Water & Wastewater Asia May/June 2019

INSIGHT | 37
In effect, the hydraulic control system
prevented a pipe break from occurring.
In fact, the electronic control system is
capable of multiple functions such as flow
control and pressure reducing. In this
instance, the hydraulic pilot can be used as
“backup insurance” where the pilot control
adjustment is set to not interfere with normal
electronic multi-function control. Normal
operation consists of electronic flow control
and electronic pressure-reducing control,
and seamlessly transfers between functions
with specialised software. In the event of
power failure, or solenoid malfunction,
the hydraulic pilot will take over and limit
downstream pressure, preventing pipe
breakage.
Electronic Flow Control Valve
with Hydraulic Protection of
Downstream Piping
Up to four modulating electronic functions are
possible, including flow, pressure sustaining,
pressure reducing, and level control. For
example, reservoir level control can include
flow control and pressure sustaining control.
Conversions of existing Altitude Control
valves often include the hydraulic Altitude
Control pilot for backup control to prevent
overflowing of a tank. Often there is a long
pipeline upstream of these valves which
is susceptible to surging during valve
closure. A hydraulic “Surge Relief
Override” pilot control prevents this
in case of faster-than-normal valve
closure.
At one recent project
start-up, an electronic flow
control valve barely cracked
open, and was unable to
open further. A check of the
downstream pressure gauge
revealed that downstream
pressure had already reached
the setting of the pressure limiting
pilot control. It transpired that the water
district had forgotten that an isolation valve
had been closed some distance downstream.
Hybrid Electronic Multi-Function Valve Conversion
with Altitude and Relief Override Pilots
Motorised valves are typically
used to control a single
function and offer limited
or no capabilities to provide
multiple electronic functions
with hydraulic backup
functions. Replacing these
valves with hybrid electronic
and hydraulic control can certainly
reduce the number of valves required
and can offer very useful “insurance”
against power failures and costly line
breaks WWA
Water & Wastewater Asia • May / June 2019