Oil Record Book — Part I (Machinery Space Operations)
The mandatory logbook documenting every oil-related operation in the machinery space: one of the first documents a Port State Control Officer (PSCO) asks to see on board.
Operational Explanation
The Oil Record Book (ORB) Part I records all operations involving fuel and lubricating oil carried out in the machinery space: ballasting and cleaning of fuel tanks, discharge of bilge water, condition of the oil filtering equipment, bunkering and internal transfers. The Oil Discharge Monitoring and Control System (ODMCS) belongs to cargo/ballast operations on oil tankers and is recorded in Part II, not here.
It is not a secondary administrative form: it is the single most scrutinised document during Port State Control inspections, and one of the main tools authorities use to detect illegal discharges (so-called "magic pipes").
Regulatory Reference
MARPOL Annex I, Regulation 17 (Oil Record Book Part I) and Appendix III (standard format). Implementation guidance in MEPC.1/Circ.736/Rev.2 (2011) — "Guidance for the recording of operations in the Oil Record Book Part I". It is the applicable guidance for entries, and it remains so. The 2019-2020 framework did not introduce a new Appendix III form: it enabled the Electronic Record Book approved by the Administration. Res. MEPC.314(74) amends Annexes I, II and V to that effect, and Res. MEPC.312(74) carries the guidelines. Res. MEPC.316(74) amends Annex VI instead, and does not concern this book.
Scope of Application
Under MARPOL Annex I, Regulation 17.1, Part I is required on every oil tanker of 150 GT and above and on every ship of 400 GT and above other than an oil tanker. There is no applicability criterion based on the presence of an oily water separator: fitting one does not bring a ship below those thresholds within the requirement. Oil tankers of 150 GT and above additionally keep Part II (cargo/ballast operations).
Procedure / How to Complete It
- Identify the correct operation code among codes A-I (A: ballasting/cleaning of fuel tanks; B: discharge of dirty ballast water; C: collection, transfer and disposal of oil residues (sludge); D: non-automatic discharge of bilge water; E: automatic discharge of bilge water; F: condition of the oil filtering equipment; G: accidental or exceptional discharges; H: bunkering of fuel/lubricating oil; I: additional operational procedures).
- Record the operation without delay, as required by Regulation 17.4, once it is completed — never in advance. The Convention sets no tolerance: there is no 24-hour or same-day allowance, and a checklist certifying compliance with one would document an accepted delay that the rule does not permit.
- State date, code/item, quantity (m³), position (for discharges) and every detail required by the IMO format.
- The officer responsible for the operation signs the individual entry.
- The Master signs each completed page, taking responsibility for it.
- Keep the log on board for at least 3 years from the last entry, available for inspection at any time.
Diagram: recording flow
Practical Example
Example of a code H — Bunkering entry:
| Date | Code | Item | Entry (summary) |
|---|---|---|---|
| 14-JUL-2026 | H | 26 | Bunkering: place and time, type and quantity — 340 MT of ISO 8217 RMG 380 HFO, 0.42% m/m sulphur, at Genoa from barge "Example": 210 MT added to tank FO1, now containing 480 MT, and 130 MT added to tank FO2, now containing 300 MT. Sub-items 26.1 to 26.4. BDN attached. Signed by the 2nd Engineer. |
| 14-JUL-2026 | C | 11.4 | Oil residues (sludge): collection from the purifier into the sludge tank, 0.8 m³, with the tank identification and the source it was collected from. This is a collection, not a disposal: code C 12 covers disposal or transfer of residues already collected, and tank capacity is not to be recorded for its sub-items. Signed by the 3rd Engineer. |
The Item column takes the number printed in the list of items in the Oil Record Book itself: a single series running from 1 to 26 across codes A to I (code C: items 11 and 12; code F: items 19 to 21; code H: item 26 with sub-items 26.1–26.4). Notations such as "H1" or "C2", formed by combining the letter with a counter, do not exist in the IMO format: they make the book hard to read during an inspection and are best avoided. The date format is the one the guidance prescribes, dd-MONTH-yyyy: the circular states it expressly and gives its example with the month abbreviated in letters. It removes the day/month ambiguity without inventing a convention, and a month written in letters stays readable to inspectors of any nationality.
What Typically Goes Wrong
Common Mistakes Mistake Library
| Mistake | Consequence | How to avoid it |
|---|---|---|
| Operation not signed by the officer in charge, or completed page not signed by the Master | PSC deficiency, possible detention | Regulation 17.4 asks for two different signatures: the officer signs each completed operation, the Master each completed page. Close-out check of each page before the end of the month or voyage |
| Entries recorded days late or in bulk | Suspicion of tampering, PSCO follow-up | Record immediately after every operation |
| Untracked erasures or corrections | Loss of the document's credibility, possible offence | Strike through with a single line, sign the correction, never use correction fluid |
| Bilge volumes inconsistent with tank capacity/consumption | Investigation into illegal discharges | Periodic reconciliation between estimated production and recorded volumes |
What the PSCO Checks
Operational Tips
- Never leave the ORB «pending»: Regulation 17.4 requires each operation to be recorded without delay, not by the end of the day.
- Use the applicable code and item number, followed by every particular that Appendix III and the recording guidance require for that item: some of them are necessarily descriptive. The code does not replace the particulars, and an unstructured narrative does not replace a prescribed entry.
- Before a PSC inspection, verify that all recent pages are signed and consistent with the Bunker Delivery Note and the bilge log.
- For an electronic ORB, make sure it has been approved by the flag State Administration.
Preparation checklist
Educational checklist. This summary supports learning and preparation only. It does not replace the vessel’s approved procedures, manuals, statutory documents, company SMS, or applicable official requirements. Completing it demonstrates neither compliance nor readiness for an inspection: it shows that a list has been read, not that the ship is in order. Always verify the current documents carried on board.
- All of this month's entries are signed by the officer responsible for the operation
- The Master has signed every completed page
- Every entry is recorded without delay after the operation (Reg. 17.4), with no accumulated backlog
- Bunker volumes match the Bunker Delivery Note
- No untracked erasure
- The log is available and has been kept for at least 3 years
FAQ
Related Topics
Last substantive revision of this page: 28 August 2026 · page fingerprint b325d0909bd6