ISO 4266-6:2024

Overview

ISO 4266-6:2024 - "Petroleum and liquid petroleum products - Measurement of level and temperature in storage tanks by automatic methods - Part 6" provides guidance for the measurement of temperature in pressurized (non‑refrigerated) storage tanks using automatic tank thermometers (ATTs). The standard is focused on fiscal/custody transfer applications where accurate temperature measurement of petroleum and liquid petroleum products is critical for volume and value calculations. It excludes caverns and refrigerated tanks.

Key topics and technical requirements

• Scope and definitions: Terminology for ATT, RTD, single‑point, multiple‑point, averaging and variable‑length ATTs.
• Selection criteria: Recommendations for choosing ATTs suitable for pressurized tanks and custody transfer accuracy.
• Accuracy and uncertainty: Treatment of intrinsic ATT error, calibration prior to installation, installation/operation error sources, and overall accuracy requirements for fiscal use.
• Equipment description: Electrical temperature elements (e.g., RTDs), temperature transmitters, thermowells and sensor configurations (single‑point, multiple‑point, variable‑length, moveable spot).
• Installation & commissioning: Best practices for sensor placement, thermowell use, and measures to minimise installation‑induced errors.
• Calibration & verification: Procedures for factory calibration, initial field verification, subsequent verification frequency, and record‑keeping requirements. The standard clarifies requirements for multiple‑point ATTs and system vs component calibration approaches.
• Precautions & safety: Safety, hazardous‑area certification, material compatibility, bonding/earthing and maintenance recommendations.
• Data handling: Guidance on data communication, readout, averaging methods and simultaneous level/temperature recording for custody transfer.

Practical applications

• Ensuring accurate temperature measurement for volume correction during custody transfer of petroleum products in pressurized storage tanks.
• Integration of ATTs with tank gauging systems and automated metering to support invoicing, inventory control and regulatory compliance.
• Use in terminals, refineries, storage depots and pipeline storage where pressurised, non‑refrigerated tanks are employed.

Who should use this standard

• Terminal and refinery operations managers responsible for custody transfer measurement.
• Instrumentation and metering engineers specifying and installing ATTs, RTDs and thermowells.
• Calibration laboratories and inspection bodies performing ATT verification and audits.
• Vendors and manufacturers of tank gauging systems and automatic tank thermometers.

Related standards

• Other parts of the ISO 4266 series (measurement of level and temperature by automatic methods).
• ISO 1998 (petroleum industry terminology), referenced for terms and definitions.
  For full implementation or procurement, consult the ISO catalogue and your national standards body for the complete ISO 4266 series and applicable national regulations.