Decreasing network pressure to minimise leakage
With reducing leakage a priority for UK utilities, calming the network with the correct use of valves can make all the difference, writes Mark Hodgens
by Mark Hodgens, Managing Director, Talis UK
Fixing and minimising the number of leakages within the water network is currently a major priority for the UK’s water companies. Although most companies are working hard to reduce leakages caused by problems such as ageing mains, leaking joints, substandard valves and pressure surges within pipes, a large proportion of the system still remains in poor condition.
According to the World Bank, $14 billion (£10 billion) is lost each year in clean water that’s wasted before it even reaches its point of consumption. Water loss is often referred to as non-revenue water (NRW) and is categorised as water that has been processed within the network but never actually reaches the customer. This can be as a result of ‘real’ losses such as leakages, but can also occur from metering inaccuracies and unbilled authorised consumption from emergency services such as the fire and rescue service.
High levels of NRW are detrimental to the water industry as it creates substantial financial losses, which ultimately puts extra pressure on paying customers. In the UK, leakages are a particular concern that requires attention as the Consumer Council for Water found the majority of people (70%) do not think water companies are actually doing enough to prevent this issue.
What causes leakages to occur?
There are a number of reasons why leakages occur on the pipe network. It could be that there are gaps along sections of the network where pipes join, and as a result, water can escape. Gaps can also occur when the pipes age over time and begin to deteriorate. Naturally, components within the water network will weather during their lifetime and can be corroded by materials around the pipe such as soil and water.
Further causes of leakages can occur particularly in the winter months. During extremely cold periods, pipes can freeze and will expand to make way for the frozen water. As the pipe is stretched beyond its limits, it could burst and the ensuing break would then allow thawed water to leak.
Leakages can also occur when accidental damage is caused to the pipe network. For instance, the vibrations from traffic travelling on the roads above could weaken the network. Also when workers are digging up the road to carry out maintenance work on the transport network, accidental damage to pipes can be caused.
Why water hammer is a cause for concern
Water hammer is one of the main causes of leakages and can be the result of a valve being closed too quickly. It occurs when the valve shuts but the water in the pipe is still moving. As the moving water hits the closed valve, it causes a shockwave to ripple backwards along the pipe. When this happens, the change in water velocity causes pressure to build up which unfortunately can cause leaks.
Leaks and pressure surges caused by water hammer can cause serious damage, including ruptures to the network. In some instances, it has been known to crack or burst water mains, put stress on pipe joints and sealing methods, bend pump shafts, deform check valve disks and even move the pipes off its supports: damage that ultimately brings hefty repair costs to the water industry.
If the network is damaged like this, the overall life of the system will be shortened and could even lead to leakages happening more often.
At present, it’s estimated that each water company is already losing one in five of every litre of water gathered, cleaned and treated through leakages. So in order to promote a more sustainable and efficient network, this issue requires urgent attention to find a viable solution.
How can the issues be resolved?
At times, changes in pressure and water velocity will occur and conditions around the pipes and surrounding environment will not remain constant. When changes are made to the network, such as if a valve position is altered, this could result in small, gradual pressure changes that are usually undetectable. Water hammer becomes a major issue when these pressure changes are not small, and when a valve is shut too quickly. Therefore, a possible solution to prevent this would be to control the closing speed of the valve to ensure that any resulting pressure changes are less abrupt.
One product that has been developed to regulate the closing speed of the valve is the WRAS-approved ERHARD ROCO wave Butterfly Valve. Its slider-crank gearbox (SKG) prevents pressure surges and manages the valves opening and closing speed. Offering optimum precision, it closes the first 70% of the valve quickly, with the last 30% closing slowly to prevent disruption to the efficient flow within the pipeline and promote a ‘calm network’. This slows down the overall speed of the close, consequently reducing the speed of the flowing water so that changes to the pressure will be more gradual.
The ‘wave’ design of the disk reduces resistance and optimises flow by ensuring that the valve is closed smoothly. ERHARD’s new ‘Wave’ butterfly disc has been designed to enhance flow performance to offer a more energy efficient isolation valve solution. Alongside this, the patented polygon connection between the shaft and disc provides optimum corrosion protection to guarantee clean potable water, resulting in safe operation throughout the entire life of the valve. This polygon connection proves to be a more positive drive force with no need for pins which could be an avenue for corrosion. This will also reduce the amount of torque required to operate the valve therefore decreasing actuation cost. Overall, the valve helps to prolong the life of the whole network as its high quality coating and reliable seals provide long-term protection against corrosion and leakages.
Calming the network
Reducing the pressure on the water system needs to remain a top focus for the UK’s water industry in order to reduce leakages and provide a more efficient service. Implementing pressure management measures will help to look after water distribution systems in the long term, while also reducing costs. This not only benefits the network by reducing maintenance and operational costs and losses in revenue, but also eases the financial burden on the customers who are ultimately footing the bill.
About the author: Mark Hodgens is Managing Director at Talis UK.
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