1150 Troubleshooting
Chromatographic symptoms
2 of 6
Jun 2001
Valves
Agilent 6890 Gas Chromatograph Service Manual
Loss of sensitivity or excessive drift
Several possible causes exist for overall deterioration of the chromatogram.
• Contamination in the valve requires a thorough cleaning.
• Internal leakage requires a complete disassembly and inspection of the
mating surfaces.
• Poor temperature control may require a full check of electronic and
thermal components.
• Lack of proper conditioning techniques, columns, etc.
• Failure or deterioration of other components (columns, detectors, etc.).
Loss of peaks in specific areas of the chromatogram
Entire sections of chromatographic data can be lost due to a valve that does
not rotate or one that rotates improperly. Other than obvious component
failures (solenoid, actuator, etc.), improper adjustments and misalignments
cause most problems.
• Check that adequate air (about 482 kPa or 70 psi) is supplied.
• Check the valve. Is it rotating?
• If the valve rotates, check for proper alignment of the actuator,
mechanical binding or slippage of connecting parts.
• Check for blocked flow paths with valve in both positions.
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