Sullair SD-1050 Series, User Manual

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USER MANUAL
Models SD-820 to SD-1710 with DDS
Rev 04 – October 2005
9
3. EQUIPMENT OPERATION
3.1 GENERAL OPERATING PRINCIPLES
This Sullair dryer has two parallel adsorption chambers filled with desiccant. While the
medium is being dried flowing bottom-up in one chamber, regeneration takes place from
the top down in the other chamber. The changeover from one chamber to the other is
controlled by the Dewpoint Dependent Switching system that monitors desiccant
performance by measuring the outlet air dew point. It operates continuously and is fully
automatic.
The standard dryer with DDS has a cycle time of 10 minutes. Dryers with the Enhanced
Dew Point option have a 4-minute cycle time.
In each case, half the cycle time is
dedicated to air drying and the other half to desiccant regeneration, with one chamber
working to dry the air while the other regenerates. The cycle time affects air flow and air
quality.
The longer cycle time allows greater saturation of the desiccant, thereby
decreasing its drying capacity over the period of the cycle. The faster cycling provided
with the EDP option ensures that the desiccant is regenerated more frequently, thereby
enhancing its drying performance. The dryer is configured at the factory. The principles
of operation are the same for both the standard (with DDS) and the EDP dryers.
Wet air enters the working desiccant chamber (it can be either the left or right) at the
inlet switching valve (bottom) and is dried as it flows upward through the desiccant bed.
Dry air exits the dryer through the outlet check valve.
At the outlet of the working chamber, a portion of the dry air (i.e., purge air) is diverted
to the regenerating chamber. That purge air, at near atmospheric pressure, will remove
previously adsorbed moisture as it flows downward through the desiccant bed and exits
through the purge exhaust muffler.
The purge air is controlled by a purge adjusting valve and purge orifices located in the
purge line.
Purge pressure is indicated on the purge pressure gauge. Refer to
Appendix B for instructions on adjusting the purge rate.
Near the end of each half cycle, the chamber being regenerated will be repressurized.
For this to occur, the exhaust valve of the chamber being regenerated closes while
purge air continues to flow.
Repressurizing the regenerated chamber to operating
pressure before placing it into service minimizes fluidization of the desiccant and helps
prevent desiccant abrasion which causes desiccant dust to prematurely block pilot filter
and afterfilter elements.
Chamber switchover takes place when both towers are fully pressurized. This
minimizes desiccant movement which, in turn, minimizes creation of dust.
When switchover is complete, the regenerated tower will be placed into service and the
exhausted tower will begin a depressurization/regeneration cycle.