ASTM D189 Standard Test Method for Conradson Carbon Residue of Petroleum Products

The standard "ASTM D189 Standard Test Method for Conradson Carbon Residue of Petroleum Products," developed by the American Society for Testing and Materials (ASTM), describes a test method for determining the amount of carbon residue remaining after the evaporation and pyrolysis of an oil. This standard also aims to provide some indication of relative coke-forming tendencies.

This test method is generally applicable to relatively non-volatile petroleum products that partially decompose during distillation at atmospheric pressure. Petroleum products containing ash-forming components, as determined by ASTM Standard Test Method D482 or IP Method 4, will have an inaccurately high carbon residue based on the amount of ash formed.

The term "carbon residue" is used throughout this test method to refer to the carbonaceous residue formed after the vaporization and pyrolysis of a petroleum product under the conditions specified in this test method. The residue is not entirely carbon, but rather a coke that may be further modified by pyrolysis. The term "carbon residue" is retained in this test method only in accordance with its common usage.

The values ​​obtained with this test method are not numerically identical to those obtained with the ASTM D524 standard test method. Approximate correlations have been derived, but because the carbon residue test is applicable to a wide variety of petroleum products, they do not necessarily apply to all materials that can be tested.

The test results are equivalent to the ASTM D4530 standard test method.

The presence of alkyl nitrates, such as amyl nitrate, hexyl nitrate, or octyl nitrate, in diesel fuel results in a higher residue value than that observed in virgin fuel, which can lead to erroneous conclusions about the fuel's tendency to form coke. The presence of alkyl nitrates in fuel can be determined using the ASTM D4046 standard test method.

The carbon residue value of the burner fuel serves as a rough estimate of the fuel's tendency to form deposits in evaporative cup and sleeve burners. Similarly, the carbon residue of diesel fuel correlates approximately with combustion chamber deposits when alkyl nitrates are not present (or when present, when testing is performed on the base fuel without additives).

Once considered an indicator of the amount of carbonaceous deposits an engine oil will form in the combustion chamber of an engine, the carbon residue value of an engine oil is now considered of questionable significance due to the presence of additives in many oils. For example, an ash-forming detergent additive may increase an oil's carbon residue value but generally reduces its tendency to form deposits.

The carbon residue value of gas oil is useful as a guide in the production of gas from gas oil. The carbon residue values ​​of crude oil residues, cylinders, and bright stocks are useful in the production of lubricants.

In short, Conradson carbon residue is a measure of the amount of carbonaceous residue remaining after a petroleum product undergoes evaporation and thermal decomposition in the absence of air. It is expressed as a percentage by weight of the original sample and is determined in accordance with ASTM D189. The Conradson carbon residue value indicates the tendency of a fuel or oil to form carbon deposits (such as coke or soot) when exposed to high temperatures. A higher value indicates a higher probability of deposits, which can lead to engine fouling, injector clogging, or other operational problems.

When measuring according to ASTM D189, a weighed sample of the petroleum product is placed in a crucible. The crucible is heated vigorously in a controlled environment (usually inside a conical hood to limit air exposure). The sample undergoes vaporization, pyrolysis, and thermal decomposition. The carbon residue remaining after the test is weighed. The result is reported as a percentage by mass of the original sample.

In short, carbon residue is a key indicator of the product's tendency to form deposits under high temperature conditions.

The ASTM D189 standard is considered important for the following reasons:

• Indicates deposit formation tendency: Helps predict the likelihood of coke or carbon deposit formation in engines, burners, or other high-temperature equipment. Essential for evaluating fuels such as diesel, fuel oils, and lubricating oils.
• Guides fuel and oil quality control: Used by refineries and manufacturers to ensure product consistency and quality. High residue values ​​may indicate the need for additional refining or blending.
• Supports equipment life: Fuels or oils with excessive carbon residue can cause contamination, reduced efficiency, and damage to combustion systems. Helps select appropriate fuels for sensitive systems.
• Industry-wide standardization: Provides a uniform test procedure recognized across industries, including petrochemical, automotive, and aerospace. Facilitates global trade and compliance by harmonizing with other specifications (e.g., ASTM D975 for diesel fuel).
• Benchmark for alternative test methods: Serves as a reference against which other carbon residue methods (e.g. microcarbon residue) can be compared.

Common applications of this method include:

• Testing diesel fuels, heavy fuel oils, lubricants and crude oils.
• Supporting specification compliance for marine fuels, aviation turbine fuels and industrial lubricants.

In summary, this standard plays a vital role in evaluating the thermal stability and cleanliness of petroleum products, ensuring operational reliability and fuel system protection.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the ASTM D189 Standard Test Method for Conradson Carbon Residue of Petroleum Products.