Troubleshooting and Service Teledyne API Model T360/T360M Operation Manual
240
If the sample pressure is reading normal but the sample flow is reading low then
it is likely that the pump diaphragm is worn or there is an obstruction downstream
of the flow sensor.
8.2.2.5. ACTUAL FLOW DOES NOT MATCH DISPLAYED FLOW
If the actual flow measured does not match the displayed flow, but is within the
limits of 720-880 cc/min, adjust the calibration of the flow measurement as
described in Section 4.13.8.
8.2.2.6. SAMPLE PUMP
The sample pump should start immediately after the front panel power switch is
turned ON. With the Sample Inlet plugged, the test function PRES should read
about 10”-Hg for a pump in good condition. Readings above 10” Hg indicate that
the pump needs rebuilding. If the test function SAMP FL is greater than 10
cm
3
/min there is a leak in the pneumatic lines.
8.2.3. Poor or Stopped Flow of Purge Gas
If sufficient purge gas is not supplied to the GFC wheel housing, cyclical
fluctuations in readings at zero or low CO
2
concentrations, such as < 100 ppm,
may occur. These fluctuations are the result of changes in the CO
2
concentration
of the ambient atmosphere throughout the course of the day and night. In isolated
areas with relatively few people working nearby the ambient CO
2
concentration
will fall during the day and rise during the night as rate of photosynthesis of the
plants in the surrounding area decreases and increases. In a lab environment with
a relatively high human occupancy the ambient CO
2
concentration will increase
during those parts of the day when the highest number of workers are present. If
the GFC wheel housing is allowed to fill with ambient air, these natural, diurnal
fluctuations might be detected by the instrument and cause it’s in its calculation
of the CO
2
concentration of the sample gas to drift.
Another possible symptom of poor or stopped purge gas flow would be the
inability to measure zero concentrations accurately at the end of a work day on a
system that was calibrated at the beginning of a workday. Although this could
also be due to local fluctuations in ambient CO
2
concentration during the day.
