TM 5-3805-260-24Double Check ValveWhen the brake pedal is pushed and the emergencybrake control valve is pushed in (OFF position), there isno pressure air at inlet passage (1). Air pressure fromthe brake control valve causes shuttle (2) to move to theright and air pressure goes to the air chamber of thetractor wheel brake. This causes the wheel (service)brakes to activate. When the brake pedal is releasedand the emergency brake control valve is pulled out (ONposition), there is no air pressure at inlet passage (3).Air pressure from the emergency pilot valve causesshuttle (2) to move to the left and air pressure againgoes to the air chambers of the tractor and scraperwheel brakes. This causes the wheel (emergency)brakes to activate.DOUBLE CHECK VALVE1. Inlet passage from emergency pilot valve. 2.Shuttle. 3. Inlet passage from brake control valve. 4.Outlet to air chambers.Air Dryer (Models 613BSNS1 and 613BSS1)The air dryer is used to remove moisture and foreignmaterial from the compressed air before it gets to the airreservoir. Clean dry air is very important for safeoperation and performance of brake systems that usecom-pressed air. Clean dry air will also prevent corrosionof parts.Desiccant beads are used to make the drying bed.The desiccant beads are of a material that cleans andmakes the air dry. Each bead has a large number ofsubmicroscopic cavities. Each desiccant bead absorbsor collects moisture and other foreign material from theair.The air dryer is installed in the vertical position in theair line between the air compressor and the first airreservoir. The dryer will help reduce corrosion andprevent possible problems in the air system, especiallythe air brake system caused by moisture in temperaturesbelow 32°F (0°C).With the use of an air dryer, it is not necessary todrain the air system reservoirs daily. The desiccantcartridge and the paper oil filter are removable and mustbe replaced at regular service intervals. The cartridgehousing is used to hold the desiccant beads. Thecartridge housing has a plate with holes in it on eachend. There is a filter cloth under each plate. The topplate is held in place by a spring and the bottom plate isheld by a shoulder near the bottom of the cartridgehousing. A long bolt is used through the center of theassembled cartridge to hold it in place in the air dryer.The end cover assembly is held to the bottom of the airdryer by a lock ring, bolts and retainers. The purge valveand heater assembly are in the cover assembly. Theheater and thermostat assembly keeps moisture fromfreezing in the purge valve drain when the air dryer isused in temperatures of 320F (0°C) or lower. The 60watt, 24 volt DC heater and thermostat assembly has anoperating range between 500F (10°C) and 850F (300C).OPERATIONThe operation of the air dryer is given in two parts, thecharge cycle and the purge cycle.CHARGE CYCLEWith the air compressor in its "loaded" orcompressing cycle, air under pressure is sent to the airdryer from the air compressor through air supply line (1).When the air enters the Air Dryer, the velocity (speed) ofthe air goes down and cools. Much of the oil and water inthe air drops into the sump (12). The direction of the airflow is to the bottom of the Air Dryer where its direction isreversed and more water and oil go into the sump. Theair now goes through the oil filter ( II) and some oil andforeign material is removed, but the water vapor is notremoved. At this point, the air is still saturated (full) ofwater.The filtered air and vapors go up into the bottom ofthe desiccant drying bed of the desiccant cartridge (10)and the adsorption procedure begins. Water vapor isremoved from the air by the desiccant.The unsaturated "dry air" goes through the check valve(7) and purge orifice (8) into the purge volume (2). Fromthe purge volume (2) the air goes through check valve(6), through line (5) to the air reservoir.2-134
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
