Teledyne 6200T - Sulfides Analyzer - Manual (Page 249)

6200T Total Sulfur Analyzer Troubleshooting
Teledyen Analytical Instruments 249
12.4.5. Inability to Zero - No ZERO Button
In general, the 6200T will not display certain control buttons whenever the actual value
of a parameter is outside of the expected range for that parameter. If the calibration
menu does not show a ZERO button when carrying out a zero calibration, the actual gas
concentration must be significantly different from the actual zero point (as per last
calibration), which can have several reasons.
 Confirm that there is a good source of zero air. If the IZS option is installed,
compare the zero reading from the IZS zero air source to an external zero
air source using SO
2
-free air. Check any zero air scrubber for performance
and replacement (refer to Section 11.3.3).
 Check to ensure that there is no ambient air leaking into the zero air line.
Check for leaks in the pneumatic systems as described in Section 11.3.6.
12.4.6. Non-Linear Response
The 6200T was factory calibrated and should be linear to within 1% of full scale.
Common causes for non-linearity are:
 Leaks in the pneumatic system. Leaks can add a constant of ambient air,
zero air or span gas to the current sample gas stream, which may be
changing in concentrations as the linearity test is performed. Check for
leaks as described in Section 12.6.
 The calibration device is in error. Check flow rates and concentrations,
particularly when using low concentrations. If a mass flow calibrator is used
and the flow is less than 10% of the full scale flow on either flow controller,
you may need to purchase lower concentration standards.
 The standard gases may be mislabeled as to type or concentration. Labeled
concentrations may be outside the certified tolerance.
 The sample delivery system may be contaminated. Check for dirt in the
sample lines or sample chamber.
 Calibration gas source may be contaminated.
 Dilution air contains sample or span gas.
 Sample inlet may be contaminated with SO
2
exhaust from this or other
analyzers. Verify proper venting of the analyzer’s exhaust.
 Span gas overflow is not properly vented and creates a back-pressure on the
sample inlet port. Also, if the span gas is not vented at all and does not
supply enough sample gas, the analyzer may be evacuating the sample line.
Ensure to create and properly vent excess span gas.
 If the instrument is equipped with an internal IZS valve option and the SO
2
span value is continuously trending downward, the IZS permeation tube
may require replacement.
12.4.7. Discrepancy Between Analog Output and Display
If the concentration reported through the analog outputs does not agree with the value
reported on the front panel, you may need to re-calibrate the analog outputs. This
becomes more likely when using a low concentration or low analog output range.
Analog outputs running at 0.1 V full scale should always be calibrated manually. Refer
to Section 5.9.3.3 for a detailed description of this procedure.