Sterlco SDA Series Medium Capacity Dehumidifying Dryer - Manual (Page 12)

Cabinet Series Dehumidifying Dryer 12
; Audible/visual critical alarm.
; Fusing for blowers and heaters.
; Dirty Filter indicator for each individual blower.
2-6 The Closed Loop Drying System
Dehumidifying dryers force hot, dry air through the resin in the drying hopper where the air picks
up moisture from the material and is drawn back to the dryer.
In the dryer, a desiccant bed strips moisture from the air. The dryer then re-heats dried process
air, and sends it back into the drying hopper to dry material again.
This system is a closed loop, because ambient (outside) air is never introduced into the process
air. See Figure 2. Our dehumidifying dryers use the closed loop system, because the process air
is typically much drier than ambient air, even after carrying moisture out of the plastic resin.
Recycling process air maintains drying efficiency at a consistently high level.
Figure 1-Dryer Air Flow Diagram
Ambient
Regen
filter
Regen
bleed
Process air
heater
From
drying hopper
Process
filter
To drying
hopper
Upper valve
Desiccant
beds
Desiccant
beds
Regen heater Regen heater
Lower valve
Regen blower Process blower