WET News

14 WET NEWS NOVEMBER 2015 • Replacing two submersible pumps proved eventful on a recent project for Ouse & Derwent Drainage Board. Pumping out the challenges Access to the wet well ONSITE MAiNtENANcE & REfuRBishMENt • the job of removing the old pumps and installing the new pumps took Axflow three days to complete. following the refit, Axflow was asked to take the old pumps to its huddersfield service Base for inspection However, that has not been the end of the project. Following the refit, AxFlow was asked to take the old pumps to its Huddersfield Service Base for inspection. Redgrove comments: "We now have the pumps at our base and having stripped them down we have found that they were in pretty good condition, even a-er 25 years. However, some oil and water has got into the motor windings, but this is not a major cause for concern. We looked at replacing the usual components that can be subjected to wear, including bearings and mechanical seals and washed out the stator windings and reassembled the pumps. "The impellers were in good condition as they clearly had a relatively easy life, even though they are in a high profile pumping station and over the years had been subjected to high levels of continuous operation." The two original pumps still operating at the Stillingfleet pumping station will be removed when time allows, and be replaced with the two overhauled pumps at AxFlow's Huddersfield workshops. From planning, maintenance and emergency response, to achieving water quality and sewer flooding ODIs, having better asset data is invaluable. Ultimately it contributes to Severn Trent offering the lowest average combined household bills and delighting our customers every day with the service we provide." S tillingfleet water pumping station was originally constructed by British Coal in the early 1990s when mining subsidence lowered the ground level and prevented water in this low-lying area draining away by gravity into the nearby beck. Now the responsibility of Ouse & Derwent Drainage Board, the facility has had two new submersible Bedford pumps installed while two pumpsets that had been removed from service have been overhauled. The work has been carried out by AxFlow. Mark Redgrove, AxFlow's technical support manager, explains: "Earlier this year the drainage board detected that the moisture readings within the pump linings were a cause for concern. "Although the pumping station is equipped with two 800mm rising main storm and two 600mm rising main dry weather pumps, the drainage board recognised that they could not be two pumps down for a prolonged period so two new submersible Bedford pumps were ordered. We were called to remove the old Bedford SB pumps and install the new pumps." Scaffolding Logistically, it appeared to be a straightforward remove and replace job with scaffolding being erected inside the wet well and a crane being used for removing and replacing the two affected storm and dry weather pumps. However, installing scaffolding was a non-starter and it was decided that a man riding basket would have to be suspended in the wet well, making it necessary to have a second crane as there was no chance of li-ing the pumps and having a man in there at the same time. According to AxFlow, it was a bit of a problem - trying to get both the man riding basket and pump into the same space with two crane jibs was a challenge. Pipework "Our plan was to remove the remove the old flange bolts and pumps and reconnect the new pumps to the existing pipework with new bolts," says Redgrove. "However, as soon as the bolts were removed from the discharge flange of the first pump, it tried to fall into the wet well. "The pump was standing on three feet on a concrete platform in the wet well and with the removal of some of the bolts the weight of the pump tries to pull it away from the discharge flange so it was necessary to leave some bolts in place. The larger pump weighed four tons and the smaller two tons." Another problem that had to be addressed was the wet well was leaking. "When we stopped the pumps the water rose up to the level of the man riding basket so one pump had to be kept running to keep the level down," says Redgrove. The job of removing the old pumps and installing the new pumps took AxFlow three days to complete. NEEd To kNoW 1 the project was not a straightforward logistical job 2 could not be two pumps down for a prolonged period 3 Get both the man riding basket and pump into the same space with two crane jibs was a challenge 4 the wet well was leaking 5 the impellers were in good condition small pump being lifted into position the pumps are ready to be installed ProjEcT SPEcS • Remove two existing pumps • install two Bedford submersible pumps at stillingfleet water pumping station • Overhaul two 'out of service' pumpsets

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