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|  MIL-S-64052
Following this test, the gun shall be cleaned in accordance with the manufacturer's
instruction (see 3.7.2). Failure of the spray gun to produce a finish which is
visibly as smooth or smoother over the entire surface than the sample provided with
this specification (see Figure 3) shall be cause for rejection.
4.4.4 Valve endurance test. The spray gun, without paint, shall be attached to a
source of regulated compressed air and adjusted for operation in accordance with the
air flow and air pressure requirements of 3.8. The spray gun trigger shall then be
fully depressed and released for a total of 10,000 strokes (see 3.10). Any screws,
connectors, or joints that vibrate loose during this test shall be cause for
rejection. Following this test, the spray gun shall be retested in accordance with
4.4.2 through 4.4.2.3. Failure of the spray gun to retain pressure after 10,000
actuations of the trigger shall be cause for rejection.
4.4.5 Operational endurance test. The spray gun shall be filled with pigmented
alkyd enamel, black to charcoal in color and thinned to a viscosity of 25 to 30
seconds using a Number 4 Ford Cup at 77 plus/minus 5 degrees F., and adjusted for
operation within the air pressure and air flow requirements of Table II. The spray
gun shall then be operated through 50 spraying cycles as described in 3.11,
refilling the cup with alkyd enamel as needed. At the completion of the fifty
cycles, and without cleaning the spray gun, the spray gun shall be retested in
accordance with 4.4.3 through 4.4.3.2. Failure of the spray gun to meet the
performance requirements of 3.7.2 and 3.7.3 after 50 spraying cycles shall cause
for rejection.
4.4.6 Durability test. The spray gun shall be emptied of paint, the paint cup
removed, and the spray gun nozzle and air connection capped or otherwise protected.
The spray gun shall then be subjected to six separate free drops through a distance
of at least six feet to a bare concrete floor (see 3.9). Any pbysical damage to the
spray gun which precludes operation in accordance with 3.7.2 or 3.7.3, or any
separation of components, shall be cause for rejection. The spray gun shall then be
retested in accordance with 4.4.2 through 4.4.3.2. Occurrence of any of the
following as a result of the six drops shall be cause for rejection:
a.
Air leakage from the spray gun sufficient to permit a drop in pressure of
more than 5 psig during any two minute period.
b.
Failure of the spray gun to meet the performance requirements of 3.7.2 and
3.7.3.
c.
Inability to manually reassemble the cup to the spray gun.
Failure of the spray gun to pass the test in 4.4.2.4.
d.
4.4.7
internal surface roughness test. The spray gun cup shall be cut in
half to expose the interior surface of the cup, and the cup interior shall be
cleaned of all paint residue. Determine the surface finish of the cup interior with
.
a profilometer or surface analyzer. The cup interior surface shall be no rougher
than 63 microinch arithmetic average (see 3.13.2). Failure to meet this requirement
shall be cause for rejection.
4.4.8 Maintainability test. The gun shall be completely disassembled and cleaned
in accordance with the manufacturer's instructions and all O-rings, gaskets,
washers, packings and other seals replaced. The spray gun cup and any parts of the
spray gun damaged during the durability test (see 4.4.6) shall also be replaced.
The spray gun shall then be reassembled and tested in accordance with 4.4.2 through
4.4.2.3, and 4.4.5. Occurrence of any of the following shall be cause for
rejection:
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