Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/1119298
6 | JUNE 2019 | WWT | www.wwtonline.co.uk The Talk: opinion JAMES BROCKETT, EDITOR, WWT T his issue of WWT sees us take aim at that perennial water industry challenge, leakage, and investigate some of the ways water companies are setting about meeting the ambitious targets that have been agreed with regulators. We take a close look at SES Water's approach to measuring below-ground asset condition (p23) as well as investigating how trenchless techniques can assist with more efficient leak repair (p26). It's clear that AMP7 will need to represent a step change in water companies' management of their pipe networks if they are to get close to the performance targets that have been set. Ofwat has challenged companies to reduce leakage by 15 per cent by 2025, but the 3,123 million litres leaking daily in England and Wales last year represents only a 7 per cent reduction on the level seen at the turn of the millennium; leakage levels have been broadly unchanged over the last five years. While it was acceptable in AMP6 to restrict ambitions to the economic level of leakage, this will not be the case in AMP7. With long-term drivers for leakage reduction including climate change, diminishing resources and the need to reduce consumption, it's hard to escape the conclusion that it is a change in political mood that has resulted in the rapid change in expectation. Digital asset management and smart technology will have a big role to play in utilities' leak reduction efforts, and you can hear our panel of senior water company figures discussing some smart approaches in this field in the report of our round-table event held with Black & Veatch on page 14. However, just as important as technology and innovation is the need for the industry's contractors and supply chain to collaborate effectively. Contractors must be brought on side and incentivised to trial and use new techniques, rather than being locked into contracts where there is no motivation to do anything but repeat the same old methods. On a related note, last month was the last print issue of WET News, WWT's sister title focusing on contractors, which has now ceased publication. While this was a sad day for a magazine that served the sector for 25 years, we're proud to say WWT will be picking up the baton with an expanded content offering that will appeal not only to our water company readers but also to their contracting partners. You'll notice that this issue of WWT is larger than usual and contains a few extra elements and perspectives. Watch this space for much more where this came from over the coming months, and don't forget our digital presence at wwtonline.co.uk, where you can read the latest water industry news, features, opinion and technical articles on a daily basis. We've thought long and hard before making this decision, and have spoken to a good selection of readers, commercial partners and industry insiders for their views on how best to serve the water contractor audience. We've noted those water contractors who are flourishing are increasingly embedded in the teams of their water company clients, working within long-term strategic partnerships and delivery alliances. Water company clients, consultants and contractors alike see themselves as facing similar challenges. That's why we think now is the time to offer a single media brand for the water industry. SPONSORED BY ROB WOOD, UK SALES MANAGER, ABB Why motors need servicing With several factors determining the ageing of a motor, a proper maintenance strategy is vital to ensuring its long life T he image accompanying this article shows the typical life cycle of a motor. The grey curve shows the condition and performance of the machine, which, over time and without a maintenance strategy, declines primarily due to ageing. How fast the performance declines depends on how well the machine copes with operational stresses, and how well it has been maintained. Machines that have an appropriate maintenance strategy in place will generally last longer than those that don't. The red curve shows the operating expenditure (OPEX). Installation and commissioning is a critical step, because complications introduced here will impact on the reliability of the motor in the future. Without a proper maintenance strategy, the motor may fail, and the OPEX will increase dramatically due to the costs of emergency repairs, urgent spares and the loss of production. The four dominant factors affecting ageing are thermal, electrical, ambient and mechanical (TEAM). Understanding TEAM and its consequences for individual machines helps select the appropriate service or maintenance strategy that will maximise process uptime, and help minimise OPEX. Thermal ageing happens during normal operation at rated output but is accelerated if the machine runs hot due to overload, fouled coolers or dirty filters. Thermal ageing also occurs during start-up as a result of long starts, stalling, repeated starts or a locked rotor. Electrical ageing includes partial discharges in the insulation, even at normal terminal voltages, network harmonics, voltage peaks in the network and phase imbalance. Ambient ageing can occur as a result of high or low ambient temperature, high humidity or air contaminated with salt, dust, sand or chemicals. Mechanical ageing results from vibrations caused by imbalances, misalignment, air gap irregularities, electrical asymmetry, resonance at natural frequencies near the operating speed, or vibrations from the driven equipment. With motors connected direct-on-line (DOL), there is a large inrush current present when the electrical supply is first applied to the machine. The size of this current, coupled with the way the rotating stator field interacts with the stationary rotor, means that thermal, electrical and mechanical stresses are significantly higher when starting than during normal operation. Therefore, repeated starts caused by network disturbances or nuisance trips can cause a significant reduction of the machine's life span. These starting stresses can be reduced if the motor is connected to a variable speed drive. If a machine is started every day, that alone could double the need for maintenance compared to one that runs continuously. This needs to be considered when planning the maintenance intervals for DOL motors that start frequently.