Water & Wastewater Asia January/February 2022

IN THE FIELD
require it during the manufacturing
process must be certified for use
according to the ATEX Category
II guideline that governs use in
atmospheres that feature gases,
vapours or air and dust mixtures that
could explode.
THE AODD SOLUTION
For those looking to optimise
their filter-press operations, no
matter the industry or product,
AODD pumps offer a number of
operational advantages, including
dry-run capability, compatibility with
liquids of varying viscosities and
pressures, good controllability, and
an inherently leak-free design that
features no gaskets or seals. AODD
pumps also have no drives, rotating
parts and rotary shaft seals.
Other PD pump technologies have
been used in conjunction with
filter presses, but each of the more
popular ones have shortcomings
that can prevent them from being the
best choice:
• Piston diaphragm: Can be
prohibitively expensive to
operate since they require both
electricity and air to function.
• Progressive cavity: Cannot dry
run or handle large abrasives,
and also require electricity to
operate.
• Hose piston: Liquid transfer
occurs through the use of
hoses, which wear out faster
than diaphragms and, at
some point, will be at risk of a
catastrophic failure.
To this end, AODD pumps are able
to outperform their PD cousins in
filter-press applications because
of their simple design and method
of operation. A pair of diaphragms
that are connected via a diaphragm
rod work in unison to move the
liquid through the pump. While one
side of the pump is in suction mode,
the other is in discharge mode. As a
diaphragm moves inwards, it creates
suction. This suction causes the balls
that are located on the check valves
to move towards each other. As this
happens, the ball on the top closes
the valve while the ball on the bottom
moves away from the valve, opening a
path that allows the liquid to enter the
pumping chamber.
As the diaphragm moves outwards,
the discharge motion causes the
balls to move away from each other.
As this happens, the top valve opens
and the bottom valve closes. This
allows liquid to exit the chambers
and discharge through the top port.
This process constantly alternates
between the two chambers to create
a continuous cycle. The pump
diaphragms are driven by pressurised
air that is directed left and right by the
movement of the main air valve.
The result is a pumping process that
remains volumetrically consistent at
flow rates of 200gpm or higher, even
with varying liquid viscosities and
transfer pressures. Start-up is also as
simple as attaching a compressedair
hose to the pump’s air distribution
system (ADS) and turning it on. AODD
All-Flo maple syrup
pumps also require a smaller footprint
than piston diaphragm or progressive
cavity pumps, which allow them to be
used in tighter operating areas.
Many manufacturers of AODD pumps
are now also producing hygienic and
sanitary models that can be used
in the production of consumable
products, or in operating atmospheres
that require a pump with an ATEX
rating. This further expands the
operational range for AODD pumps
that can be used in conjunction with
filter presses.
CONCLUSION
The filter press has been proven
to perform reliably in a number of
industrial applications that require
the separation of solids and liquids,
but its application range, it has been
found, does not end there. The
producers of consumer goods, some
of which are manufactured in extreme
atmospheres, are finding that filter
presses can be indispensable parts
of their manufacturing operations, but
only if partnered with the proper pump
technology. More and more, the best
technology for use with filter presses
is proving to be the AODD pump, the
operational characteristics of which
can help optimise operations in a
number of critical industries.
36 WATER & WASTEWATER ASIA | JANUARY/FEBRUARY 2022