BENDIX BW1948 manual Braking System Protection, Roadside Inspection, Temporary AIR Dryer Bypass

3.“Fan” the service brakes to reduce system air pressure to governor cut-in. Note that the system once again builds to full pressure and is followed by a purge at the AD-IS®air dryer exhaust.

4.It is recommended that the total air system be tested for leakage to assure that the AD-IS®air dryer will not cycle excessively.

See Bendix publication BW-5057 “Air Brake Handbook.”

BRAKING SYSTEM PROTECTION

The DRM™ dryer module allows the system to maintain one brake circuit up to about 100 psi even after a pressure loss in the other brake circuit. This allows a vehicle to be moved (in an emergency), but with reduced braking capacity. Compare this to a conventional system where a loss of pressure in one service tank leaves the vehicle with a limited number of reduced braking capacity applications before the parking brakes automatically apply and stay on.

ROADSIDE INSPECTION

In the event of a roadside inspection the system behavior will be as follows: When the system is charged to governor cut out, and then one reservoir drain valve is opened, initially both reservoir gauges will fall, however, the AD-IS®air dryer's primary and secondary pressure protection valves will close at pressures above 70 psi, protecting the remaining brake circuit from further loss of pressure.

TEMPORARY AIR DRYER BYPASS

To temporarily bypass the air dryer, the following procedure needs to be followed.

Follow the Maintenance Precautions outlined elsewhere in this document.

Make sure that all residual pressure has been released, then remove the air supply line from the compressor to the inlet port (1 IN). Remove the safety valve from the AD-IS®air dryer body (see Figure 1 for location) and install a T-fitting into the port. Using any adapters necessary, re-install the safety valve in one of the branches of the T-fitting. Using any adapters necessary, install the air supply line into the remaining T-fitting port. After testing the T-fitting for any air leakage, using a soap solution after charging system pressure (a 1” bubble in 10 seconds is acceptable), the vehicle may be returned to temporary service.

Note: This is a temporary bypass of the air dryer, and full repair of the unit must be carried out at the earliest opportunity. With the air dryer removed from the system, contaminants will be entering the air system: reservoirs will need to be manually drained daily until the repairs are

completed. At end of each working day, park vehicle and slowly drain pressure through the drain valves – leave open to the atmosphere, for several hours if possible. When repairs are carried out, be sure to check that all reservoirs (including the purge reservoir incorporated into the secondary reservoir) are emptied of all contaminants.

If after bypassing the dryer reservoir module the system pressure still does not build, use the following procedure to remove, clean and reinstall the delivery check valve.

DELIVERY CHECK VALVE CLEANING PROCEDURE

(Note: This is only required if system pressure does not build after temporary bypass is completed.)

See Figure 7 throughout this procedure. Depressurize the air brake system following the general safety precautions outlined elsewhere in this document.

This procedure does not require removal of the AD-IS®air dryer from the vehicle.

1.Remove line from governor and mark for easy reinstallation.

2.Remove bolts attaching the governor to the AD-IS®air dryer and retain for reassembly.

3.Remove governor and the adapter’s o-ring.

4.The spring/delivery check valve can now be removed. (Note: The spring/delivery check valve may be a previous design. See Figure 7.)

5.Remove o-ring from check valve body.

CLEANING & INSPECTION

1.Use a suitable solvent to clean all metal parts, and use a cotton swab to clean the bore (Note: Do not use abrasives or tools to clean the bore: any scratches caused may necessitate replacing the AD-IS®air dryer.) Superficial external corrosion and/or pitting is acceptable.

2.Clean the o-rings with a clean dry cloth. Do not use solvents.

3.Inspect for physical damage to the bore and the check valve seat. If the bore is damaged (by scratches etc. that would prevent delivery check valve from seating), replace the AD-IS®air dryer.

4.Inspect the delivery check valve, o-rings, etc. for wear or damage. Replace if necessary using the check valve replacement kit available at authorized Bendix parts outlets.

5.Inspect all air line fittings for corrosion and replace as necessary.

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