Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | FEBRUARY 2016 | 19 Project focus Pumps Pumping station upgrade for Stillingfleet Project focus ● Ouse & Derwent Drainage Board updates surface water pumping station ● New submersible pumps required a er damp electrical equipment caused concern ● Two cranes required for work in constrained space of wet well W orking on behalf of the Ouse & Derwent Internal Drainage Board, pump supplier AxFlow has installed two new submersible Bedford pumps at the Stillingfleet Surface Water Pumping Station. The two pumps removed from service are also being overhauled. The purpose of the pumping station is to li surface water which can no longer drain by gravity into the nearby beck because mining subsidence has lowered the surface ground level. The pumping station was constructed by the British Coal Corporation in the early 1990s as part of its mining remediation plans. The reason for the installation of two new pumps was that high moisture readings were being recorded within the pump linings containing the electrical equipment. "This was causing an operational concern," reports Mark Redgrove, AxFlow's Technical Support Manager. "The pumping station is equipped with two large 800mm rising main storm and two 600mm rising main dry weather pumps. To fix the problem the pumps needed removing; however the pumping station required its pumping capacity to be sustained. The solution was to purchase two new submersible Bedford pumps which could replace the existing ones when they were removed. We were called to remove the old Bedford SB pumps and install the new pumps. "Logistically, at first it appeared to be a straightforward job to remove and replace the pumps using scaffolding. The scaffolding is usually erected inside the wet well with a crane being used for removing and replacing the pumps to be changed. However, installing scaffolding in the pump wet well was not practical. This was because of the limited space along with the fact that the pumping station wet well was not totally sealed from the flows. The rising water levels requiring one pump running on and off to keep the level down," says Redgrove. In view of this, the potential practical options and health and safety implications of a confined space were considered as to how safely the work could be carried out. The option to be progressed required the utilisation of a man riding basket suspended in the wet well from a crane because of the constrained area and conditions. This made it necessary to have two cranes on site, one for li ing the pumps and a second crane for operating the man Access into the wet well

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