EN 12662 Liquid petroleum products - Determination of total contamination in middle distillates, diesel fuels and fatty acid methyl esters
11 Procedure
WARNING - Electrostatic charges can be generated during the filtration of petroleum products; therefore the filter apparatus shall be earthed.
11.1 Filter the test sample (9.2.5, 9.3.6 or 9.4.6) using the filter after its preparation (10.2) applying suction or vacuum as necessary to reach an absolute pressure of 2 kPa to 5 kPa (6.14) inside. The sample shall be transferred into the filtration apparatus (6.1) in small portions. Be careful not to let the filter assembly dry during this transfer.
If foaming is observed in the receiving flask, check the vacuum pressure. A pressure lower than that mentioned above may lead to foaming.
If the filtration of the sample is not completed after 30 min, turn off the vacuum system and record the volume filtered. A correction on the mass of the sample test portion, mE, may be applied.
11.2 Using the wash bottle (6.12) wash the sediment from the beaker (6.3) or the glass bottle (6.5) onto the filter (6.2) with heptane (5.1). Carefully rinse the inside wall and base of the beaker (6.3) and filter the rinsings. Repeat the washing operation twice more.
11.3 Using the wash bottle (6.12) wash the inside wall of the funnel of the filtration apparatus (6.1) and filter (6.2) with heptane (5.1) and dry under suction. The funnel should be washed with a gentle stream and circumferential movement. Repeat the washing operation two more times.
11.4 Carefully remove the funnel and with the vacuum applied, wash the filter (6.2) from the periphery inwards by directing a gentle stream of heptane (5.1). Take care not to wash any of the particulate from the surface of the filter (6.2). Maintain the vacuum after the final washing for approximately 10 s to 15 s or until all excess heptane is removed from the filter.
11.5 Release the vacuum slowly and then remove carefully the filter (6.2) from the filter holder by means of the forceps (6.10), place it on the Petri dish (6.8) (see 10.2) and apply cover. Place the Petri dish (6.8), including the filter (6.2), into the oven (6.6), remove the cover and dry at 110 °C +/- 5 °C for 45 min. Allow to cool down to room temperature for approximately 45 min in the desiccator (6.7) located close to the analytical balance using the Petri dish cover.
11.6 Using the analytical balance (6.9), weigh the filter (6.2) without the Petri dish (6.8) to the nearest 0.1 mg. Record this mass m2. The filter shall be weighed to a constant value.
Temperature and time given in 11.5 are adequate to remove the washing medium. However, it is necessary to verify that the filter has reached a constant mass. If not, the filter is further dried according to 11.5.
12 Calculation
Calculate the total contamination as a mass fraction µ in mg/kg, using the following formula:
µ = 1000(m2 - m1)/mE
where
m1 is the mass of the filter, in milligrams (see 10.2.4);
m2 is the mass of the filter with the contaminant in milligrams (see 11.6);
mE is the mass of the sample test portion in grams (9.2.5, 9.3.5 or 9.4.5).
