WET News

wwtonline.co.uk | JULY 2018 WET NEWS 21 off causes rapid changes in flow. These flow changes are followed by rapid pressure transients, causing an effect known as water hammer. Water hammer occurs when the flow of water in a pipe is stopped suddenly, causing a shock wave to ripple through the water and impact on the structure of the pipes, leading to damage. This can damage pipes, pipes support and valves and causes leaks. As pipework is replaced and leaks are repaired, pressure may build up in other parts of the system instead, causing new leaks in new locations. VSDs reduce mechanical stress on pipes, pumps, valves and other key equipment, and diminish the likelihood of water hammer by enabling the flow rate to be increased gradually and safely. Cutting pressure also means reducing pumping energy costs, while controlling leaks also avoids spending money twice to process and pump extra water. Leakages cut by half One company that has been using VSDs to good effect in its fight against leakage is Scottish Water. Since 2006, it has reduced its leakage rates by half. More recently it has been working with ABB authorised value provider EDC (Scotland) to focus on pumping stations and the effect they can have on leakage rates. Leaks can occur both upstream and downstream of the stations and were one of the main causes of customer complaints. A project to identify and intervene in the stations most prone to causing burst pipes has contributed to signifi- cant decreases in the number of burst pipe incidents. The program has prevented 1000 bursts in three years. For around 100 of the most trouble- some sites, the project has seen an 80 percent reduction in bursts. Complaints about discol- ouration and low or intermittent pressure due to leakages have fallen 35 percent. Installing ABB VSDs to control the pressure has been a major contributor to the program's success. Overall, for an investment of Variable speed drives, such as ABB's ACQ580, can play a role in managing pressure £650,000, Scottish Water has so far saved £1.2 million on repair- ing burst pipes, as well as £35,000 on energy due to the efficient running of the pump motors by the VSDs. It is pro- jected that savings will rise to a total of £4.5 million by 2021. The numbers game It's clear that the water industry needs to improve leakage rates, but to control flow rates and pressures and thus leaks, we need to measure them. This is where metering comes in. Using data from night time flow meas- urements enables water compa- nies to accurately pinpoint any unexpected continual increases in water consumption, which might suggest a burst or an undetected leak. Traditional mechanical meters do not offer the accuracy needed and cannot cope with the low flows seen at night. By contrast, electromagnetic meters offer improved accuracy over a far superior range of flows. In fact, modern meters could even detect a toilet flushing. Accurate flow measurement plays a crucial role in Scottish Water's leakage reduction programme. To get more information on the pressure transients and the bursts they cause, high-speed data loggers are used to meas- ure the pressure at a radius of one, three and five kilometres around the site. 128 data sam- ples a second are taken. The positioning of the data loggers allows the cause of the burst to be traced to a particular pumping station. If the pipes connected to a pump are experi- encing excessive pressure, EDC surveys the site and makes rec- ommendations to improve its performance. In instances where pumping stations are already using so™ starts, which ramp up the pump speed and hence the pressure gradually, EDC recommends using an ABB drive solution. With energy costs only going up and environmental concerns rising, highly controllable VSDs and accurate measurement of flow rates is the route to keep- ing on top of leaks. IN THE MOST DEMANDING ENVIRONMENTS IMX12 - Cabinet Condition Monitor Keeps You Informed www.turckbanner.co.uk What's going on behind closed doors? Cabinet Monitoring for early warning of potential problems. * Single unit monitors: Temperature, Humidity, Ambient light, Door closure & external sensor inputs. * Versatile Communications. Internal datalogging and status over Bus. * Intrinsically Safe. Turck Banner Ltd. Blenheim House, Blenheim Court, Wickford, Essex, SS11 8YT Tel: 01268 578888 pa@turckbanner.co.uk Your Global Automation Partner

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