BENDIX SD-08-2418 manual Purge Cycle Refer to Figure

DESICCANT

BED

OIL COALESCING FILTER

(BENDIX® AD-IS®PURAGUARD®

OIL COALESCING AIR DRYER)

		PURGE	PURGE
			RESERVOIR
	DELIVERY	ORIFICE
PURGE	CHECK VALVE	PRESSURE
	(CLOSED)
CONTROL		PROTECTION
		VALVES
CHANNEL
GOVERNOR
UNLOADER
PORT

SUPPLY	PURGE VALVE			A	B	C	D
PORT
	(OPEN)			PRIMARY
		TURBO	SAFETY
				PORT (PRI)			PURGE
		CUT-OFF	VALVE
	ENGINE	VALVE	SECONDARY				RESERVOIR
		(CLOSED)					DRAIN VALVE
	TURBO		PORT (SEC)
						PRIMARY
	COMPRESSOR	EXHAUST			RESERVOIR		SECONDARY
							RESERVOIR
						AUXILIARY PORTS
						(TO ACCESSORIES)

DIAGRAM SHOWS ALL PRESSURE

PROTECTION VALVES OPEN.

FIGURE 3 - BENDIX® AD-IS®AIR DRYER AND RESERVOIR SYSTEM PURGE CYCLE

accessories. If the pressure protection valves are preset to different values the valves will open—in order of lowest setting to highest setting—when charging a flat system.

The air dryer and purge reservoir will remain in the charge cycle until the air brake system pressure builds to the governor cut-out setting of approximately 130 psi.

PURGE CYCLE (Refer to Figure 3.)

When air brake system pressure reaches the cut-out setting of the governor, the governor unloads the compressor activating the purge cycle of the air dryer and reservoir.

The governor unloads the compressor by allowing air pressure to fill the line leading to the compressor unloader mechanism. This suspends the delivery of compressed air to the Bendix® AD-IS®air dryer and reservoir system.

Similarly, the governor also supplies air pressure to the air dryer. The pressure also moves the air dryer purge piston down, opening the purge valve to atmosphere and closing off the compressor air supply to the turbo cut-off valve (covered in the Turbo Cut-off Feature section of this document). Water and contaminants captured are expelled immediately when the purge valve opens. In addition, air—which was flowing through the desiccant cartridge—changes direction and begins to flow toward the open purge valve. Contaminants collected by the air dryer are removed by air flowing from the purge reservoir through the desiccant drying bed to the open purge valve.

The initial purge and desiccant cartridge decompression lasts only a few seconds, evidenced by an audible burst of air at the air dryer exhaust.

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