Operation; Normal Operation; Dewpoint Dependent Switching (Dds) - Parker BA-DME012-E Guide De L'utilisateur

5 Operation

5.1 Normal Operation

During normal operating conditions, the BA-DME is fully automatic and
requires no further attention until shutdown. In this state the power indicator will
be illuminated continuously.
The BA-DME range of desiccant dryers operate on the Pressure Swing
Adsorption (PSA) principle to produce a continuous stream of clean dry air. A
dual chamber column, filled with desiccant material, is capped by an inlet and
outlet head to produce a two bed system (A + B). When one bed is online,
drying the compressed air, the other bed is offline regenerating the desiccant.
Drying Compressed Air - Compressed air enters the dryer at the inlet head
and is directed to the online bed by the inlet valves. As the compressed air
flows over the desiccant material, water vapour transfers from the wet air to the
dry desiccant. The clean dry air flows into the to the outlet head, via the outlet
valves, and exits the dryer.
Regenerating the Desiccant - A controlled volume of dry compressed air
(purge air) is used to regenerate the desiccant material within the offline bed.
The bed is at full line pressure when it goes off line. Opening the exhaust valve
causes the pressure to drop and allows the purge air to flow, from the upper
manifold, into the bed. The air within the bed expands from line pressure to
atmospheric pressure and flows downwards over the desiccant material.
Changeover - To maintain the pressure and dewpoint of the air leaving the
dryer, the offline bed must be re-pressurised before the beds change over.
Closing the dryer's exhaust valve allows the purge air to pressurise the
regenerated bed.
A
B

5.2 Dewpoint Dependent Switching (DDS)

The fixed timing cycle above is based upon the dryer operating at its full capacity and the desiccant bed being fully saturated at the point of
change over. In reality dryers rarely operate at full capacity and therefore the desiccant is not likely to be saturated. As the energy used to
regenerate a bed is fixed, more energy (purge air) is consumed than is actually required.
The DDS energy management system incorporates a hygrometer (BA-DME DS models only) that monitors the pressure dewpoint of the air at the
outlet of the dryer. At the end of the half cycle, when the regenerating bed is pressurised (3 minutes), both beds will be at line pressure and no
purge air will be consumed. The dryer is in a state of zero energy consumption. If at this time the air at the outlet is drier than the pre-set dewpoint
o
(-40 C), regeneration is not required and change over is delayed. The economy indicator will illuminate continuously in this state.
Change over will occur when the pressure dewpoint of the air at the outlet of the dryer reaches the preset level or when the moisture override time
has been exceeded.
Key:
A
B
Regenerating Repressurising
13
Column A pressure gauge
1
Column B pressure gauge
2
Power indicator / Status indicator
3
Economy (DDS) Indicator
4
Drying Energy Saving