Water & Wastewater Treatment

22 | APRIL 2016 | WWT | www.wwtonline.co.uk Project focus: Pumps and pumping systems The replacement li station is in full working order this issue by installing new pumps capable of delivering an increased flow rate at new head conditions; the urgency of the situation meant eHT was given a brief that would require the company to deliver a fully operational li station within a three week time frame. "I saw things happening that took place in time frames that I had never experienced before," continues Hay. "A major part of this was Pumps Solutions' ability to deliver two KSB KRT-F submersible pumps, along with the wet well made by US Composite Pipe, in a very short space of time." Pump Solutions worked closely with KSB USA to identify the right pumps and types of impellers for the job. The preferred design of impeller was a vortex impeller specified by Hay. In his opinion, the vortex was the best type for the application, even though there had never been a problem with grit, solids or ragging. Being such a high profile project Pumps Solutions and eHT wanted to put in the best possible option for current and future demands on the system. In fact, such was the speed of the project no actual specification was developed. The sole objective was to get the pump station up and running within the City's exacting deadline. "Because of the time frame, we had a lot of hoops to jump through," says Pump Solutions' Charles Norman. "Our solution was based on the existing conditions and the technical brief given in respect to flow, hydraulic duty points and head, and it was our job to deliver a li station complete with pumps, pre- cast wet well with access cover and the necessary control panels for the station." The pumps that were finally selected were two 24hp KSB KRT-F models running at 1160rpm, with a design point of 975 US gpm at 30 TDH for a velocity of 3/sec. and fitted with 105/8 inch (270mm) diameter vortex impellers. Equipment sourcing "Having to source the vortex impeller pumps, wet well, piping, wet well access hatch and li station control panels within three weeks was a very tall order," explains Norman. "Normally a li station of this size and specification would take up to 12-14 weeks to complete. The advantage of working with KSB is that they have wet well pumps where the impellers can be swapped out. Their inventory revealed two K-type multi-vane impeller pumps in their warehouse which we could swap to F-type vortex impellers. What's more, the hydraulics and motors were a good fit for the job, so we had a potential solution." However, the vortex impellers in stock were of the wrong dimensions, and calls to other KSB distributors around the USA drew a blank. KSB's application engineers proposed another solution, which was to use one of their European castings suppliers to manufacture two new impellers and have them air-freighted to KSB's plant in Henrico VA for pump assembling and testing. This was achieved in two weeks, giving KSB one week to do the assembly and testing. Sourcing the wet well access hatch and control panels also posed a challenge, but fortunately, Pump Solutions' regular hatch supplier, US Fabrications in Florida, had a unit of the right dimensions le over from another project. The final element was getting the control panels manufactured by Quality Controls & Integration in New Prague, Minnesota and supplied to site, a process that normally takes 6-8 weeks. The supplier was able to accelerate the process, providing state-of-the-art controls including a touch screen panel linked to a submersible transducer in the wet well, enabling rapid data acquisition and monitoring of the water level in the wet well, raising alarms to indicate any changes taking place and monitoring pump performance. Summary The stability of the new li station had to be given major consideration, and for this reason it was not built on the original site. A decision was made to move the li station further away from the area where the land collapsed and the underground drain. New ground works had to be put in place, with some rerouting of the pipes and associated infrastructure. This disaster has had a positive outcome for the City of Granbury, in that it now has a robust and efficient li station that has increased pumping capacity to accommodate future growth, and ensures the safe transfer of wastewater and effluent away from the Brookshire's parking lot and Lake Granbury. The new pump station occupies a new site on the edge of the car park

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