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ZEKS Eclipse 90ZPA Technical Manual
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ZEKS Eclipse ZPA 90-5000 Desiccant Dryerswww.zeks.com56.1 INTRODUCTIONAs described in Section 1, water vapor is removed fromcompressed air by diverting air flow alternately betweentwo towers filled with desiccant. While one tower process-es the compressed air stream, adsorbing water vapor, theopposite tower is regenerated by desorbing the water va-por and venting it to atmosphere. Refer to the Process andInstrumentation Diagram (P&ID) for a visual representa-tion of the drying and regenerating cycles.Timing of the drying and regenerating cycles is automati-cally controlled by a Solid State Timer (SST). An optionalprogrammable dryer controller is available.6.2 DRYING CYCLESaturated compressed air enters the dryer and is divertedto the appropriate tower by the Inlet Flow Valves. Refer-ring to the P&ID, the Left Inlet Flow Valve is actuated to aclosed position to prevent air flow from entering the regen-erating tower. Simultaneously, the Right Inlet Flow Valveis actuated to an open position, allowing air flow to theright hand tower. During this time, the Right Tower PurgeValve is actuated to a closed position, preventing thecompressed air from venting to atmosphere. As the com-pressed air flows through the desiccant material at pres-sure, removal of water vapor from the air stream beginsto occur through adsorption. In the adsorption process,the desiccant material draws water vapor out of the com-pressed air and “holds” it until the right tower drying cycleis complete. Compressed air flows out of the tower for de-livery to the process use. The Outlet Flow Check Valvesprovide air flow diversion to the outlet air connection of thedryer. The Right Outlet Flow Check Valve allows air flowthrough to the outlet connection of the dryer while The LeftOutlet Flow Check Valve checks off to prevent flow back tothe regenerating tower.6.3 REGENERATION CYCLEPreviously adsorbed moisture, removed from the processstream, gets stripped or desorbed from the desiccant ma-terial in the regeneration process. The first stage of re-generation is tower depressurization. After the Inlet FlowValves are switched to divert air flow away from the regen-erating tower, the appropriate Purge Valve will be openedand the tower will be depressurized. Through rapid de-pressurization, a significant portion of the previously ad-sorbed water vapor is stripped off of the desiccant materialand exhausted to atmosphere.The second stage of regeneration uses a portion of thedry, compressed air, expanded to atmospheric pressure tocomplete the desorption process. As shown on the P&ID,the compressed air exits the drying tower and a portion ofthe air flows through the Purge Adjustment Valve and thePurge Orifice. Once the air has passed through the PurgeOrifice, it expands to atmospheric pressure and continuesthe regeneration process. Desorption occurs as the desic-cant releases water vapor into the regeneration air and isexhausted through the Purge Muffler.Eclipse Heatless Dryers may be equipped with an optionalDownstream Purge feature. By adding additional checkvalves to the upper manifold, a dryer equipped with theDownstream Purge option is able to use air from a down-stream source to purge the regenerating tower. This op-tional feature is useful for applications with downstream(dry) storage tanks, as pulling air from a downstreamsource can minimize cycling of the air compressor.6.4 SETTING THE REGENERATION AIR FLOWIt is necessary to manually set the purge air flow to achieveproper dryer performance. Setting the purge flow too highwill waste compressed air and if set too low, the dryer willnot achieve proper dew point performance.The purge adjustment manifold consists of the Purge Ad-justment Valve, the Purge Pressure Gauge and the PurgeOrifice. When the left tower is the drying tower (pressur-ized) and the right tower is depressurized (0 PSIG), man-ually adjust the Purge Adjustment Valve until the gaugereading on the purge pressure gauge matches the PurgePressure Gauge setting listed on the laminated tag affixedto the Orifice Plate Assembly.6.0 PRINCIPLES OF OPERATION! NOTICEThe right tower must be the drying tower for properpurge adjustment setting. When the left tower is thedrying tower, the Purge Adjustment Gauge will readclose to line pressure.! NOTICEOn dryers equipped with the optional NEMA 4/DPC™Package, or when using the optional Moisture LoadControl feature, the purge valve MUST be set to thefactory set point to ensure proper operation of thesefeatures. See Appendix A-6. |
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