The specialist capability of Exsel Pumps was once again called in to action at Chichester CLIPS PS following the failure of two of the installed pumps in the plant and concern over the back-up pump. The access to where the sewage was extremely limited such that submersible pumps could not be utilised. In addition, the sump area could only be accessed through a restricted opening so the use of a number of smaller diesel pumps was also not possible.
The incoming flow was such that at times less than 30 minutes was all that was available before sewage would spill over onto the works.
It was necessary to bypass the failed system that was handling sewage with flow potential up to 3,000 m3/h in storm conditions. The sewage was on a 5 metre suction lift and had to be pumped vertically up to the discharge point about 10 metres high.
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 electric pumps were the only solution.
Two 12” (300mm) H12K-HD pumps were utilised with dedicated vacuum priming systems to provide the required cover for the maximum flow condition. The pumps were set up in parallel with a lead/lag automatic stop/start configuration using probes to sense the level in the suction sump. The PLC control containers utilised controlled the speed of the pumps via VSD controls to ensure that the level of flow was kept at a constant so as not to overwhelm the system upstream. 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 project.
Exsel Pumps was called in to assist as other pump rental companies had walked away from the complexity of the project. A solution was provided and maintained whilst repairs could be completed on the installed pumps. Exsel’s fleet capabilities of operating surface mounted pumps with vacuum priming along with PLC controls has proven in a number of critical cases to be the only solution available.