Chemical Engineering October 2011 - 60

Feature Report
" conceived out of necessity, born in
the arms of innovation, and inspired
by sheer will and determination, "
operates by displacing fluid from
one of two liquid chambers upon
each stroke completion through the
action of an air valve and a pair of
diaphragms that are connected by a
common shaft [7].
This simple design, where the diaphragms
act as a separation membrane
between the compressed air
supply and the liquid, has stood the
test of time. Evidence of this is borne
out everyday at CPI facilities around
the globe where AODD pumps -
whether metal or plastic, ductile iron
or stainless steel, clamped or bolted
- play a critical role in ensuring
that product transfer of thin liquids,
corrosives, abrasives, particle-laden
slurries and more continues apace in
a cost-effective, energy-sensitive, environmentally
friendly manner.
Like all other types of pumping
systems, no matter their method
of operation, AODD pumps operate
at their best efficiency when maintained
properly, either through preventive
or protective maintenance.
Thankfully for the operators of CPI
facilities, the AODD pump's design
means that maintenance is easily
and efficiently performed.
A preventive-maintenance schedule
should be set up for the following
AODD pump parts to ensure that
the pump is serviced prior to pump
wear [8]:
* Diaphragms
* Valve seats
* Valve balls
* O-rings
When performing routine AODD-pump
maintenance checks, there are three
main areas that demand attention:
Air valve piston/spool and casing
- Ensure that the piston/spool can
move freely and remove any debris.
Diaphragms - Make sure there is
no swelling, cracking or other damage
to the diaphragm surface.
Balls/seats/O-rings - Make sure
that no swelling, cracking or other
damage is apparent, and lubricate
the shaft, if needed.
Another top-of-mind maintenance
concern is seal replacement since
proper seal installation is critical to
pump performance. Care must be
taken to ensure that seals are placed
in the proper grooves and not damaged
during installation. Incorrect
seal location will render the pump
inoperable, while damaged seals may
cause decreased performance and
shorter seal life.
Troubleshooting
Due to the design of AODD pumps,
there are only a few rare complications
that may surface during their
operation. Fixing these problems
can be a simple process in many
cases. Below you will find a list of
potential problems and solutions
that pump users might find in CPI
operations [7]:
Pump will not run or runs slowly
- Solutions: Check for obstructions
in the air passageways or objects that
can obstruct the movement of internal
parts.
Pump runs but little or no product
flows - Solutions: Check for pump
cavitation, slow down pump speed
to allow material to enter pumping
chambers, then increase speed accordingly.
Check for sticking ball check
valves and, if necessary, replace check
valves with proper elastomers. Check
to make sure all suction connections
are air tight.
Air bubbles in pump discharge
- Solutions: Check for ruptured
diaphragm. Check tightness of
clamp bands, especially at the intake
manifold.
Product comes out air exhaust
- Solutions: Check for ruptured diaphragm.
Check tightness of large
clamp bands. Check tightness of piston
plates to shaft, if applicable.
Pump rattles - Solutions: Create
false head or suction lift.
Over the years, the AODD pump
technology has been modified to fit
specific pumping applications. One
of the modifications that has benCircle
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Chemical Engineering October 2011

Table of Contents for the Digital Edition of Chemical Engineering October 2011
