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2000-OSM, F1
6-1
SECTION 6. TROUBLESHOOTING
TROUBLESHOOTING GUIDELINES
This section provides troubleshooting information by category. Included in this information are
symptoms, causes, and suggested tests for further fault isolation. These tests are described in
Section 7, listed by Test Procedure (TP) number.
BASELINE PROBLEMS
Baseline or Signal Offset (TCD)
Symptom: Baseline (detector signal) is continually offset to the positive or the negative with no short
term drift up or down scale (see Figure 6-1). This is indicated on the graphic display, output recorder,
and the detector signal.
NORMAL
OFFSET
BASELINE
BASELINE
AMOUNT OF
OFFSET
TIME
TIME
Figure 6-1. EXAMPLE OF BASELINE OFFSET
Background: A thermal conductivity detector (TCD) contains a measurement and reference filament
detector configured in an electronic bridge circuit. With no sample eluting the column, both
measurement and reference filaments are responding to carrier gas only. Therefore, the resistance
of both the measurement and reference filaments should be within one ohm of one another (cold) and
the detector in balance.
Causes:
1. Temperatures incorrect. Perform
Test Procedure 30
(Checking Temperature Table Values),
steps 1 to 3 , and 8 to 12 to verify or change temperature settings.
2. No carrier gases applied to analyzer. Perform
Test Procedure 1
(Carrier, Makeup, and Utility
Gas Supplies).
3. Large difference in reference and column carrier flow rate (example: reference 1 cc/min, column
20 cc/min). Perform
Test Procedure 2
(Carrier and Makeup Gas Flow Adjustments).
4. Column broken or connection in column train disconnected, restricted or leaking. Perform
Test
Procedure 1
(Carrier, Makeup, and Utility Gas Supplies) and
Test Procedure 2
(Carrier and
Makeup Gas Flow Adjustments). If there is no carrier gas flow or the carrier gas flow is
restricted, perform
Test Procedure 7
(Column Train Problems).
5. Defective carrier regulator. Perform
Test Procedure 1
(Carrier, Makeup, and Utility Gas
Supplies),
Test Procedure 2
(Carrier and Makeup Gas Flow Adjustments), and
Test Procedure
4
(Carrier or Makeup Gas Regulator), as applicable.
6. Column flooded with liquid sample. Perform
Test Procedure 3
(Sample Valve Leaking/Column
Flooding).
7. Detector balance adjustment needed. Perform
Test Procedure 5
(TC Detector Balance).