Fuel changeover into a 0.10% sulphur ECA: viscosity collapse and a leaking high-pressure pipe
M/V Ternhaven, a 47,000 dwt product tanker with a MAN B&W 6S50MC-C main engine, is on passage and enters a 0.10% sulphur emission control area at 0600 tomorrow. The ship burns RMG380 (about 380 cSt at 50 °C) outside the area and will change over to a 0.08% sulphur distillate with a viscosity of about 2.5 cSt at 40 °C. At 2200 the third engineer starts the changeover. The fuel oil viscosity controller is left on its HFO set point of 15 cSt at the engine inlet, and the distillate service tank, already heated to 45 °C, is on line. After forty minutes the inlet viscosity alarm reads 1.6 cSt, the fuel pump index on all units falls sharply, inlet fuel pressure fluctuates, and the No.4 unit exhaust gas temperature drops 45 °C below its sisters. A fuel smell is reported near No.4 unit and a fine weep is found at a high-pressure fuel pipe connection. The changeover logbook has not been started.
1. Diagnose what is happening and set out the immediate actions, in order of priority.
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Diagnosis
The viscosity controller was never moved to the distillate set point, and the distillate was already at 45 °C, so the fuel reaching the engine inlet is far too thin at 1.6 cSt. Two-stroke engines typically require 2–14 cSt at the inlet, and the maker's minimum is about 2 cSt. Below that:
- internal leakage past the plunger/barrel rises, so the effective delivery and injection quality fall and the fuel index drops;
- lubricity is lost and plunger scuffing or seizure becomes a real risk;
- atomisation and combustion deteriorate, which explains the 45 °C spread on No.4 unit;
- the weep at the high-pressure connection is a fire hazard next to hot, oil-soaked lagging.
Immediate actions, in order
- Stop the changeover and protect the engine: reduce load to a level where combustion is stable and the exhaust spread is controllable.
- Put the viscosity controller onto the distillate regime and cool the fuel so that inlet viscosity comes back above 2 cSt (typically aim for 2–6 cSt on distillate). Restore the fuel index and check all unit exhaust temperatures.
- Treat the leaking high-pressure pipe as a fire risk: do not attempt to run on it, isolate the unit, stop the engine if necessary, replace the pipe, and remove oil-soaked lagging.
- Check the fuel leak-off, drain tanks and the double-bottom/overflow arrangements for distillate ingress, then record the event and inform the master and company.
The sequence matters: restoring viscosity limits further damage while the leak is being dealt with.
2. Set out how the changeover should have been planned and recorded, citing the applicable requirements.
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Planning
- The changeover must be completed before entry into the area, not started at the boundary; the ship's procedure should allow a gradual transition of at least about an hour per fuel line so that pump temperatures change slowly and thermal shock to plungers and barrels is avoided.
- Temperature and viscosity controllers must be reset for both fuels before the first distillate reaches the engine, and the service tank temperature adjusted so the inlet viscosity stays within the maker's band.
- Sufficient compliant fuel must be on board and the changeover sequenced so that purifiers, settling and service tanks are not mixed inadvertently.
- Engine settings, exhaust temperatures and fuel index should be logged through the changeover so that trends are visible.
Recording
MARPOL Annex VI Regulation 14.6 requires that where a ship uses separate fuel oils to comply, the date, time and position at which the changeover is completed are recorded in a logbook prescribed by the Administration; this is normally the changeover log or the engine room log. The Oil Record Book is not the correct home for a sulphur changeover (it records Annex I operations), though some flags accept an engine log entry.
Judgement point: the boundary is a legal line. A partial changeover at 0600 with 0.08% fuel still working through the system means non-compliant fuel is being used inside the area. If the plan cannot be met, the correct decision is to slow down, wait or bunker compliant fuel before entry, and to tell the company and charterers immediately.
3. The distillate ordered for the ECA has not arrived and only 30 tonnes of compliant fuel remain on board. Evaluate the options, including whether a fuel oil non-availability report solves the problem.
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Options
- Delay entry or wait outside the area. The cheapest compliant option if the delay is short. Cost it honestly: 18 t/day at 0.1% distillate to run a generator is cheap compared with a port State detention or a MARPOL prosecution.
- Bunker elsewhere or from a barge before the boundary. Usually the right answer if there is time and a supply point.
- Enter with the 30 tonnes and complete the changeover as ordered. Work out the consumption at the planned load and see whether the fuel lasts to the next bunkering port; entering with a fuel plan that runs dry inside the area is a premeditated breach.
- Fuel oil non-availability report (FONAR). MARPOL Annex VI Regulation 18.2 allows a ship that cannot obtain compliant fuel to present evidence of the attempts made, and requires notification to the flag Administration and to the port State of destination. The Administration may then allow the ship to use non-compliant fuel. This is not a self-granted exemption: it does not permit the ship to enter without notifying both States, it requires documented evidence of the attempts to obtain compliant fuel, it cannot be used where compliant fuel was obtainable, and many Administrations will refuse it. It should therefore be presented to the master and company as a last resort, not a plan.
Recommendation: delay entry or bunker compliant fuel; simultaneously prepare the FONAR evidence trail in case neither is possible, and record every step. Do not sail into the area on HFO while hoping the paperwork will cover it.