Water & Wastewater Treatment Magazine
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8 | APRIL 2018 | WWT | www.wwtonline.co.uk The Talk: Opinion DR PHIL ALDOUS DIRECTOR OF WATER THOMSON ECOLOGY The environmental consequences of leakage reduction Reducing leakage is a priority for water utilities, but stemming the leaks might have unexpected environmental consequences for urban trees L eakage control models are the sophisticated part of industry's water management systems and are important in terms of resource efficiency, whether that is water, energy or carbon emissions. There is always a need to balance costs as well as taking into account environ- mental pressures, whether that is pushing for the utopian low leakage rate, the development of new water resources or the need to reduce abstraction volumes in environmentally sensitive catchments. In all these cases, leakage rates or percentages are important aspects in the promotion of development projects and SPONSORED BY ABB DAVE HAWLEY GENERAL MANAGER – MOTORS, ABB LTD Why do motors fail? Pump motors can run for half a century if they are properly maintained T here is a lot of debate about whether it is better to repair or replace a failed pump motor. A far better option is to ensure it doesn't fail in the first place. In theory, a motor could run for as long as 50 years, well beyond the retirement date of the connected machine. This can be achieved with regular preventive maintenance targeting the most common points of failure. Keep your eye on the ball Some 51 per cent of motor failures are down to bearings, with incorrect lubrication accounting for around 80 per cent of these. Problems can arise from using too much, too little or the wrong type of lubricant. play a role in determining whether such development projects go ahead. There is a growing realisation that urban ecology contributes enormously to a range of ecosystem services and health benefits. Large trees are excellent filters for urban pollutants and fine particulates. Spending time near trees is also linked to improved physical and mental health. Therefore, maintaining and increasing urban biodiversity, including trees, is essential. With increased concrete coverage and sustainable drainage systems (Suds) only becoming the norm on new developments, the availability of naturally percolating rainwater into the ground for tree support is limited. Reducing the amount of water leaking into the soil may therefore have a signifi- cant effect on the health and long-term viability of urban trees. I am not suggest- ing we should remove or replace trees un- necessarily, but with reduced leakage and water availability, we need to manage and care for trees as part of longer-term pro- grammes. For existing trees close to leak- age reduction programme pipe networks, consideration needs to be given to the introduction of surface water diversion to replace the lost water. Retrospective Suds and replacement permeable pavements could form part of such schemes. It is not all doom and gloom for urban trees – different species respond different- On average, regreasable bearings need servicing every 2,000 hours. But don't over-grease, because this can overheat bearings and lead to failure. It is important to use the manufacturer's specification to lubricate the bearings, taking into account how the motor is mounted, its speed and the type of bearings installed. Don't let your motor catch a fever Overheating is another common cause of premature motor failure. Heat comes from many sources – the loading on the motor, the ambient temperature, mechanical stress and even the thickness of the paint. Any of these can cause the motor's insulation to break down, putting the motor under stress and causing it to fail. Check the motor's insulation class to ensure the designed temperature rise is not being exceeded. The running time and load on the drive-end sha' also need to be considered. Motors that run continuously need to be fitted with bearings able to cope with high operating hours, and will have to be relubricated in line with the manufacturer's recommendations. High load on the drive-end sha' can also put unnecessary stresses through the sha' bearings, which can cause excessive ly to reduced water availability. Therefore, an understanding of tree species and their requirements is important. For new devel- opments, landscape architects may need to consider more carefully the trees they recommend for planting. With new robust networks, longer-term lower leakage levels and climate change, water availability will change. Although these changes will be offset by a full Suds being installed, this does not necessarily mean native trees will be planted, because many exotic species can adapt to dry conditions, poor nutrient availability and temperature fluctuations. Neil Francis, head of arboriculture at Thomson Ecology, suggests that a wider range of planting equipment is needed, including underground watering systems, as well as incorporating surface water drainage into tree planting schemes. I think that where pipe replacement occurs, a wider review of reinstatement techniques is required to protect urban trees and ensure that wider environmental benefits are gained. However, where leakage control and trees coincide, there is an argument for investment in retrospective Suds to reduce stormwater sewage flows and ensure urban trees do not pay the penalty for what is termed good water resource management. For more information about Thomson Ecol- ogy's work, visit www.thomsonecology.com friction and eventual overheating to the point of failure. Overheating can also contribute to winding failures. Increasing the running temperature by just 15°C can halve the lifetime of the winding. Protect against external factors External factors account for 16 per cent of failures. If it is not feasible to move the motor, then it must be protected. High humidity can allow moisture to enter the motor, causing damage and corrosion. However, users can combat this problem with measures such as opening the drain hole and using enhanced paint systems. Where motors are operating in harsh outdoor conditions, consider the effects of cold as well as heat. For example, condensation heaters should be fitted to motors used outdoors in cold winter months to minimise condensation. Finally, ingress of foreign particles into the enclosure can cause damage – particularly to the bearings or windings – so it is important to use the correct IP ratings to protect your motor. To find out more ways to prevent motor failure, email energy@gb.abb.com and request ABB's motor tips e-book, or download your copy at http://bit.ly/2EUvDZ7