ASTM D4860 Standard Test Method for Free Water and Particulate Contamination in Mid-Distillate Fuels (Clear and Bright Numerical Rating)
4. Summary of Test Method
4.1 Visual inspection of the fuel sample for free water and particulate matter is performed immediately when the sample is taken. A glass container is used to view for water haze, and the fuel sample is swirled to create a vortex to detect the presence of particulate matter.
4.2 A numerical rating for free water is obtained by filtering a portion of the fuel sample at a programmed rate (50 mL/45 s) through a standard fiberglass coalescer/filter. A portion of the effluent is used to establish a reference (100) level by a light transmittance measurement. Another portion of the unprocessed (unfiltered) fuel sample is then compared to the 100 reference level. The results are reported on a 50 to 100 scale to the nearest whole number. A test can be performed in 5 to 10 min.
NOTE 1 - The standard fiberglass coalescer/filter consists of a precision machined, aluminum housing, containing fiber-glass material that has been selected to specific air flow characteristics. These criteria have a direct bearing on the test results.
5. Significance and Use
5.1 The test provides a field test to evaluate visually a fuel sample for particulate matter and free water similar to Test Method D4176 plus a numerical rating for free water. High numerical ratings indicate that the fuel is relatively free of free water. The degree of water and particulate contamination can be measured using other methods such as Test Methods D1744, D2276, and D2709.
5.2 The color of the sample does not affect the measurement. Limited laboratory evaluations of samples have determined the degree of free water can be rated in fuels with dark opaque color having a darker rating than 5 in Test Method D1500.
6. Interferences
6.1 When a fuel is visually inspected at or below the cloud point temperature of the fuel, small amounts of solid wax particles can be confused with a water-induced haze or cloudiness.
6.2 The presence of free water or particulate can be obscured and missed during visual inspection of the fuel, if the ASTM color rating is greater than five.
