Steady under pressure

Paul Boughton

Dave Godfrey explains how electric actuation delivers accurate pressure control for an Australian city’s water supply network

Advanced electric control valve actuators are enabling the Sydney Water Corporation in Australia to control the pressure in the city’s water supply network with greatly increased response and accuracy. Water authorities need to control the supply pressure in their potable water pipeline networks throughout the day in response to user demand. Pipeline pressure also needs to be controlled to reduce network water leaks and to mitigate pipe bursts and consequential expensive repairs. To perform this vital function on the Sydney water supply network, Rotork Australia has supplied more than 150 Rotork CVL500 linear control valve actuators with adaptation for fitting to pilot valves.

Accurate network control
Typically, spring pressure in a pilot valve is modulated over a short 1-4mm stroke; this controls the output of the pilot valve, which in turn controls the pipeline pressure. Network pressure can range from 15m to over 90m head. The characteristic of the CVL500 actuator enables very accurate control of the network in increments of 0.4m of head pressure. For the Sydney Water network this is an improvement on the previous coarse control resolution of up to 7m head, just by changing to the new actuator. Using a proportional integral derivative (PID) control loop, the CVL500 provides repeatable and reliable ongoing pressure control. The actuator can operate in a flooded pit, as the enclosure is IP68-rated, whilst only low power 24V DC or 240V mains is needed. The CVL500 uses Bluetooth to enable remote configuration and monitoring from outside the pit or confined space. With the integral manual override control the actuator allows operation with or without power by electrical and mechanical engineers as well as site operators.

The CVL500 linear, electric process control actuator, offers a highly accurate and responsive method of automating control valves, without the complexity and cost of a pneumatic supply. With an increased focus on production costs and efficiency, accurate control of product through the pipeline is paramount. With resolution figures better than 0.1% and the ability to eliminate position overshoot, the CVL500 helps to maximise product quality and plant capacity.

The CVL500 is part of Rotork’s popular CVA range, which delivers a range of sizes suitable for almost all linear and rotary control valve applications requiring highly accurate positioning. It offers end users high standards in performance, build quality and overall value.

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Dave Godfrey is with Rotork Australia

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