Fig. 5 AD-2 Operational Charge Cycle

REMOVAL OF DESICCANT CARTRIDGE AD-1 & AD-2

TM-5-3820-256-24-4 Drilling System Well Rotary Truck Mounted Air Transportable 600 Feet Capacity Model LP-12 NSN 3820-01-246-4276 Manual
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SERVICE MANUAL Fig. 5 AD-2 Operational Charge Cycle The unsaturated "dry air" passes through the ball check valve and purge orifice into the purge volume. From the purge volume air flows through a check valve and into the first reservoir. The AD-1 Air Dryer does not incorporate an integral check valve. The single check valve in an AD-1 installation would be located in the line between the AD-1 outlet port and the first reservoir. Purge Cycle (Fig. 6) When desired system pressure is reached the governor cuts out, pressurizing the unloader cavity of the compressor which unloads the compressor (non- compressing cycle). The line connecting the governor unloader port to the end cover purge valve port (bottom of the air dryer) is also pressurized, opening the exhaust of the purge valve to atmosphere. With the exhaust of the purge valve open, contaminants in the discharge line and dryer sump are purged or forced past the open exhaust out to atmosphere. The reverse air flows across the desiccant and starts the removal process of moisture from the desiccant surface. Dry air flowing from the purge volume through the purge orifice and across the drying bed further dries the desiccant The combination of these reverse flows strips the water vapor from the desiccant (drying bed). This normally takes between 12-15 seconds. Fig. 6 Operational Purge Cycle The desiccant becomes activated from this cycle and is now ready for another charge cycle, which occurs when the compressor returns to the compressing cycle. It is for this reason the air dryer must be purged for 20 seconds after receiving moisture saturated air for a maximum of 60 seconds from a 1.2 _m2 (12 CFM) compressor. MAINTENANCE & CHECKING SERVICEABILITY Every 37,000 km (23,000 miles) or every three months: 1. Inspect for moisture in the air system by opening reservoirs, drain cocks or valves and checking for presence of water. In areas where more than approximately a 170 C (300 F) range of temperature is common, small amounts of water can accumulate in the air brake system due to condensation. The presence of small amounts of water due to condensation is normal and should not be considered as an indication that the dryer is not performing properly. The desiccant cartridge should be replaced or rebuilt when it has been determined that the desiccant is contaminated and does not have adequate water adsorption capacity. However, the following checks should be made before replacing the desiccant cartridge to ascertain that the water accumulation is not related to the following listed items: a. An outside air source has been used to charge the system. This air did not pass through the drying bed. CTS-4079 - CHAPTER XIV - Page 5

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