Standard Test Method for
Undissolved Water In Aviation Turbine Fuels1
This standard is issued under the fixed designation D 3240; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
1.1 This test method covers the measurement of undissolved
water in aviation turbine fuels in flowing fuel streams without
exposing the fuel sample to the atmosphere or to a sample
container. The usual range of test readings covers from 1 to 60
ppm of free water. This test method does not detect water
dissolved in the fuel, and thus test results for comparable fuel
streams can vary with fuel temperature and the degree of water
solubility in the fuel.
1.2 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. Terminology
2.1 Definition of a Term Specific to This Standard:
2.1.1 free water—water not dissolved in the fuel.
3. Summary of Test Method
3.1 A measured sample of fuel is passed through as uranine
dye-treated filter pad. Undissolved (free) water in the fuel will
react with the uranine dye. When the pad is subsequently
illuminated by ultra violet (UV) light, the dye previously
contacted by free water will fluoresce a bright yellow with the
brightness increasing for increasing amounts of free water in
the fuel. The UV light-illuminated pad is compared to a known
standard using a photocell comparator, and the free water in the
fuel sample is read out in parts per million by volume. By
varying the fuel sample size, the range of the test method can
be increased.
4. Significance and Use
4.1 Undissolved (free) water in aviation fuel can encourage
the growth of microorganisms and subsequent corrosion in the
tanks of aircraft and can also lead to icing of filters in the fuel
system. Control of free water is exercised in ground fueling
equipment by use of filter-coalescers and water separators.
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