Bunkering & Oil Transfer: Precautions & Procedures

The scuppers, hoses, signals and tank-changeover discipline that prevent a spill and a bad fuel problem.

7 min read

Intermediate

Safety

Key Principles at a Glance 6 points

Before bunkering, plug all deck scuppers, drain water off the deck, and replace plugs only if local regulations allow; check hoses for damage and avoid tight bends; and check the vent pipes are clear for free escape of gases.
Pipeline tension caused by incorrect mooring or tidal effects must be watched, and an accidental spillage must be cleaned up and disposed of ashore or to bunker tanks.
Communication and emergency shutdown signals between ship and shore must be checked and fully understood, internal oil transfer stopped and unnecessary valves shut, and fire-fighting/pollution equipment and oil spill dispersant made ready, with day/night signals clearly exhibited.
During transfer, the bunker tank changeover must be known to all engineers and the Master, and tanks must not be changed in bad weather, coastal navigation or ports.
On the first changeover, transfer for 5–10 minutes to another tank or an overflow tank and confirm there is no sludge or water before shifting to the settling tank; after transfer, verify through the drain cock that no sludge or water was carried over.
Check the purifier condition and operation (a malfunctioning purifier can pump water into service tanks in bad weather), be extra careful when diesel oil is pumped directly to service tanks, and NEVER change tanks during manoeuvring conditions.

1. Precautions Before Receiving Bunkers

Before bunkering starts, all deck scuppers are plugged. Any water accumulating on deck is drained off and the plugs replaced only if local regulations allow.
Attention is paid to pipeline tension due to incorrect mooring or tidal effects.
Bunker hoses are checked for damage, and are not bent into tight bends resulting in high stress.
An accidental spillage is cleaned up and disposed of ashore or to bunker tanks.
Communication and emergency shutdown signals between ship and shore are checked and fully understood.
Tank vent pipes are checked to ensure free escape of gases.
Internal oil transfer is stopped completely and unnecessary valves are shut down.
Fire-fighting and pollution-prevention equipment and oil spill dispersant are ready for immediate use.
The day/night signal is exhibited clearly.

Scuppers = The Last Line of Defence

Plugging the deck scuppers is the simplest and most effective spill-prevention measure: if a hose bursts or a tank overflows, the plugged scuppers keep the oil on deck, where it can be contained and cleaned, instead of going over the side.

Figure 1: Before Bunkering. Scuppers plugged, hoses checked, pipeline tension watched, communication/emergency shutdown agreed, vents clear, internal transfer stopped, fire/pollution equipment ready and signals exhibited.

2. Precautions During Oil Transfer

The bunker tank changeover should be known to all engineers and the Master.
Avoid changing bunker tanks in bad weather, coastal navigation or in ports.
On the initial/first transfer, when changing over the tank, carry out 5–10 minutes of transfer to another bunker tank or overflow tank and confirm there is no sludge or water in the oil before shifting to the settling tank.
After transfer to the settling tank, verify through the drain cock that no sludge or water has been transferred.
Check the purifier condition and that operation is correct.
Note that purifiers can pump water into service tanks during bad weather if malfunctioning.
If diesel oils are pumped directly to service tanks, be more careful during the transfer.
Inform all engineers and the Master that the tank changeover is successful after verifying the settling/service tank drains, purifier operation and filters.
NEVER change tanks during manoeuvring conditions.

Why Tank Changeover Is Critical

Most fuel-related engine problems (blocked filters, purifier upset, contaminated service tanks) trace back to a bad tank changeover. The 5–10 minute flush to another/overflow tank and the drain-cock check are what prevent sludge and water from reaching the engine.

Figure 2: During Oil Transfer. The DO list (inform, flush 5–10 min, drain-cock verify, check purifier/filters) versus the DON'T list (never during manoeuvring, avoid bad weather/coastal/ports, beware malfunctioning purifier).

3. Tank Changeover & Quality Control

The Correct Changeover Sequence:

Plan and inform — the changeover is known to all engineers and the Master before it begins.
Flush — on the first changeover, transfer for 5–10 minutes to another bunker tank or an overflow tank.
Confirm — check for sludge/water in the oil before shifting to the settling tank.
Settle — transfer to the settling tank and verify through the drain cock that no sludge/water came across.
Purify — confirm the purifier is in correct condition and operating properly.
Filter — check filters and the service tank; then declare the changeover successful.

Quality Control Points:

Sludge/water in the settling tank — drawn off via the drain cock before fuel is passed forward.
Purifier performance — a purifier that is not set correctly can pass water into the service tank.
Direct diesel to service tank — extra care, because there is no settling stage to catch contamination.
Filters — checked after the changeover for sludge loading.

Figure 3: Tank Changeover Sequence. Plan/inform → 5–10 minute flush → confirm no sludge → settle and drain-cock check → correct purification → filter check, then declare the changeover successful.

4. Emergency Preparedness & Golden Rules

Emergency Preparedness:

Fire-fighting and pollution-prevention equipment and oil spill dispersant ready for immediate use before transfer begins.
Emergency shutdown signals agreed with shore and fully understood by both sides.
Spill response — a spill is contained on deck (scuppers plugged) and cleaned, then disposed of ashore or to a bunker tank.
Watchkeeping — tanks are monitored during transfer for level and overflow; venting is confirmed clear.

Golden Rules:

Plug the scuppers first.
Know the changeover plan before you start.
Never change tanks during manoeuvring.
Avoid tank changeovers in bad weather, coastal navigation or ports.
Flush and verify before sending fuel forward.
Beware the purifier — a malfunction can pass water into service tanks.

Surveyor Asks

Surveyors commonly ask: "What precautions do you take before and during bunkering?" Split your answer into before (scuppers, hoses, tension, signals, vents, internal transfer stopped, fire/pollution gear, signal) and during (changeover known, avoid bad weather/coastal/port, flush 5–10 min, drain-cock check, purifier, filters) — and always add the rule: never change tanks during manoeuvring.

Figure 4: Emergency Preparedness & Golden Rules. Equipment and signals ready, spill contained on deck, plus the six rules — scuppers, plan, never in manoeuvring, avoid bad conditions, flush/verify, and beware the purifier.