BENDIX BW1811 manual AD-IPINTEGRAL Purge AIR Dryer Charge Cycle

OIL

SEPARATOR

DESICCANT

BED

PURGE

ORIFICE

PURGE

CONTROLVOLUME

PORT

PURGE
CONTROL	SUPPLY
LINE
	PORT

GOVERNOR				DELIVERY
				CHECK VALVE
				(OLD STYLE
			PURGE	SHOWN)
		TURBO		DISCHARGE
COMPRESSOR	ENGINE		VALVE
	TURBO	CUTOFF	EXHAUST	PORT
		VALVE

FIGURE 4 - AD-IP™INTEGRAL PURGE AIR DRYER CHARGE CYCLE

Air, along with the remaining water vapor, is further cooled as it exits the oil separator and continues to flow upward between the outer and inner shells. Upon reaching the top of the cartridge the air reverses its direction of flow and enters the desiccant drying bed.Air flowing down through the column of desiccant becomes progressively drier as water vapor adheres to the desiccant material in a process known as “ADSORPTION.” The desiccant cartridge using the adsorption process typically removes most of the water vapor from the pressurized air.

Dry air exits the bottom of the desiccant cartridge and flows through the center of the bolt used to secure the cartridge to the end cover. Air flows down the center of the desiccant cartridge bolt, through a cross drilled passage and exits the air dryer delivery port through the delivery check valve. 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 7.

Dry air flowing through the center of the desiccant cartridge bolt also flows out the cross drilled purge orifice and into the purge volume.

The air dryer will remain in the charge cycle until the air brake system pressure builds to the governor cutout setting.

PURGE CYCLE (refer to Figure 5)

As air brake system pressure reaches the cutout 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 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 cutoff valve to close off the supply of air from the compressor (this will be further discussed in the Turbo Cutoff 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 initial purge and 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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