DESCRIPTION
The function of both the Bendix® AD-9si™air dryer and the Bendix® AD-9si™PuraGuard® oil coalescing air dryer is to collect and remove air system contaminants in solid, liquid, and aerosol form before they enter the brake system. The AD-9si includes a spin-on style cartridge for easy servicing, and most include a fully integrated governor to control air system charging.
The air dryer provides clean, dry air to the components of the brake system, which increases the life of the system and reduces maintenance costs. The need for daily manual draining of the reservoirs is eliminated.
The Bendix AD-9si PuraGuard oil coalescing air dryer has an identical appearance to the standard Bendix AD-9si air dryer, but contains a coalescing media at the inlet of the desiccant bed. This coalescing media provides a higher level of oil removal over the standard AD-9si air dryer. The AD-9si PuraGuard oil coalescing air dryer has all of the same functions as the standard AD-9si air dryer and is used in applications where lower oil concentration levels are required.
IMPORTANT! When servicing, note that standard AD-9si air dryers or air dryer cartridges may be serviced with PuraGuard oil coalescing air dryers or cartridges, however, PuraGuard oil coalescing air dryers or cartridges MUST only be serviced with like replacements.
Note: Unless otherwise stated in this document, AD-9si air dryer refers to both the standard and PuraGuard oil coalescing air dryer.
The AD-9si air dryer consists of a “spin on” desiccant cartridge secured to a base assembly. The base assembly contains a delivery check valve assembly, safety valve, heater and thermostat assembly, integrated governor (in most assemblies), threaded air connections, internal purge volume, and purge valve assembly.
The removable purge valve assembly incorporates the purge valve mechanism and a turbocharger cut-off feature that is designed to prevent loss of engine “turbo” boost pressure during the purge cycle of the AD-9si air dryer. For ease of maintenance, all replaceable assemblies should be serviceable without removal of the air dryer from its mounting on the vehicle — provided adequate clearance exists between the air dryer and the vehicle components. Refer to the Preventive Maintenance section of this document.
BENDIX AD-9si AIR DRYER OPERATION: GENERAL (Refer to Figures 2 through 5.)
The Bendix AD-9si air dryer is designed to receive compressed air from the vehicle air compressor, clean and dry the air, deliver air to the vehicle’s air reservoirs and control the compressor/dryer charge cycle. The AD-9si air dryer is available with an internal governor (Figures 2 and 3) or without an internal governor (Figures 4 and 5).
AIR DRYER OPERATION: GENERAL
The Bendix AD-9si air dryer alternates between two modes or “cycles” during operation: the Charge Cycle and the Purge Cycle. The following describes these “cycles” of operation.
| Air | Function/ | |
| Connection | Quantity |
| Connection |
| Port ID | |
| | |
| IN 1 | Inlet Port (air in) | 1 |
| OUT 21 | Delivery Port Out | 2 |
| PT 22 | Extended Purge | 1 |
| CON 2-4 | Governor Unloader | 1 |
| 3 | Governor Exhaust | 1 |
TABLE 1 - PORT DESIGNATIONS
