Exsel Pumps was called in to provide an alternative solution to over-pumping a gravity main during a diversion of a sewer pipe. The access point was right outside the front entrance to a new Tesco store and the discharge point had to cross a public access road. A competitive solution offered by a national pump hire company was deemed not suitable by the customer due to the high risk involved in getting the project wrong. The suction lift was about six metres and the overall site plan was restricted as the location of the equipment was in the Tesco car park. There were also severe time constraints as Tesco quite rightly wanted limited disruption to their customers. Quite simply any errors and raw sewage would be flowing through the Tesco store entrance.
Exsel developed a plan after listening to all the parties concerned, particularly the time constraints, the risk factors and the continued public access both to the store and to the public road that intersected the only available discharge run.
Utilising 6 x F10K Hidrostal immersible pumps, surface mounted and set up in two units of three pumps. Each pump utilised a CAD designed pipework system for the suction side that allowed the three suction pipes to be within the minimal space possible. This allowed the contractor to cut two pre-determined saddles in the existing main for the pipes to sit into. Four generators were utilised on an auto changeover system and the pumps were controlled by two PLC control containers with variable speed drives, hydrostatic level controls and stand-alone vacuum priming systems, one for each set of pumps.
The overall set up provided a number of levels of back-ups. The peak flow condition could be covered by three of the six pumps installed. Any combination of the six pumps could be used at any given time. Two generators were required to provide the necessary power—therefore two back-up generators were immediately available in the case of any generator failure. The dual pumping station set-up was in as small a footprint as possible to minimise the impact on the Tesco car park.
To overcome public access, Exsel built two pipe bridges out of the 500 mm diameter discharge pipe of flanged steel. One over the pedestrian access area and the other spanned across a 6 metre public access road. This bridge had to cater for high vehicles delivery to the Tesco store. But also the bridge had to be set up quickly to reduce access restrictions to the store deliveries and to a neighbouring restaurant. These two bridges meant that the contractor did not have to spend time and a lot of money, let alone the disruption in burying the pipes below ground.
Working closely with the contractor the project was completed on time and with total success.