Teledyne 6200T - Sulfides Analyzer - Manual (Page 247)

6200T Total Sulfur Analyzer Troubleshooting
Teledyen Analytical Instruments 247
exists, contact customer service. If there is no flow or low flow, continue with the next
step.
Check that the sample pressure is at or around 28 (or about1 in-Hg-A below ambient
atmospheric pressure).
12.3.2. High Flow
Flows that are significantly higher than the allowed operating range (typically ±10-11%
of the nominal flow) should not occur in the M unless a pressurized sample, zero or span
gas is supplied to the inlet ports. Be sure to vent excess pressure and flow just before the
analyzer inlet ports.
When supplying sample, zero or span gas at ambient pressure, a high flow would
indicate that one or more of the critical flow orifices are physically broken (very
unlikely case), allowing more than nominal flow, or were replaced with an orifice of
wrong specifications. If the flows are more than 15% higher than normal, we
recommend that the technician find and correct the cause of the flow problem,
12.4. Calibration Problems
This section provides information regarding possible causes of various calibration
problems.
12.4.1. Negative Concentrations
Negative concentration values may be caused due to the following:
 A slight, negative signal is normal when the analyzer is operating under
zero gas and the signal is drifting around the zero calibration point. This is
caused by the analyzer’s zero noise and may cause reported concentrations
to be negative for a few seconds at a time down to -5 ppb, but should
alternate with similarly high, positive values.
 Mis-calibration is the most likely explanation for negative concentration
values. If the zero air contained some SO
2
gas (contaminated zero air or a
worn-out zero air scrubber) and the analyzer was calibrated to that
concentration as “zero”, the analyzer may report negative values when
measuring air that contains little or no SO
2
. The same problem occurs, if the
analyzer was zero-calibrated using ambient air or span gas.
 If the response offset test function for SO
2
(OFFSET) are greater than
150 mV, a failed PMT or high voltage supply, or sample chamber
contamination, could be the cause.
12.4.2. No Response
If the instrument shows no response (display value is near zero) even though sample gas
is supplied properly and the instrument seems to perform correctly,
 Confirm response by supplying SO
2
span gas of about 80% of the range
value to the analyzer.
 Check the sample flow rate for proper value.
 Check for disconnected cables to the sensor module.
 Carry out an electrical test with the ELECTRICAL TEST procedure in the
diagnostics menu, refer to Section 5.9.5. If this test produces a
concentration reading, the analyzer’s electronic signal path is working.