Spirax SafeBloc™ Double Block and Bleed valves have helped SCA
Hygiene in Prudhoe, in Northumberland, to eliminate unscheduled
boiler shutdowns costing up to £20,000 each in lost production.
SCA Hygiene runs a 24/7 process, producing branded tissue. It is the
company’s practice to only carry out maintenance work on a live
steam system behind double block and bleed isolation.
The company frequently suffered minor problems with blocked level
gauge glasses on its boilers. However, because 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.
“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, enabling us to maintain production,” explains Mr. Neil
Carroll, Area Engineering Leader at SCA Hygiene, Prudhoe Mill.
“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) is the industry’s best practice for
double isolation for safe maintenance without having to shut down
the entire system.
Double isolation is achieved 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.
The innovative, patented design of 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. No other commercially available product provides double block
and bleed isolation in such an integrated, compact unit.
This was one of the main advantages for SCA Hygiene: “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.” Mr. Carroll continues, “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.”
An added advantage of Spirax SafeBloc is that a retrofit can be
undertaken quickly, eliminating 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.
This high quality, UK manufactured and easy-to-fit unit is robust
enough for industrial environments. It uses proven technology from
the Spirax Sarco range of bellows sealed globe valves that offer
zero gland leakage, while ensuring tight shut-off conforming to DIN
3230 BO1 and ISO 5208 Rate A specifications.
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