Pub. No. OM-A-10E — April 2004
11
FIGURE 2 — SDG-1: SEQUENCE OF OPERATION DIAGRAM
Shutdown Procedure
Externally Heated dryers are typically installed in 24 Hr.
operations. The dryers operate on a standard time cycle
of 8 hours, 4 hours drying and 4 hours regenerating. This
cycle should not be interrupted (except for servicing). If the
dryer needs to be shut down for a certain shift or
weekend; the dryer should be turned off at the end of the
4 hour regenerating cycle, and with both towers at line
pressure. If servicing is required advance the time
sequence so the purge valves close, and pressurize both
towers. At this time, the dryer can be turned off.
1.
If the compressed air system has been
piped with a bypass around the dryer, then
the following should be completed
:
a. Open the bypass valve to allow process flow to
continue downstream, then close the dryer outlet
isolation valve.
b. Turn the dryer ON/OFF switch to the OFF
position.
c. Close the dryer inlet isolation valve on the dryer
bypass piping. At this time the dryer is isolated
and can be depressurized for servicing.
2.
If the compressed air system has not been
piped with a bypass, then the following
should be completed:
a. Turn the power switch to the OFF position.
b. The tower switching valves are normally open
valves; therefore, with the power off the inlet
valves to the towers will be open, and the purge
valves will close. This will give you extended
drying time until desiccant chambers are
saturated.
1
LEFT TOWER
SWITCHING
ON
OFF
ZERO
ZERO
240 MINUTES
240 MINUTES
480 MINUTES
480 MINUTES
ZERO
R TOWER
HEATING
R TOWER
COOLING
240 MINUTES
150
390
480 MINUTES
2
RIGHT TOWER
SWITCHING
ON
OFF
3
LEFT TOWER
REGENERATING
ON
OFF
4
RIGHT TOWER
REGENERATING
ON
OFF
5
DEMAND
CYCLE
ON
OFF
N/A
HEATER
TIMING STAGE:
ON
OFF
6
LEFT TOWER
DEPRESSURIZING (OPT.)
ON
OFF
7
RIGHT TOWER
DEPRESSURIZING (OPT.)
ON
OFF
L TOWER
HEATING
L TOWER
COOLING
