Overview
ISO 23765:2021 - "Ships and marine technology - Marine environment protection - Specification for collecting data on ship's fuel oil consumption" specifies a uniform method for ships of 5 000 gross tonnage (GT) and above to collect and report annual fuel oil consumption data required by MARPOL Annex VI (regulation 22A). The standard clarifies practical measurement approaches, defines required ship and fuel-consumer information, and includes an example ship fuel oil consumption data collection plan (Annex A) plus guidance and standardized reporting formats (Annexes B and C).
Key topics and technical requirements
- Scope and applicability: Data collection for ships ≥ 5 000 GT to comply with MARPOL Annex VI data-collection obligations.
- Ship and consumer information: Required vessel particulars (IMO number, flag, GT, DWT, ship type, EEDI if applicable) and list of fuel oil consumers (main engine, auxiliary engines, boilers, etc.), including power, type/model and fuel conversion factors.
- Measurement methods for fuel oil consumption:
- Bunker Delivery Notes (BDNs): Calculation of annual consumption using BDNs and tank inventory (Q = T1 + R − S − T2), with BDN data elements defined (quantity, density@15 °C, sulfur content, supplier declaration).
- Flow meters: Use of mass/volume flow meters and related calibration/verification practices.
- Fuel tank monitoring (sounding): Remote sounding gauges and manual sounding procedures, with density correction methods.
- Supporting measurements: Methods to measure distance travelled (actual distance over ground, nautical miles) and hours underway (time under own propulsion).
- Data aggregation and quality control: Requirements for aggregated annual reports, validation checks for BDNs, flow meters and tank readings, and documented evidence to resolve discrepancies.
- Emissions linkage: Use of conversion factors to relate fuel consumption to CO emissions; provision for direct CO measurement.
- Annexes: Example data collection plan (A), technical specs and test requirements for automatic data collection systems (B), and a standardized data reporting format (C).
Practical applications and users
ISO 23765:2021 is used by:
- Shipowners, operators and technical superintendents preparing SEEMP Part 2 (fuel oil consumption data collection plan).
- Flag Administrations, classification societies and recognized organizations verifying compliance with MARPOL Annex VI.
- Onboard and shoreside environmental/compliance officers implementing measurement procedures (BDN reconciliation, flow meter calibration, tank sounding).
- Vendors of automatic data collection systems (ADCS) and flow-meter manufacturers aligning equipment to Annex B guidance.
- Auditors, researchers and ports seeking standardized, traceable fuel-consumption data for regulatory reporting and energy-efficiency analysis.
Related standards
- IMO MARPOL Annex VI (Regulations for the prevention of air pollution from ships) - normative reference for the regulatory requirement and BDN content.
- ISO 23765 complements IMO SEEMP guidelines (Part 2) by providing detailed methods and reporting formats for fuel oil consumption data collection.
Keywords: ISO 23765:2021, fuel oil consumption data collection, MARPOL Annex VI, SEEMP Part 2, bunker delivery note, flow meter, tank sounding, ship fuel consumption reporting.
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