ISO 4266-6:2002

Overview

ISO 4266-6:2002 provides guidance for the selection, accuracy, installation, commissioning, calibration and verification of automatic tank thermometers (ATTs) used to measure the temperature of petroleum and liquid petroleum products in pressurized, non‑refrigerated storage tanks. The standard is focused on fiscal/custody transfer applications and clarifies that it is not applicable to temperature measurement in caverns or refrigerated tanks.

Keywords: ISO 4266-6, automatic tank thermometers, ATTs, temperature measurement, pressurized storage tanks, custody transfer, petroleum.

Key topics and technical requirements

• Scope and applicability
  • Measurement of temperature in pressurized, non‑refrigerated storage tanks for petroleum products.
  • Excludes caverns and refrigerated tanks.
• Terminology
  • Definitions include ATT, RTD (resistance temperature detector), single‑point (spot) ATT, multiple‑point ATT, averaging ATT and temperature transmitters (see ISO 1998 for terminology).
• Precautions and safety
  • Safety and material compatibility requirements, hazardous‑area certification, and measures to equalize electrical potential with tank structures.
  • Chemical compatibility of wetted parts and adherence to manufacturer instructions.
• Accuracy and uncertainty
  • Emphasis on ATT intrinsic error, calibration traceable to national standards, and matching temperature accuracy with level measurement to protect overall volume measurement accuracy.
• Selection and description of equipment
  • Guidance on RTDs and other electrical temperature elements, single‑point and multiple‑point configurations, mobile spot elements, thermowells, and transmitters.
• Installation and commissioning
  • Proper mounting locations (spot, multiple, averaging), use of thermowells for electronics and verification, and avoidance of installation‑induced errors.
• Calibration and verification
  • Calibration options: as a complete system or by components; initial field verification; periodic subsequent verification and record‑keeping for custody transfer use.
• Data communication
  • Requirements for transmitting and receiving temperature data for remote readout and recording.

Applications

• Custody/fiscal transfer measurements for refinery terminals, tank farms, pipeline storage terminals and petroleum distribution centers.
• Onsite instrumentation selection, installation and commissioning for operations that require legally traceable temperature measurements for inventory and transfer reconciliation.
• Support for metrology and compliance activities (type approvals, verification by national measurement organizations).

Who should use this standard

• Terminal operators, metrology authorities, instrumentation and control engineers, calibration laboratories, and auditors involved in custody transfer and inventory management of petroleum products.

Related standards

• ISO 4266 series (Parts 1–5): related guidance on level and temperature measurement in atmospheric tanks, marine vessels and other contexts.
• ISO 1998 (petroleum industry terminology): normative reference for terms and definitions.