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TM00358 Rev. A
6.3 TURRET PURGING
To maintain a dry internal environment, all turrets must be purged when humidity exceeds safe operating limits. If a
dry internal environment is not maintained there is a high risk of condensation forming on the interior of the turret.
Internal condensation can cause irreparable damage to optical elements or circuit card assemblies.
During both pre-flight and post-flight inspections (provided turret has been allowed to cool and acclimate to ground
temperature and humidity), the turret's external humidity indicator should be checked (do not confuse with the
desiccant humidity indicator). If the upper quadrants labeled 30 & 40 are lavender (pink), the system must be
purged until all 4 quadrants return to a blue color prior to any further flight operations. Purging should not take
longer than 90 minutes. If purging takes longer than 90 minutes ensure the following:
•
Nitrogen is flowing in and out of the turret.
•
Nitrogen is only escaping from the relief valve.
Operational or a Purged turret.
Table 6-3 Turret Purging — Parts and Support Equipment
Description
Purge kit
Table 6-4 Turret Purging — Consumables
Description
*Nitrogen, technical – Type 1, grade
B, Class 1
* Or equivalent material grade and purity.
L-3 WESCAM
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30
40
50
60
Showing
All Quadrants Blue
2 Quadrants Lavender (Pink) / 2 Quadrants Blue
indicating
Non-Operational or turret that should be purged.
Figure 6-1 Humidity Indicator
Part Number
42424
Part Number
A-A-59503-1-B-1
30
40
Lavender
(Pink)
50
60
Blue
Showing
indicating
Quantity
1
For older systems, use of P/N:
41453 as an alternative is
appropriate.
Quantity
1
Oil free with 99.95% purity.
Moisture content maximum of
26 ppm (v/v or mole/mole).
Chapter 6 - Turret Purging
Notes
Notes
October 2007
103
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