Overview
ISO 6297:1997 specifies a test method for determining the electrical (rest) conductivity of aviation and distillate fuels, with or without static-dissipator additives. The standard defines how to measure conductivity when the fuel is electrically uncharged (“rest conductivity”), using either portable meters (field or laboratory samples) or in-line meters (continuous monitoring). Results are reported in picosiemens per metre (pS/m).
Key topics and requirements
- Measurement principle: apply a d.c. voltage across two electrodes immersed in fuel and record the current almost instantaneously to avoid ion depletion/polarization.
- Measurement range: nominally 1 pS/m to 2 000 pS/m; the range can be extended above 2 000 pS/m with appropriate electrode and current-measurement selection.
- Instrument types:
- Portable conductivity cell with rapid current-measuring capability.
- In-line conductivity cell with flow control and devices to remove residual electrostatic charge before measurement.
- Sampling and sample handling:
- Use in-situ measurement where possible, or follow ASTM D4057 / ISO 3171 sampling practices for collected samples.
- Minimum recommended sample size: 1 litre.
- Containers: fully epoxy-lined or PTFE (polytetrafluoroethylene).
- Rinse containers and cell at least three times with the fuel; test samples as soon as possible.
- Calibration and temperature:
- Calibrate instruments per manufacturer instructions immediately before use.
- Measure and report sample temperature to the nearest 1 °C; conductivity varies with temperature and laboratories should establish any temperature-correction relationships for their fuels.
- Safety and operational notes:
- Observe grounding/earthing to prevent static discharge; allow relaxation of residual charge (a recommended 30 min wait after pumping into storage tank is noted).
- Avoid contact with water or condensation on electrodes-this can give off-scale readings.
- Reagents and apparatus:
- Cleaning solvents noted: propan-2-ol and toluene.
- Temperature sensor, measuring vessel, and appropriate cell depths per manufacturer instructions.
- Reporting and precision:
- Express results in pS/m and include temperature and any deviations from the standard procedure.
- Precision (repeatability and reproducibility) is provided (see standard table) for portable meters at 20 °C; reproducibility limits have specific caveats.
Applications and users
ISO 6297:1997 is used by:
- Fuel testing laboratories and quality control departments
- Airlines and aircraft fuel suppliers for fuel handling and safety checks
- Refineries and terminal operators implementing in-line monitoring and storage tank checks
- Equipment manufacturers of portable and in-line conductivity meters
- Regulatory and safety bodies assessing electrostatic risk mitigation in fuel systems
Practical applications include verifying static-dissipator additive performance, monitoring fuel handling operations for electrostatic hazards, and providing quality-control data for fuel transfer and storage.
Related standards
- ISO 3171 - Petroleum liquids: automatic pipeline sampling
- ASTM D4057 - Manual sampling of petroleum and petroleum products
- ISO 4259 - Determination and application of precision data for test methods
Keywords: ISO 6297:1997, electrical conductivity, fuel conductivity measurement, aviation fuels, distillate fuels, rest conductivity, pS/m, portable meter, in-line meter, fuel sampling.