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For more information, contact us at 1-877-844-7226 or info@graco.com. Visit us at www.graco.com
Graco’s Innovations in Safety for Chemical
Transfer
Chemical transfer applications demand maximum performance and superior
chemical containment. ChemSafe pumps feature 100% PTFE and UHMWPE fluid
paths and are chemically safe.You can use these pumps with a variety of materials,
plus they deliver unmatched chemical compatibility with challenging corrosive
acids and destructive slurries. The precision-machined body features a tie-bolt
design that ensures reliable sealing surfaces free of leaking.
WHITE PAPER
AUTHOR:
Michael Sandlin
Product Marketing Manager
Graco Inc.
88 11th Ave NE
Minneapolis, MN 55413
/chemsafe

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Graco’s Innovations in Safety for Chemical
Transfer
Two steps forward, one step back. That’s what it feels like to run an operation with a
leaky pump. Leaky pumps inevitably lead to unscheduled downtime and increased
maintenance needs. This stalls productivity and costs the average company hun-
dreds of thousands of dollars per hour of downtime. Now add hazardous chemicals
into the equation.Aggressive acids and slurries can cause pumps to leak much fast-
er, and they create an unsafe work environment. While these chemicals are neces-
sary for the production of pharmaceuticals, printing inks, steel production, ceramic
finishing, and more, they are also a huge liability. Selecting and maintaining the
proper equipment to control hazardous materials is crucial to the long-term success
of a business, but it isn’t easy. With so many different pump designs on the market,
end-users are having a tough time distinguishing between the pumps that will cost
them and the pumps that will save them.
AODD Chemical Pumps
Air-Operated Double Diaphragm Chemical Pumps (AODD) offer many benefits to
manufacturers who require the use of hazardous materials. While most other pump
designs rely on mechanical seals for chemical containment, mechanical seals are
known to be prone to chemical erosion and leaking. AODD chemical pump designs
eliminate the need for mechanical seals by using bolts to secure the pump togeth-
er and create an effective seal. In addition, the AODD pump’s diaphragms move in
gentle cycles to minimize turbulence and protect the liquid from shearing. In many
instances, these chemicals can be as fragile as they are hazardous, and any mild
turbulence can alter their chemical properties, wasting the material and costing
money. Lastly, because AODD pumps are powered by compressed air rather than
electric motors, they can dry run and deadhead without the risk of burning, seizing,
or harming internal components. The problem with AODD chemical pumps is that
their designs can vary in quality and effectiveness, which means that end-users
must select their pump carefully. The crucial factors of the AODD chemical pump
selection process are chemical containment capabilities, corrosion resistance, and
icing prevention.
Leaky AODD Chemical Pumps
Safety is the primary concern when moving dangerous chemicals. Chemicals must
be properly contained in order to fulfill their intended purpose without harming em-
ployees. This requires a pump with a leak-free design. Unfortunately, even some of

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Graco’s Innovations in Safety for Chemical
Transfer
the best AODD pumps struggle with leaks over the course of the pump’s lifespan.
Although leaking may seem natural or unavoidable, costs of employee injury and
wasted materials are too great to ignore. A few design features stand above the rest
to address certain factors that lead to leaking.
In the case of plastic AODD pumps, leaking is often a result of cold flow and creep,
which are caused by high temperatures, amount of time under load, and level of
torqueing stress. While metal pumps are rarely damaged by loads at low tempera-
tures, plastic pumps can be damaged by continuous loads at fluctuating tempera-
tures, which is termed, “cold flow.” As temperature increases, the effects of cold
flow on a plastic AODD pump escalate. Cold flow causes deformation of the plastic
pump over time, causing its components to release against compression points and
begin to leak. Creep refers to the total deformation of the pump beyond the immedi-
ate strain of loading and can cause significant leakage. PTFE is one pump material
that is most susceptible to leaking caused by cold flow because PTFE tries to escape
the load as it gets warmer. PTFE is one of the most chemically compatible materi-
als for resisting corrosion, which would make it a desirable pump material if not for
its susceptibility to cold flow. The material, UHMWPE, is second to PTFE in terms of
chemical compatibility, but it is similarly susceptible to cold flow leaking, although at
a lower rate. In addition, the violent forces of operation and continuous loading can
eventually loosen the AODD chemical pump’s bolts and create leak paths. End-users
are recommended to re-torque bolts regularly. Some AODD pump designs require
even further leak prevention steps, such as the use of reinforcing metallic plates in
attempt to evenly distribute the load from the housing bolts. While these quick fixes
may work in the short term, constant checkups and reinforcements are far from ideal
when controlling hazardous fluids in a fast-paced work environment.
Solution to Creep and Cold Flow
A proven solution for leak prevention is a machined body reinforced with a dual
force, tie-bolt design. Overall, machined housing components are an essential fea-
ture to provide a precision fit that will distribute the load evenly and greatly reduce
leaking. With this design, components made with PTFE and UHMWPE, which are
highly susceptible to creep and cold flow, are held securely by tie-bolts that are
resistant to the effects of cold flow and violent forces. This allows the pump design
to make use of these chemically compatible materials without allowing leakage due
to cold flow.
Chlorine Dioxide Transfer

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Graco’s Innovations in Safety for Chemical
Transfer
Corrosion Resistance
Pumps that have exposed metal or wet parts composed of metal are highly vulnerable to
corrosion. Therefore, AODD chemical pumps designed with metal free exteriors will be
more durable in corrosive environments. Similarly, interior corrosion can be prevented us-
ing PTFE and UHMWPE fluid paths to ensure chemical compatibility. This means that the
entire fluid path—from entering the inlet, passing the first check ball, leaving the fluid
chamber through the second ball, and finally exiting the outlet of the pump—is either PTFE
or UHMWPE, so there is no need to worry about incompatible chemicals eating away the
pump’s interior.
Air Motor Icing Stalls Production
Because AODD pumps are operated by compressed air, they are subject to rapid changes
in temperature.The air is very hot when it’s compressed and cools rapidly as it expands.Air
motors operate compressed air at about 20 to 180 psi (1.4 to 12.4 bar) and exhaust air at
atmospheric pressure, approximately 14.7 psi (1.0 bar). This is an extremely high percent-
age of pressure decrease occurring in a short timespan. Since the exhaust air will be below
freezing temperatures when it exits, moisture in the air freezes and crystallizes inside the
air valves. This buildup of ice can cause the air valves to stall, creating unplanned down-
time and increased maintenance needs. One possible feature of an AODD pump for icing
resistant air systems includes parallel pilot shifting valves. This stall-free design reduces
icing and maintenance needs while keeping production moving.
Summary
Several visual clues can indicate whether it is time to replace an old or deteriorated pump
with current technology. These include a corroded pump exterior, leaks around the mani-
folds, worn internal fluid bowls, and discoloration on the floor caused by severe leakage.
Premature deterioration can be prevented by carefully selecting the best quality pump for
operational needs.A dual force, tie-bolt design and precision machined components offers
a leak-free precision fit for effective chemical containment and safe operations. Wherever
harmful chemicals are present, business owners must be mindful of the proper safety
precautions and continue to educate themselves on current trends for chemical handling.