Assuring good results with plural-component spray.pdf

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Basic
Training
Assuring Good Results
with Plural-Component Spray
By Caleb Meacham, Solutions Consultant-WIWA LP
M
equipment.
ost plural-component spray op-
erators are familiar with using
and maintaining positive dis-
placement pumps. A positive
Building a Better Mousetrap
In an effort to promote what some original
equipment manufacturers view as industry
progress and 21
st
-century thinking, spray
equipment manufacturers have enlisted the
services of their engineering departments
to come up with new ways of designing
protective coating application equipment.
These ideas include, but are not limited to,
more precise analytics such as measuring
the gallons per minute (GPMs) dispensed,
temperature deviations and pressure imbal-
ances. For the contracting companies that
Workers applying plural-component spray
coating to pipe exterior.
Photos courtesy of WIWA LP
displacement, or fixed ratio pump, traps a
fixed amount of fluid inside the pump body
and discharges it down a high-pressure
paint hose. This is a reciprocating style of
positive displacement and is used in the ma-
jority of two-component (2K) airless spray
Electronic variable ratio (EVR) pumps
are a more advanced technology but they
require more operational and maintenance
knowledge. This article will provide informa-
tion about eliminating some potential prob-
lems when using EVR pumps.
employ personnel with an understanding of
electronic dosing and metering these ideas
certainly have a home within the industry.
One might go as far as to say that in the
paintsquare.com / JPCL April 2015 23
Basic Training
Plural-component shop application.
future, the directors and general managers
who are responsible for hiring personnel
into their organizations may use this as a
measuring stick to decide who is consid-
ered for a position and who isn’t. But at
this point in time, suffice it to say that these
applicators are, respectfully, few and far
between.
What the original equipment manufactur-
ers fail to realize however, is that applica-
tors have one primary goal: to transfer the
coating from its storage container into the
spray system and then onto the surface,
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24 JPCL April 2015 / paintsquare.com
the appropriate temperature) of the coating
before it’s transferred to the mix manifold,
whether it’s mixed locally at the pump or
remotely at the end of a hose bundle.
not been heated to the optimal tempera-
ture (i.e., the temperature specified in the
product data sheet) pumps will be working
much harder to move the material out to
the mix manifold and the operator will need
to turn up the pressure at the air mainte-
nance unit in order to get the two com-
ponents to atomize properly at the spray
Hot & Cold
Regardless of pump type, when material
is introduced into the fluid section that has
ew
N
Coating applied to secondary containment
and run-off.
Coating Thickness Gages
as quickly and as efficiently as possible.
When an applicator has spent weeks, and
in some cases months, familiarizing him or
herself with the equipment that they have
at their disposal and are then introduced
to a different unit that calculates every
aspect of the application right down to the
hose sizes, it can be very intimidating and
the results counterproductive.
There may come a time when the
majority of protective coating applicators
who apply coatings with plural-component
spray, will be using more of the EVR-style
equipment that relies on dosing and meter-
ing assemblies to determine and maintain
mix ratios, but we are not there yet.
n
n
n
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Out There in the Field
Having been a field service technician
myself, I understand the frustration that
can come from premature equipment
failure and lost production. Negligence on
the part of the pump operator can not only
cause a slowdown in production but can
also cost the owner of the equipment a
lot of money to repair. Regardless of the
system being used, there are several tech-
niques that can, and should, be implement-
ed to ensure that the equipment continues
to perform at its maximum capability.
The first is that applicators must direct
attention to the conditioning (bringing to
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A free web-based application
offering secure centralized
management of thickness readings
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+ 1 (315) 393-4450 • techsale@defelsko.com
paintsquare.com / JPCL April 2015 25
Basic Training
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26 JPCL April 2015 / paintsquare.com
These heaters are a must when
applying any 100%-solids material. If an
Protective coating being applied to control
box panels.
temperature decrease that takes place
when the material travels from the pump
to the mix manifold, especially when the
hoses are resting on a cold concrete floor,
can add up to 10 degrees, not to mention
temperature loss due to ambient condi-
tions and the temperature of the material
in the supply containers. To combat this
applicator is running a hose bundle from
the pump to a remote mix manifold, simply
insulating the hoses without running either
hot-water-jacketed hoses or an electrical
heat trace ribbon inside the bundle will be
gun. This practice can cause excessive
wear on the packings which will ultimately
cause them to wear out faster, requiring
replacement.
On a fixed ratio system, improperly heat-
ed material can put the main fluid pumps
at risk of cavitation and premature packing
degradation. Improperly heated material
will hinder the dosing/metering valve’s
ability to perform correctly.
With an electronic variable ratio (EVR)
system, improperly heated material will
hinder the dosing/metering valve’s ability
to perform correctly. Heat becomes a ma-
jor factor in this situation due to the much
smaller fluid passages inside the dosing/
metering valve housing. If cold material
is forced into these chambers not only
will the integrity of the coating come into
question but if the system is functioning
correctly it will continuously shut down to
prevent an off-ratio mix, costing the owner
time, production, and in many cases, the
added wear can result in preventable repair
costs.
Whether the system is being fed by
transfer pumps pulling material of out
55- gallon drums or by feed hoppers
mounted on the cart of the unit, proper
conditioning is paramount and must never
be rushed. In the same vein, additional
heating components such as drum band
heaters, heat blankets and hose bundle
heat can be just as important if high levels
of production are to be achieved. Most
plural-component systems come equipped
with inline paint heaters to assist in bring-
ing temperatures up at the pump before
the operator throws the switch into spray
mode.
detrimental to successful application. The
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paintsquare.com / JPCL April 2015 27

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