Ship-to-Ship Transfers in Oil Trading: Operations, Safety and Documentation
Ship-to-ship transfers are precision cargo operations. In oil trading, they let crude or refined products move between vessels when a direct berth or terminal call is not the best option, but the transfer only works when the location, the plan, the people, the hoses, and the paperwork all line up.
That is why STS should be treated as a controlled workflow, not a last-minute marine task. IMO has warned that open-ocean transfers can be high-risk, while OCIMF frames STS as a full planning and execution process with step-by-step checks, human factors, and document control.
"This Guide provides comprehensive guidance on the planning and execution of Ship to Ship (STS) transfer operations."(OCIMF, Ship to Ship Transfer Guide)
What Ship-to-Ship Transfer Means in Oil Trading
The OCIMF Ship to Ship Transfer Guide says STS operations apply whether the transfer is conducted at sea or in port, and it recommends keeping the guide on board every vessel and terminal involved. For oil traders and supply teams, that matters because STS is not just a marine event, it is part of the wider execution chain.
At Nedjma, our NOOR-Trading division treats that handoff as part of the commercial process, with market intelligence, commercial structuring, and risk review completed before operations begin.
How an STS Operation Usually Unfolds
1. Pre-transfer planning and notification
MARPOL Annex I regulation 42 requires advance notification for STS operations within a Party's territorial sea or exclusive economic zone, and the notice must include the ship identities, the planned date, time and geographical location, whether the transfer is at anchor or underway, the oil type and quantity, the planned duration, the advisory control contact, and confirmation that the STS Operations Plan is on board. If the ETA changes by more than six hours, a revised ETA must be sent.
That makes the transfer area part of the compliance record, not just a navigational choice. The location has to be fixed early enough for the authorities, the vessels, and the service provider to work from the same set of facts.
2. Approach, mooring, and connection
OCIMF's Ship to Ship Safety Checklist turns the approach and mooring sequence into a practical discipline. Before run-in and mooring, the checklist calls for fenders to be visually inspected and correctly positioned, no overhanging projections on the berthing side, a proficient helms person at the wheel, and agreed course, speed, and speed-control method.
OCIMF's guidance on STS hose handling, storage, maintenance and testing adds a simple rule that is easy to underestimate: hose strings are repeatedly lifted, bent, and folded during side-by-side transfers, so they must be handled, stored, maintained, inspected, and tested correctly at appropriate intervals.
3. Cargo transfer and monitoring
Once the vessels are connected, the transfer itself should be run as a monitored sequence, with bridge communications, cargo watchkeeping, pressure control, and agreed stop criteria. The current OCIMF guide includes a dedicated human factors chapter, which is a useful reminder that decision quality, fatigue, and communication discipline are part of the safety system.
That is also where disciplined handover matters. If the operation is moving quickly, the team still has to protect the quality of the figures, the line of communication, and the ability to stop the transfer cleanly if conditions change.
4. Completion, disconnection, and closeout
After the cargo stops moving, the crew should disconnect cleanly, confirm final figures, and close out the evidence trail while the operation is still fresh. MARPOL requires STS records to be retained on board for three years and to be readily available for inspection.
Safety Controls That Matter Most
Safety in STS is about layers, not a single checkbox. The OCIMF guide, the safety checklist, and the hoses guidance all point to the same pattern: verify the place, the people, the equipment, and the abort criteria before any cargo moves.
Choose a permitted and risk-assessed transfer area. Regulation 42 requires advance notification for STS operations within a Party's territorial sea or exclusive economic zone, and IMO's warning on open-ocean transfers shows why they deserve extra caution.
Keep the mooring and approach sequence disciplined. Fenders, line handling, speed control, and bridge teamwork need to be agreed before the vessels come together.
Protect hose strings as critical equipment. They should be handled, stored, maintained, inspected, and tested at appropriate intervals because repeated bending and lifting create wear.
Build for human factors. The current OCIMF guide includes a dedicated human factors chapter, which supports a more realistic view of fatigue, communication, and decision-making.
Documentation, Approvals and Records
The paperwork is not an afterthought. MARPOL regulation 41 requires an approved STS Operations Plan, written in the working language of the ship, and it allows the plan to be incorporated into an existing Safety Management System where that applies. It also says the person in overall advisory control must be qualified, and the operation records must stay onboard for three years.
The IMO list of certificates and documents required on board is a practical reminder that inspectors look for a complete onboard file, not just a cargo handover note. The Oil Record Book, the Shipboard Oil Pollution Emergency Plan, and the STS operations plan all belong in that pack.
Documents and approvals at a glance
Control point | What to confirm | Why it matters |
|---|---|---|
STS Operations Plan | Approved by the Administration, written in the working language of the ship, and aligned with the best-practice STS guidance. | It is the mandatory baseline for the operation. |
Advance notification | For STS operations within a Party's territorial sea or exclusive economic zone, the notice includes the location, oil type and quantity, planned duration, and contact details for the person in overall advisory control or service provider. | It gives the authority a clear picture before the transfer starts. |
Oil Record Book and emergency plan | Keep the Oil Record Book and the Shipboard Oil Pollution Emergency Plan available, alongside any vessel-specific records that apply. | These are the core pollution-prevention and response documents. |
Retention and inspection | Keep STS records onboard for three years and make them readily available for inspection. | This is the audit trail that proves the transfer was run under control. |
OCIMF also makes a broader governance point: the guide is intended for ship operators, Masters, Marine Superintendents, STS service providers, local administrations, and other stakeholders, and it recommends that the guide be kept on board every vessel and terminal involved in STS operations.
Risk Management and Compliance Vigilance
Open-ocean STS is where vigilance matters most. IMO has described open-ocean transfers as high-risk and warned that they can undermine maritime safety, environmental protection, liability, and compensation frameworks. IMO has raised concerns about transfers involving vessels with unclear ownership, inadequate insurance or poor maintenance records.
That does not mean every STS transfer is suspect. It means the commercial, marine, and compliance teams should work from the same evidence pack, with counterparty review, location approval, cargo data, and document closeout tied together. In that sense, STS risk management is as much about structured execution as it is about sea conditions.
FAQ
What is ship-to-ship transfer in crude oil trading and why is it used?
It is the transfer of oil cargo between two tankers, usually to move a parcel onward when a terminal call is not the best fit. The OCIMF guide says STS operations apply at sea or in port, and MARPOL requires an approved STS Operations Plan for oil tankers involved in the activity. In practice, the method is used because it adds flexibility to trading and logistics, but only when the operation is planned and documented properly.
What are the key safety considerations during oil STS transfers?
The basic priorities are location, mooring, hose integrity, communication, and human factors. The OCIMF checklist asks for fender condition, correct positioning, no overhanging projections, an alert helms person, and agreed course and speed. OCIMF also notes that hose strings need proper handling and testing, and the current guide includes a dedicated human factors chapter.
What documentation and approvals are required for ship-to-ship transfers of oil?
MARPOL regulation 41 requires an approved STS Operations Plan, written in the ship's working language, and records kept on board for three years. Regulation 42 adds advance notification in the territorial sea or exclusive economic zone of a Party, including the location, oil type and quantity, duration, and the person in overall advisory control. The IMO document list also flags the Oil Record Book and the Shipboard Oil Pollution Emergency Plan.
Who is responsible for operations and risk management during a ship-to-ship transfer?
Responsibility is shared, but it must be coordinated. MARPOL says the person in overall advisory control must be qualified, and the STS plan can sit inside the ship's Safety Management System. OCIMF says the guide is intended for ship operators, Masters, marine superintendents, STS service providers, and local administrations, which is a useful reminder that no single department can manage the risk alone.
How do regulatory guidelines such as OCIMF and MARPOL govern ship-to-ship oil transfers?
MARPOL sets the mandatory minimum, including the approved plan, notification, and recordkeeping. OCIMF provides the practical execution layer, including the STS transfer guide, the step-by-step safety checklist, and hose handling guidance. IMO's warning on open-ocean transfers shows why compliance is also a risk-management issue, not just a paperwork issue.
What to Do Next
If your team is reviewing an STS workflow, start by aligning the commercial structure, the operating location, and the document pack. To discuss a specific operation, contact Nedjma Corporation, read more about the company, or return to the homepage.
