AC Drive UpGrade breathes new life into plantOver 65% energy saving and a payback of only seven months has been achieved by Severn Trent following the replacement of three, 37kW AC drives on water process pumps.
DrivesAdvantage
The catalyst for the drives overhaul is a new service scheme introduced by the ABB Drives Alliance. Called DrivesAdvantage, the scheme is particularly aimed at water utilities and offers several bespoke programmes aimed at upgrading or replacing drives. Brian Dick, of Sentridge Control, part of the ABB Drives Alliance explains: “Many drives were installed some 15 years ago. Since then, drives have become smaller, more efficient, more reliable and less costly to purchase, install and run. So it makes good business sense to check up on our installed base and dig out the massive savings that are right under our noses.”
Severn Trent’s Dan Hulse, Instrument and Electrical Engineer, was introduced to the scheme during a free one-day training seminar provided by the ABB Drives Alliance. “The day opened our eyes to the real benefits offered by using variable speed drives. I reported the findings to our management and without hesitation the funds were found to invest in drive technology. We could see that our investment would be rewarded virtually immediately and this has proved to be the case. “We had not appreciated just how far drives technology had advanced in recent years. After experimenting with ABB’s demo drive and seeing how easy it is to use – particularly the keypad, designed like a mobile phone, with its clear text and simple language – we knew it was time for us to change. There is so much more that we can do with the drive.”
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Extending the scopeFollowing the success of the Wanlip process pump drives, Severn Trent turned its attention to other applications including the installation of ABB standard drives on two aerators. The installation was suffering from a failed brush unit and large inrush currents caused by the star-delta starter, both of which contributed to high running costs. Using star-delta starting, the average energy consumption was just over 90kWh. Following the installation of an ABB standard drive, the energy consumption fell to a little over 70kWh. “For an investment of only £5,000, Severn Trent saved over 167 kWh resulting in annual savings of £5,800 and a payback of only 11 months,” says Dick. “This is a saving of over £29,000 during the ABB five year warranty period of the drive.”
At the nearby Lake Terrace pumping station in Melton, star-delta starters were replaced with ABB drives to combat the spikes infiltrating the power network when the pumps were started up and exceeded demand. Following the installation of six, 75kW ABB standard drives, it is possible to slow the pumps down to 42Hz, thereby keeping the process running slower rather than the severe starting and stopping that was experienced previously. This eliminates the peak demand being exceeded whilst giving better control performance. A surprise advantage of installing drives was the reduced maintenance and wear of the large non-return valves. The one metre diameter hinged valves would clatter to a close when the water flow ceased. This constant crash closing of the valve damaged the seal and wore out the hinge mechanism. But by ramping down the flow gradually, the non-return valves are gently lowered.
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DriveAdvantage WorksCommitment and knowledge
“We were very impressed with the commitment and knowledge of ABB Drives Alliance partner Sentridge Control,” says Jeremy Jones, Area Maintenance Manager, Leicester and Melton Area. “The installation was not easy as cabling need to be channelled through an existing concrete floor. The ABB Drives Alliance partners accepted the challenge without question, drilling long and laborious channels and manufacturing aluminium covers to further protect the cables.” Although a competitor’s drives had been widely used on the site, ABB Drives Alliance forward thinking and new approach convinced Severn Trent of the merits of using its drives and service and support network. “ABB was the first company to put forward a comprehensive service scheme with its DrivesAdvantage,” says Jones. “Coupled with no cost training; its enthusiasm to strike up a partnership; and the drive features including a five year no-quibble-warranty, we felt that ABB was well ahead of its competitors.
“The DrivesAdvantage scheme parallels the successful model used by Severn Trent under the MSP programme. We had already struck up a partnership with ABB Motor Service Partners (MSP’s). This organisation has completely revolutionised the way motors are supplied, installed and maintained. Their technology, their experience and their set-up is a breath of fresh air. They are most definitely high-tech and not 100 years behind the times. They are continually looking for new solutions that will improve our process.
“And then along comes Sentridge Control and the ABB Drives Alliance who actually want to help us and deliver all the technical support at our local level and they want to save us money as well!
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