-isolation valves were fitted to the gauge glasses, the boiler had to be shut down and depressurised to enable maintenance engineers to fix the problem safely, halving production output for up to 10 hours.

SCA, therefore, replaced the existing single isolation valves with four Spirax SafeBloc valves on each of its boilers, so that any future maintenance work on gauge levels can be done without having to shut down a boiler, according to Neil Carroll, area engineering leader at the Prudhoe Mill.

Previously, a boiler shutdown could cost up to £20,000 in production downtime, noted Carroll, who estimates that the four valves had paid for themselves three times over within six months.

DBB valves function by closing two isolation valves, with the intermediate bleed valve being left open to provide a sealing integrity check to ensure the downstream pipeline remains safely isolated during maintenance work.

“Spirax 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,” said Carroll. “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.”