Grain Systems PNEG-1743 - Manual (Page 35)

PNEG-1743 Vision for Tower Dryers 35
6. Moisture Control Options
Moisture Control Options
Moisture Control is used to regulate the moisture of the outgoing grain. For example, if a user is drying
corn, the desired moisture content of the dried corn is usually around fifteen percent (15%). The moisture
control schemes are designed to achieve that value with minimal effort from the user.
Continuous Flow Drying
There are two (2) parameters the dryer can monitor to adjust Continuous Flow operation in an attempt to
have consistent outgoing moisture: Temperature and Moisture. When we say “Adjust Continuous Flow
Operation”, this means changing the unload rate of the dryer. By varying the unload rate, this changes the
amount of time the grain stays in the drying chamber. This results in heating the grain more or less,
depending on whether the unload rate is increased or decreased.
The following is a depiction of how the Continuous Flow modes break down.
Temperature Controlled Schemes
The temperature controlled schemes use the grain temperature sensors as a reference parameter. As the
grain temperature varies, the controls adjust the unload rate accordingly.
For example, we will assume a grain temperature setpoint of 105°. If the grain temperature sensor on
the dryer is reporting 110°, the grain is 5° hotter than we would like it to be. To adjust the operation,
the control scheme would realize the grain is getting too hot and increase the speed of the unload to
lessen the amount of time the grain is exposed to the heating chamber. The opposite is true if the grain
temperature sensor on the dryer reports lower than the setpoint. The unload rate would decrease. This
means the grain temperature is directly proportional to the unload rate. If the grain temperature rises, the
unload rate should increase.
The temperature controlled schemes have an exclusive option available for drying rice. This option is
available in the two (2) temperature modes by switching the “COMP” dipswitch on the Display I/O board.
The only change in the 2 Speed and 5 Speed temperature modes when drying rice is instead of monitoring
the four (4) temperature sensors located at the 60% point of the column, it monitors the temperature
sensor at the discharge. This allows the kernel temperature to stay at or below a set temperature with
a kernel temp shutdown alarm during multiple pass drying common in rice. This is an exclusive
GSI Group feature.
Control Scheme
Control Parameter
Drying Mode
Continuous
Flow
Temperature Moisture
Variable 5 Speed 5 Speed 2 Speed