TM 43-0139
CHAPTER 5
APPLICATION TECHNIQUES AND EQUIPMENT
Section I. SPRAY GUNS AND PRESSURE CANS
WARNING
Before beginning any painting-related activity, read Chapter 1, Section II, Safety Summary.
5-1. SPRAY GUN APPLICATION
a.
Use. Spray gun equipment can be used for any type of finish and on any surface. It does not replace the brush
for certain operations, yet there are definite types of work it can do more easily and better than the brush. The spray gun
is obviously a tremendous time-saver and its use is recommended when a large volume of work is encountered. The
spray gun is particularly adaptable to touchup and maintenance work when the ability to blend old and new surfaces is
important. Spray application of any finish type requires respiratory equipment.
b.
Training. The proper operation of spray guns and auxiliary equipment is not difficult to learn, but the necessity
exists for training operators. Only through such training can the full flexibility and operation of spray guns be realized.
5-2. SELECTION OF SPRAY GUNS
a.
Definition. A paint spray gun (see figure 5-1) is a mechanical means of bringing compressed air and paint
together, atomizing or breaking up the paint stream into a spray, and ejecting it for the purpose of applying a coating.
b.
Types. There are two types of spray guns: attached containers and separate containers. These types can be
further subdivided into bleeder and non bleeder, external and internal mix, and suction and pressure feed types. The
commercially available pressure cans belong to the attached container type. They have a limited use for touchup where
compressed air is inaccessible to the job. Airless, portable spray equipment that requires an electric connection also
belongs to this type.
(1)
Bleeder and nonbleeder guns.
(a)
A bleeder-type gun is characterized by an intentional continuous leakage of air from some part of the
gun. This prevents building up air pressure within the hose and permits its use with small compressing systems that are
not equipped with an automatic pressure-controlling device. The trigger in a bleeder-type gun controls only the flow of
fluid.
(b)
A nonbleeder-type gun is one in which the trigger controls the passage of both air and fluid. Some
type of pressure-controlling device must be used with it.
(2)
External and Internal Mix.
(a)
An external-mix gun is one which mixes air and fluid outside the air cap.
(b)
An internal-mix gun mixes air and fluid within the air cap.
NOTE
The term internal mix applies to the air cap alone.
(3)
Suction and Pressure Feed.
(a)
A suction-feed gun is designed to feed the fluid into the air stream through a vacuum created by
raising the fluid tip above the air cap. Generally, guns of this type are used with quart-size or smaller containers.
5-1
