GB/T 33400-2016 Determination of total contamination in middle distillates, diesel fuels and fatty acid methyl esters

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GB/T 33400-2016, Determination of total contamination in middle distillates, diesel fuels and fatty acid methyl esters, specifies the gravimetric determination of total contamination after vacuum filtration through a pre-weighed membrane filter.

Evidence note: The content of this page was compiled from the original text of this standard held in the Origin Standard library (where marked [to be verified], the source is [source unclear]); for individual values and the current status, please refer to the original standard page and the product certificate.

Scope: Applicable to: determination of total contamination in middle distillates, diesel fuels with a fatty acid methyl ester volume fraction not greater than 30 %, and pure fatty acid methyl esters (BD100). Applicable viscosity: samples with a kinematic viscosity at 20 °C not greater than 8 mm²/s, or a kinematic viscosity at 40 °C not greater than 5 mm²/s (for example diesel fuels and pure fatty acid methyl ester BD100). Applicable content range: samples with a total contamination content of 12 mg/kg to 30 mg/kg, for which precision is specified; also applicable to samples with a total contamination content outside this range, but their precision is not specified. May also be used for: diesel fuels with a fatty acid methyl ester volume fraction greater than 30 % and products whose kinematic viscosity is outside the above range, but the precision of the method has not been established. NOTE 1: Excessive contamination in a fuel system can cause filter blockage and/or hardware failure. NOTE 2: The results obtained by this standard in determining the total contamination content of pure fatty acid methyl esters differ considerably from those of the relevant standard, see Annex A. Not applicable: the original does not list “not applicable” content in a dedicated clause (it only limits cases outside the range by “precision not specified”).

Principle: A quantity of sample is weighed and filtered under vacuum through a pre-weighed membrane filter. The membrane filter with the residue is washed, dried and weighed. The total contamination content is calculated from the mass difference of the membrane filter and is expressed in milligrams per kilogram (mg/kg). For pure fatty acid methyl esters and liquid petroleum products with a kinematic viscosity at 20 °C greater than 8 mm²/s or at 40 °C greater than 5 mm²/s, the weighed sample needs to be diluted with solvent before filtration.

Apparatus: All glassware and sample containers shall be cleaned as described in Clause 7. General laboratory apparatus and glassware are given in 6.2 to 6.19. 6.2 Filtration assembly: as shown in Figure 1, suitable for the membrane filter described in 6.3 (Figure 1 components: 1 — ground wire; 2 — clamp; 3 — funnel; 4 — support screen; 5 — receiving flask; 6 — vacuum tube; 7 — safety flask; 8 — vacuum gauge; 9 — to vacuum pump; 10 — lead). 6.3 Membrane filter: high-retention glass fibre, diameter 47 mm, nominal pore size 0.7 μm, for sample filtration. 6.4 Beaker: capacity 500 mL and 1000 mL, conforming to the requirements of GB/T 15724. 6.5 Graduated cylinder: capacity 500 mL and 1000 mL. 6.6 Glass bottle with lid: 0.5 L and 1 L. 6.7 Oven: static (without fan-assisted circulation), explosion-proof, capable of heating to 110 °C ± 5 °C. 6.8 Desiccator: containing freshly activated self-indicating silica gel (or an equivalent desiccant). 6.9 Petri dish with lid: diameter greater than 50 mm. 6.10 Analytical balance: accurate to 0.1 mg. 6.11 Tweezers: flat tips, without serrations, for handling membrane filters. 6.12 Water bath or oven: capable of controlling the temperature at 40 °C ± 1 °C and 60 °C ± 1 °C. 6.13 Wash bottle with nozzle: suitable for n-heptane (5.1). 6.14 Balance: capable of weighing up to 1500 g, accurate to 0.1 g. 6.15 Vacuum device: capable of controlling the absolute pressure in the filtration assembly at 2 kPa to 5 kPa. NOTE: A water-ring vacuum pump does not meet the requirement. 6.16 Suitable clean sample containers and sampling vessels. 6.17 Timer: capable of measuring 30 min ± 1 min. 6.18 Clean watch glass or aluminium foil. 6.19 Membrane filter: nominal pore size 0.45 μm, for filtering reagents.

Reagents and reference materials: n-Heptane: purity (volume fraction) not less than 99.0 %, filtered through the membrane filter described in 6.19. NOTE: The reference fuel n-heptane in GB/T 5487 meets the requirement. 5.2 Xylene: analytical reagent, filtered through the membrane filter described in 6.19. 5.3 Isopropanol: purity (volume fraction) not less than 99.0 %, filtered through the membrane filter described in 6.19. 5.4 Solvent: thoroughly mix 750 mL of n-heptane (5.1) and 250 mL of xylene (5.2) (i.e. n-heptane:xylene = 3:1). 6.8 Desiccator: containing freshly activated self-indicating silica gel (or an equivalent desiccant).

Key conditions: Filtration absolute pressure: 2 kPa to 5 kPa (6.15, 11.1). Drying temperature/time: 110 °C ± 5 °C, at least 45 min (10.2.2); after the test, dry at 110 °C ± 5 °C for 45 min (11.5). Cooling: cool in a desiccator for about 45 min (10.2.3, 11.5). Sample preheating: middle distillates and diesel fuels in a water bath or oven at 40 °C for 30 min to 60 min (9.2.1); pure fatty acid methyl esters in a water bath or oven at 60 °C for at least 2 h to 2.5 h (9.3.1); high-viscosity liquid petroleum products in a water bath or oven at 40 °C for 30 min to 60 min (9.4.1). Standing after dilution: pure fatty acid methyl esters, after adding solvent, stand at room temperature for 2 h (9.3.6). Filtration time limit: if the sample has not finished filtering within 30 min, stop filtration and record the volume of sample filtered (11.1 b). Room-temperature operating range: generally 15 °C to 25 °C (9.1, NOTE).

Calculation and results: Calculate the total contamination content ρ (mg/kg) in the sample according to equation (1): ρ = (m2 − m1) × 1000 / mE where: m1 — mass of the membrane filter (10.2.4), in milligrams (mg); m2 — mass of the membrane filter after filtration (11.6), in milligrams (mg); mE — mass of the sample (9.2.5, 9.3.5 or 9.4.6), in grams (g). (NOTE: the equation is typeset in [source unclear] as “K-1000/ms一m.” and has been restored to the above form according to the context and the symbol table; the symbols are subject to the symbol descriptions in the original, [to be verified] ([source unclear]).)

Quality control: General: judge the reliability of the test results as specified below (95 % confidence level). The precision of this standard was obtained by statistics on the test results of several laboratories with reference to ISO 4259. 14.2 Repeatability: the difference between two consecutive test results obtained by the same operator, under the same operating conditions, using the same instrument and following the procedure specified in the method on the same sample shall not exceed the value specified in equation (2): r = 0.064 4X + 1.6099 … (2) where: X — arithmetic mean of the two consecutive test results, in milligrams per kilogram (mg/kg). 14.3 Reproducibility: the difference between two single, independent test results obtained by different operators, in different laboratories, using different instruments and following the procedure specified in the method on the same sample shall not exceed the value specified in equation (3): R = 0.164 4X + 4.1110 … (3) where: X — arithmetic mean of the two single, independent test results, in milligrams per kilogram (mg/kg). NOTE: The reproducibility formula in Table A.1 of Annex A is recorded as “R=0.164 4X+1.1110”, which is inconsistent with equation (3) in the body of the text, “R=0.164 4X+4.1110”, [to be verified] ([source unclear]).

Normative references: Normative references (Clause 2): GB/T 4756 Petroleum liquids — Manual sampling GB/T 15724 Laboratory glassware — Beakers GB/T 27867 Petroleum liquids — Automatic pipeline sampling EN 14275 Automotive fuels — Assessment of petrol and diesel fuel quality — Sampling from retail site pumps and commercial site fuel dispensers References: [1] GB/T 5487 Determination of octane number of gasoline — Research method [2] ISO 4259 Petroleum products — Determination and application of precision data in relation to methods of test [3] EN 12662:1998 Liquid petroleum products — Determination of contamination in middle distillates Annex A (informative) Main technical differences between this standard and EN 12662:1998 (Table A.1): Membrane filter: this standard specifies a high-retention glass fibre membrane with an average pore size of 0.7 μm; EN 12662:1998 specifies a cellulose nitrate membrane with an average pore size of 0.8 μm. Sample size: about 300 mL in this standard; 250 g to 500 g in EN 12662:1998. Sample pretreatment (middle distillates and diesel fuels): this standard uses a water bath or oven at 40 °C for 30 min to 60 min, cooling to room temperature, taking about 300 mL of sample, weighing and then determining; EN 12662:1998 weighs 250 g to 500 g of sample, heats it in an oven at 40 °C for about 30 min and filters it directly. Sample pretreatment (pure fatty acid methyl esters): this standard uses an oven or water bath at 60 °C for at least 2 h to 2.5 h, cooling, taking about 300 mL of sample, weighing it, diluting it with 300 mL of solvent (n-heptane:xylene=3:1), and determining after standing for 2 h; the available material does not provide a corresponding item for EN 12662:1998. Precision (repeatability): this standard r=0.064 4X+1.6099 (X is the arithmetic mean of the two results); EN 12662:1998 requires the difference between two test results not to exceed 10 % of their arithmetic mean. Precision (reproducibility): this standard R=0.164 4X+1.1110 (as given in Table A.1, X is the arithmetic mean of the two results); EN 12662:1998 requires the difference between two independent test results not to exceed 30 % of their arithmetic mean.

Verification note: [To be verified] and [source unclear] mark points that still need to be checked against the original standard text; they do not mean the values have been verified. Do not use these values or procedures directly as a basis for work.

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