SERVICE MANUAL Fig. 3  Sectional View of AD-1 Air Dryer 1. Outlet 2. Nut 3. Check Valve 4. “O” Ring 5. Safety Valve 6. Oil filter 7. Retaining Ring 8. Exhaust Deflector 9. Heater 10. Purge Valve 11. Desiccant 12. Inlet 13. Purge Orifice 14. Jam Nut 15. Purge Volume Charge Cycle (Fig. 5) With the compressor in its "loaded" or compressing cycle,   air   from   the   compressor   enters   the   air   dryer through the discharge line. When  the  air  along  with  the water and  contaminants  enter  the  air  dryer,  the  velocity or speed of the air reduces substantially and much of the entrained  liquid  drops  to  the  bottom  or  sump  of  the  air dryer.  The  initial  air  flow  is  toward  the  bottom  of  the dryer, but air flow direction changes 180 degrees at the bottom  of  the  air  dryer  dropping  some  water  and  oil. Fig. 4 Sectional View of AD-2 Air Dryer 1. Check Valve 2. Outlet 3. Lock Nut 4. Spring Retainer 5. Perforated Plate 6. Oil Filter 7. Heater 8. Thermostat Enclosure 9. Electrical Terminal 10. Purge Valve 11. Control Port 12. Purge Valve Piston 13. Retaining Ring 14. Cartridge Bolt 15. Inlet 16. Desiccant Sealing Plate The air now passes through the oil filter which removes some oil and foreign material but does not remove water vapor. At this point, the air remains saturated with water. The filtered air and vapors penetrate the desiccant drying bed and the  adsorption  process  begins.  Water  vapor  is removed from the air by the desiccant. CTS-4079 - CHAPTER XIV - Page 4