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Engine

Fuel changeover (ECA)

How long before an emission control area (ECA) to start changing over to low-sulphur fuel, so the engine burns fuel at or below 0.10 % sulphur from the boundary: the time, the moment to turn the valve and the distance to go.

% m/m

From the bunker delivery note

% m/m
% m/m

0.10 in an ECA; lower for a margin

m³

Changeover valve to engine: mixing column, pipes, filters

t/day
kg/m³
Planning (optional)
min
kn
°C

HFO at the engine inlet, e.g. 135

°C

e.g. 40 for MGO

Fill in the fields to see the result.

How it works

The fuel between the changeover valve and the engine (mixing column, pipes, filters, and the service tank if the change is made there) is treated as one well-mixed volume V, flushed by the consumption Q. Sulphur at the engine then falls as S(t) = Snew + (Sold − Snew) · e−Qt/V, so the time to reach the target is t = (V/Q) · ln((Sold − Snew) / (Starget − Snew)). Changeover calculators such as Lloyd's Register's FOBAS work on the same principle.

The volume matters most: take it from the fuel system drawings or the ship's changeover procedure. Real systems mix less evenly, so add a margin and record the changeover (time, position, tank levels) in the log as MARPOL Annex VI requires. Engine makers limit the temperature change to about 2 °C a minute when going from heated HFO to distillate, to protect the fuel pumps.

For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.

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