Bunkering & Oil Transfer: Precautions & Procedures

1. Precautions Before Receiving Bunkers

Comprehensive Bunkering Procedure & Safety Checklists:

Bunkering is considered a high-risk operation with significant environmental and safety repercussions. In MEO oral examinations, surveyors expect candidates to detail the step-by-step operation from pre-arrival preparation through connection, pumping, continuous sampling, topping off, and disconnection.

1. Pre-Arrival Preparation & Tank Soundings. The Chief Engineer establishes a detailed Bunker Plan: calculates required quantities, designates tanks to be filled (leaving 10–15% expansion margin), verifies stability, list, and trim. Sound all fuel oil double bottom, settling, and service tanks; verify high-level alarms (≥95%) and overflow tank alarms.
2. Deck Containment & SOPEP Equipment Readiness. Plug all deck scuppers tightly using tapered wooden plugs wrapped in burlap or mechanical rubber expansion plugs; drain the deck of water before fitting them, and replace a plug that falls out during the operation only where local regulations allow it. Watch the bunker line for pipeline tension as the ship works her moorings or the tide makes her move. Empty drip trays and manifold savealls, ensuring saveall drain valves are tightly closed. Deploy the SOPEP response kit at the manifold: non-sparking bronze shovels, scoops, buckets, sorbent pads, sawdust, and rig an air-operated portable diaphragm pump (Wilden pump) with static earth grounding. Position dry chemical powder fire extinguishers and connect two fire hoses fitted with fog nozzles to nearby hydrants.
3. Pre-Bunkering Safety Conference & Barge Agreement. Hold a face-to-face safety conference with the bunker barge master / shore representative. Complete and jointly sign the Ship-to-Shore / Ship-to-Barge Safety Checklist. Agree upon: fuel grade and ordered quantity; maximum allowable pumping pressure (≤ 5.0 bar); initial slow start rate and maximum full pumping rate; emergency stop signals and shutdown response time; dedicated VHF communication channels and backup hand signals; topping-off notice times (e.g. 15-minute warning before tank switch); and representative sampling protocols.
4. Hose Connection & Warning Signals. Inspect the bunker hose for damage along its length and lay it out without tight bends or high stress. Connect it using a new oil-resistant gasket; ensure every flange bolt hole has a bolt tightly torqued (no missing bolts). Connect static bonding wire if mandated by terminal regulations. Hoist Flag Bravo by day, or illuminate an all-round red light by night. Post "NO SMOKING / NO NAKED LIGHTS" warning notices at access gangways and manifold areas.
5. Initial Slow Start & Line Verification. Open designated tank filling valves and manifold valve; leave all other tank valves firmly shut. Confirm barge starts pumping at a slow initial rate (≤ 20–25% capacity). Check manifold pressure gauge. The engineer officer immediately inspects the designated tank to confirm fuel is entering and checks adjacent tanks to confirm no inadvertent cross-filling. Verify all pipe flanges, saveall trays, and air vent heads for leaks or air expulsion.
6. Full Pumping Rate & Continuous Drip Sampling. Once line integrity is verified, signal barge to increase to full agreed pumping rate. Start the continuous drip sampler at the receiving manifold. Measure ullages/soundings every 15–20 minutes and cross-check receiving rate against barge discharge rate. Never perform internal oil transfers or purifier desludging while bunkering.
7. Topping-Off Protocol (≤ 85–90% Volume). Notify barge 15–20 minutes before topping off to reduce pumping rate to minimum. Top off tanks to a maximum of 85% to 90% of capacity (leaving expansion space for thermal expansion when fuel is heated by heating coils, preventing overflow through vent pipes into the saveall or overflow tank). When changing from a full tank to the next empty tank, open the valves to the new tank before closing the valves of the full tank (prevents deadhead pressure surge).
8. Blowing Through, Line Draining & Disconnection. Upon completion of pumping, blow through the bunker line with compressed air (only if mutually agreed and following company safety limits) or allow line to drain into the bunker tank. Close the manifold valve, vent line via purge cock, drain manifold drip tray into saveall, and blank off manifold flange with a blank flange and full set of bolts. Disconnect hose and verify barge blanked off.
9. Final Soundings, BDN Verification & Sample Sealing. Allow oil to settle for 30 minutes to release entrained air ("cappuccino effect"). Take final soundings and temperatures of all bunker tanks; compute net standard volume and metric tons using density at 15 °C and ASTM Table 54B. Inspect the Bunker Delivery Note (BDN): verify density, viscosity, sulfur content (≤ 0.50% VLSFO / ≤ 0.10% ECA), and flash point (≥ 60 °C). Sign and retain BDN on board for 3 years. Seal and witness the MARPOL sample bottles.

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.

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. In bad weather the sloshing carries sludge and water forward from the settling tank; in coastal navigation or in port there is too little time to react to a problem.
• 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 — the risk is fuel starvation or a blackout at the worst possible time.

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.

3. Tank Changeover & Quality Control

The Correct Changeover Sequence:

1. Plan and inform — the changeover is known to all engineers and the Master before it begins.
2. Flush — on the first changeover, transfer for 5–10 minutes to another bunker tank or an overflow tank.
3. Confirm — check for sludge/water in the oil before shifting to the settling tank.
4. Settle — transfer to the settling tank and verify through the drain cock that no sludge/water came across.
5. Purify — confirm the purifier is in correct condition and operating properly.
6. 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.

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: "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.

5. Representative Continuous Drip Fuel Oil Sampling (MARPOL Annex VI)

Statutory Representative Sampling (IMO Res. MEPC.182(59) / MEPC.96(47)):

MARPOL Annex VI Regulation 18.8.1 mandates that a representative sample of the fuel oil delivered to the ship must accompany the Bunker Delivery Note (BDN). This sample is known as the MARPOL Delivered Sample. Under IMO guidelines, the only recognized statutory method for obtaining a truly representative sample is continuous drip sampling at the receiving ship's bunker manifold throughout the entire bunkering operation.

• Mandatory sample set: 4 bottles.
• Minimum volume per bottle: ≥ 750 mL.
• MARPOL sample retention: 12 months.
• BDN statutory retention: 3 years.

Continuous Drip Sampler Operation:

• Location: The sampling device (manual needle valve sampler or automatic probe) must be mounted directly onto the receiving ship's bunker manifold flange—never on the barge manifold or at storage tank suction.
• Adjustment: The needle valve is adjusted at the start of pumping to provide a steady, continuous drip (approx. 20–30 drops per minute) into a clean, sealed container throughout the entire duration of the delivery.
• Homogenization: When bunkering completes, the collected bulk sample (typically 4–5 litres) is thoroughly shaken and agitated to ensure complete homogeneity before dividing into individual sample bottles.

Every delivery yields four mandatory sample bottles, each with its own purpose:

1. MARPOL Delivered Sample

Primary Statutory Bottle: Sealed with a tamper-evident numbered security seal, signed and countersigned by both the Chief Engineer and the Bunker Supplier Representative. Retained on board in the designated hazardous oil sample locker under the custody of the Chief Engineer until the fuel is substantially consumed, but in any case for not less than 12 months from delivery. Handed over only to Flag State or Port State Control authorities upon official demand for sulfur verification.

2. Commercial Fuel Analysis Sample

Quality Assurance Bottle: Dispatched immediately via courier to an accredited fuel testing laboratory (e.g. DNV Petroleum Services, FOBAS, Veritas). Tested against ISO 8217 parameters (viscosity, density @ 15°C, water content, flash point, pour point, MCR, catalytic fines Al+Si, TSP). The fuel should not be consumed until lab test results confirm compliance.

3. Ship's Retention Sample

Owner / Defense Bottle: Kept on board in the vessel's sample locker as a legal backup in case of commercial disputes, engine damage claims (e.g. high cat-fine abrasive wear), or discrepancy between lab results and barge declarations.

4. Bunker Supplier / Barge Sample

Supplier Bottle: Handed over to the bunker barge master/representative for the supplier's quality assurance and retention records.

Bunker Delivery Note (BDN) Cross-Check

Before signing the BDN, the Chief Engineer must verify that the seal numbers recorded on the BDN match the physical seal numbers on the sample bottles. The BDN must state: name/IMO number of vessel, port, date of delivery, fuel grade, quantity in metric tons, density at 15 °C, sulfur content (% m/m), and a declaration signed by the supplier confirming the fuel complies with MARPOL Annex VI Regulation 18.3 and Regulation 14.1 (Sulfur cap ≤ 0.50% global / ≤ 0.10% ECA).