Calculate the Calculated Carbon Aromaticity Index (CCAI) for marine fuels using density and viscosity values with this CCAI calculation tool. Perfect for anyone needing quick CCAI calculations – from marine engineers evaluating fuel ignition quality to fuel procurement managers assessing fuel specifications, or vessel operators verifying bunker fuel compliance with engine manufacturer requirements.
Value format example: 975.5
Use of this calculator/converter is at own risk. Please conduct extra calculations or consult a specialist to verify results.
How to Use the CCAI Calculator
- Enter your value in any of the input fields (value format example: 975.5)
- When all values are entered you get instant conversions
- Delete or click “Clear All” to do a new calculation
The calculator provides accurate results using the standard CCAI formula, ensuring precision for professional maritime fuel operations, engine performance optimization, and fuel quality assessment.
What is CCAI (Calculated Carbon Aromaticity Index)?
The Calculated Carbon Aromaticity Index (CCAI) is a critical parameter for evaluating marine fuel oil ignition quality and combustion characteristics. CCAI provides a numerical indicator of how easily a residual fuel will ignite in marine diesel engines, with lower values indicating better ignition quality and smoother combustion performance.
CCAI is calculated using fuel density at 15°C and kinematic viscosity at 50°C—two standard parameters measured during bunker fuel testing and specified in fuel delivery documentation. This calculation method makes CCAI a practical tool for assessing fuel quality without requiring expensive laboratory testing equipment.
CCAI Formula:
CCAI = Density at 15°C – 81 – 141 log(log(Viscosity at 50°C + 0.85))
Where:
- Density at 15°C is measured in kg/m³
- Viscosity at 50°C is measured in centistokes (cSt)
- log represents the base-10 logarithm
CCAI Values and Fuel Quality Assessment
CCAI Range Interpretation
Excellent Ignition Quality:
- CCAI < 800: Superior ignition characteristics, minimal combustion issues
- Typical for high-quality residual fuels and blended products
- Reduced risk of engine problems and maintenance requirements
Good Ignition Quality:
- CCAI 800-850: Acceptable ignition quality for most marine diesel engines
- Standard range for many commercially available residual fuels
- Suitable for engines designed for residual fuel operation
Marginal Ignition Quality:
- CCAI 850-870: Marginal ignition quality requiring careful engine management
- May require fuel treatment or blending to improve combustion
- Increased monitoring recommended for engine performance
Poor Ignition Quality:
- CCAI > 870: Poor ignition characteristics, high risk of combustion problems
- May cause engine starting difficulties, incomplete combustion, deposits
- Often requires fuel treatment, blending, or engine parameter adjustment
Engine Manufacturer CCAI Limits
Different engine manufacturers specify maximum acceptable CCAI values for their engines:
Typical CCAI Limits by Engine Type:
- Modern medium-speed engines: CCAI maximum 850-860
- Older medium-speed engines: CCAI maximum 860-870
- Low-speed two-stroke engines: CCAI maximum 860-870
- High-speed auxiliary engines: CCAI maximum 840-850
Always verify specific engine manufacturer recommendations, as CCAI limits vary by engine design, fuel injection system, and operational parameters.
CCAI Calculation Examples
Example 1: High-Quality Residual Fuel
Given Parameters:
- Density at 15°C: 960 kg/m³
- Viscosity at 50°C: 180 cSt
Calculation:
- CCAI = 960 – 81 – 141 log(log(180 + 0.85))
- CCAI = 960 – 81 – 141 log(log(180.85))
- CCAI = 960 – 81 – 141 log(2.2575)
- CCAI = 960 – 81 – 141 × 0.3536
- CCAI = 960 – 81 – 49.86
- CCAI = 829.14
Assessment: Excellent ignition quality, suitable for all marine diesel engines
Example 2: Standard VLSFO Fuel
Given Parameters:
- Density at 15°C: 980 kg/m³
- Viscosity at 50°C: 380 cSt
Calculation:
- CCAI = 980 – 81 – 141 log(log(380 + 0.85))
- CCAI = 980 – 81 – 141 log(log(380.85))
- CCAI = 980 – 81 – 141 log(2.5808)
- CCAI = 980 – 81 – 141 × 0.4117
- CCAI = 980 – 81 – 58.05
- CCAI = 840.95
Assessment: Good ignition quality, acceptable for most marine engines
Example 3: High-Density Residual Fuel
Given Parameters:
- Density at 15°C: 991 kg/m³
- Viscosity at 50°C: 380 cSt
Calculation:
- CCAI = 991 – 81 – 141 log(log(380 + 0.85))
- CCAI = 991 – 81 – 141 log(log(380.85))
- CCAI = 991 – 81 – 141 log(2.5808)
- CCAI = 991 – 81 – 141 × 0.4117
- CCAI = 991 – 81 – 58.05
- CCAI = 851.95
Assessment: Marginal ignition quality, verify engine compatibility
Example 4: Low-Viscosity Marine Gas Oil
Given Parameters:
- Density at 15°C: 890 kg/m³
- Viscosity at 50°C: 6 cSt
Calculation:
- CCAI = 890 – 81 – 141 log(log(6 + 0.85))
- CCAI = 890 – 81 – 141 log(log(6.85))
- CCAI = 890 – 81 – 141 log(0.8357)
- CCAI = 890 – 81 – 141 × (-0.0779)
- CCAI = 890 – 81 + 10.98
- CCAI = 819.98
Assessment: Excellent ignition quality, typical for distillate fuels
Understanding CCAI in Marine Fuel Operations
CCAI and Fuel Density Relationship
Higher fuel density generally increases CCAI values, indicating reduced ignition quality. Dense fuels contain higher proportions of aromatic compounds and heavier hydrocarbon molecules that are more difficult to ignite and burn completely. This relationship makes density at 15°C a critical parameter in fuel quality assessment.
When evaluating bunker fuel specifications, compare density values against typical ranges for the fuel grade. Very Low Sulphur Fuel Oil (VLSFO) typically ranges from 960-991 kg/m³, while Marine Gas Oil (MGO) ranges from 850-900 kg/m³. Higher densities within these ranges correlate with higher CCAI values and potentially reduced ignition quality.
CCAI and Fuel Viscosity Relationship
Viscosity at 50°C affects CCAI calculations through the logarithmic term in the formula. Higher viscosity fuels generally result in lower CCAI values (better ignition quality) when density remains constant, though this relationship is complex due to the logarithmic calculation.
However, in practice, high-viscosity fuels often have higher densities as well, so the overall CCAI may still be elevated. The CCAI formula balances these parameters to provide a single indicator of ignition quality that accounts for both density and viscosity effects.
CCAI vs. Cetane Index
CCAI and Cetane Index both measure fuel ignition quality but use different approaches:
CCAI (Calculated Carbon Aromaticity Index):
- Used for residual fuels (HFO, IFO, VLSFO)
- Calculated from density and viscosity
- Lower values indicate better ignition quality
- Typical range: 800-870 for residual fuels
Cetane Index:
- Used for distillate fuels (MGO, MDO)
- Calculated from density and distillation characteristics
- Higher values indicate better ignition quality
- Typical range: 35-55 for marine distillates
Both parameters help predict combustion performance, but CCAI is specifically designed for the heavier residual fuels commonly used in large marine diesel engines.
CCAI and ISO 8217 Fuel Specifications
ISO 8217 marine fuel specifications do not directly specify CCAI limits, but the standard’s density and viscosity requirements indirectly control CCAI values. By limiting maximum density and specifying viscosity ranges for each fuel grade, ISO 8217 ensures fuels generally fall within acceptable CCAI ranges for marine engine operation.
ISO 8217 Parameters Affecting CCAI:
- Maximum density at 15°C (varies by grade)
- Kinematic viscosity at 50°C (specified range by grade)
- These parameters directly feed into CCAI calculation
When receiving bunker fuel, verify that density and viscosity values on the Bunker Delivery Note (BDN) fall within ISO 8217 specifications for the ordered grade. Calculate CCAI from these values to confirm ignition quality meets your engine manufacturer’s requirements.
CCAI and Fuel Blending
Fuel blending operations use CCAI calculations to predict the ignition quality of blended fuels. When mixing residual fuels with distillates or combining different residual grades, the resulting CCAI can be estimated by calculating density and viscosity of the blend, then applying the CCAI formula.
Blending Considerations:
- Blending low-CCAI distillates with high-CCAI residuals reduces overall CCAI
- Density and viscosity blend non-linearly, affecting CCAI predictions
- Always verify blended fuel CCAI through calculation before use
- Consider compatibility testing when blending different fuel sources
Onboard fuel management systems may blend fuels to achieve target CCAI values that optimize engine performance while managing fuel costs and availability.
CCAI and Engine Performance
CCAI directly impacts marine diesel engine combustion quality, affecting:
Engine Starting:
- Low CCAI fuels ignite more readily, improving cold starting
- High CCAI fuels may require extended cranking or preheating
Combustion Efficiency:
- Low CCAI fuels burn more completely, maximizing energy extraction
- High CCAI fuels may exhibit incomplete combustion and reduced efficiency
Exhaust Emissions:
- Low CCAI fuels produce cleaner exhaust with lower particulate matter
- High CCAI fuels increase smoke, carbon deposits, and unburned hydrocarbons
Engine Deposits:
- Low CCAI fuels minimize combustion chamber and injector deposits
- High CCAI fuels accelerate deposit formation, increasing maintenance
Fuel Consumption:
- Low CCAI fuels optimize specific fuel oil consumption (SFOC)
- High CCAI fuels may increase fuel consumption due to incomplete combustion
Monitoring CCAI values for bunker fuels helps predict and prevent engine performance issues before they impact operations.
CCAI Calculation Accuracy
CCAI calculations depend on accurate density and viscosity measurements. Errors in these input parameters directly affect calculated CCAI values:
Measurement Accuracy Requirements:
- Density at 15°C: ±0.5 kg/m³ for reliable CCAI calculation
- Viscosity at 50°C: ±2% for reliable CCAI calculation
- Temperature control during measurement: ±0.1°C for density, ±0.2°C for viscosity
Always use calibrated instruments and follow ISO test methods (ISO 3675 for density, ISO 3104 for viscosity) to ensure accurate CCAI calculations. Third-party fuel testing laboratories provide verified measurements when onboard testing capabilities are limited.
CCAI in Fuel Procurement and Operations
Bunker Fuel Specification
When ordering bunker fuel, specify maximum acceptable CCAI values based on your engine manufacturer’s recommendations. Include CCAI limits in bunker specifications alongside standard ISO 8217 parameters:
Sample Specification Language:
- “VLSFO 0.50% S, ISO 8217:2017 RMG 380, maximum CCAI 850”
- “IFO 380, ISO 8217:2017 RMB 380, maximum CCAI 860”
This specification approach ensures suppliers provide fuel meeting both regulatory compliance and engine compatibility requirements.
Bunker Delivery Note Verification
Upon receiving bunker fuel, calculate CCAI from the density and viscosity values listed on the Bunker Delivery Note (BDN). Compare calculated CCAI against:
- Your specified maximum CCAI limit
- Engine manufacturer’s recommended CCAI range
- Historical CCAI values for similar fuel grades at the same port
Significant deviations warrant further investigation through representative sampling and independent laboratory testing.
Fuel Quality Disputes
CCAI calculations provide objective evidence in fuel quality disputes. If fuel causes engine performance issues, calculate CCAI from BDN parameters and compare against:
- Contractual specifications
- Engine manufacturer limits
- Industry standards for the fuel grade
Document CCAI values alongside other fuel parameters (density, viscosity, sulphur content, compatibility) when filing claims for off-specification fuel or engine damage caused by poor fuel quality.
Operational Fuel Management
Calculate CCAI for all bunker fuel receipts and maintain records in your fuel management system. Track CCAI trends by:
- Port of supply
- Fuel supplier
- Fuel grade
- Season/time period
This historical data helps identify reliable fuel sources, predict potential quality issues, and optimize fuel procurement strategies across your fleet operations.
Frequently Asked Questions
What is CCAI and why is it important for marine fuels?
CCAI (Calculated Carbon Aromaticity Index) is a numerical indicator of marine fuel ignition quality calculated from fuel density at 15°C and viscosity at 50°C. Lower CCAI values indicate better ignition characteristics and smoother combustion performance. CCAI is important because it predicts how easily residual fuel will ignite in marine diesel engines, helping prevent engine starting difficulties, incomplete combustion, excessive deposits, and reduced efficiency. Engine manufacturers specify maximum acceptable CCAI values, typically 850-870, to ensure fuel compatibility with their engines.
How do I calculate CCAI from bunker fuel specifications?
Calculate CCAI using the formula: CCAI = Density at 15°C – 81 – 141 log(log(Viscosity at 50°C + 0.85)). Obtain density (in kg/m³) and viscosity (in centistokes) from your Bunker Delivery Note or fuel test report. For example, fuel with density 980 kg/m³ and viscosity 380 cSt yields CCAI = 980 – 81 – 141 log(log(380.85)) = 840.95. Use a scientific calculator or online CCAI calculator for accurate logarithmic calculations.
What CCAI value is acceptable for marine diesel engines?
Most modern marine diesel engines accept CCAI values up to 850-860, though specific limits vary by manufacturer and engine type. CCAI below 800 indicates excellent ignition quality suitable for all engines. CCAI 800-850 represents good quality acceptable for most applications. CCAI 850-870 is marginal, requiring verification against engine specifications. CCAI above 870 indicates poor ignition quality with high risk of combustion problems. Always verify your specific engine manufacturer’s CCAI recommendations in the engine manual or technical documentation.
How does CCAI relate to fuel density and viscosity?
CCAI increases with higher fuel density and decreases with higher viscosity, though the relationship is complex due to logarithmic calculations. Higher density fuels contain more aromatic compounds and heavier molecules that are harder to ignite, increasing CCAI. Viscosity affects CCAI through a logarithmic term that dampens its influence compared to density. In practice, both parameters must be considered together—high-density, high-viscosity fuels typically have elevated CCAI values indicating reduced ignition quality compared to lower-density distillate fuels.
Can I use CCAI to compare different fuel grades?
Yes, CCAI provides a standardized method to compare ignition quality across different fuel grades. Marine Gas Oil (MGO) typically has CCAI 800-830, Very Low Sulphur Fuel Oil (VLSFO) ranges 830-860, and High Sulphur Fuel Oil (HSFO) may reach 850-870. Lower CCAI values indicate superior ignition quality regardless of fuel grade. However, remember that CCAI is just one quality parameter—also consider sulphur content, compatibility, stability, and other ISO 8217 specifications when comparing fuels.
What should I do if bunker fuel has high CCAI?
If bunker fuel exceeds your engine’s maximum CCAI limit, consider: (1) Blending with lower-CCAI distillate fuel to reduce overall CCAI, (2) Consulting engine manufacturer for guidance on operating parameters, (3) Increasing fuel injection temperature to improve atomization, (4) Enhanced fuel treatment and purification, (5) Increased monitoring of engine performance and exhaust quality, (6) Filing a claim with the fuel supplier if CCAI exceeds contractual specifications. Document all CCAI calculations and engine performance data to support quality claims.
How accurate are CCAI calculations?
CCAI calculation accuracy depends on the precision of density and viscosity measurements. Using calibrated instruments and following ISO test methods (ISO 3675 for density, ISO 3104 for viscosity), CCAI can be calculated to within ±2-3 points. However, measurement errors in density (±0.5 kg/m³) or viscosity (±2%) propagate through the calculation. For critical applications, verify CCAI using laboratory-tested density and viscosity values rather than estimated or uncalibrated measurements. Third-party fuel testing provides the most reliable CCAI calculations.
Is CCAI specified in ISO 8217 fuel standards?
No, ISO 8217 does not directly specify CCAI limits. However, the standard’s density and viscosity requirements indirectly control CCAI values. By limiting maximum density and specifying viscosity ranges for each fuel grade, ISO 8217 ensures fuels generally fall within acceptable CCAI ranges for marine engines. Engine manufacturers, not fuel standards, specify maximum acceptable CCAI values. When ordering fuel, specify both ISO 8217 grade compliance and maximum CCAI limits to ensure fuel meets both regulatory and engine compatibility requirements.
How does CCAI differ from Cetane Index?
CCAI and Cetane Index both measure ignition quality but for different fuel types. CCAI is used for residual fuels (HFO, IFO, VLSFO) and calculated from density and viscosity, with lower values indicating better ignition. Cetane Index is used for distillate fuels (MGO, MDO) and calculated from density and distillation characteristics, with higher values indicating better ignition. CCAI typically ranges 800-870 for residual fuels, while Cetane Index ranges 35-55 for distillates. Use CCAI for heavy fuels in main engines and Cetane Index for distillates in auxiliary engines.
Gulf-Bunkering provides marine fuel trading solutions worldwide, connecting vessel operators with compliant fuel products through our knowledge of global supply networks, regional logistics, and port coordination. Understanding CCAI calculations helps optimize fuel procurement decisions and ensure engine compatibility across international operations. For marine fuel trading services, contact us at contact@gulf-bunkering.com