Overview
ISO 11223:2004, "Petroleum and liquid petroleum products - Direct static measurements - Measurement of content of vertical storage tanks by hydrostatic tank gauging," provides guidance for the use of hydrostatic tank gauging (HTG) to directly measure the static mass of liquids in vertical cylindrical storage tanks. The standard covers selection, installation, commissioning, maintenance, validation and calibration of HTG systems intended for high‑accuracy and custody transfer applications. It also explains how to derive standard volume from measured mass using independently measured reference density or density measured by the HTG system itself.
Key applicability:
- HTG systems using pressure sensors with one port open to atmosphere
- Vertical, cylindrical, atmospheric tanks with fixed or floating roofs
- Not applicable to pressurized tanks
Key Topics and Requirements
- System components and description: HTG architectures (pressure sensors for liquid head, ullage/ambient pressure, optional density channel), temperature sensors, HTG data processor and interface.
- Selection & installation: Guidance on sensor placement, reference points, and tank‑side mounting to ensure reliable hydrostatic pressure measurements.
- Commissioning: Initial checks and procedures required to bring an HTG system into service for accurate mass measurement.
- Maintenance, validation & calibration: Periodic validation and calibration of pressure and temperature sensors, plus procedures to maintain measurement uncertainty appropriate for custody transfer.
- Calculations & outputs: Converting measured pressures and temperatures into head mass, product mass, observed and standard volumes using tank capacity (tank table) and reference density information. Annexes provide a calculation overview and methods for volume measurement using independent or HTG‑measured density.
- Safety and second‑order influences: Mechanical and electrical safety considerations and treatment of secondary effects (see normative Annex D).
Applications and Who Uses It
ISO 11223 is intended for organizations and professionals involved in accurate inventory and commercial transfer of petroleum and liquid petroleum products:
- Oil and fuel terminal operators and tank farm managers
- Custody transfer engineers and metrology teams
- Instrumentation and automation engineers specifying HTG systems
- Calibration and testing laboratories supporting custody transfer measurement
- Companies implementing automated tank gauging (ATG) and integrated inventory systems
Practical benefits include improved mass‑based inventory accuracy, standardized procedures for commissioning and calibration, and traceability for commercial transactions.
Related Standards
ISO 11223 references and aligns with other petroleum measurement and density standards, for example:
- ISO 7507‑1 - Calibration of vertical cylindrical tanks (strapping method)
- ISO 12185 - Determination of density (oscillating U‑tube)
- ISO 4266‑4 - Measurement of temperature in atmospheric tanks
- ISO 3838 / ISO 3675 - Laboratory density methods
- IEC 60079‑0 - Electrical apparatus for explosive gas atmospheres
Keywords: ISO 11223, hydrostatic tank gauging, HTG, vertical storage tanks, custody transfer, tank gauging, pressure sensors, tank calibration, petroleum measurement.