Great Lakes Air Products GPS-500 Gebrauchsanweisung - Seite 7
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Seite druckenDEWPOINT DEMAND CONTROLLER
The Dewpoint Demand Controller is an option designed to limit energy consumption to the minimum
required for optimum dryer performance. The option works off the premise that not all compressed air
conditions are stable and continuous. Each desiccant tower is designed to adsorb the moisture load of
full rated flow and rated conditions for 5 minutes. For example; if at the end of 5 minutes your flow has
fluctuated from 20 to 100% of rated load, the desiccant bed has an unused adsorption capacity of
roughly 40%. At the end of the 5 minutes the demand cycle control holds the freshly regenerated tower
in a pressurized standby mode so the on-line tower can continue to adsorb moisture to the design limit.
While the dryer is in this standby mode no energy is being expended and the overall average energy
consumption is reduced. As the dew point meter (the heart of the Dewpoint Demand Control) signals
that the proper moisture loading of the on-line tower is approaching, the towers invert bringing the
standby tower on-line and beginning the regeneration of the previously saturated tower.
STARTUP
Pressurize the system with the dryer bypass open and the dryer inlet and outlet closed. Then open the
dryer outlet valve allowing it to pressurize the dryer from the outlet.
backwards through the outlet, it allows the control air system to be energized first and properly seat the
control and process valves.
S-L-O-W-L-Y pressurize the rest of the dryer by gradually opening the inlet valve upstream of the dryer.
This will allow compressed air to enter and completely pressurize the dryer. When the tower pressure
gauges indicate line pressure, close the bypass valve and allow compressed air to flow through the
entire dryer package.
Pressurization of the dryer should never be initiated by suddenly pressurizing the dryer towers from the
dryer inlet. The sudden rush of high velocity air in the desiccant bed would cause the desiccant bed to
fluidize. Desiccant fluidization will create desiccant breakdown and or excessive desiccant fines.
This section refers to systems with the optional Dewpoint Demand Systems only
The final step prior to initiation of the dryer is to verify flow to the dewpoint probe in the sample flow
cell. Open the isolation valve upstream of the sample cell filter. The sample cell is now pressurized.
An orifice in the sample cell outlet lets a small flow of air over the probe. After the orifice there is a
check valve that prevents atmospheric air from migrating into the sample cell when the compressed
air system is depressurized. The coil of tubing on the outlet of the sample cell is to prevent
atmospheric moisture from migrating into the sample cell during sampling.
Initiate the "power on" selector switch or push button. Almost immediately one tower will depressurize to
atmospheric pressure through the purge exhaust valve and muffler. At this time verify that the purge
flow indicator (pressure gauge in the purge loop piping) is reading the pressure indicated by the factory
tag located on the piping behind the gauge (the pressure setting for the flow indicator should be
between 45 & 55 PSIG). If the indicator does not match the tag, adjust the globe valve directly above
the indicator until the setting matches. This pressure/flow can be set only during a purge cycle (air
exiting the muffler). The setting will change during repressurization then return to the setting in the next
purge cycle. From this point the system should cycle as outlined in the operation section of this manual.
Once the purge flow is set it will fluctuate slightly during the day if the system operating pressure
fluctuates. It is best to set the purge flow during a time when the system pressure is at a low point, so
the dryer purge requirements are not starved during lower pressure operating periods.
GPS Heatless Regenerative
Page 7 of 14
By pressurizing the dryer