Vessel Fuel Sampling Rules 2025: IMO Compliance Update

The IMO’s updated fuel oil sampling guidance (MSC‑MEPC.2/Circ.18) introduced in 2024 significantly tightens how representative bunker samples are obtained, handled and documented. The change affects both MARPOL Annex VI compliance and SOLAS flashpoint verification, and it raises the bar for every party in the bunker supply chain — shipowners, bunker suppliers, and on‑board teams must adjust procedures now to avoid costly disputes or operational restrictions.

Representative sampling is the core principle. The guidance stresses that a retained sample must reflect the physical and chemical properties of the whole delivery, not a convenient subset. Practically, this means continuous collection at the receiving ship’s bunker manifold across the entire delivery period. Three approved collection methods are described: manual valve‑setting continuous‑drip samplers, time‑proportional automatic samplers, and flow‑proportional automatic samplers. Each has tradeoffs — manual samplers are simple but vulnerable to human error; time‑proportional systems are straightforward for steady deliveries; flow‑proportional samplers deliver the most accurate representation across variable flow rates.

A major operational shift is the minimum sample volume: MSC‑MEPC.2/Circ.18 raises the retained sample requirement from 400 ml to 600 ml. This 50% increase requires larger, clearly‑labelled containers and changes to storage logistics. Containers must be filled to approximately 90% capacity (±5%) to allow thermal expansion while avoiding air contamination. Prior to finalising retained sample preparation, primary samples should be thoroughly agitated to homogenise the contents.

Contamination control and equipment cleaning are non‑negotiable. Even trace residues from low‑flashpoint solvents can skew laboratory results, so cleaning protocols must avoid solvents that could alter fuel properties. After collection, samples must be immediately sealed with tamper‑proof security seals that bear unique identifiers. The guidelines require the sealing and labelling process to be witnessed by both the supplier’s and the receiving ship’s representatives — a dual‑witness approach that strengthens legal defensibility and traceability.

Documentation enhancements are extensive. Retained samples must carry labels specifying sampling location and method, start and end times of delivery, bunker tanker identification, receiving ship and IMO number, signatures, and seal numbers. Crucially, seal identifiers must be cross‑referenced on bunker delivery notes and in the sample log so a direct link exists between the physical sample and the transaction record.

Storage and retention rules protect sample integrity. Samples should be kept out of accommodation zones in cool, ventilated areas shielded from direct heat and sunlight. A 12‑month minimum retention period is recommended to cover typical fuel burn cycles and potential post‑delivery disputes; companies should implement tracking systems to monitor location, seal status and any subsampling or testing performed.

Laboratory handling and chain‑of‑custody procedures are equally rigorous. When subsamples are extracted for testing, extractions must occur under witnessed conditions and any remaining retained portion must be resealed with a new tamper‑proof seal whose identifier is recorded. Lab reports should detail analytical methods and include identifying sample numbers so results can be traced unambiguously to the original delivery.

Operationally, this guidance increases expectations for trained personnel. Sampling crews must understand equipment calibration and manufacturer instructions, sealing procedures, and the legal importance of accurate documentation. Companies should formalise training and competency records rather than relying on informal practices.

For risk management, shipowners and suppliers should take immediate steps: review and upgrade sampling equipment where necessary (prioritise flow‑proportional samplers for larger, variable deliveries), update shipboard procedures and bunker delivery templates to include seal identifiers, train crews in witnessed sealing and chain‑of‑custody recording, and implement digital logs with printed backups. If disputes arise, robust documentation and continuous sampling records materially improve defence and reduce operational disruption.

In short, MSC‑MEPC.2/Circ.18 tightens the technical and documentary standards for fuel sampling. Early investment in equipment, training and record systems will reduce compliance risk and avoid lengthy investigations or operational limits arising from disputed fuel quality or flashpoint results. The new rules make representative sampling and traceable documentation the frontline defence in fuel quality governance for 2025 and beyond.