Filling The Charging Cylinder; Checking System For Leaks - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
3. Remove exhaust port cap and open valve on pump. Turn on pump and open the low and high
pressure and vacuum control valves on the charging station. (Refer to Figure 14-37.)
4. Operate pump until 26 to 28 inches vacuum is attained. Continue to operate pump for 25
minutes after 26 to 28 inches vacuum is reached.
NOTE
Reduce vacuum reading one inch for each 1000 feet altitude above
sea level.
5. While system is evacuating fill charging cylinder as outlined in paragraph c.
6. If 28 inches of vacuum cannot be attained, close valve 3 (vacuum control), stop pump and
check system for leaks per paragraph d.
7. After evacuation, close valve 3 (vacuum control) stop pump. Check system for leaks per
paragraph d.
8.
When no leaks are evident proceed with charging per paragraph e.
c. FILLING THE CHARGING CYLINDER.
I. Be sure refrigerant drum valve is open.
2. Open valve at base of charging cylinder and fill cylinder with required amount of refrigerant
to charge system (4.0 Ibs. for full charge on PA-31-350 System). Liquid refrigerant can be seen rising in
sight glass.
3. As refrigerant stops filling the cylinder, open valve at top of cylinder behind control panel
intermittently to relieve pressure and allow refrigerant to continue filling cylinder.
4. When refrigerant reaches desired level in the sight glass, close both the valve at the base of
the charging cylinder and the valve at the refrigerant tank. Be certain that the top cylinder valve is fully
closed.
NOTE
If bubbling occurs in sight glass, reopen the cylinder base valve
momentarily to equalize drum and cylinder pressure.
d. CHECKING SYSTEM FOR LEAKS.
1. Open valve at bottom of charging cylinder and allow two pounds of refrigerant to enter
cylinder.
2. With system evacuated per paragraph b, close all charging station valves. Open valve 4
(refrigerant control) and valve 2 (high pressure control) and allow one pound of refrigerant to enter system.
3. Using the Bacharach Leakator or equivalent electronic leak detector, check all joints and
repair any leaks.
4. Evacuate again for 15 minutes and add another one pound of refrigerant to system.
5. Release the one pound of refrigerant from the system and re-evacuate for 5 minutes to be
certain as much contamination is removed from the system as possible. The system is now ready for
charging per paragraph e.
e. Charging System - Full Charge.
1. With 4 pounds of refrigerant in the cylinder per paragraph c, valve 2 (high pressure control)
fully open, and valve 1 (low pressure control) closed, open valve 4 (refrigerant control) and allow as much
liquid refrigerant to enter the high side of the system as possible. It will be necessary to slightly warm the
base of the charging cylinder. (If charging station does not have a cylinder heater use heat from a 75 to 100
watt bulb and watch that system pressure does not exceed 150 psig) in order to drive the last portion of
charge into the system. Do not use open flame or other high heat source for warming cylinder.
Reissued: 9/23/80
ACCESSORIES AND UTILITIES
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