ASTM D6748 for Determination of Potential Instability of Middle Distillate Fuels
ASTM D6748 Standard Test Method for Determination of Potential Instability of Middle Distillate Fuels Caused by the Presence of Phenalenes and Phenalenones (Rapid Method by Portable Spectrophotometer)
1. Scope
1.1 This test method covers a procedure for the rapid determination of phenalenes and phenalenones in middle distillate fuels, including marine, automotive, heating, and gas turbine fuel such as those specified in Specifications D396, D975, D2069, and D2880. Phenalenes and phenalenones affect the potential instability of fuels, leading to fuel degradation products during storage, which may cause performance problems.
1.2 This test method is applicable to both dyed and undyed fuels at all points in the distribution chain from refinery to end-user. It is not applicable to fuels containing residual oil. The portable apparatus allows the whole test to be conducted on site or in a laboratory and does not require the test sample to be heated.
1.3 This test method is suitable for testing samples with a relative absorbance of up to 5.00 absorbance units (AU).
NOTE 1 - The precision of the test method has been established on relative absorbance up to 1.00 AU. For relative absorbance above 1.00 AU the precision may not apply.
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 and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D396 Specification for Fuel Oils
D975 Specification for Diesel Fuel Oils
D2069 Specification for Marine Fuels
D2880 Specification for Gas Turbine Fuel Oils
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4306 Practice for Aviation Fuel Sample Containers for Tests Affected by Trace Contamination
D4625 Test Method for Middle Distillate Fuel Storage Stability at 43°C (110°F)
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
D6468 Test Method for High Temperature Stability of Distillate Fuels
E 131 Terminology Relating to Molecular Spectroscopy
E 275 Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers
2.2 Other Standards:
Def Stan 05-50 Methods for Testing Fuels and Lubricants and Associated Products, Part 40 - Storage Stability of Diesel Fuels
Def Stan 91-4 Fuel, Naval, Distillate NATO Code: F76 Joint Service, Designation DIESO F76
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms relating to absorption spectroscopy see Terminology E 131. Terms of particular significance are the following:
3.1.2 radiant energy, n - energy transmitted as electromagnetic waves.
3.1.3 radiant power P, n - the rate at which energy is transported in a beam of radiant energy.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbance, A, n - the logarithm to the base 10 of the reciprocal of the transmittance, T. In symbols:
A = log10(1/T)= -log10T
where:
T = transmittance as defined in 3.2.5.
3.2.2 absorbance units (AU), n - units of relative absorbance reported by the portable spectrophotometer.
3.2.3 pathlength of test portion b, n - the distance in mm, measured in the direction of propagation of the beam of radiant energy, between the surfaces of the portion on which the radiant energy is incident and the surface of the test portion from which it emerges.
3.2.4 relative absorbance, n - the difference between the absorbance (near infrared-visible band results) measured at the two wavelengths, and reported in AU.
3.2.5 transmittance, T, n - the ratio of the radiant power transmitted by the test portion in the test cuvette to the radiant power transmitted by the Reagent 1 control in the cuvette. Expressed in the following equation.
T = PT/PR1
where:
PT = radiant power transmitted by the test portion, and
PR1 = the radiant power transmitted by the Reagent 1 control.