ASTM D7261 Standard Test Method for Determining Water Separation Characteristics of Diesel Fuels by Portable Separometer
7. Apparatus
7.1 A Micro-Separometer instrument is used to perform the test. The unit is portable and self-contained, capable of operating on an internal rechargeable battery pack or being connected to an ac power source using power cords which are available for various voltages. Connection to an ac power source will provide power to the unit and affect battery recharge. The accessories can be packed in the cover of the lockable case. There are two versions of the Micro-Separometer: the Mark V Deluxe and the upgraded version, Mark X.

NOTE 3 - An extensive study was performed to verify that the Mark X Micro-Separometer gives equivalent results to the Mark V Deluxe Micro-Separometer. See Research Report RR:D02-1647.

7.1.1 The Emcee Model 1140 Micro-Separometer Mark V Deluxe and associated control panel are shown in Fig. 1.

NOTE 4 - Of the lettered (A-G) push buttons on the Mark V Deluxe, only the D push button is applicable to this test method.

7.1.2 The Emcee Model 1140 Micro-Separometer Mark X and associated control panel are shown in Fig. 2. Table 1 lists the manual and audio operating characteristics of the instrument.

NOTE 5 - Of the lettered push buttons that select the test mode, only the DIESEL push button is applicable to this test method.

7.1.3 Both the Mark V Deluxe and Mark X Micro-Separometers have the emulsifier located on the right side of the raised panel and the syringe drive mechanism on the left side. The control panel containing the operating controls (push buttons) is mounted on the fixed panel in the left side of the case. A circuit breaker located on the control panel provides protection for the ac power circuit. The turbidimeter is located under the main control panel and consists ofa well in which the sample vial is placed, a light source, and a photocell.

7.2 Beaker, Catch Pan, or Plastic Container - (Supplied with each Micro-Separometer) used to receive the waste fuel during the coalescence period of the test.

7.3 Pipet - An automatic 50 µL hand pipet (supplied with each Micro-Separometer) designed to accept a disposable plastic tip.

8. Reagents and Materials
8.1 Aerosol OT, (AOT), solid (100 % dry) bis-2-ethylhexyl sodium sulfosuccinate.

8.2 Dispersing Agent - Toluene solution (Warning - Flammable. Vapor harmful.) containing 1 mg of Aerosol OT per milliliter of toluene.

8.3 Expendable Materials needed to perform the test are shown in Fig. 3 and consist of the following:
8.3.1 Syringe Plug, (A) - A plastic plug used to stopper the syringe during the clean and emulsion cycles.

8.3.2 Syringe, (Barrel (B) and Plunger (C)) - A disposable 50 mL plastic syringe.

8.3.3 Vials, (D), 25 mm outside diameter vial premarked for proper alignment in the turbidimeter well.

8.3.4 DCell or DBCell Coalescer, (E) an expendable, pre-calibrated aluminum coalescer cell with a tapered end to fit the syringe. It is labeled in a white background with black lettering:
DCELL®, DIESEL FUEL, D7261
DBCELL®, DIESEL FUEL, D7261

8.3.4.1 In order for a coalescer to be acceptable for this test method, it shall have passed factory calibration tests for air flow and leakage.

8.3.5 Disposable Plastic Pipet Tip (F) - Used with an automatic 50 µL hand pipet (Fig. 3, G).

8.3.6 Container (H) - A clean container of double-distilled water (8.7).

8.4 Reference Fluid Base - A surfactant-free, clean, distillate diesel fuel which is used to verify proper operation and is prepared in the manner described in Annex A1 (see 3.3.2). (Warning - Flammable. Vapor harmful.)

8.5 Reference Fluid - (Warning - Flammable. Vapor harmful.) A fluid used for checking the operational performance of the Micro-Separometer instrument), consisting of increasing concentrations (0 mL/L to 1.6 mL/L) of dispersing agent added to the reference fluid base. The DSEP ratings for this range of concentrations appear in Tables 2-5. The reference fluids are prepared and tested as described in Sections 12 and 13.

8.6 Toluene, ACS reagent grade. (Warning - Flammable. Vapor harmful.)

8.7 Water, clean, double-distilled and surfactant-free: D1193 Type IV reagent water, re-distilled. In practice, re-distillation of commercial distilled water has proven to be satisfactory.
8.7.1 Use ofwater other than double-distilled water (such as tap water) will render test results invalid.

9. Hazards
9.1 The primary hazard in this test method is the flammability of the fuels that are tested. Take suitable precautions to avoid sparks, flames or sources of ignition.

9.2 Minimize worker exposure to breathing fuel vapors.