Robinsons R66 - 12-82 Desiccant Replacement; 12-83 Leak Detection

SEP 2012 R66 Maintenance Manual Chapter 12 Servicing Page 12.19
12-82 Desiccant Replacement
Refer to R66 Illustrated Parts Catalog (IPC) Figure 21-7.
NOTE
Replace desiccant when condenser or refrigerant system is
exposed to air. To eliminate moisture, replace desiccant, then
immediately vacuum system for charging per Section 12-81.
1. Remove engine cowling per Section 53-21.
2. Recover refrigerant per Section 12-81, if not previously accomplished. Remove
condenser cap and replace desiccant.
3. Install cap, special torque cap per Section 20-33, and torque stripe.
4. Charge system with refrigerant per Section 12-81.
12-83 Leak Detection
Leaks may be detected using several techniques, depending on equipment available. Leak
detection should not be attempted with the aircraft/system running. In addition to safety
hazards, leaks are more difficult to detect with the varying pressures and temperatures of
an operating system.
An empty system should hold full vacuum (27 to 29 inches mercury vacuum at sea level)
with no assistance from the vacuum pump for 20 minutes minimum. If a vacuumed system
creeps up in pressure, a leak may be present. The technician should be thoroughly familiar
with vacuum equipment to ensure leak is in aircraft system and not in vacuum equipment
or connections.
Leaks in a charged system may be detected using a mild soap and water solution applied
to lines and fittings in suspected leak areas (bubbles indicate leaks) or using commercially
available electronic refrigerant detectors. Follow detector manufacturer’s instructions.
Large leaks may be detected audibly if area is quiet or by formation of frost in area of leak.
NOTE
Frost does not necessarily indicate a leak. Normal system
operation and/or charging procedures can cause frost to
accumulate on some components.
NOTE
System pressure is not a reliable indicator of charge state or
the presence of leaks. Because R134a is a liquid/vapor mixture
with the system at rest, pressure will remain constant as more
liquid vaporizes until majority of charge is lost.
Very small leaks can be detected by charging the system with helium gas. Helium molecules
are smaller than R134a molecules and will leak more quickly. Charge system to 200
psi maximum. Use commercially available electronic helium detector or soap and water
solution to locate leaks.
Leaks are most likely to occur at fittings and crimped transitions between hard line and
flexible hose. Concentrate initial leak detection efforts in these areas.