BENDIX BW2077 manual Turbo CUT-OFF Feature, High Volume Mode, Preventive Maintenance

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 which have collected in the dryer 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.

Liquids and other contaminants collected by the liquid separator are removed by air flowing from the purge reservoir through the desiccant 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 one of the AD-IS®EverFlow™ assembly’s purge exhaust. The actual reactivation of the desiccant 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.

The flow of dry air through the drying bed removes water vapor from the desiccant material. The purge lasts 30 seconds. The delivery check valve assembly prevents air pressure in the brake system from returning to the purging air dryer during the purge cycle. After the purge cycle is complete, the air dryer is ready for the next charge cycle to begin.

TURBO CUT-OFF FEATURE

The primary function of the turbo cut-off valve is to prevent loss of engine turbocharger air pressure through the AD-IS®EverFlow™ assembly when both dryers are in the unloaded mode. At the onset of the purge cycle, the downward travel of the purge piston is stopped when the turbo cut-off valve (tapered portion of purge piston with a soft seat) contacts its mating metal seat in the purge valve housing. With the turbo cut-off valve seated (closed position), air in the compressor discharge line and AD-IS®EverFlow™ assembly inlet port cannot pass through the air dryer. In this manner the turbo cut-off effectively maintains turbo charger boost pressure to the engine. Delivery pressure in excess of 175 PSIG can cause the purge valve to cycle rapidly between load and purge mode. All AD-IS®EverFlow™ Assemblies require a soft seat purge valve.

HIGH VOLUME MODE

If the GOV port of the electronic module indicates that the compressor has been charging for longer than 30 seconds, the dryers will alternatively purge every 30 seconds. This is an indication of high volume through the dryer. When the governor signal indicates the charge cycle is complete, the assembly returns to normal brake cycling.

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. Because no two vehicles operate under identical conditions, 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 presence of water. If moisture is present, the desiccant cartridges 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.

C.Discharge line length too short. The minimum line length from the compressor to the dryer should be: 6' & 1/2" ID On low duty cycle applications (0-20%) 10' & 5/8" ID On high duty cycle applications (20-40%)

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.

Note:

1.Replace both desiccant cartridges at one time. Failure to change both could cause one dryer to pass wet air and the other dryer pass dry air. This would lead to a wet brake system.

2.A small amount of oil in the system is normal and should not be considered as a reason to replace the desiccant cartridges. Oil at the dryer purge exhaust is normal.

3.Visually check for physical damage such as chaffed or broken air and electrical lines and broken or missing parts.

4.Check the AD-IS®EverFlow™ assembly and purge reservoir bolts for tightness. See Figure 1. Re-torque the three air dryer bolts to 360-420 inch pounds and the four purge reservoir bolts to 300-360 inch pounds.

5.Perform the Operation & Leakage Tests listed in this publication.

6.The assembly will not operate without electrical power. Ensure electrical power is at the assembly during vehicle operation.

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