TM00358 Rev. A
Chapter 6 - Turret Purging
L-3 WESCAM
October 2007
All Rights Reserved
103
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.
Figure 6-1 Humidity Indicator
Table 6-3 Turret Purging — Parts and Support Equipment
Description
Part Number
Quantity
Notes
Purge kit
42424
1
For older systems, use of P/N:
41453 as an alternative is
appropriate.
Table 6-4 Turret Purging — Consumables
Description
Part Number
Quantity
Notes
*Nitrogen, technical – Type 1, grade
B, Class 1
A-A-59503-1-B-1
1
Oil free with 99.95% purity.
Moisture content maximum of
26 ppm (v/v or mole/mole).
* Or equivalent material grade and purity.
30
40
50
60
Showing
All Quadrants Blue
indicating
Operational or a Purged turret.
30
40
50
60
Showing
2 Quadrants Lavender (Pink) / 2 Quadrants Blue
indicating
Non-Operational or turret that should be purged.
Blue
Lavender
(Pink)
