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|  MIL-S-64052
4.4.1 Hardness test. The spray gun fluid nozzle shall be tested for hardness on
a non-sealing surface. Failure of the nozzle to display a Rockwell C hardness of 48
to 60 shall be cause for rejection (see 3.13.5).
4.4.2 Leak tests. For the following tests, the spray gun shall be connected in
series with an air pressure gage and a leak-free shut-off valve to a source of
compressed air. The air pressure gage shall be located between the shut-off valve
and the spray gun, and the assembly shall be as direct and compact as possible to
minimize the volume of air which can be entrapped between the shut-off valve and the
Spray gun. The pressure gage shall be accurate within one percent of reading over
the range of 75 to 125 psig and readable to the nearest psig. The gage shall be
calibrated, traceable to a National Bureau of Standards. The source of compressed
air shall be capable of providing regulated pressures of from 0 to 100 psig or more
(see 3.12).
4.4.2.1 Cup leak test. With the spray gun in fully operating condition the spray
gun shall be supplied with compressed air at a pressure of 45 to 50 psig. The cup
pressure regulator adjustment(s) and the spiny gun trigger shall then be manipulated
as necessary to verify the ability of the cup pressure regulator to provide and
maintain pressurization of the cup within 5 psig of any chosen point within the full
range sale of the cup air pressure gage. The force required to fully depress
the trigger shall then be measured. The cup pressure shall then be set at 50 psig
and the shut-off valve closed with the spray gun trigger in the normal (valves
closed) position. The cup pressure gage shall then be observed for a period of not
less than two minutes (see 3.13.2). Occurrence of any of the following during the
test shall be cause for rejection:
Visible damage to or deformation of any part of the spray gun.
a.
Failure of the cup pressure regulator to provide and maintain cup pressure
b.
within 5 psig of any nominal point within the stated ranges, both with the
trigger in the normal position and in the fully depressed position.
c.
Air leakage from the cup sufficient to cause a drop in pressure of more
than 2 psig during the two minute period.
d.
Ability to fully depress the trigger with less than four pounds of force,
or inability to fully depress the trigger with seven pounds of force (see
3.13.7).
4.4.2.2 Valve seat leak test. The cup shall be removed for this test. Hoses and
connections from the gun to the cup shall be blocked or capped at the cup end of the
hose or connection. The trigger shall remain in the normal (closed) position
throughout this test. The air pressure to the gun shall be increased to no less
than 100 psig and held at that pressure for no less than two minutes. At the end of
the two minute period, the air supply valve shall be closed. The pressure gage
shall then be observed for a period of not less than one minute. Any due to or
deformation of any part of the spray gun, or any drop in air pressure of more than
10 psig during the one minute period shall be cause for rejection (see 3.12.1).
4.4.2.3 Valve packing leak test. The air and liquid ports in the nozzle and air
cap shall be blocked by fitting the spray gun with a blank nozzle and air cap, or by
other means employing the standard air cap retainer or connection. The cup shall be
removed and the cup connections to the gun body shall be capped or blocked. The
trigger shall be fully depressed throughout this test so that the air and liquid
valves are both fully open. The air pressure in the gun shall then be raised to 100
psig and the shut-off valve then closed to entrap the compressed air in the spray
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