Specifications
15. What is the nozzle
combination?
In practice, the air cap, fluid tip,
needle and baffle are selected as a
unit, since they all work together to
produce the quality of the spray
pattern and finish. These four
items, as a unit, are referred to as
the nozzle combination.
16. What are standard fluid tip
sizes and flow rates?
The standard sizes, corresponding
fluid tip opening dimensions and
flow rates are:
Conventional Air Spray
Table 2
HVLP
Table 3
17. How are fluid tip and needle
sizes identified?
DeVilbiss fluid tips and needles are
identified by the letters stamped on
the tip and the needle.
The identification letters on these
components should match. See
the appropriate DeVilbiss spray gun
catalog for the proper selection of
fluid tip and needle combinations.
18. What fluid tip and needle
combination sizes are most
common?
E, EX, FF and FX are most
generally used. The EX
combination is used for suction
feed, while FF and FW are used for
gravity Feed. For pressure feed the
most common tips are FX, FF
and E.
19. How are nozzle combinations
selected?
Five basic considerations are
involved in selecting the nozzle
com-bination:
• type and viscosity of material
being sprayed
• physical size of object being
finished/fan pattern size
• desired speed/finish quality
• gun model being used
• available air volume (cfm) and
pressure (psi) from compressor
(1) The type and viscosity of the
material being sprayed is the
first factor to consider.
Table 4
NOTE: Viscosity conversion charts
are available to convert one
viscosity cup reading to another
from any material or equipment
supplier.
(2) The physical size of the object
to be painted must also be
considered. As a general rule, use
the largest possible spray pattern
consistent with the object size.
Remember that different air caps
deliver various pattern characteris-
tics. This can reduce both spraying
time and the number of gun
passes.
(3) The next consideration in
evaluating nozzle combinations is
the speed with which the finish will
be applied and the desired level of
quality.
For speed and coverage, choose a
nozzle combination which
produces a pattern as wide as
possible.
When quality is the deciding factor,
choose a nozzle combination
which produces fine atomization
and a smaller pattern size, thereby
giving greater application control.
(4) The model of the gun itself will
limit the selection of nozzle
combination.
For a DeVilbiss suction feed gun,
there are several nozzle types
available which are suitable for
finishing operations. These nozzles
2. Air Atomizing Spray Guns (Cont’d)
7
Tip ID Flow Rate
Pressure Feed Systems
G .028"/.7mm up to 12 oz/min
FX .0425"/1.1mm up to 20 oz/min
FF .055"/1.4mm up to 30 oz/min
E .070"/1.8mm over 30 oz/min
EE .070"/1.8mm porcelain enamel
D .086"/2.2mm heavy body mtls
AC .110"/2.75mm heavy body mtls
Suction Feed Systems
EX .070"/1.8mm up to 12 oz/min
FW .062"/1.6mm up to 10 oz/min
Gravity Feed Systems
FF .055"/1.4mm up to 30 oz/min
FW .062"/1.6mm up to 30 oz/min
Tip ID Flow Rate
Pressure Feed Systems
FX .0425"/1.1mm up to 10 oz/min
FF .055"/1.4mm up to 14 oz/min
E .070"/1.8mm up to 20 oz/min
D .086"/2.2mm over 20 oz/min
Suction Feed Systems
D .086"/2.2mm up to 9 oz/min
DE .070"/1.8mm up to 8 oz/min
Gravity Feed Systems
FF .055"/1.4mm up to 12 oz/min
FW .062"/1.6mm up to 12 oz/min
Rule of thumb
Optimum fluid pressures are 8-20
psi. Pressures greater than this
generally indicate the need for a
larger fluid tip size.
Rule of thumb
The lower the viscosity of the
material, the smaller the I.D. of
the fluid tip.
Material Production Tip
Viscosity Rate Size
#2 Zahn
up to 23 sec Low FX(.042)
23-28 sec Med FF(.055)
28-48 sec High E(.070)
over 48 sec High D(.086)