Replacing direct-on-line starters with ABB variable speed drives eliminates pipe bursts at Scottish Water pumping station. Over £12,000 in maintenance costs is saved per year by eliminating burst pipes through the installation of ABB drives on two booster pumps.
Scottish Water, a utility providing water and sewerage services across Scotland, suffered nine pipe bursts per year, on average, at its Castle Road pumping station. Each burst was estimated to cost £1,400 through leakage detection, repair materials and labour.
The bursts were caused by pumps being started direct-on-line (DOL). This crude start/stop control created pressure waves causing pipes to fracture and leak. For example, water may be moving at a flow rate of 10 metres per second. If the pump is then switched off, this moving water suddenly hits a dead end, surging back, shocking the network.
EDC (Scotland) fitted two 5.5 kilowatt (kW) ABB water and wastewater drives, one for each of the two booster pumps. The drives provide a soft ramp up and a controlled slow down to maintain supply pressure in the pipe network. The project was completed in two stages to ensure no disruption to public water supplies.
Data loggers were used to gather information on pressure transients around the Castle Road site. Before the ABB drives were installed, the data revealed that on DOL starting, pressures were peaking at 140 metres head. Following installation of the drives, pressure data was again logged, revealing that starting and stopping the pumps using the VSDs reduced maximum pressures to 83 metres head.
Since the installation was commissioned in November 2016, the utility has had zero pipe bursts. The VSDs have also reduced the energy consumption of the pumps, saving an additional £200 per year. The return on the £5,500 investment in drives was achieved in five-and-a-half months.