INFICON HAPSITE Smart Plus Chemical Identification System - Manual (Page 465)

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HAPSITE Smart Plus Operating Manual
a Concentrator is installed, the HAPSITE’s sampling pathway initially bypasses the
Concentrator and then switches to sampling through the concentrator for the time
period specified in the method.
14.7.3 Dry Purge
For a HAPSITE method that utilizes the Concentrator, a dry purge event follows
sample collection to expel moisture from the Concentrator. The SituProbe provides
a nitrogen flow of approximately 20 mL/min through the transfer line and the
HAPSITE’s Concentrator, sample pump, and exhaust port pathway.
This completes the SituProbe sampling portion of the analysis. The HAPSITE
continues with the analysis as it would for any other collected air sample.
14.8 SituProbe Operation
14.8.1 Headspace Creation
A series of several system checks are initiated when a SituProbe method is started.
One of the most critical conditions to check is the presence of a headspace in the
sampling probe. VOCs will be collected into the headspace, but more importantly
the headspace volume must be maintained throughout the sampling process to
prevent the water sample from being pulled into the SituProbe module and the
HAPSITE.
The water level in the Sample Probe is determined by conductivity measurements
from electrodes located in the sampling probe head. The state of the electrode
sensors is displayed through the LEDs mounted on the SituProbe accessory. At the
start of a method, the system will always attempt to create a headspace or reinforce
an existing headspace by flowing Nitrogen gas into the probe head for five
seconds. The headspace creation step is not part of any method’s events and does
not require any operator input. If the water level is within the proper range, the
method will continue. Otherwise, the method will stop and require operator
attention to correct the water level error before proceeding.
14.8.2 Purge Rate Adjustment
Following headspace creation is the SPLoopFill event. During this event, Nitrogen
purges into the probe sampling tube while the HAPSITE’s sample pump begins
sampling from the headspace. The purge rate must exceed the sample pump rate
to maintain the headspace volume. Adjust the purge flow by changing the
"SituProbe Flow Pres." (pressure) parameter in the method editor. See
Figure
14-3 . Increasing the parameter value will increase the purge flow rate. The purge
flow setting will be correct when a few bubbles are observed exiting the upper holes
in the purge tube during the sampling events (sample pump ON). See
Figure 14-4 .
Once the proper setting is determined, it can be used for all methods.
NOTE: The parameter change can only be made between runs.