BENDIX SD-08-2433 manual Purge Cycle Refer to Figures 3

DESICCANT

BED

COMPRESSOROIL

COALESCING

FILTER

		CONTROL		PURGE
		LINE		ORIFICE
				PURGE AIR
CONTROL				EXTENDED
				PURGE
PORT				PORT
TURBO				REAR
CUT-OFF				RESERVOIR
VALVE				DELIVERY
(CLOSED)				CHECK
				VALVE
SUPPLY
PORT
	SAFETY			FRONT
	VALVE	EXHAUST		RESERVOIR
		PURGE
		VALVE		DELIVERY
			GOVERNOR
		EXHAUST		PORT

FIGURE 3 - BENDIX® AD-9si™AIR DRYER WITH GOVERNOR—PURGE CYCLE

PURGE CYCLE (Refer to Figures 3 and 5)

When air brake system pressure reaches the cut-out setting of the governor, the integral governor unloads the compressor by supplying a pressure signal through the control port (CON 2-4). This signal activates the purge cycle of the air dryer.

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-9si™air dryer.

Similarly, the governor also supplies this air pressure signal to the purge valve. The pressure 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 (described 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 from the purge volume toward the open purge valve. Contaminants collected by the air dryer filters and desiccant are removed by air flowing from the purge volume 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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