AMIAD - AUSTRALIA & ASIA PACIFIC NEWS - VOLUME 9 - APRIL 2017 MARCH 2014 Vol.3 | Page 10

THE D-025MI AIR VALVE MAKES ITS MARK IN
DEWATERING IN THE GOLDFIELDS AND PILBARA
|Jamie Pickford/ WA State Manager, Business Development Manager- Mining, Oil & Gas
For the maintenance crews of endless kilometres of
pipelines stretching across Australia’s mining fields, air

valves that dot the pipelines can be passed by without a
second glance. It’s not until the air valve is seen releasing
water that it grabs the passer-by’s attention.
Far from the mine’s maintenance shed, the isolation valve
located under the air valve is closed, the leak stops and the
crewman continues down the pipeline. This can continue
over many months until a large proportion of the air valves
are now isolated unable to carry out the very duty they were
installed for.
It’s a common thought that air valves are only required for
commissioning, and once the dewatering line has filled with
water by displacing the air through the valves, the air valves
duties are complete. It is this thought that allows the
maintenance crew to continue to isolate the air valves,
totally unaware that they a contributing to lowering the
efficiency of the dewatering and transfer of water
throughout the pipework system on their mine site.
Air is always present in water and it separates from the fluid
due to various causes including normal pressure reduction
along the pipeline due to friction. Once the air separates it
gathers in high points along various sections of the pipeline.
In a carefully designed pipeline system, these points
attracting the air have an air valve that releases the air. But
what happens if it’s been isolated by a maintenance
crewman? The air that is entrapped along the pipelines acts
as a restriction to the fluid being pumped through the
network. It’s as if someone had installed a series of isolating
knife gate or butterfly valves and partially closed them
down along the pipeline. The pipeline pumping efficiency
gradually deteriorates as more air accumulates, and the
diesel costs to operate the system begin to increase. But is
wasted energy the only risk? In an example on the Western
Australian Goldfields, a pipeline in a dewatering system ran
for some years, with no one questioning the continual climb
in diesel consumption. Then for the first time, the diesel
system was not refuelled in time and the engine suddenly
cut out. The pump was located in a pit nine kilometres from
the discharge point of the pipeline and the elevation to this
point was several hundred metres. The resulting backwards
flow and water hammer, was amplified many times greater
than what would have been normally experienced. This was
caused by the entrapped air being pressurised by the
returning water column and also by the fact that no air could
re-enter the pipe through operating air valves to break the
vacuum caused and dampen the violent action of hammer.
The pump was blown off its cast feet and the pipeline torn
apart in front of the pump.

PAGE 10 - March 2014

Air valve model: D-025 MI

Air valve model: D-025 MI, ST/ST