WEDGE AS 3984018 - Caterpillar

If replacement of a component is necessary or repair to a component is necessary, the refrigerant in the system must be recovered. Also, if the system has lost any charge after a long period of time, the refrigerant in the system must be recovered. It is necessary to perform the evacuating procedure to delete the system of all air and moisture. You must run the pump for 90 minutes in order to remove water vapor. Also, you must run the pump for 90 minutes in order to attain the vacuum that is listed in Table 1. A complete charge must never be given to a system without first performing the evacuating procedure. Before you evacuate the system, refer to the following manual.
Testing and Adjusting, "Refrigerant Leakage - Test"
Testing and Adjusting, "Refrigerant Recovery"
Testing and Adjusting, "Refrigerant Compressor Oil - Check"If the system has been left open for more than 1/2 hour, the system has been exposed to air and to moisture. Therefore, a new receiver-dryer, an in-line dryer or a desiccant accumulator needs to be installed. Moisture will combine with metals in the refrigerant system. This will produce highly corrosive by-products. The by-products are oxides, iron hydroxide and aluminum hydroxide. Moisture can freeze the expansion valve and moisture can freeze the orifice tube. If there is water in the system, the water must be removed by pulling a vacuum and boiling the water for 90 minutes. Refer to Table 1 that is shown below.
Table 1
Boiling Point of Water Under Vacuum
Temperature of Work Area (°C (°F)) Vacuum That Is Required In Order To Boil Water In An Air Conditioning System (m bar (Hg))
38 (100) 948 (28.0)
32 (90) 965 (28.5)
27 (80) 975 (28.8)
21 (70) 988 (29.2)
All refrigerant must be recovered before the evacuating procedure is started. Never discharge the refrigerant through the vacuum pump.
Flow Chart for the Evacuation Process
Illustration 1 g00476489Installing the Manifold Gauge Set (Evacuation)
Illustration 2 g00469391
(1) Low pressure valve
(2) High pressure valve
(3) Low pressure hose
(4) High pressure hose
(5) Service valve (low pressure side)
(6) Charging hose
(7) Vacuum pump
(8) Service valve (high pressure