LEAK CHECKING

TM5-4120-376-14 b. Brazing. (1) Heat evenly to recommended temperature. Keep the torch moving constantly in a “figure-eight’’ motion. (2) Apply silver brazing alloy to the heated parts. Do not heat (melt) the silver brazing alloy with the torch. (3) Cool the joint. (4) Clean the joint, using warm water and a brush. (5) Be sure all flux has been removed. 5-11. LEAK CHECKING. CAUTION Rapid discharge will cause oil to be blown out of the compressor. NOTE The electronic leak detector is sensitive to the presence of refrigerant gas (Table D-1, Item 11) in the atmosphere. When refrigerant gas is present in the atmosphere of the work area, false indications can result. Use in a well ventilated but draft-free area. a. Connect a manifold gauge to the suction service valve on the unit and a cylinder of refrigerant (Table D-1, Item 11). Open both service valves and the cylinder shutoff valve. Let refrigerant flow into the system until the pressure gauge indicates 50 psig (3.5 kg/cm²). Close cylinder shutoff valve and suction service valve and disconnect the refrigerant cylinder. b. Connect a cylinder of dry nitrogen (Table D-1, Item 8) to the suction service valve. Open the nitrogen cylinder shutoff valve and the suction service valve and pressurize the system to 350 psig (22 kg/cm²). Close both valves and test for leaks using an electronic leak detector or the soap bubble method as described below: (1) Electronic Leak Detector. Turn the electronic unit on and slowly pass the probe around all points of the refrigeration system at which a leak could exist. Depending upon the type of detector used, leak will be indicated by an audible signal, a light, or by meter deflection. (2) Soap Solution. Brush soap solution on all possible points of leakage and watch for bubbles. Follow a definite sequence to avoid missing any joints that should be tested. Wipe the solution from all joints and mark any point at which a leak is found. (3) Discharge the system after leak checking by connecting a hose to the suction service valve and cracking the valve open slightly to slowly discharge the gas. If leaks were detected, repair them and retest in accordance with paragraph 5-11. If the system is tight, double evacuate and charge the system in accordance with paragraphs 5-12 and 5-13. 5-13