ASTM D976-21
(Test Method)Standard Test Method for Calculated Cetane Index of Distillate Fuels
Standard Test Method for Calculated Cetane Index of Distillate Fuels
SIGNIFICANCE AND USE
4.1 The Calculated Cetane Index is one tool available for estimating ASTM cetane number where a test engine is not available for determining this property. It may be employed for approximating cetane number where the quantity of sample is too small for an engine rating. In cases where the cetane number of a fuel has been initially established, the index is useful as a cetane number check on subsequent samples of that fuel, provided its source and mode of manufacture remain unchanged.
4.2 Test Method D4737 may also be used to approximate the ASTM cetane number of diesel fuels.
4.2.1 Procedure A of Test Method D4737 was developed as a result of a larger degree of offset between Test Method D976 Cetane Index and the results of Test Method D613 over the entire range of the correlation. Generally, it has been found that use of Test Method D4737 results in less offset than use of Test Method D976, but there can be specific cases where this is not true.
4.2.2 Procedure A of Test Method D4737 is recommended to estimate the cetane number of diesel fuels with sulfur contents above 500 ppm or No. 1–D diesel fuels.
4.2.3 Procedure B of Test Method D4737 is recommended to estimate the cetane number of No. 2–D diesel fuels with sulfur contents at or below 500 ppm.
4.3 Calculated Cetane Index, as described in Test Method D976–80, is recognized by the United States EPA as an alternative method to meet the U.S. Federal Diesel aromatics limit for diesel fuels containing less than 500 ppm sulfur. The equation for Calculated Cetane Index in Test Method D976–80 and in this version (D976–06) of the test method are the same.
SCOPE
1.1 This test method covers the Calculated Cetane Index formula, which represents a means for directly estimating the ASTM cetane number of distillate fuels from API gravity and mid-boiling point. The index value, as computed from the formula, is termed the Calculated Cetane Index.2
1.2 The Calculated Cetane Index is not an optional method for expressing ASTM cetane number. It is a supplementary tool to estimate cetane number when used with due regard for its limitations.
1.3 The Calculated Cetane Index formula is particularly applicable to straight-run fuels, catalytically cracked stocks, and blends of the two.
Note 1: This test method is temporarily retained because the proposal to the U.S. EPA to control diesel fuel aromatics concentrations via a 40 Calculated Cetane Index minimum is based on the correlation between Test Method D976 and aromatics concentration. Test Method D4737 is the preferred method as estimator of cetane number.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D976 − 21
Standard Test Method for
1
Calculated Cetane Index of Distillate Fuels
This standard is issued under the fixed designation D976; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2. Referenced Documents
3
2.1 ASTM Standards:
1.1 This test method covers the Calculated Cetane Index
D86 Test Method for Distillation of Petroleum Products and
formula, which represents a means for directly estimating the
Liquid Fuels at Atmospheric Pressure
ASTM cetane number of distillate fuels from API gravity and
D287 Test Method for API Gravity of Crude Petroleum and
mid-boiling point. The index value, as computed from the
2
Petroleum Products (Hydrometer Method)
formula, is termed the Calculated Cetane Index.
D613 Test Method for Cetane Number of Diesel Fuel Oil
1.2 The Calculated Cetane Index is not an optional method
D1298 Test Method for Density, Relative Density, or API
for expressing ASTM cetane number. It is a supplementary tool
Gravity of Crude Petroleum and Liquid Petroleum Prod-
to estimate cetane number when used with due regard for its
ucts by Hydrometer Method
limitations.
D2887 Test Method for Boiling Range Distribution of Pe-
troleum Fractions by Gas Chromatography
1.3 The Calculated Cetane Index formula is particularly
D4052 Test Method for Density, Relative Density, and API
applicable to straight-run fuels, catalytically cracked stocks,
Gravity of Liquids by Digital Density Meter
and blends of the two.
D4175 Terminology Relating to Petroleum Products, Liquid
NOTE 1—This test method is temporarily retained because the proposal
Fuels, and Lubricants
to the U.S. EPA to control diesel fuel aromatics concentrations via a 40
D4737 Test Method for Calculated Cetane Index by Four
Calculated Cetane Index minimum is based on the correlation between
Variable Equation
Test Method D976 and aromatics concentration. Test Method D4737 is the
4
preferred method as estimator of cetane number.
2.2 ASTM Adjuncts:
Nomograph for Calculated Cetane Index
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1 For definitions of terms used in this test method, refer to
mine the applicability of regulatory limitations prior to use.
Terminology D4175.
1.5 This international standard was developed in accor-
4. Significance and Use
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4.1 The Calculated Cetane Index is one tool available for
Development of International Standards, Guides and Recom-
estimating ASTM cetane number where a test engine is not
mendations issued by the World Trade Organization Technical
available for determining this property. It may be employed for
Barriers to Trade (TBT) Committee.
approximating cetane number where the quantity of sample is
too small for an engine rating. In cases where the cetane
number of a fuel has been initially established, the index is
useful as a cetane number check on subsequent samples of that
1
This test method is under the jurisdiction of ASTM Committee D02 on
fuel, provided its source and mode of manufacture remain
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.E0 on Burner, Diesel and Non-Aviation Gas Turbine Fuels.
unchanged.
Current edition approved Nov. 1, 2021. Published November 2021. Originally
approved in 1966. Last previous edition approved in 2016 as D976 – 06 (2016).
DOI: 10.1520/D0976-21.
2 3
A method of calculating cetane index was developed by the Diesel Fuels For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Division, Coordinating Fuel and Equipment Research Committee of the Coordinat- contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ing Research Council. See Young, H. D., “Methods for Estimating Cetane Number,” Standards volume information, refer to the standard’s Document Summary page on
Proceedings, PPIRA, American Petroleum Institute, Vol. 30 M [III], 1950. This the ASTM website.
4
method was revised in 1960 by Research Division I of Committee D02 to conform Available from ASTM International Headquarters. Order Adjunct No.
to the revised Test Method D613. ADJD0976. Original adjunct produced in 1989.
*A Summary of Changes section appears at the end of this standard
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...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D976 − 06 (Reapproved 2016) D976 − 21
Standard Test Method for
1
Calculated Cetane Index of Distillate Fuels
This standard is issued under the fixed designation D976; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers the Calculated Cetane Index formula, which represents a means for directly estimating the ASTM
cetane number of distillate fuels from API gravity and mid-boiling point. The index value, as computed from the formula, is termed
2
the Calculated Cetane Index.
1.2 The Calculated Cetane Index is not an optional method for expressing ASTM cetane number. It is a supplementary tool to
estimate cetane number when used with due regard for its limitations.
1.3 The Calculated Cetane Index formula is particularly applicable to straight-run fuels, catalytically cracked stocks, and blends
of the two.
NOTE 1—This test method is temporarily retained because the proposal to the U.S. EPA to control diesel fuel aromatics concentrations via a 40 Calculated
Cetane Index minimum is based on the correlation between Test Method D976 and aromatics concentration. Test Method D4737 is the preferred method
as estimator of cetane number.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
3
2.1 ASTM Standards:
D86 Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
D287 Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method)
D613 Test Method for Cetane Number of Diesel Fuel Oil
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
1
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.E0 on Burner, Diesel, Diesel and Non-Aviation Gas Turbine, and Marine Turbine Fuels.
Current edition approved April 1, 2016Nov. 1, 2021. Published May 2016November 2021. Originally approved in 1966. Last previous edition approved in 20112016 as
D976 – 06 (2011).(2016). DOI: 10.1520/D0976-06R16.10.1520/D0976-21.
2
A method of calculating cetane index was developed by the Diesel Fuels Division, Coordinating Fuel and Equipment Research Committee of the Coordinating Research
Council. See Young, H. D., “Methods for Estimating Cetane Number,” Proceedings, PPIRA, American Petroleum Institute, Vol. 30 M [III], 1950. This method was revised
in 1960 by Research Division I of Committee D02 to conform to the revised Test Method D613.
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D976 − 21
D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4737 Test Method for Calculated Cetane Index by Four Variable Equation
4
2.2 ASTM Adjuncts:
Nomograph for Calculated Cetane Index
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology D4175.
4. Significance and Use
4.1 The Calculated Cetane Index i
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