Anglian Water always has three backup pumps on standby at its Newton Water Treatment Works, Lincolnshire, which supplies the city of Lincoln with its residential and industrial water needs. These units provide emergency back-up in the event of failure of one or both of the two 500l per second pumping units.A mystery fault with one of the company’s existing 250kW softstarts of another make was causing one of the backup pumps to repeatedly breakdown on start-up. To help rectify this problem, Anglian Water turned to ABB Softstart Alliance partner, Inverter Drive Systems.Gavin Hall, works technician optimiser for Anglian Water, said: “We have five pumps running in parallel, two with a softstarter and three with a variable speed drive (VSD). At any one point in time, we have two pumps running, one with a VSD and one with a softstarter. This allows for flexibility within the system and also saves costs. To cope with any fluctuations, we need one pump constantly running at full speed and one that can have its speed varied. As a softstarter is a fraction of the price of a VSD, we opted to use a softstarter to drive one pump constantly at full speed while a VSD drives the second one, adjusting the speed depending on the required output.”When Anglian Water’s existing emergency softstarter broke down, they were left without any back-up at all. “This could have been a disaster if one of the functioning pumps had broken down as well,” said Hall.Working with Inverter Drive Systems, Anglian Water installed ABB’s PSTB470 softstarter to replace the failed one. The PSTB470 softstarter features a LCD screen which uses plain text to display a range of data on multiple parameters, including output current, voltage, number of starts, total run time and motor temperature. Operators are also able to set advanced warning parameters, allowing potential problems to be identified before real problems occur.“The ability to know about any problems before they develop further is a major benefit for us,” commented Hall. “In this way we should be able to prevent unnecessary downtime and ensure that we always have our back-up pumps ready to go online.”Previously, the station also suffered a power failure, which was attributed to one of the external protection devices serving the old softstarter. As the PSTB470 softstarter has an integrated bypass contactor and thermal overload, Anglian Water was able to remove the existing protection devices, eliminating the risk of a similar failure occurring again.
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