BENDIX SD-08-2414 Purge Cycle Refer to Figure, Bendix AD-IPINTEGRAL Purge AIR Dryer Purge Cycle

OIL

SEPARATOR

DESICCANT

BED

PURGE

ORIFICE

PURGE

VOLUME

CONTROL

PORT

PURGE

CONTROL

LINE

SUPPLY

PORT

								DELIVERY
GOVERNOR								CHECK VALVE
							DISCHARGE
							PORT
	ENGINE					PURGE
			TURBO	EXHAUST
COMPRESSOR	TURBO	CUT-OFF VALVE			VALVE

FIGURE 3 - BENDIX® AD-IP®INTEGRAL PURGE AIR DRYER PURGE CYCLE

Note: the early end cover designs incorporated a vertical delivery check valve while the newer versions have a horizontal check valve. Both have the same function, but the components are not interchangeable. See Figure 4.

A small amount of the air flowing through the center of the desiccant cartridge bolt flows out the cross drilled purge orifice and into the purge volume, for regenerating the desiccant. The air dryer will remain in the charge cycle until the air brake system pressure builds to the governor cut-out setting.

PURGE CYCLE (Refer to Figure 3)

As air brake system pressure reaches the cut-out setting of the governor, the governor unloads the compressor (air compression is stopped) and the purge cycle of the air dryer begins. When the governor unloads the compressor, it pressurizes the compressor unloader mechanism and the line connecting the governor unloader port to the Bendix® AD-IP®air dryer end cover control port. The purge piston

moves in response to air pressure causing the purge valve to open to the atmosphere and the turbo cut-off valve to close off the supply of air from the compressor (this will be further discussed in the Turbo Cut-off Feature section). Water and contaminants in the end cover sump are expelled immediately when the purge valve opens. Also, air which was flowing through the desiccant cartridge changes direction and begins to flow toward the open purge valve. Liquid oil and solid contaminants collected by the oil separator are removed by air flowing from the purge volume through the desiccant drying bed to the open purge valve.

The desiccant cartridge decompression lasts only a few seconds and is evidenced by an audible burst of air at the AD-IP air dryer exhaust. No purging of air should occur after 30 seconds.

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