| Tweet |
Custom Search
|
|
|
||
 TM 55-1905-220-14-9
CHAPTER 4
OPERATOR MAINTENANCE INSTRUCTIONS FOR
AUXILIARY EQUIPMENT (CONTINUED)
SECTION IV. TROUBLESHOOTING - SYMPTOM INDEX (con't)
4-35. THERMAL EXPANSION VALVE - AIR CONDITIONING - MAINTENANCE INSTRUCTIONS (Cont).
a. General.
(1) Thermal expansion valve troubles can usually be traced to dirt or moisture collecting at the valve
seat and orifice. Dirt will get between the valve seat and stem, or moisture will freeze at the valve port, and
prevent the passage of refrigerant. External frost on the inlet side of the valve indicates an obstruction and the
need for cleaning.
(2) To clean, inspect, or repair a thermal expansion valve, pump down the strainer and controls as
explained in paragraph b and disassemble the valve.
(3) A new power or cage assembly, or both, can be installed without removing the valve body flange
from the line.
NOTE
In an emergency, expansion valve freeze up may be avoided by adding to
system not more than 1 cc of anhydrous methyl alcohol per pound of refrigerant
charge.
b. Pumping Down.
To replace the thermal expansion valve, proceed as follows:
(1) Close the cut-out valve on the inlet side of the strainer, and operate system to pump down.
(2) As the pressure is reduced, the strainer will become cold and then begin to warm up as soon as
liquid refrigerant has been removed.
(3) Close the cut-out valve on the outlet side.
(4) Disassemble valve.
(5) Remove thermal expansion valve in accordance with standard soldering methods. Be careful to
retain all the solder in the connections. Refer to paragraph 4-35.6 for soldering procedures.
4-975
|
||
|
||
