40
Pro Dry Instruction Manual
|
Walker Filtration
|
www.walkerfiltration.com
Section 7:
Energy Management
Using a Dew Point Transmitter and Process Controller
for Purge Control
The best option for purge control if the delivered dryness
(pressure dew point) of the air from the dryer is critical. If the
air is deemed dry enough, than the purge can be shut off until
the air’s moisture starts to climb. If the purge is turned off,
care must be taken to ensure that the desiccant beds are not
allowed to wet out too far before the purge is turned back on.
Also, after turning the purge back on, the air’s pressure dew
point may increase a bit before starting to drop again. This
should be taken into consideration to ensure that the air flow
remains sufficiently dry.
It is extremely important to understand that the purge may
only be shut off during periods of low or no demand. This
feature, if used otherwise, can result in permanent damage
to the desiccant beds resulting in loss of drying capacity
and possibly mechanical failure. The cartridges must not be
allowed to become fully saturated at any time.
The following schematic offers an overview of the devices
mentioned as they might be connected for use in controlling
a dryer’s purge function. Please note that specific details
differ between device manufacturers, so in all cases the
manufacturer’s specifications should be adhered to.
Making Connections between a Switching Device &
Dryer EM Contact
Cable / Wire Selection Criteria:
Selected wire should have...
•
at least 2 conductors. More conductors can be useful
in the case of a conductor break. Conductors can be
swapped without having to run new cable.
•
a conductor gauge of no greater than 18 awg is
recommended to fit comfortably into the DIN connector
insert.
• an outside diameter of no greater than 6mm (1/4”). Larger
diameters do not fit well into the cable gland of the EM
DIN connectors.
•
an insulation type compatible with the environment that
it will be run in.
Figure 7.5: Using process controller
DRYER
CONTROLLER
DC POWER
SUPPLY
ELECTRONIC
PRESSURE SWITCH
RELAY
* Normally Closed, open to turn purge off
PIN 1 (puts out
+5 VDC signal)
PIN 2
SIGNAL BACK
SIGNAL OUT
N.C.*
N.O.
N.C.*
N.C.*
N.O.
* Normally Closed, open to turn purge off
MANUAL SWITCH
(Field Installed)
DRYER
CONTROLLER
PIN 1 (puts out +5 VDC signal)
PIN 2
SIGNAL BACK
SIGNAL OUT
* Normally Closed, open to turn purge off
MANUAL SWITCH
(Field Installed)
DRYER
CONTROLLER
PIN 1 (puts out +5 VDC signal)
PIN 2
SIGNAL BACK
SIGNAL OUT
CO
M
SI
GN
AL
O
UT
+
VD
C
+
VD
C
-V
DC
(C
O
M
)
DRYER
CONTROLLER
* Normally Closed, open to turn purge off
PROCESS
CONTROLLER
DC POWER
SUPPLY
DEW POINT
TRANSMITTER
RELAY
PIN 1 (puts out
+5 VDC signal)
PIN 2
SIGNAL BACK
SIGNAL OUT
SIGNAL
+VDC
COM
N.C.*
N.O.
CO
M
SI
GN
AL
O
UT
SI
GN
AL
IN
+
VD
C
+
VD
C
-V
DC
(C
O
M
)
This setup is for example only. This configuration can be
ammended, depending on application.
