ISO 4266-3:2002

Overview

ISO 4266-3:2002 - Petroleum and liquid petroleum products - Measurement of level and temperature in storage tanks by automatic methods - Part 3: Measurement of level in pressurized storage tanks (non-refrigerated) - provides guidance for the use, installation, commissioning, calibration and verification of automatic level gauges (ALGs) for petroleum and liquid petroleum products with vapour pressure < 4 MPa. It covers both intrusive and non‑intrusive ALGs and includes provisions for custody/fiscal transfer applications. The standard excludes caverns and refrigerated storage tanks.

Key topics and technical requirements

• Types of ALGs: Guidance for intrusive (float, servo) and non‑intrusive (microwave, radar) level gauges, and innage- vs ullage‑based measurement.
• Accuracy and calibration: Requirements for intrinsic ALG error, factory calibration prior to installation, and factors affecting overall accuracy (installation and operating conditions).
• Installation guidance: Mounting location, still‑well (stilling‑well) design, guide wires, manufacturer requirements and precautions for pressure‑rated tanks.
• Commissioning & initial verification: Procedures for initial setup, field verification tolerances, checks for free movement, critical distances and influences of vapour/liquid properties.
• Subsequent verification & maintenance: Recommended verification frequency, comparison with previous verifications, adjustment procedures and record keeping.
• Safety & equipment precautions: Hazardous‑area certification, electrical equipotential bonding, chemical compatibility with product/vapour, and securing ALGs against tampering (sealing for custody transfer).
• Data handling: Advice on data communication, time‑correlation of tank parameters (vapour pressure, temperature) with level readings, and prompt recording for bulk transfer.

Applications and users

ISO 4266-3 is intended for organizations and professionals involved in accurate tank level measurement for pressurized, non‑refrigerated petroleum storage, including:

• Terminal and storage operators (refineries, tank farms)
• Instrumentation and mechanical engineers (tank gauging systems)
• ALG manufacturers and calibration laboratories
• Custody transfer and metrology authorities
• Health, safety and compliance auditors

Typical uses: custody/fiscal transfers, inventory control, leak detection support, automated tank gauging for pressurized storage.

Related standards

Part of the ISO 4266 series on automatic measurement in tanks. Closely related parts:

• ISO 4266-1 (atmospheric tanks)
• ISO 4266-2 (marine vessels)
• ISO 4266-4 to -6 (temperature measurement in tanks)

Keywords: ISO 4266-3, automatic level gauges, ALGs, pressurized storage tanks, petroleum measurement, custody transfer, calibration, tank gauging, still‑well, ullage, innage.