Working Principle
The MAXUM Edition II separates mixture components in a chromatographic column and measures them using detectors (commonly TCD, FID, and application-specific detector options). A controlled carrier gas pushes the sample through injection valves and columns. Each component exits the column at a different retention time, producing a chromatogram. The system integrates peak areas, applies calibration factors, and reports concentration.
- Injection: fixed sample volume injected via valve switching
- Separation: columns (often in ovens) separate components by retention time
- Detection: detector converts component concentration into signal
- Computation: integrator/software calculates composition and outputs to DCS/PLC
Main Components (Technician View)
- Carrier gas system (supply, regulator, filtration, pressure control)
- Sample conditioning system (filters, regulators, heat tracing, knockout, fast loop)
- Injection valves (rotary valves, solenoids, valve block/manifold)
- Columns (packed/capillary, often in one or more ovens)
- Oven temperature control (heaters, sensors, control loop)
- Detectors (e.g., TCD/FID) + electronics
- Controller/PC (method control, integration, calibration)
- I/O & Communications (4–20 mA, Modbus, OPC, Ethernet mapping)
Calibration / Verification Procedure (Practical)
1) Stabilize utilities: verify carrier pressure stability, correct carrier type, no leaks, stable ambient.
2) Stabilize sample: confirm sample pressure/flow, filters clean, fast loop stable, no condensation/liquid carryover.
3) Run baseline check: confirm detector baseline is stable (noise, drift acceptable).
4) Run a calibration standard (certified gas mixture or liquid standard): record chromatogram and peak ID alignment.
5) Verify retention times: if shifted, check column/oven temp, carrier flow, valve timing.
6) Apply/update response factors only after stability is confirmed; save and document changes.
7) Validate with 2–3 repeat injections: results should be repeatable before returning to process.
Note: Never “calibrate to fix instability.” Fix flow/pressure/temperature stability first, then calibrate.
Major Troubleshooting (Top Field Issues)
- Baseline noise/drift — carrier impurities, leaks, detector contamination, unstable oven temp, electrical grounding
- Retention time shift — carrier flow change, column/oven temp error, valve timing drift, pressure regulator hunting
- Poor repeatability — injection valve wear, sample pressure instability, liquid carryover, contamination in valve/loop
- Missing peaks / wrong peak ID — method mismatch, column degradation, wrong stream selection, timing issue
- FID flameout (if FID) — fuel/air issues, ignition failure, dirty jet, incorrect gas pressures
- Oven not ready — heater/sensor fault, controller output, fan/airflow (if applicable)
- Communication/DCS mismatch — OPC/Modbus mapping, tag scaling, channel assignment, network stability
Field tip: If only one component is wrong (others OK), suspect peak ID/cal factors.
If everything is wrong, suspect flow/pressure/temperature or a major sample issue.
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