ASTM D5304 Standard Test Method for Assessing Middle Distillate Fuel Storage Stability by Oxygen Overpressure
10. Procedure
10.1 Place two unweighed nylon membrane filters in a filter funnel. Prefilter, under vacuum (see 6.5), 220 mL of fuel to be tested. Transfer 100 mL of the filtered fuel to each of two glass sample containers (see 6.1). Place these sample containers plus two blank sample containers in the pre-heated pressure vessel(s) (see 9.4). If more than one fuel is to be tested simultaneously, additional glass sample containers are required. However, only a single pair of blank containers is required. Close the pressure vessel(s) after inspecting the vessel seals and replacing if necessary.
10.2 Set the oxygen cylinder secondary regulator to deliver 800 kPa (absolute) (100 psig). Connect the pressure vessel to an oxygen cylinder via the preset regulator and pressurize slowly to about 800 kPa (100 psig). (Warning - See 4.1.) Release the pressure slowly, repeat the pressurization and release the pressure slowly. The third and final time, pressurize to 800 kPa +/- 10 kPa (100 psig +/- 1 psig) as preset on the secondary regulator. (Warning - See 6.2.)
10.3 Close the pressure vessel isolation valve and maintain temperature at 90 °C +/- 1 °C for 16 h +/- 15 min using the thermometer specified in 6.10.
10.4 At the end of the aging period, measure and record the pressure. The test is invalid if the pressure has dropped more than 20 kPa (absolute) (2 psig) and must be repeated after replacing the pressure vessel seals. Slowly release the pressure to atmospheric, then open the reactor.
10.5 Remove the sample containers from the pressure vessel(s) and allow the containers to cool slowly to ambient (25 °C +/- 5 °C) in the dark for a minimum of 1 h. Do not expose the samples to light prior to filtration.
10.6 Place the two filters from a preweighed weighing assembly from 9.3 in a filter assembly and apply suction. Completely filter the contents of a sample container. After the sample container is empty and the filter is dry, (1) relieve the vacuum, (2) thoroughly rinse the inside of the sample container with at least 25 mL of filtered hydrocarbon solvent (see 7.3), and pour into filter holder, and (3) pull solvent through filter with vacuum. Repeat steps (1) through (3). Wash down filter holder with filtered hydrocarbon solvent from a rinse bottle and pull through filter.
10.7 Wash down the inside of the funnel and the outside of the joint between the funnel and the filter base with filtered hydrocarbon solvent.
10.8 With the vacuum applied, carefully separate the funnel from the filter base. Wash the periphery of the membrane filter by directing a gentle stream of filtered hydrocarbon fluid from the edge to the center, exercising care not to wash any of the particulate from the surface of the membrane filter.
10.9 Maintain vacuum after the final washing for 10 s to 15 s to remove excess filtered hydrocarbon solvent from the membrane filter.
10.10 Carefully rinse the sample container with two consecutive 15 mL portions of TAM solvent. Be sure to contact the entire inner surface of the sample container with solvent. Pour both solvent rinses into the upper dish of the nested aluminum weighing dish assembly (see 9.2) from which the filters were taken in 10.6 (see 9.3).
10.11 Place the nested aluminum dishes on a hot plate and slowly evaporate the TAM just to dryness. Follow this same procedure with each of the blank correction containers.
10.12 Put the two test filters in the upper dish of the nested aluminum dish assembly from which they were taken in 10.6. Place these weighing assemblies in the drying oven at 105 °C to 115 °C for at least 30 min. Remove from the oven and allow approximately 1 h to cool to ambient temperature (25 °C +/- 5 °C). Weigh each of the weighing assemblies to the nearest 0.1 mg.
11. Calculation
11.1 Calculate the total insolubles in mg/100 mL as follows:
TI = B - C - D
D = (E - F)/2
where:
TI = total insolubles of an individual sample,
B = mass of an individual sample weighing assembly after filtering of aged sample, mg,
C = mass in mg of an individual sample weighing assembly before filtering of aged sample, mg,
D = blank correction for an individual sample. Blanks (D) can gain or lose weight. Remember to correct for either by ensuring the calculations reflect the sign (+/-) correctly.
E = the sum of the two blank weighing assemblies after filtering, and
F = the sum of the two blank weighing assemblies before filtering.
NOTE 2 - Blanks (D) can gain or lose weight. Remember to correct for either by ensuring the calculations reflect the sign (+/-) correctly.
