Exsel Pumps was called in to a major sewage treatment works following the failure of one of the installed pumps in the plant. It was necessary to by-pass the failed pump that was handling raw sewage with flow potential up to 2,000 m3/h in storm conditions. Added to the problem was the daily failure of a competitor’s pump set up where their pumps constantly ragged up and blocked. In addition, it was noticed during scoping that inferior pipework was being used which was leaking sewage.
The rag-laden sewage was on a 6 metre suction lift with a 50 metre discharge and a final static lift of 8 metres to an alternative part of the works. Due to the dry conditions however the level of rag content had built up and was a key issue to overcome.
Exsel carried out the complete temporary installation providing the total solution. The wet well had restricted access that did not allow submersible pumps to be utilised. Therefore surface mounted diesel pumps were the only solution.
Two 8” (200mm) Betsy diesel pumps and one 12” (300mm) Betsy diesel pump were utilised to provide the required cover for the maximum flow condition. The pumps were set up in parallel with a lead/lag/lag automatic stop/start configuration using probes to sense the level in the suction sump. To ensure that the pumps were always ready to go Exsel provided a double battery arrangement and trickle chargers on each unit. The low noise and fully bunded protection ensured that there was no impact on the local environment. The pumps were also supplied with bunded fuel bowsers and diesel spill kits by Exsel to ensure that a full environmental protection capability was in place.
In addition, to minimise the potential for sewage spillage, all the 12” (300mm) pipework was flanged and bolted. Exsel completed the full installation well within the time stipulated by the client considering also the emergency nature of the contract.