Step 7.
Screw purging wrench and adapter assembly into gas inlet (needle valve) driver's
viewer tightly; then using the large knob on the purging wrench and adapter
assembly, loosen the gas inlet needle valve one-half turn.
Step 8.
Purge driver's viewer by pumping vacuum handle until purge device gauge
indicates greater than 20 inches of Hg.
Step 9.
Position purge device LEAK TEST/PURGE switch (10) to LEAK TEST and
observe that the purge device gauge (9) indicates a steady vacuum of 20 inches of
Hg or higher. If unable to observe a steady vacuum or reading, a leak is present.
Stop purge procedure and seal night vision device. If purge device gauge (9)
indicates a steady vacuum, position purge device LEAK TEST/PURGE switch
(10) to PURGE.
Step 10.
Set purge device PUMP/NITROGEN switch to NITROGEN and observe that the
purge device gauge indicates 3 1 PSI.
Step 11.
Position purge device LEAK TEST/PURGE switch (10) to LEAK TEST and
observe that the purge device gauge (9) indicates a steady reading of 3 1 PSI. If
unable to observe a steady reading of 3 1 PSI, a leak is present. Stop purge
procedure and seal night vision device leak(s). If purge device gauge (9) indicates
a steady pressure, position purge device LEAK TEST/PURGE switch (10) to
PURGE.
Step 12.
Repeat steps 8 through 11 three additional times.
Step 13.
Press in large knob on the purging wrench and adapter assembly until it engages
gas inlet valve on driver's viewer and then rotate it clockwise until valve is closed.
Step 14.
Set purge device PUMP/NITROGEN switch to PUMP, and LEAK TEST/PURGE
switch to PURGE.
Step 15.
Unscrew purging wrench and adapter assembly from driver's night vision viewer
gas inlet valve.
Step 16.
Screw purging wrench and adapter assembly into gas inlet (needle valve)
eyepiece housing assembly; then, using the large knob on the purging wrench and
adapter assembly, loosen the gas inlet needle one-half turn.
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