Overview
ISO 6996:2024 - Bunkering: Meter verification using master Coriolis mass flow meter defines the metrological and procedural requirements for using a master Coriolis mass flow meter (MFM) to verify a duty meter on a bunker tanker or at a terminal. The standard sets criteria to qualify and maintain a master meter, prescribes meter verification processes (including safety and documentation), and establishes uncertainty and calibration requirements to support custody transfer measurements.
Key Topics and Requirements
- Master meter qualification
- Laboratory calibration in water with direct traceability to SI units (ISO/IEC 17025 competent labs).
- Water-calibrated errors between Qmin and Qmax ≤ ±0.033% (with water rig measurement uncertainty ≤ 0.017%).
- Combined water and oil calibration measurement uncertainty ≤ 0.10% (evidence via reports from a national metrology institute or OIML authority).
- Oil calibration using bunker fuels (or equivalent) across Qmin–Qmax with at least five evenly distributed calibration points and three runs per point.
- Master meter may be used only in the flow direction for which it was calibrated and must be re-calibrated annually to maintain master-meter status.
- Meter verification process
- Verification performed by a competent third‑party test service provider and overseen by a qualified verification officer.
- Verification flow rates chosen from historical operational data to represent typical bunkering flows (between Qmin and Qmax).
- Procedures include pre-test meetings, setup checks, run sequences, critical parameter checks (Annex C), and a formal meter verification report (Annex D).
- An uncertainty budget for site verification is provided (Annex B).
- Safety and environment
- Mandatory PPE (helmet, safety shoes, gloves, life jackets) and use of multi‑gas detectors onboard; Annex A details safety, health and environmental controls.
Applications and Users
ISO 6996:2024 is intended for organizations involved in bunkering custody transfer and measurement assurance:
- Bunker tanker operators and terminal operators
- Third‑party test service providers and verification officers
- Meter manufacturers and calibration laboratories
- Quality, metrology and compliance teams managing custody transfer accuracy and audit trails
Practical benefits include reduced downtime and cost compared to full recalibration, improved meter stability tracking, and documented traceability for custody transfer transactions.
Related standards
- ISO 22192 (flow measurement - Coriolis MFMs)
- ISO 6963 (bunkering measurement practices)
- ISO/IEC 17025 (laboratory accreditation)
- OIML guidance for calibration traceability
Keywords: ISO 6996:2024, bunkering, meter verification, master Coriolis mass flow meter, Coriolis MFM, custody transfer, calibration, measurement uncertainty, master meter, duty meter.
