Electricity + Control July 2019

CONTROL VALVES + ACTUATORS

Water loss savings – a new approach Simplified control valves to reduce water losses

Peter Telle, Ultra Control Valves

The valves traditionally used for reducing pressures in water networks are pilot operated pressure reducing valves. Most network piping systems have leaks and, by reducing pressures in a network, losses can be reduced. Engineers realised some 20 years ago that if pressure is reduced to an absolute minimum during low demand times, huge savings on water losses could be achieved.

Ratio pressure reducing valves are very simple and made to meet African operating conditions. Take Note!

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Smart PRVs This resulted in the development of battery- driven electronic devices which could change the setting on pilot operated pressure reducing valves (POPRVs) at different times of the day. This strategy proved to be the quickest and easiest way to reduce ‘unaccounted for water losses’ substantially and led to a number of control valve companies developing electronic controllers to convert pressure reducing valves (PRVs) into ‘smart PRVs’. However, the strategy also presents some problems. It is: - Costly – upwards of R50 000 additional to valve cost

- Complicated – operators do not always understand how smart PRVs work - Maintenance intensive – when the valves stop working some operators disconnect the electronics. In addition, control valves often have to operate beyond their design parameters and, with smart PRVs preset to control pressures in the system, this can result in cavitation damage and Instability. Installers of smart PRVs naturally focus on the successes of installations and not the problems and losses, which are as important to note.

So what is the problem for control valves? 1) Cavitation – the Achilles heel of control valves.

Pressure reducing valves in a water network can reduce water losses.

Pilot operated pressure reducing valves with electronic ‘smart’ controllers.

26 Electricity + Control

JULY 2019