3-11
3.2.5.1 Purge Procedure
1) From the idle Control/Display screen press [PRG]. The pump and compressors start and
purge gas begins flowing within several seconds. Or, if the system is currently running in
the Generate mode, press [PRG GEN*] to switch to Purge mode. Within a few seconds,
the following screen appears.
2) Using the [CHNG SETP] key, adjust setpoints to desired settings.
A) Typical purge flow rate is 1 liter/minute. Lower flows (minimum 0.1 L/min) will
conserve gas while higher flow rates (maximum 5 L/min) will decrease purge time.
B) Saturation temperature should be set to the lowest temperature desired in the
humidity generation sequence. However, when starting from a power-on condition,
allow the generator to purge at the default setpoint (10 °C) for several hours before
adjusting the setpoint to a lower value. The higher the saturation temperature during
purge, the quicker the system will dry down. This makes it easier to evaporate any
condensate that may exist in the saturator outlet tubing.
To change the saturation temperature setpoint, edit one of the humidity control
setpoints to a desired minimum target value. The saturation temperature setpoint will
automatically adjust. (See note 1.)
3) Remain in the Purge mode for 24 to 48 hours if possible, depending on (1) flow rate, (2)
how low the saturation temperature setpoint is, and (3) the length of time that the system
purged while at a higher saturation temperature (discussed in step 2B above). Lower
flow rates and lower saturation temperatures require longest purge times.
Notes
-
1. Entering a humidity control setpoint value causes the generator to automatically
determine a suitable saturation temperature for that humidity. Saturation temperature
setpoint must always be at least 2 °C above the frost point setpoint, and in general will
not be more than 20 to 30 °C above frost point setpoint. If an attempt is made to
directly adjust the saturation temperature setpoint outside these bounds, it will
automatically readjust to a suitable value for the setpoint of the current humidity
control parameter.
2. When in the Purge mode, if the flow rate will not achieve setpoint or drops to zero,
icing may have occurred within the saturator passages, the saturator vent, or at the
saturator inlet causing the generator to shutdown due to Error 4 - Low Supply
Pressure. If this condition occurs, restart the generator, adjust the mass flow setpoint
to zero, adjust the saturation temperature setpoint to 5 °C or warmer and allow to
stabilize. Perform the Saturator Clear procedure (Section 3.2.6), then readjust
setpoints and continue in the Purge mode.
SetPnt Actual
*FRST PT
o
C -10.00
DEW PT
o
C -11.23
PPMv 2581.
PPMw 1605.
%RH 10.39
SATUR psi 70.29
14.48
SATUR
o
C 10.00
10.00
TEST psi 14.70
TEST
o
C 21.10
FLOW l/m 1.000
1.001
03/25/11 15:23:37 [294.6]
CHNG
SETP
CLR
PRG*
GEN
STOP
