The actual regeneration of the desiccant drying bed begins as dry air from the purge reservoir flows through the purge orifice into the desiccant bed. Pressurized air from the purge reservoir expands after passing through the purge orifice; its pressure lowers and its volume increases. The flow of dry air through the drying bed regenerates the desiccant material by removing any water vapor adhering to it. Approximately 30 seconds are required for the entire contents of the purge reservoir of a Bendix® AD-IS®air dryer and reservoir system to flow through the desiccant drying bed.
The delivery check valve assembly prevents air pressure in the brake system from returning to the air dryer during the purge cycle. After the purge cycle is complete, the air dryer and reservoir system is ready for the next charge cycle to begin.
TURBO CUT-OFF FEATURE (Refer to Figure 3.)
The primary function of the turbo cut-off valve is to prevent loss of engine turbocharger air pressure through the AD-IS air dryer when the dryer is in the purge mode.
At the onset of the purge cycle, the downward travel of the purge piston is stopped when the turbo cut-off valve (the tapered portion of purge piston) contacts its mating metal seat in the purge valve housing. With the turbo cut-off valve seated (in the closed position), air in the compressor discharge line—as well as the AD-IS air dryer inlet port— cannot enter the air dryer. By completing these actions, the turbo cut-off effectively maintains turbo charger boost pressure to the engine.
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing any intrusive maintenance procedures. An extended warranty may be voided if intrusive maintenance is performed during this period. Purge valve maintenance is permissible during the warranty period only when using a genuine Bendix® purge valve kit.
Because no two vehicles operate under identical conditions, maintenance and maintenance intervals will vary. Experience is a valuable guide in determining the best maintenance interval for any one particular operation.
Every 900 operating hours, or 25,000 miles, or three
(3) months:
1.Check for moisture in the air brake system by opening reservoir drain valves and checking for the presence of water. If moisture is present, the desiccant cartridge may require replacement; however, the following conditions can also cause water accumulation and should be considered before replacing the desiccant:
A.An outside air source has been used to charge the system. This air did not pass through the drying bed.
B.Air usage is exceptionally high and not normal for a highway vehicle.
This may be due to accessory air demands or some unusual air requirement that does not allow the compressor to load and unload (compressing and non-compressing cycle) in a normal fashion. Check for high air system leakage. If the vehicle vocation has changed, it may be necessary to upgrade the compressor size. Refer to Bendix Specification
BW-100-A / Appendix D, to determine if any changes are necessary. Specification BW-100-A is available from the Bendix TechTeam at 1-800-247-2725 or www.bendix.com.
C.The location of the air dryer and reservoir system is too close to the air compressor. Refer to Bendix
Specification BW-110-A / Appendix B, for discharge line lengths.
D.In areas where more than a 30 degree range of temperature occurs in one day, small amounts of water can temporarily accumulate in the air brake system due to condensation. Under these conditions, the presence of small amounts of moisture is normal.
For Bendix® AD-IS®air dryers: Preventive Maintenance is as easy as 1-2-3
Adhering to a preventive maintenance schedule is crucial to keeping a vehicle’s air system clean and ensuring superior performance of all components that utilize system air— such as brakes, emissions equipment and automated manual transmissions. Depending on vocation, Bendix recommends a 1, 2 or 3-year air dryer cartridge replacement on vehicles equipped with a Bendix® compressor.
For severe service application—such as residential refuse trucks or school buses—the air dryer cartridge should be replaced every year or 100,000 miles; for pick-up and delivery operations, or for double- and triple-trailer line haul trucks, every two years or 200,000 miles is the recommendation. Line-haul operations using a single trailer should swap the filter out every three (3) years or 300,000 miles. The recommended intervals for trucks equipped with non-Bendix compressors are 6 months (50,000 miles), one year (100,000 miles) and two years (200,000 miles), respectively.
More frequent intervals may be required depending on a vehicle’s age, its compressor condition, use of a non-Bendix compressor, the operating environment, the vehicle’s vocation, and its usage. In conjunction with these guidelines, fleets can determine the functionality of their filters by checking for moisture in the air brake system monthly. If moisture is present, the air dryer cartridge may require replacement. Reference the Bendix Service Data Sheet of the specific air dryer for additional information.
