FREE WATER IN MID-DISTILLATE FUELS: D4860
TEST SUMMARY
This test is similar to D4176 just described. The color of sample does not affect the measurement. The test uses a rapid, portable means of visually inspecting for particulate matter and rating numerically for free water in aviation turbine and distillate fuels, both in field and in a laboratory.
The inspection for particulate matter is done the same way as in Test Method D4176. A numerical rating for free water is obtained by filtering a portion of the fuel sample at a programmed rate through a standard fiberglass coalescer/filter. A portion of the effluent is used as a reference against an unfiltered portion to obtain the rating.
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. 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.
TEST PRECISION
Visual particulate matter is a pass-fail test, and a statement of precision is not appropriate. The repeatability for the numerical rating of free water is 6, and a reproducibility is 7.
This test method has no bias.
