BENDIX SD-08-2415A manual Purge Cycle Refer to Figure

				DESICCANT
	OIL
	COALESCING
	FILTER
	PURGE				REAR
REMOTE	ORIFICE			DELIVERY	RESERVOIR
PURGE	REMOTE			CHECK
RESERVOIR				VALVE
	PURGE
	PORT
	CONTROL
	PORT
PURGE	SUPPLY				FRONT
CONTROL LINE					RESERVOIR
	PORT
GOVERNOR
		TURBO	SAFETY	DELIVERY
	ENGINE	CUT-OFF		PORT
			VALVE
	TURBO	EXHAUST		PURGE
		PORT		VALVE
COMPRESSOR

FIGURE 4 - BENDIX® AD-RP™AIR DRYER SYSTEM - RELIEF VALVE OPERATION

cartridge, located between the outer and inner shells of the cartridge — removes water in liquid form, as well as liquid oil and solid contaminants.

After exiting the oil separator, air enters the space between the desiccant drying bed and the outer cartridge shell and fl ows down through the column of desiccant. Flowing through the desiccant column, air becomes progressively more dry as water vapor adheres to the desiccant material in a process known as “ADSORPTION.” Using the adsorption process, the desiccant cartridge typically removes 95% of the water vapor from the pressurized air.

Dry air exits the bottom of the desiccant cartridge through its center opening and returns to the air dryer body assembly. The air then fl ows through the delivery check valve assembly and out the delivery port to the fi rst (supply) reservoir of the air system.

The air dryer will remain in the charge cycle until the air brake system pressure builds to the governor cut- out setting. To protect against over pressurization of the Bendix® AD-RP™air dryer, the purge valve incorporates an integral relief valve feature. In the event

that the compressor unloader mechanism or governor malfunctions, at approximately 200 psi — supply air pressure, the AD-RP air dryer purge valve will open (without control pressure) and vent excess air pressure to atmosphere. (Refer to Figure 4)

PURGE CYCLE (Refer to Figure 5)

When air brake system pressure reaches the cut-out setting of the governor — typically 130 psi — the compressor unloads (air compression is stopped) and the purge cycle of the air dryer begins. When the governor unloads the compressor, it pressurizes both the compressor unloader mechanism and the line connecting the governor unloader port to the control port of the AD-RP air dryer body. Air entering the control port is simultaneously directed to the turbo cut-off valve and the purge valve control piston. The initial purge cycle consists of two simultaneous occurrences: (a) the closing of the turbo cut-off valve; and

(b)the opening of the purge valve. Each is discussed below under a separate subheading.

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