8
5.0 Instrumentation
The following instrumentation helps in monitoring dryer
operation and performance. Instruments which are avail-
able as options are so noted.
Externally Heated Purge Air dryers are rated NEMA 4 and
include the following:
• Solid State Controls
• Chamber Pressure Gauges
• Purge Flow Pressure Gauge
• Switch Failure Alarm
• Purge Save Module (Option A)
• Energy Management (Option A)
• Dew Point Transmitter (Option B)
5.1 Controls
The solid-state dryer controls are located in a polycarbon-
ate, NEMA Class 4/4X, IP66 rated electrical enclosure
mounted to a center panel located between the two desic-
cant towers. Control features include:
• 15 LED’s to indicate operating status and fault condi
-
tions.
• Two line text display to provide status and diagnostic
messages.
• Upon power loss, dryer “fails safe” (inlet valve remains
in position). On power recovery, controller resumes
where power was lost.
5.2 Chamber Pressure Gauges
A gauge mounted on the gauge panel indicates which
chamber is on-stream and which is regenerating. The
gauge for the on-stream tower indicates operating pres-
sure; the gauge for the regenerating tower indicates 0 psig.
5.3 Purge Flow Pressure Gauge
A gauge mounted on the gauge panel of the dryer indicates
purge airflow.
5.4 Valve Switch-Failure Alarm
Pressure sensors located on each chamber trigger an
alarm when the drying chambers are not in the correct
pressure state (for example: chamber does not depres-
surize at the completion of its drying cycle). The chamber
pressure switch should be closed on the on-stream cham-
ber and open on the regenerating chamber. If triggered,
the dryer control system will energize the red alarm LED
on the control panel and de-energize the common alarm
relay. The alarm automatically clears once the alarm
conditions are corrected.
5.5 Venturi Blower
This precision engineered venturi blower uses ambient
air to boost the bed regeneration flow-through capacity.
It is included with the Energy Management System.
5.6 Energy Management System
The optional Energy Management System (EMS) au-
tomatically adjusts dryer operation to compensate for
changes in operating conditions. Air samples are con-
tinuously taken from the on-stream tower and passed
over a moisture probe which senses both temperature
and relative humidity. The moisture content of the air
within the desiccant bed is then precisely determined.
The on-stream tower will not depressurize and regener-
ate until a predetermined set point has been reached.
This elimination of unnecessary regeneration reduces
energy consumption and extends dryer desiccant and
component life.
5.7 Dew Point Transmitter
This option monitors and displays outlet pressure dew
points and provides an alarm signal if the dew point
exceeds user-specified set point. Recommended cali
-
bration interval is 12 months. Contact the service depart-
ment for details.
Operation – The dew point is measured at the dryer oper-
ating pressure and is displayed in the operator interface.
If the dew point is outside of the temperature range, the
display will indicate an over-range (high dew point) or
under-range (low dew point) condition. A defective sen-
sor assembly or an electronics malfunction could also
cause the transmitter to indicate under-range.
