13
3.1.2 SLOWLY pressurize dryer to full line pressure (open inlet isola-
tion valve, outlet isolation valve remains closed).
NOTE:
During initial start-up check entire system for leaks. If neces-
sary, depressurize and correct any leaks.
3.1.3 Energize dryer using the power switch located on the control
panel.
NOTE: Switching failure alarm: alarm (light) may be activated if unit is
energized before it is pressurized. To deactivate alarm, allow dryer to
cycle to next step and press the reset button.
3.1.4 Adjust the purge rate valve.
3.1.4.1 Determine:
1) Maximum working pressure (MWP) of dryer from the dryer serial
number tag
2) Air pressure at inlet to dryer
3.1.4.2 Refer to Table 3A for proper purge rate pressure setting at the
conditions found in 3.1.4.1
3.1.4.3 Adjust purge rate valve until purge flow indicator reads re-
quired pressure setting.
NOTE: Adjustment must be made while a tower is purging (air exhaust-
ing from muffler).
IMPORTANT
INSUFFICIENT PURGE AIR WILL EVENTUALLY RESULT IN SATURA-
TION OF DESICCANT BED AND WET AIR DOWNSTREAM. MAKE CER-
TAIN THAT CYCLE TIME, PURGE ECONOMIZER SWITCH, AND PURGE
PRESSURE ARE CORRECTLY SET.
3.1.5 Establish normal flow through dryer (open outlet isolation
valve). Close air by-pass valve if present.
NOTE: When dew points below -40°F (-40°C) are required, the dryer
must be run with an inlet flow rate of less than 50% of maximum until
the desired dew point is attained. Depending on the initial dryness of
the desiccant, this can take as long as 2 to 3 days. This stabilization
period is required on initial startup, after dryer has been shutdown
for extended periods of time, or after dryer maintenance (desiccant
change, etc.).
3.1.6 With the inlet pressure to the dryer at its minimum level, read-
just the purge pressure as determined in 3.1.4.
NOTE: Adjustment must be made while a tower is purging (air exhaust-
ing from muffler).
3.2 Operational Check Points
3.2.1 Standard Unit
3.2.1.1 Power to unit -
Check periodically that there is power to the unit (indicating lights il-
luminated).
3.2.1.2 Moisture Indicator -
Every four hours check moisture indicator. Indicator should be green.
Outlet relative humidity of the desiccant dryer is indicated by the color
change humidity indicator. Green indicates a R.H. below 3% and yellow
indicates a R.H. above 3%. Table 3C (page 16) indicates outlet dew point
when moisture indicator changes from green to yellow at various inlet
temperatures.
NOTE: During start-up the indicator may be yellow, however, it should
begin to change to green within four hours.
3.2.1.3 Purge Flow Indicator -
Every four hours check the purge pressure and adjust as required. Ad-
justment should be made when the inlet pressure to the dryer is at its
minimum level.
NOTE: Adjustment must be made while a tower is purging (air exhaust-
ing from muffler).
Units with Standard Board Operation
3.2.1.4 Alarms
Periodically check for flashing red alarm light. Alarm light will flash if
either tower fails to pressurize or depressurize to the required levels at
the proper time or if optional high humidity alarm indicates high exiting
dewpoint.
NOTE: Alarm will activate if dryer is energized without being pressur-
ized. If this occurs allow dryer to cycle to next step and press reset
button.
NOTE: Alarm light will continue to flash even if fault clears. To clear
alarm, press reset button.
NOTE: If the tower being regenerated fails to repressurize, the dryer
will not switch towers. The switching failure alarm will be activated and
the dryer will remain in this mode until the tower repressurizes.
Switching Failure
The switching failure alarm operates by sensing tower pressures after
tower changeover. If towers have failed to pressurize or depressurize to
the required levels, an alarm condition exists. The alarm light blinks while
the alarm condition exists. Depressing the reset switch will extinguish the
light, but will not interrupt the drying cycle.
If the tower being regenerated fails to repressurize, the dryer will not
switch towers. The switching failure alarm will be activated and the dryer
will remain in this mode until the tower repressurizes.
3.2.1.5 Tower Status Lights -
Illuminated light indicates which tower is on-line drying or off-line re-
generating.
3.2.1.6 Tower pressure gauges
3.2.1.6.1 Periodically check tower pressure gauges to verify that tower
pressure gauge of tower on-line reads line pressure and tower
pressure gauge of tower off-line reads below 2 psig.
NOTE: Read off-line tower gauge when tower is purging (air exhaust-
ing from muffler)
3.2.1.6.2 Check mufflers for back pressure
Excessive back pressure may result due to the accumulation of dust in
the muffler. This sometimes occurs after start-up because of dusting of
the desiccant during tower filling and dryer transport.
If the tower pressure gauge of the off-stream tower rises out of the black
area on the gauge dial, muffler elements should be replaced. A set of
purge exhaust muffler replacement elements is supplied with the dryer.
