ASTM D7170 Standard Test Method for Determination of Derived Cetane Number (DCN) of Diesel Fuel Oils (Withdrawn 2019)

ASTM D7170 Introduction

The cetane number of diesel fuels is a sensitive factor of ignition quality and combustion performance. Higher cetane fuels have an easier ignition, which results in smoother operation, less noise, and less emissions. The ASTM D7170 was developed to give a consistent bench-scale approach in calculating the Derived Cetane Number in a constant volume combustion chamber. This method enabled laboratories to accurately recreate combustion in a controlled manner without the variability of engine-based methods. The consistent range injection period eliminated errors attributed to fuel delivery systems. Although the standard was retired in 2019, its technique greatly impacted later standards, and the idea of DCN has endured to the present day as the foundation of fuel quality testing. The historical significance of ASTM D7170 lies in its contribution to the transition from conventional engine testing to laboratory-based testing.

ASTM D7170 Test Method

ASTM D7170 Equipment and Sample Preparation

ASTM D7170 Test Results and Interpretation

The ignition delay from the combustion chamber test was converted to a Derived Cetane Number via a pre-defined correlation. Smaller ignition delays were associated with higher DCN values, indicating better ignition quality. Test repeatability tended to be within a small band, reflecting reliability when compared with engine-based tests. Results assisted in classifying diesel fuels for use in various climatic environments and performance conditions. Fuels that do not meet acceptable DCN values were commonly excluded from use with high-efficiency diesel engines.

ASTM D7170 Related Articles

ASTM D613 specifies the engine-based test method for measuring the cetane number of diesel fuels, serving as the primary reference procedure. ASTM D6890 provides a more modern ignition delay-based method using a constant volume combustion chamber with variable conditions. ASTM D7668 defines another alternative DCN test method using a modified combustion system for improved accuracy.

Materials Commonly Tested with ASTM D7170 

ASTM D7170 was generally used for petroleum-based diesel fuel oils. It was also used on synthetic diesel fuels and biodiesel blends, as long as the fuels remained liquid, uniform, and free of contaminants that would hinder injection or combustion. The testing was generally conducted on reference fuels, too, which were used to confirm chamber performance and calibration.

Applications of ASTM D7170 in Industry

The technique was extensively used in fuel formulation and refining laboratories for certification and quality control. Original equipment manufacturers of automobiles and heavy-duty engines used DCN values obtained by the technique to assess fuel appropriateness for compression ignition engines. The technique was also used by fuel research institutes to analyze the combustion performance of novel blends and additives under controlled laboratory conditions.

Safety and Best Practices in ASTM D7170 

ASTM D7170 emphasized strict security guidelines to handle flammable diesel fuel and high-pressure injection systems. Laboratory personnel were required to use protective equipment, including flame-resistant coats and safety shields. The combustion chamber is operated at high pressure and temperature, which demands strict adherence to calibration and operational protocols. Ventilation was also required to prevent the risk of combustion gases.

Importance of ASTM D7170 

Although superseded, ASTM D7170 is historically important in the evolution of bench-scale cetane measurement. It gave laboratories a balance between reproducibility, safety, and accuracy at a time when alternatives were not well established. Its influence carries forward in later test standards that improved the methodology but retained the underlying idea of correlating ignition delay. The significance of the standard is not just in its operational usability over its period of active use but also in its continued influence on contemporary fuel testing practice.

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