• a fluid hose to supply coating to the
Applicator Training
Bulletin
spray gun (if using a pressurized gun);
• an air hose to supply atomizing air to the
spray gun; and
• an air spray paint gun.
The most important element in air spray
application is the person operating the
gun. The operator is responsible for applying the coating, using a technique best
suited to the job, and keeping equipment in
good working order.
Air Compressor
The air compressor needs to supply clean,
dry air of sufficient volume and pressure for
all of the components in the air spray system. Typically, each full-production spray gun
requires 15–20 CFM of compressed air, and
each air-driven agitator requires 10–15 CFM
of compressed air. Air pressure at the air
It is essential to follow proper equipment setup and
maintenance procedures during air spray coating
operations. All photos and figures courtesy of
Finishing Brands, Inc. (DeVilbiss, Ransburg, BGK,
and Binks).
compressor of 90–100 psi is recommended.
Air compressors are usually equipped with an
air receiver tank, drain, and oil separator.
Setting Up, Operating, and
Maintaining Air Spray Equipment
F
Compressed Air Filter
An air filter will be needed between the compressor and the pot, especially on humid
days. It is important to periodically drain
irst, why spray? Use of spray
the proper methods of setting up, operat-
moisture from the air filtration unit. If the
technology to apply your coating
ing, and maintaining air spray equipment,
unit is equipped with an automatic drain,
brings advantages of speed; uni-
specifically conventional and high volume
ensure that a preventative maintenance pro-
formity of application for quality
low pressure (HVLP) technologies. Low vol-
gram is in place.
control and lower coating costs;
ume medium pressure (LVMP) technology is
and reduced labor expenses when com-
also addressed.
pared with using a brush or roller, especially
on irregular surfaces and intricate shapes.
The two most common methods of paint
Air Supply Hose
Check the air hose and fittings from the air
Setting Up Air Spray Operations
compressor to the paint tank or pump to
Figure 1 shows one configuration of an air
make sure they are in good condition and
spray application are air atomized spray and
spray equipment system. Components need-
free of leaks. The inside diameter (ID) of the
airless spray. Air atomized spray uses com-
ed to apply coatings by air spray are:
air hose needed is based on the length of
pressed air to atomize, or transform, a
• an air compressor;
the hose and the number of guns and air
coating into very fine particles or droplets
• a compressed air filter;
agitators used. Typically, for a one-gun set-
as it exits the spray gun. In airless spray, a
• an air supply hose from compressor to
up, a 3⁄8-inch ID air hose up to 50 feet long
pump pressurizes the coating at a high level
paint tank or pump;
is sufficient.
and forces it through a small elliptical ori-
• air regulators with gauges;
fice, or opening, as it exits the spray gun,
• a container for the coating (pressure-feed
Coating Containers
causing the paint to atomize hydraulically.
tank or pot, gravity/siphon cup, or paint pump);
Siphon or gravity gun setups use a cup
• a paint agitator, if necessary;
attached to the gun to deliver the coating.
This Applicator Training Bulletin describes
16 JPCL June 2014 / paintsquare.com
For bigger jobs that require more paint,
using a pressure-feed paint tank, also called
a pressure pot, is an economical method of
supplying coating to the spray gun. Flow is
positive and uniform as paint is forced out of
Editor’s Note: This Applicator Training Bulletin is an update of an original article
on conventional air equipment, written by Herb Chilman and Jerry Gonser of
Spray-Quip, Inc. The article originally appeared in the June 1989 issue of the
JPCL and was updated for this issue by Steve Stalker for Finishing Brands, Inc.
(DeVilbiss, Ransburg, BGK, and Binks).
the tank by applying compressed air to the
coating. Increasing or reducing the tank air
to the gun. As with a tank, the paint pres-
The standard paint hose liner is nylon; the
pressure increases or decreases the flow of
sure is controlled by the pump air regulator.
standard air hose liner is a synthetic rubber.
paint from the tank. Maximum tank working
The paint pump has several advantages
pressures can vary from 60–110 psi. Read
over a pressure tank. The pump normally
Spray Gun
the rating on a tank before using it.
draws the paint from the original paint con-
The operation of an air atomized spray gun
tainer, can operate at higher pressures, is
involves atomizing a stream of fluid with a
able, clamp-on lid that has a sealing gasket.
lighter in weight, and is easier to clean than
stream of compressed air. The air-to-paint
The lid forms an airtight seal when securely
the tank. However, a pump is more complex
balance is controlled by the viscosity (thin-
clamped to the tank shell. Sizes of tanks vary
than a tank and does not deliver paint as
ness or thickness) of the paint and the air
from two quarts to twenty gallons; two and
uniformly as a tank.
pressure put on the paint in relation to the
The tank is a metal container with a remov-
volume and pressure of atomizing air. The
five gallon tanks are the most common.
Hoses
spray gun has a fan control knob for adjust-
tube and an outlet manifold (or a bottom out-
The fluid and air hoses that supply paint and
ing fan width within the limits of the air cap.
let used with heavy or highly-filled paints), a
atomizing air from the tank or pump to the
Figure 2 shows the various parts of a typi-
fluid outlet valve, a safety relief valve on the
spray gun should be serviceable, clean, and
cal air spray gun.
tank lid, a tank air vent valve, and tank air
of the proper size and inside wall construc-
pressure regulator(s) with gauge(s). Consider
tion. The normal sizes are ⁄16-inch ID for
sure (LVMP) guns have been developed. LVMP
accessories such as an air-driven paint agita-
paint and 3⁄8-inch ID for air. When paint is vis-
has the atomization benefits of conventional
tor to easily mix or keep paint in suspension.
cous (thick, for example), highly filled, or
air spray and the efficiency of HVLP. If you are
Tank liners also make cleanup easier.
pressure-sensitive, or when the hose run is
not required by a regulatory agency to use
over 50 feet long, a ⁄8-inch ID paint hose
HVLP, LVMP is highly recommended.
Other features of the tank are a fluid-riser
A paint pump can be used in place of a
5
3
pressure pot. The paint pump pressurizes
may be recommended. Follow the paint man-
paint and forces it from a source container
ufacturer’s instructions on proper hose size.
In recent years, low volume medium pres-
If you are not using a spray gun designed
in the last ten years, the air reduction savings for modern spray guns will typically be
greater than the cost of purchasing new
spray guns.
Start-Up Procedure and
Operation
Begin setting up the equipment by connecting the air hose and the paint hose to the
spray gun and pressure tank. Then, turn the
tank and gun air regulator handles counterclockwise so there will be zero pressure
when the main air supply is connected to
the tank. Next, pull the ring on the safety
pressure relief valve on the tank, to make
Fig. 1: Typical air spray pressurized system (single regulated)
configuration, using a pressurefeed paint tank
Fig. 2: Various parts
of a typical spray gun
sure it operates freely. Close the main air
supply valve on the tank, and tighten the
tank lid clamps. You are now ready to connect the main air supply hose to the tank.
paintsquare.com / JPCL June 2014 17
Applicator Training Bulletin
Once the main air supply hose is securely
connected to the pressure tank, slowly
bubbles are pushed out and a solid
trigger open until the paint begins to run.
stream is achieved.
There should be even distribution of the paint
across the full width of the pattern. The fan
open the main air supply valve on the tank.
Look at the regulator air gauge. If it shows
Setting Pressures on a
control knob is normally adjusted fully
pressure, turn the handle counter-clockwise
Pressurized System
counter-clockwise. If the distribution is not
to reduce pressures to zero.
• Step 1: Using control knob on fluid regu-
even but is symmetrical, a different fluid tip
lator, set fluid pressure at 5–10 psi.
may help. If the pattern is not symmetrical,
check for proper operation of the tank and
• Step 2: Using control knob on air regulator,
there is a problem with either the air cap or
fittings. Adjust the tank regulator to 10 psi
set air atomization pressure at 30–35 psi.
the fluid tip/needle that must be corrected.
to pressurize the tank. Look and listen for
• Step 3: Spray a test pattern (fast pass)
• Step 2: If the pattern produced by the
leaks around the tank lid and fittings on the
on a piece of paper, cardboard, or wood.
above test appears normal, rotate the air cap
lid, as well as leaks at paint hose connec-
From that test pattern, determine if the par-
back to a normal spraying position and begin
tions to the tank and the gun.
ticle size is small enough and uniform
spraying. (Check the service literature for typi-
throughout the pattern to achieve the
cal pattern size for the cap you are using).
air, adjust the fluid adjustment screw until
required finish quality. If particle size is too
• Step 3: With the fluid adjusting screw
the trigger can be fully pulled toward the
large or is giving too much texture in the fin-
properly set, and the air pressure set at
rear of the gun. While holding the trigger to
ish, turn the atomization pressure up in 3–5
approximately 30 psi, make a few test
its maximum travel, turn the fluid adjust-
psi increments until particle size and texture
passes with the gun on some clean paper. If
ment knob clockwise until it stops.
Prior to loading the paint into the tank,
Prior to connecting the gun to fluid and
of finish is acceptable.
there are variations in particle size specks
Adjust the air regulator to the spray gun
• Step 4: Spray a part with these settings.
and/or large globs, the paint is not atomiz-
to 20 psi. Check for air leaks at hose and
If you are not able to keep up with the pro-
ing properly.
gun connections.
duction rate required or if the finish is
• Step 4: If the paint is not atomizing proper-
starved for material, increase the fluid pres-
ly, increase the air pressure slightly and make
etc.) to the correct spraying viscosity sug-
sure in 2–4 psi increments using the fluid
another test pass. Continue this sequence
gested by the manufacturer. Remember that
regulator control knob (or use a larger
until the paint particle size is uniform.
spraying viscosity can vary considerably
capacity fluid tip) until required wet cover-
• Step 5: If the pattern seems starved for
with the temperature of the paint.
age is accomplished.
material, and the fluid adjusting screw is set
• Step 5: Remember, as you turn up the
to maximum travel, the atomization air pres-
ture will help ensure the consistent atomiza-
fluid pressure, the particle size will increase.
sure may be too high, or the material may
tion of the coating. Load the prepared paint
Once the coverage required is obtained, it
be too heavy. Recheck the viscosity or
into the pressure tank. Clamp the lid tight,
will be necessary to re-adjust the atomization
reduce the air pressure.
tum the air regulator handles counter-clock-
pressure in 3–5 psi increments, as explained
• Step 6: If the material is spraying too
wise so that zero pressure shows when the
in Step 3, to insure required particle size and
heavily and sagging, reduce the material
main air supply is on, and then tum on the
finish texture is achieved.
flow by turning the fluid adjusting screw
main air supply.
• Step 6: If using HVLP, use an “Air Cap
(clockwise).
Prepare the coating (by mixing, thinning,
Maintaining a consistent coating tempera-
Hold the spray gun and point it toward
Test Kit” to verify that the air cap pressure
The proper spray technique is to hold the
a grounded waste container. Trigger the
is not above 10 psi, if required by a regula-
gun perpendicular to the surface to be
spray gun fully. No air or paint should be
tory agency.
sprayed at a distance of approximately 12
flowing from the gun. While holding the
Proper setup utilizes no more fluid and
gun with the trigger fully depressed, you
air pressure than is needed to produce the
should then fill the paint hose with paint
required quality and a flow rate that will
by increasing the tank pressure regulator
meet production requirements.
to 5 psi for thin materials or 10 psi for
inches. Swinging the gun in an arc will greatly
reduce the quality of the painted surface.
Maintenance
Following a few maintenance procedures
thick materials. Remember, the hose is
Setting Pressures on a Gravity or
can help ensure the quality of your work.
full of air, so keep the gun open to
Suction Feed System
• During start-up and operation, periodically
remove the air. Let the stream of paint
• Step 1: Spray a horizontal test pattern (air
check air gauges and pressure relief valves.
continue to flow from the gun until all air
cap horns in a vertical position). Hold the
• Drain air filters periodically. Lubricate and
18 JPCL June 2014 / paintsquare.com
adjust the spray gun paint needle packing
To clean the equipment, first pour a small
remove and roll up the air supply hose. All
daily.
amount of cleanup solvent into the tank,
components should then be stored in a
• Because the gun air cap and fluid nozzle
and wash the sides of the tank and the
secure area.
determine the quality of your spray pattern,
paint riser tube, agitator, etc. Then, install
you should clean the air cap and fluid noz-
the tank lid, pressurize the tank, shut off
Conclusion
zle as needed, following the manufacturer’s
the atomizing air to the gun, remove the air
The success of any spray job depends on
directions.
cap, and trigger the gun. Be sure to catch
the skill of the operator and on his or her
• Use only the proper wrenches and clean-
the cleanup solvent in a grounded waste
understanding of the equipment with which
ing brushes. Do not use items such as
container. Repeat the operation until the
he or she is working. To ensure a success-
channel locks or steel brushes, which will
tank, hose, and gun are clean. During the
ful spray application, remember these key
damage the cap or nozzle.
final operation, blow the system dry using
points.
compressed air. Next, remove the spray
• Follow paint and equipment manufactur-
Cleanup
gun, wipe it clean, and lubricate it. Do not
ers’ recommendations.
To prepare for the cleanup procedure, turn
put the gun in a bucket of solvent to clean
• Use properly sized equipment.
off the tank air pressure, vent the tank,
it; the solvent will attack the packings, caus-
• Follow the spraying, maintenance,
loosen the air cap ring of the spray gun by
ing the gun to leak. Remove the air and fluid
cleanup, and safety procedures described
turning it three times, hold a cloth over the
hoses and roll them up. Remove the tank
above.
air cap, and pull the trigger to force paint
lid, wipe the tank and the lid clean, and
• Use common sense.
back into the tank. Remove the tank lid
reassemble them. Once these parts are
from the tank, and pour paint from the tank
reassembled, tum off the air at the com-
back into the original container.
pressor, relieve the air pressure, and
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