| Tweet |
Custom Search
|
|
|
||
 TM 55-1905-220-14-8
4-29. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
(e) Continue dehydrating until a temperature of 35 (1.7 ) s reached on vacuum indicator
F
C
(corresponding to a vacuum of .2" Hg (0.675 kPa ) absolute pressure). The time required to
complete dehydration depends on the amount of moisture in the system and the size of the
plant. The operation will probably take from 18 to 72 hours. If a temperature of 35 (1.7 )
F
C
cannot be reached on the vacuum indicator, it may be due to one or more of the following
faults:
1 Leak in system or connecting tubing to vacuum pump.
2 Closed line valves.
3 Inefficient vacuum pump.
4 Defective vacuum indicator.
5 Ambient temperature too low ( below 60 F I 1 C; 6 C) )
Dehydration Pulldown Curve
(f) With pump still running, open system at a point furthest from pump and admit air through a
dryer. Close system and repeat steps (d) and (e). Moisture left in the system can thus be
greatly diluted and almost completely removed by "double dehydration .
(g) When dehydration is completed, close shut-off valve at Vacuum indicator, charging valve,
shut-off valve at vacuum pump and Stop pump in that sequence. Do not allow pump to
operate longer than absolutely necessary after connection is broken. Disconnect vacuum
pump and vacuum indicator.
4-899
|
||
|
||
