Maguire Products VBD-150 Installation Operation & Maintenance page 21

Maguire Products, Inc.
VBD® - Vacuum Dryer®
What is happening when the dryer is running:
During the Pre-heat operation material in the heating hopper is brought up to temperature (T1s). Preheat
time is determined by the specified Preheat Time on the Pre-Start screen (timed preheat, default 35 minutes)
or by the Preheat Setup Auto option, which sets an inlet to outlet temperature delta and a minimum preheat
time.
After pre-heat, approximately one third of the material in the heating hopper is dispensed into vacuum
chamber, and the first vacuum cycle begins. Each vacuum cycle has a minimum vacuum time, set on the
Pre-start screen, or the main run screen (VTs). (default is 20 minutes).
The loader loads the Heating Hopper with new material as the Vacuum Chamber receives the heated material
and heating cycle begins concurrent to vacuum cycle (the first vacuum cycle is timed). The new batch of
material in the upper portion of the heating hopper will take less time to heat. Minimum time in the heating is
dictated vacuum time.
After first vacuum cycle, material is then dispensed into retention hopper ready for use. Material in the
retention hopper is blanketed with dry air.
The rate of consumption of dried material from the retention hopper ultimately dictates the amount of time that
the material will be preheated and under vacuum. Examples: If it takes 25 minutes to deplete the retention
hopper, the vacuum cycle will run past its 20 minute setpoint (pre-start screen) to 25 minutes. This is normal
operation. However if the retention hopper is depleted in 15 minutes and the vacuum time is set to 20
minutes, there will be a 5 minute window where no material is available. This indicates that the throughput of
the dryer has been exceeded. If the Throughput Alarm is enabled (Alarm Setup), a Throughput Alarm (Alarm
Code 20) will be triggered.
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Rev. August 31, 2016 – VBD-150