ISO 4266-5:2024

Overview

ISO 4266-5:2024 - part of the ISO 4266 series - specifies requirements and guidance for the use of automatic tank thermometers (ATTs) to measure temperature of petroleum and liquid petroleum products in cargo tanks on marine vessels (tankers and barges). It addresses fiscal/custody transfer applications for products with a Reid vapour pressure less than 100 kPa. The standard excludes refrigerated and pressurized tanks (see ISO 8310).

Key topics and technical requirements

• Scope and applicability: Focus on marine ATTs used in custody transfer; refrigerated and pressurized cargo tanks are out of scope.
• Accuracy and uncertainty: Sets expectations for intrinsic ATT error, calibration of systems or components, multi‑point vs single‑point measurement, and how installation/operating conditions influence overall accuracy.
• Sensor types: Describes electrical temperature elements (commonly RTDs) and the role of temperature transmitters and readout devices.
• Selection and specification: Guidance on choosing ATTs suitable for fiscal/custody transfer, environmental conditions, and product vapour pressures.
• Installation and mounting: Requirements for sensor location, thermowells for security/sealing, earthing of metal parts to ship hull, and design for inerted or corrosive services.
• Commissioning, calibration and verification: Procedures for calibration prior to installation, initial verification (shipyard or sea trials), calibration of single‑ and multiple‑point systems, and subsequent on‑board verification and record keeping.
• Safety and equipment precautions: Compliance with IMO, IEC, CENELEC, ISGOTT, and relevant classification society rules; hazardous‑area certification; mechanical and electrical safety; maintenance expectations.
• Data communication: Guidance on transmitters, remote readouts and recording of temperature data for custody transfer.

Practical applications and users

ISO 4266-5:2024 is intended for:

• Ship operators and tanker owners managing cargo temperature data for fiscal/custody transfer
• Terminal operators and surveyors performing opening/closing gauges and custody transfer checks
• Manufacturers and suppliers of ATTs, RTDs, transmitters and marine instrumentation
• Calibration laboratories and onboard technicians performing commissioning and periodic verification
• Classification societies and regulatory bodies specifying instrumentation and safety compliance

This standard helps ensure reliable, auditable tank temperature measurements critical to volume/quantity correction and commercial transfers on board marine vessels.

Related standards

• ISO 4266 series (other parts covering level measurement and auto methods)
• ISO 8310 (refrigerated/pressurized tanks)
• ISGOTT and IMO/IEC/CENELEC rules for marine electrical and hazardous‑area equipment

Keywords: ISO 4266-5:2024, automatic tank thermometers, marine ATT, tank temperature measurement, RTD, custody transfer, calibration, tankers, barges, installation, verification.