Set regulator valve handle (1) for zero by rotating control (counterclockwise) until
there is no spring pressure on control.
Open nitrogen tank valve (5). The high pressure gauge (4) will indicate tank
pressure. If pressure is below 50 pounds, replace tank.
Set purge device (8) PUMP/NITROGEN switch (11) to PUMP and LEAK
TEST/PURGE (10) switch to PURGE.
Slowly adjust regulator handle (1) by turning it clockwise until low pressure
gauge (3) indicates 3 1 PSI. Purge device gauge (9) should indicate 0 1 PSI
and you should hear gas escaping.
Use a torque screwdriver (with number 1 Phillips bit) and tighten all cover
attaching screws with a torque of 3 to 4 inches/pounds. If the IR window
subassembly or eyepiece assembly has just been replaced, also check the
attaching screws of the replaced assembly.
Remove the valve cap from the pressure valve (8, Figure 3-4) on the front panel
of the viewer, and attach the air chuck to the purging hose assembly, then to the
pressure valve. Tighten firmly finger tight.
Purge viewer body by pumping vacuum handle (12) until purge device gauge (9)
indicates greater than 20 inches of Hg.
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, a leak is present. Stop purge
procedure and seal infrared device leak(s). If purge device gauge (9) indicates a
steady vacuum, position purge device LEAK TEST/PURGE switch (10) to
Position purge device PUMP/NITROGEN switch (11) to NITROGEN and
observe that the purge device gauge (9) indicates 3 1 PSI.