Ham Baker, Unitspark design, install penstock at Wandle Valley Pumping Station
Ham Baker and Unitspark completed the installation of a penstock at a pumping station in London, England, and overcame a restricted access issue with a cost-effective engineering solution.
As part of Thames Water’s ongoing program to replace aging assets before the end of their forecast life, a 1.2 by 1.2 meter penstock was required at Wandle Valley Pumping Station in London. But with this size, it was too large for the 9-meter deep shaft and pipe; thus, installation of a standard penstock would have caused significant delays and costly disruption.
Thames Water called upon engineering consultant Unitspark and Ham Baker to design what became known as the jigsaw penstock, which is crafted in segments.
“We have penstocks installed all over the world, but this one required a very different way of thinking,” said Paul Higginson, director for Ham Baker Group. “Designing a two-leaf segmented penstock (to extremely fine tolerances) that would have to be lowered down and traverse up a pipe for a very precise installation certainly called upon all our experience. Together with Unitspark, we very much wanted to provide a long term solution for Thames Water, producing a high quality penstock made from stainless steel, including every single component part with exacting attention to detail.”
Following manufacture by Ham Baker, Unitspark planned the fastest and most effective way to carry out the installation of the jigsaw penstock with only minimum disruption. The task was made more challenging by the discovery of live assets and a 3-meter thick block of concrete that had not appeared in the former sewage treatment works plans.
“We are used to wet and difficult environments and this was no exception, also having to deal with high levels of hydrogen sulphide," said Rob Horne, director for Unitspark. "Lifting, rotating and positioning the jigsaw penstock down the 9-meter shaft required the utmost skill and precision, before which our engineers had to first build a fabrication bench to later assemble the penstock and its 30 component parts.”
Brett Willis, project engineer for Thames Water, added: “Ham Baker and Unitspark successfully made this a specialist mechanical job, rather than a very costly and disruptive civil engineering project. The installation has been completed in just one week, with no need for major civils, new shafts or cofferdams. The benefits in savings are substantial. Working close to a river and major strategic discharge mains drastically reduced the risk to the environment and the catchment. It is a credit to all concerned that this exercise in serious asset management was completed in such a professional manner.”