6
Legend
Item
Description
Standard Components
V1 & V2
Left & Right inlet valves, butterfly valve with
double acting actuator
V3 & V4
Left & Right purge valves, butterfly valve with
spring return actuator
V5 & V6
Left & Right depressurization valves, 2-way
solenoid valve
V7 & V8
Left & Right outlet check valves
V9 & V10
Left & Right purge check valves
V11 & V12
Left & Right inlet pilot valves, Namur mount,
dual solenoid
V13 & V14
Left & Right purge pilot valves, Namur mount,
single solenoid
V15
Repressurization valve, ball valve with double
acting actuator
V16
Repressurization pilot valve, Namur mount,
single solenoid
V17
Pilot air shut-off valve, ball valve
RV1 & RV2
Left & Right tower pressure relief valve
B1
Purge air blower with TEFC motor
F1
Blower intake filter
F2
Pilot air filter, general purpose air line filter
H1
Purge air heater
M1 & M2
Left & Right depressurization muffler
O1 & O2
Repressurization (flow control) orifices
PI1 & PI2
Left & Right tower pressure indicators (gauges)
PPS
Pilot Air pressure switch kit
PS1 & PS2
Left & Right tower pressure switches
PS3
Blower pressure switch
TI1 TI2
Left & Right tower temperature indicators (gauges)
TS1 &TS2
Left & Right tower temperature switches
TC1
Heater outlet thermocouples
TC2
Heater high limit thermocouple
TC4
Blower hi-limit thermocouple
Optional Dew Point Monitor
V21
Dew point transmitter isolation valve
DPT
Dew point transmitter with integral inlet filter and
outlet flow orifice
Figure 4.2
4.3 Operating Sequence Description
(see Figure 4.2)
A. Fixed Cycle - One Stage Regeneration (Standard)
(1) Left Tower Drying - Right Tower Regenerating
At the start of the drying cycle, both inlet valves
(V1,V2) are open. The right inlet valve (V2) is then
closed to isolate the two towers. Wet, compressed
air flows up through the left tower where it is
dried. The dry air exits the dryer through the outlet
check valve (V7).
Next, the right depressurization valve (V6) is
opened and the right tower is slowly depressurized.
Air exits through an exhaust muffler (M2).
Next, the right purge valve (V4) is opened and the
blower (B1) and heater (H1) are energized. The
heated air flows through check valve (V10), down
through the right tower, and exits through the right
purge valve (V4). The blower intake air is filtered
(F1) to keep dust and dirt from entering the dryer.
The blower (B1) and heater (H1) are de-energized
when the temperature at the bottom of the right
tower, as sensed by temperature switch (TS2),
reaches the design set point. This indicates the bed
has been fully heated.
Finally, the right purge valve (V4) is closed and the
repressurization valve (V15) is opened. The right
tower slowly repressurizes to full line pressure and
is ready to go back on-line.
(2) Right Tower Drying - Left Tower Regenerating
At the start of the drying cycle, both inlet valves
(V1,V2) are open. The left inlet valve (V1) is then
closed to isolate the two towers. The right tower is
now on-line, drying the compressed air. The left
tower will be regenerated, following a similar
sequence as described in Section 4.3.A.(1) for the
right tower.
Connections - An air sample for the transmitter is
taken from the dryer outlet. An isolation valve is
provided in the sample line in case the transmitter
must be removed for service. The flow cell on the
transmitter has a 2 micron filter in the inlet connec-
tion and an orifice fitting in the outlet connection.
The orifice sets the sample flow rate to approxi-
mately 1 scfh at 100 psig.
High-Limit Temperature Controller (TC 4) - The
Controller (see HHC2 on the electrical schematic
supplied separately with dryer) monitors the air
temperature in the piping between the blower and
the heater. If the temperature exceeds the factory
setting of 175ºF during first stage regeneration
(heating), the blower and heater are de-energized
and Alarm (L5 or R5) will be activated.
High Outlet Dew Point Alarm (L8 and R8) - If the
dryer outlet dew point exceeds the alarm set point,
the high outlet dew point alarm for the on-line
tower will be activated. To prevent nuisance
tripping following tower switch-over (see Section
2.0D), the alarm is disabled for the first 57 minutes
of the drying cycle. While the alarm is disabled, the
dryer outlet dew point is displayed on the operator
interface.
F2
B1
S
V5
S
V6
RV1
RV2
V10
V9
V7
V8
F1
AIR OUTLET
AIR INLET
H1
M1
M2
S
V13
S
S
V11
S
S
V12
S
V14
V3
V1
V2
V4
O1
PS
3
TC
2
PI
1
PS
1
TI
1
PI
2
PS
2
TI
2
TS
2
TS
1
O2
LEFT TOWER
RIGHT TOWER
S
V16
V15
V17
V21
DPT
DEW POINT TRANSMITTER
(OPTIONAL)
TC
4
TC
1
PPS
