ASTM D3948 Determining Water Separation Characteristics of Aviation Turbine Fuels
ASTM D3948 Standard Test Method for Determining Water Separation Characteristics of Aviation Turbine Fuels by Portable Separometer
4. Summary of Test Method
4.1 A water/fuel sample emulsion is created in a syringe using a high-speed mixer. The emulsion is then expelled from the syringe at a programmed rate through a standard fiber-glass coalescer and the effluent is analyzed for uncoalesced water by a light transmission measurement. The results are reported on a 0-to-100 scale to the nearest whole number. High ratings indicate the water is easily coalesced, implying that the fuel is relatively free of surfactant materials. A test can be performed in 5 to 10 min.
5. Significance and Use
5.1 This test method provides a measure of the presence of surfactants in aviation turbine fuels. Like Test Methods D2550 and D3602, this test method can detect carryover traces of refinery treating residues in fuel as produced. They can also detect surface active substances added to or picked up by the fuel during handling from point of production to point of use. Certain additives can also have an adverse affect on the rating. Some of these substances affect the ability of filter separators to separate free water from the fuel.
5.2 The Micro-Separometer has a measurement range from 50 to 100. Values obtained outside of those limits are undefined and invalid. In the event a value greater than 100 is obtained, there is a good probability that light transmittance was reduced by material contained in the fuel used to set the 100 reference level. The material was subsequently removed during the coalescing portion of the test, thus, the processed fuel had a higher light transmittance than the fuel sample used to obtain the 100 reference level resulting in the final rating measuring in excess of 100.
5.3 Test Mode A function of the separometer will give approximately the same rating for Jet A, Jet A-1, MIL JP 5, MIL JP 7, and MIL JP 8 fuels as Test Methods D2550 and D3602. Using Mode A water separation characteristic ratings of Jet B and MIL JP 4 fuels will not necessarily be equivalent to Test Method D2550 but will give approximately the same rating as Test Method D3602. All Micro-Separometers have test Mode A capability.
5.4 The Test Mode B option is used to determine water separation ratings for MIL JP 4 fuels containing fuel system corrosion and icing inhibitors. These ratings are approximately the same as those obtained using Test Method D2550.
5.5 Selection of Mode A or Mode B depends on the specific fuel and specification requirement. Table 1 identifies the recommended test method for various fuels.
5.6 The basic difference between Modes A and B is the flow rate at which the water/fuel emulsion is forced through the standard fiberglass coalescer cell. The lapsed time required to force the emulsion through the coalescer cell in Mode A is 45 ± 2 s; whereas, Mode B requires 25 ± 1 s.
