Yokogawa GC8000 — Process Gas Chromatograph

Online GC for continuous gas composition monitoring (refinery / gas plant / fuel gas / process control). Focus: sampling, carrier gas, valves, oven stability, detector stability, and DCS communication.

← Back to Search Alarm Decision Trees → Alarm Codes →
Technician rule: Fix carrier gas + sampling issues first. Most GC alarms are caused by pressure/flow instability, contamination, or valve switching issues — not electronics.

Working Principle

GC separates gas components in a column and measures each component using a detector. The instrument runs a cycle: inject sample → separate → detect peaks → calculate composition.

  • Separation: components travel at different speeds through the column.
  • Detection: detector converts eluting components into a signal.
  • Calculation: peak areas converted using calibration factors.

Accuracy depends on: stable carrier flow/pressure, clean sample, consistent valve switching, and stable oven temperature.

Main Components (Field Focus)

  • Sample system: conditioning, filters, regulators, drains.
  • Carrier gas system: supply, regulators, traps.
  • Injection & switching valves: sample loop, rotary/solenoid valves.
  • Oven / temperature control: heater, sensors, controller.
  • Column & detector: column module + electronics.
  • Controller & comms: HMI, I/O, Modbus/OPC/Ethernet.

Calibration Procedure (Technician Sequence)

1) Confirm stable analyzer cycles.
2) Verify carrier pressure/flow stable.
3) Apply calibration gas; allow 2–3 stable runs.
4) Update calibration / response factors.
5) Run verification standard.
6) Return to process; confirm stable trends.

Tip: If peaks shift or area is unstable, do not calibrate — fix sampling/flow/valves first.

Major Troubleshooting (Top Issues)

  • Unstable composition: carrier instability, leaks, contamination.
  • Retention time shift: oven drift, flow change, column aging.
  • Missing peaks: injection valve issue, restriction, detector fault.
  • Bad repeatability: valve timing, pressure hunting.
  • DCS not updating: comms mapping, scaling, polling.
Use Decision Trees → Chromatogram Guide →

Discussion

Share GC8000 troubleshooting tips, valve issues, peak problems, and calibration experiences. (Requires GitHub login.)