Fuel Changeover, a Seized Fuel Pump and an Approaching ECA
At 22:00 your 45,000 dwt product tanker is 40 nm from the 0.10% sulphur ECA boundary and making 12 kn. The main engine is a MAN B&W 6S50MC burning 380 cSt HFO at 3.30% S. The changeover procedure requires completion at least 1 hour before the boundary. Changeover has started, but at 23:10 the fuel oil viscosity at the engine inlet falls rapidly, the fuel pump plunger seizes, and the engine trips. The vessel is in a narrow traffic separation scheme with a 0.8 NM nearest approach to a laden VLCC. The emergency generator starts. The second engineer reports the HFO settling tank has 1.2 m of water and the MGO tank has only 18 m³ remaining. The ECA boundary will be crossed in 2 hours and there is no tug available.
1. Explain the likely cause of the fuel pump seizure during changeover and how the procedure should have prevented it.
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The most likely cause is an uncontrolled changeover that allowed the fuel viscosity at the engine inlet to fall too far and too quickly. A 380 cSt HFO is heated to give about 10–15 cSt at the pump; MGO is much less viscous and has poorer lubricity. If cold MGO enters a hot pump, the plunger and barrel can lose their hydrodynamic film, and differential thermal contraction can reduce clearance. The result is scuffing and seizure. The 1.2 m of water in the HFO settling tank is a second warning: water can cause corrosion, cavitation and erratic fuel delivery, and it should have been drained before changeover.
A proper procedure would change over gradually, maintain the manufacturer's viscosity and temperature limits, monitor viscosity at the engine inlet continuously, and change filters as the solvent effect of distillate loosens deposits. It would drain water from settling tanks, check the purifier, use a clean MGO service tank, and allow enough time to complete the changeover before the boundary. It would also record temperatures, viscosities and times. The rapid viscosity drop reported here shows the control was not effective; the engine was probably switched too quickly or the viscosity controller was not in automatic control.
2. State the immediate actions to regain propulsion and manage the traffic risk.
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Bridge and traffic. Confirm the engine has tripped and the emergency generator is online. If the vessel is not under command, display the NUC lights and shapes, sound the appropriate signals, and make a safety broadcast to vessels in the TSS. Inform the VTS and port authority, and request tug assistance immediately rather than waiting. Estimate drift and set; the nearest approach to the VLCC must be monitored continuously. Use emergency steering and any bow thruster available. If depth and holding ground permit, prepare to anchor clear of the lanes and pipelines, but do not anchor in a narrow channel without assessing the risk.
Engine room. Isolate the fuel supply, check for fire or fuel leakage, and inspect the seized pump. Do not attempt to force the plunger. Try to turn the engine by turning gear; if it is free, change to the MGO service tank, purge the system, and attempt a controlled restart. If the pump is seized, propulsion is unavailable until it is replaced or isolated.
Management. Notify the company, DPA and charterers; preserve fuel samples and the engine log; record all times and communications. The priority is to keep the vessel clear of the VLCC and the TSS while repair options are assessed.
3. What regulatory and documentary actions are required for the ECA and the fuel system failure?
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The vessel must not enter the 0.10% sulphur ECA unless it is burning compliant fuel. If the changeover cannot be completed, the correct action is to remain outside the ECA, divert to a safe anchorage or port, and arrange repair and compliant bunkers. Switching back to HFO to 'make the boundary' would be a deliberate non-compliance and must not be considered.
Records. Make entries in the engine log, fuel changeover record and oil record book as applicable. Record the times of changeover, viscosity and temperature, the engine trip, the water found in the settling tank and all remedial actions. Retain fuel samples from the HFO and MGO systems, bunker receipts and supplier certificates. If the fuel is contaminated or off-specification, issue a letter of protest to the supplier and arrange independent analysis.
Notifications. Inform the flag State and the port State if the vessel cannot comply, and keep the charterers advised of the delay. Do not falsify or backdate records. If the engine failure creates a pollution or navigational risk, report it under the SMS and to the coastal State. The master should also prepare a statement of facts covering the sequence of events, because the delay and any ECA breach may later be examined by charterers, insurers or authorities.