WET News

20 WET NEWS JULY 2018 | wwtonline.co.uk Ease off the pressure to keep leaks in check W ith 3,300 mega litres of water lost per day, the UK's water supply companies face a continuing and expensive problem. Losing 15 to 25 percent of its annual production of potable water every year is not sustainable and despite the great success many water companies have had in finding and stopping leaks, there is always more that can be done. Part of the challenge is that most pipework leaks remain hidden underground. Where losses stem from relatively small but steady leaks from a joint or fitting, such leaks can be espe- cially hard to detect, particu- larly where the installation envi- ronment prevents water from rising to the surface. Going unreported, many thousands of litres of water can be lost before the leak is detected. A big cause of these • Keeping leaks in check is a major challenge for water companies but one that can be met with variable speed drives to control pressure and highly accurate advanced flow measurement, says ABB water framework manager, Dan Banks 'background leaks' is elevated supply pressures. While pres- sure is high, water is forced out into any existing leaks. New leaks can be generated at any points of strain such as joints in the pipework. The danger is exacerbated by older pipe work which may have suffered from corrosion and wear. The reason for these elevated pressures is that pump capacity is usually selected based on a maximum requirement for flow or head, o‹en with a safety mar- gin built in and even extra capacity to meet future require- ments. Yet normal pumping requirements will be only a frac- tion of the maximum capacity, and during low periods of demand it will be even less. Putting a brake on pressure Leakage can be reduced signifi- cantly by even a small reduction INSIGHT LEAKAGE in pressure: a 20 percent reduc- tion in pressure can reduce leak- age rates by up to 50%. This reduction in pressure is readily achieved using variable speed drives (VSDs). The ability of VSDs to control the speed of motors and thus pumps means that mains pressure can readily be controlled. Using VSDs, flow rates can be adjusted to ensure that pres- sure levels are adequate. As modern drives are easy to oper- ate and making adjustments is not difficult, settings can be approximately altered at instal- lation and then fine-tuned over time. For example, a system with 5 bar in the day could be automatically reduced to 3 bar at night using the inbuilt control. VSDs can also help to avoid the large variations in pressures that can lead to leaks in the first place. Switching pumps on and

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