Why sulphur blending is done
MARPOL Annex VI limits fuel sulphur to 0.50% m/m globally and 0.10% m/m in Emission Control Areas, unless the ship uses an approved scrubber. Ships sometimes mix a higher-sulphur stem with a lower-sulphur stem to reach the limit. Compatibility still matters: two fuels that meet sulphur on paper can sludge if they are not compatible. Always check a compatibility test before a large blend.
How this calculator works
Blend sulphur = (Q1 × S1 + Q2 × S2) ÷ (Q1 + Q2). If a target is entered and Fuel A quantity is known, the tool also estimates how much Fuel B is needed: Q2 = Q1 × (S1 − Target) ÷ (Target − S2). That only works if one fuel is above the target and the other is below it. The result is a mass-balance estimate only. Use BDN sulphur figures and the chief engineer’s changeover procedure for the legal record.
Who should use it
Useful for engineers planning a changeover or a tank mix. It does not replace laboratory analysis or the company’s fuel-changeover checklist.