ASTM D7224 Standard Test Method for Determining Water Separation Characteristics of Kerosine-Type Aviation Turbine Fuels Containing Additives 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 specific fiberglass coalescer, the MCell Coalescer, and the effluent is analyzed for uncoalesced water (that is, dispersed water droplets) by a light transmission measurement. The Micro-Separometer instrument has an effective range of 50-to-100 scaled to the nearest whole number. A test can be performed in 5 min to 10 min.
5. Significance and Use
5.1 This test method provides a measurement of the presence of surfactants in aviation turbine fuels. Like previous obsolete Test Methods D2550 and D3602 and current Test Method D3948, this test method can detect trace amounts of refinery treating chemicals in fuel. The test methods can also detect surface active substances added to fuel in the form of additives or picked up by the fuel during handling from point of production to point of use. Some of these substances degrade the ability of filter separators to separate free water from the fuel.
5.2 This test method yields approximately the same (low) MSEP ratings as Test Method D3948 for fuels that contain strong surfactants.
5.2.1 This test method will give approximately the same MSEP ratings for Jet A, Jet A-1, JP-5, JP-7, and JP-8 fuels as Test Method D3948 when testing reference fluids.
5.3 The MSEP ratings obtained by this test method are less affected by weak surfactants than Test Method D3948. Somewhat higher MSEP ratings for Jet A, Jet A-1, JP-5, JP-7, and JP-8 fuels are obtained by this test method than those obtained by Test Method D3948 when additives such as static dissipater additives (SDA) and corrosion inhibitors are present in the fuel. This correlates with the satisfactory performance of filter separators for such fuels, when wet. However, these same additives adversely affect the MSEP ratings obtained by Test Method D3948 by erroneously indicating that such additized fuels would significantly degrade the ability of filter separators to separate free water from the fuel in actual service.
5.4 The Micro-Separometer instrument has an effective measurement range from 50 to 100. Values obtained outside of those limits are undefined and invalid.
NOTE 1 - In the event a value greater than 100 is obtained, there is a good probability that light transmittance was reduced by material, typically water, contained in the fuel that was used to set the 100 reference level. During the coalescing portion of the test, the contaminating material as well as the 50 µL +/- 1 µL of distilled water was subsequently removed during this 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.
6. Interferences
6.1 Any suspended particles, whether solid or water droplets or haze, in a fuel sample will interfere with this test method, which utilizes light transmission of a fuel sample after emulsification with water and subsequent coalescence.
