- What the Oil Record Book is — and who must keep it
- The codes explained: Part I, A to I
- What a correct entry actually looks like
- The ten mistakes that generate deficiencies
- What the inspector cross-checks (the part nobody explains)
- Going electronic: the e-ORB route
- Building ORB discipline that survives crew changes
What the Oil Record Book Is — and Who Must Keep It
The Oil Record Book (ORB) is the statutory log of oil-related operations required under MARPOL Annex I. It exists to make oil handling on board traceable and auditable — every litre of sludge, bilge water and bunker fuel accounted for from generation to disposal.
- Part I — Machinery space operations. Required on every ship of 400 GT and above (and oil tankers of 150 GT and above).
- Part II — Cargo/ballast operations. Required additionally on oil tankers of 150 GT and above.
Three procedural rules underpin everything else: entries are made operation by operation (not batched at month end), each entry is signed by the officer in charge of that operation, and each completed page is signed by the Master. The book must be readily available for inspection and retained for the period required by the regulation.
The ORB is a legal document. In several jurisdictions, false entries have been prosecuted as criminal offences independent of any actual pollution — the record itself is the offence. That is why "tidy it up later" is never an acceptable practice.
The Codes Explained: Part I, A to I
Most ORB deficiencies begin with a code letter chosen incorrectly. Part I operations are coded as follows:
| Code | Operation | Typical entries |
|---|---|---|
| A | Ballasting or cleaning of oil fuel tanks | Ballasting a fuel tank; cleaning a tank previously containing oil fuel |
| B | Discharge of dirty ballast or cleaning water from oil fuel tanks | Discharge of the water from a tank covered under Code A |
| C | Collection, internal transfer and disposal of oil residues (sludge) | Weekly collection of residues; transfer between sludge tanks; landing sludge ashore; incineration |
| D | Non-automatic discharge overboard, transfer or disposal of bilge water accumulated in machinery spaces | Manual operation of the 15 ppm equipment overboard; pumping bilges to a holding tank; landing bilge water ashore |
| E | Automatic discharge overboard, transfer or disposal of bilge water | Where the system operates automatically — record the system's operation |
| F | Condition of the oil filtering (15 ppm) equipment | Failures, repairs, alarm tests and maintenance of the OWS and 15 ppm alarm |
| G | Accidental or other exceptional discharges of oil | Spills, leaks, overflows — circumstances, quantity, reasons |
| H | Bunkering of fuel or bulk lubricating oil | Each bunkering: place, time, type, quantity, tanks |
| I | Additional operational procedures and general remarks | Anything not covered above; explanations and clarifications |
The single most cited confusion: C versus D. Sludge — oil residue generated by purifiers, drains and fuel treatment — is Code C. Bilge water — accumulated water in machinery spaces — is Code D (or E if automatic). Transferring sludge and logging it as a bilge operation is a classic finding, and it also makes your quantities stop reconciling.
What a Correct Entry Actually Looks Like
A defensible entry answers four questions without the inspector having to ask: what, how much, from/to where, and when. Compare:
| Weak entry (invites questions) | Strong entry (closes the question) |
|---|---|
| "Sludge transferred." | Code C — Transfer of oil residues from Sludge Tank No.1 (retained qty 12.4 m³) to Sludge Tank No.2 (retained qty after transfer 18.9 m³); quantity transferred 6.5 m³; date/time; officer signature. |
| "Bilges pumped out." | Code D — Bilge water from Machinery Space Bilge Holding Tank discharged through 15 ppm equipment; quantity 3.2 m³; start/stop position and time; equipment operated normally; officer signature. |
| "Bunkers received." | Code H — Bunkering at [port]; VLSFO 480.0 MT to Tanks 3P/3S; sounding before and after; BDN reference; date/time; officer signature. |
Note what the strong entries share: identified tanks, quantities before and after, and a retained quantity that a surveyor can verify against a sounding. That is the difference between a record and an assertion.
Formats vary by flag and by the printed book in use — always follow the instructions printed in your own ORB and any flag-State guidance. The examples above illustrate the level of detail expected, not a mandated wording.
The Ten Mistakes That Generate Deficiencies
- Wrong code letter. Above all, sludge logged as bilge (C ↔ D). Fix the understanding, not just the entry.
- Missing quantities. An operation without a quantity, and without the tank's retained quantity, cannot be verified.
- No weekly residue collection entry. Residues accumulate continuously; a book showing no routine collection for weeks contradicts the machinery's operation.
- Retrospective completion. A month of entries in identical ink and handwriting is immediately obvious and is treated as evidence the record is not contemporaneous.
- Missing signatures. The officer in charge per entry; the Master per completed page.
- Quantities that don't reconcile with sounding books, tank capacity or the previous entry's retained figure.
- Unrecorded 15 ppm equipment failures. Code F exists precisely for this; silence looks like concealment.
- Improper corrections. Errors should be struck through with a single line, corrected, initialled and dated — never erased, overwritten or covered.
- Tank identities that don't match the ship. Names in the book must match the approved plans and the tank markings.
- Blank pages or skipped lines that invite the question of what was removed.
What the Inspector Cross-Checks — the Part Nobody Explains
Here is what most guidance omits: the inspector does not read the ORB in isolation. They read it against other records, looking for stories that do not agree. Expect these comparisons:
| ORB entry | Checked against | What a mismatch suggests |
|---|---|---|
| Sludge retained quantities (Code C) | Sounding book; physical sounding of the tank taken during the inspection | Undeclared disposal, or a book kept for show |
| Bilge operations (Code D/E) | Engine room log; 15 ppm equipment counter/alarm printout; OWS running hours | Overboard discharge not recorded |
| Bunkering (Code H) | Bunker Delivery Notes; fuel consumption figures; noon reports | Unaccounted fuel — a favourite thread to pull |
| Sludge landed ashore | Waste reception receipts from the port facility | Missing receipts against declared landings |
| Incinerator use | Incinerator log/running hours | Declared incineration the equipment could not have performed |
| Equipment defects (Code F) | PMS defect and maintenance history | Known failures absent from one system or the other |
This is why ORB integrity is not really a paperwork problem — it is a data consistency problem across several systems. When soundings, maintenance history and bunkering records live in disconnected books and spreadsheets, mismatches are almost guaranteed. When they share one dataset, the mismatch is caught by you rather than by an inspector. See our PMS guide for the maintenance-history side of that.
Going Electronic: the e-ORB Route
Since IMO Resolution MEPC.312(74), an approved electronic record book may be used in lieu of the hard-copy book. Done properly this removes several whole categories of deficiency at once:
- Code selection is guided rather than remembered, so C-versus-D errors largely disappear.
- Mandatory fields prevent entries without quantities or tank identities.
- Timestamps are tamper-evident, so retrospective completion is structurally impossible.
- Running balances are calculated, so retained quantities cannot drift out of reconciliation.
Two conditions matter: the system must meet the required standards (audit trail, tamper-proof timestamps, secure authentication, backup), and your flag Administration must issue a Declaration of MARPOL Electronic Record Book which is carried on board. Not every flag or port State experience is identical — verify before committing the fleet. We cover the decision in detail in our electronic record books guide.
Building ORB Discipline That Survives Crew Changes
- Make entries at the operation, not at the desk. The habit is the control.
- Sound before and after. Every quantity you write should be one you measured.
- Run a monthly self-audit comparing ORB against soundings, engine log and BDNs — exactly the comparisons in the table above. Find your own mismatches first.
- Brief every joining engineer on the C/D distinction and this ship's tank naming. Rotation is when discipline slips.
- Never leave the book to accumulate. If entries are behind, that is the finding, regardless of what the operations were.
- Treat Code F honestly. A recorded, repaired failure is a functioning safety system; an unrecorded one is a concealed defect.
Stop chasing records across five different books
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Request a DemoFrequently Asked Questions
What is the Oil Record Book?
The statutory MARPOL Annex I record of oil-related operations. Part I covers machinery-space operations (ships 400 GT+); Part II covers cargo/ballast operations on oil tankers (150 GT+).
What is the difference between Code C and Code D?
Code C is oil residues (sludge) — collection, internal transfer and disposal. Code D is bilge water accumulated in machinery spaces discharged or transferred non-automatically. Confusing the two is the most commonly cited ORB error.
What are the most common ORB mistakes?
Wrong code, missing quantities and tank identities, no weekly residue collection entry, retrospective completion, missing signatures, and figures that don't reconcile with soundings, engine logs and bunker delivery notes.
Can the ORB be kept electronically?
Yes — following IMO Resolution MEPC.312(74), with a compliant system and a flag-issued Declaration of MARPOL Electronic Record Book carried on board.
How long must it be retained?
MARPOL Annex I requires retention for three years after the last entry, readily available for inspection. Verify current requirements and any flag-specific expectations.
Scope & Sources
This guide summarises publicly available material on MARPOL Annex I record-keeping and common Port State Control findings. The regulation text, the instructions printed in your own Oil Record Book, and your flag Administration's guidance always take precedence over this summary. Requirements and interpretations evolve — verify before acting. Nothing here constitutes legal advice.