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Marine Fuel Quality Parameters

MEO Class 2
MEO Class 4

times asked: 36; times asked
questions: 4; questions
last asked: 2026; last asked

The slides, written out

AI-drawn illustration. Simplified to explain the idea, not to scale.

Slide 1 · AN OVERVIEW

AN OVERVIEW OF MARINE FUEL QUALITY PARAMETERS Understanding CCAI, Flash Point, Na:V Ratio & Cetane Number FUEL QUALITY ENGINE PERFORMANCE SAFETY & COMPLIANCE RELIABILITY AT SEA

Slide 2 · CCAI

CCAI (CALCULATED CARBON AROMATICITY INDEX) An indicator of ignition quality for residual fuels. Derived from density & viscosity WHAT IT INDICATES Empirical value calculated from density and kinematic viscosity Estimates the ignition quality of a residual fuel HIGHER CCAI MEANS Longer ignition delay More fuel injected before combustion starts Harder combustion with steeper pressure rise Increased thermal and mechanical loading OPERATIONAL ACTION Monitor combustion performance Follow engine-maker guidance Review injection timing or fuel-quality lever settings if required BETTER IGNITION QUALITY POORER IGNITION QUALITY LOWER CCAI HIGHER CCAI ISO 8217 LIMITS Typical range: 850 – 870 ISO 8217 specifies maximum CCAI values depending on the residual fuel grade, commonly ranging between 850 and 870. Fuels approaching the applicable grade limit may require closer operational attention.

Slide 3 · OPEN VS CLOSED

OPEN VS CLOSED FLASH POINT Measures the temperature at which fuel vapours ignite momentarily in the presence of an external flame. CLOSED CUP Fuel is heated in a closed container Vapours are retained Generally lower than open-cup flash point Regulatory value for marine fuels SOLAS minimum closed-cup flash point = 60°C OPEN CUP Fuel is heated in an open container Vapours exposed to atmosphere Generally higher than closed-cup flash point Operational safety reference Important for hot work, tank cleaning and entry operations KEY TAKEAWAY Closed-cup flash point is the regulatory standard for bunkering and storage. Open-cup flash point is used for operational safety and hot work considerations.

Slide 4 · SODIUM & VANADIUM

SODIUM & VANADIUM RATIO & CETANE NUMBER Key fuel quality factors that impact engine durability and combustion performance. SODIUM & VANADIUM (Na:V RATIO) CETANE NUMBER (For Distillate Fuels) WHAT HAPPENS? Sodium contamination can react with vanadium compounds to form low-melting sodium vanadates. These molten compounds increase the risk of high-temperature corrosion. Corrosion severity depends on both sodium and vanadium levels and their interaction within ash deposits. AFFECTED COMPONENTS Exhaust valves Turbocharger nozzle rings Other hot-gas-path surfaces WHAT IT MEASURES Ignition quality of distillate fuels (e.g., MDO, MGO). HIGHER CETANE Shorter ignition delay Smoother combustion Better engine performance LOWER CETANE Longer ignition delay Rough running Higher thermal loading REMEMBER CCAI is used mainly for residual fuels. Cetane Number is used for distillate fuels.

In exams

Asked 36 times across 4 different questions, most recently in 2026. Asked most in MEO Class 2 (23), MEO Class 4 (13).

Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.

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