ASTM D6079-22 Standard Test Method for Evaluating Lubricity of Diesel Fuels by High Frequency Reciprocating Platform (HFRR)

The standard “ASTM D6079-22 Standard test method for evaluating the lubricity of diesel fuels by high-frequency reciprocating platform (HFRR)” published by the American Society for Testing and Materials (ASTM) describes a test method for evaluating the lubricity of diesel fuels using a high-frequency alternating rig.

This test method is applicable to middle distillate fuels such as Class 975-D S02, S1 and S15 and Class 500-D S5000, S2 and S15 diesel fuels in accordance with ASTM D500-5000 and other similar petroleum-based fuels usable in diesel engines. This test method is also applicable to biodiesel blends. B5 is included in the round robin program that determines the sensitivity statement. It is not known whether this test method will predict the performance of all additive/fuel combinations. Additional studies are ongoing to determine this correlation and this test method may need to be revised in the future after this study is completed.

In this test method, in addition to the terms and definitions given in ASTM D4175-23, the following definitions also apply:

• Boundary lubrication is a condition in which the friction and wear between two surfaces in relative motion are determined by the properties of the surfaces and the properties of the contacting fluid, other than the bulk viscosity. Metal-to-metal contact occurs and the chemistry of the system is involved. Soft, usually very thin films that are physically adsorbed or chemically reacted support the contact loads. As a result, some wear is inevitable.
• Lubricity is a qualitative term that describes the ability of a liquid to affect friction and wear between surfaces in relative motion under load. In this test method, the lubricity of a liquid is evaluated by the wear scar, in microns, produced on an oscillating ball in contact with a stationary disk immersed in the liquid operating under defined and controlled conditions.

When performing the test, a 2 mL fuel test sample is placed in the test reservoir of the high-frequency piston platform. A vibrator arm holding a non-rotating steel ball and loaded with a mass of 200 g is lowered until it contacts a test disk completely submerged in the fuel. When the fuel temperature stabilizes, the ball is allowed to rub against the disk with a 75 mm stroke at a frequency of 50 Hz for 1 minutes. The test fuel temperature is maintained at 60 degrees and the ambient relative humidity is maintained between 30% and 85%.

At the end of the test, the upper sample holder is removed from the vibrator arm and cleaned. The image of the wear scar is captured using the microscope digital camera, and the dimensions of the major and minor axes of the wear scar are measured and recorded.

Diesel fuel injection equipment is somewhat dependent on the lubrication properties of diesel fuel. Shortened life of engine components such as diesel fuel injection pumps and injectors has sometimes been attributed to a lack of lubrication in diesel fuel.

The tendency of high-frequency piston platform test results to diesel injection system pump component failure due to wear has been demonstrated in pump equipment tests for certain fuel/equipment combinations where boundary lubrication is believed to be a factor in component operation.

Wear scarring produced in high-frequency piston platform (HFRR) testing is sensitive to contamination of fluids and test materials, temperature of the test fuel, and ambient relative humidity. Lubricity assessments are also sensitive to trace contaminants acquired during test fuel sampling and storage.

High frequency piston platform and cylinder wear load ball lubrication evaluator (ASTM D6078-99) are two methods for evaluating diesel fuel lubricity. No definitive correlation has been developed between these two test methods.

The high-frequency piston platform can be used to evaluate the relative effectiveness of diesel fuels in preventing wear under anticipated test conditions. The correlation of these test results to field performance of diesel fuel injection systems has not yet been determined.

This test method is designed to evaluate boundary lubrication properties. In this test method, the effects of viscosity on lubrication are minimized, if not completely eliminated.

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