Donaldson Torit DFT 2-8 - Delta P Plus Control System

Downflo II, Model DFT 2-8 through 4-128
35
Delta P Plus Control
Description
The Delta P Plus Control monitors the differential
pressure between the clean and dirty air plenums,
providing a visual display of the filter condition.
When combined with a pulse timer, it controls the
pressure drop by turning the cleaning mechanism
On and Off at the chosen limits. There are three (3)
set points: High Pressure Drop On, Low Pressure
Drop Off, and Alarm. The first two, High Pressure
Drop On and Low Pressure Drop Off, control the
filter cleaning system. The third, Alarm, provides a
relay output to activate an external alarm supplied
by others.
The user can program the Delta P Plus Control to
pulse while the collector is running, to maintain a
relatively constant pressure drop across the filters,
pulse only after the collector is shut down (after-
shift cleaning), or a combination of both, cleaning
while running as well as end of the shift.
Operation
Normal
The Delta P Plus Control monitors the pressure on
both sides of the tubesheet while the unit is running.
The blower draws air through the filters, creating a
pressure drop. The Delta P Plus Control measures
the pressure drop and provides a visual display in
inches water gauge or metric (SI) units.
Filter Cleaning
The Delta P Plus Control offers three filter cleaning
options.
1. Differential Pressure Cleaning (DFF) - When the
pressure drop across the filters reaches the
control's High setpoint, the control closes an
output relay allowing a sequential timer to
trigger the cleaning valves. When the control
senses that the pressure drop has decreased to
the Low setpoint, the relay opens and the
cleaning cycle stops. This sequence continues as
long as the collector is in use, maintaining the
pressure drop within a narrow range.
2. Down Time Cleaning (DTC) - The Delta P Plus
Control monitors the collection system. It
watches for the blower to start, the pressure
drop to exceed the Low setpoint, and then for
the pressure drop to approach zero. After the
blower has come to a stop, the Delta P Plus
engages the cleaning mechanism for a pre-
selected time.
3. Combined Differential and Down Time Cleaning
(ALL) - The Delta P Plus Control combines the
two functions described above; maintaining the
pressure drop in a narrow band and down time
cleaning the filters when the collector is shut
down. The down time cleaning function can be
toggled On or Off from the keyboard.
Alarm
The alarm setpoint is set to a higher setting than
used to start the filter cleaning cycle. It indicates
situations when the cleaning system cannot reduce
the pressure drop due to cleaning system failure,
lack of compressed air, or the end of the filter's
useful life. There is a time delay prior to setting the
alarm to prevent nuisance trips. The Delta P Plus
Control also provides an input connection for a
remote alarm reset.
For complete information, see the most current
version of the Delta P Plus Installation, Operation,
and Maintenance manual.
Delta P Plus Control Display
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