Overview
EN ISO 3735:1999 - Crude petroleum and fuel oils: Determination of sediment (extraction method) specifies a laboratory procedure for measuring sediment content in crude oil and fuel oils by extraction with methylbenzene (toluene). The method is intended for sediment levels in the range 0.01% to 0.40% (m/m) (higher levels can also be measured). The standard includes apparatus requirements, sample handling and mixing rules, extraction and drying procedures, calculation and reporting formats, and precision data.
Key topics and technical requirements
- Principle: A test portion (≈10 g) is placed in a refractory extraction thimble and extracted with hot toluene until the residue reaches constant mass. Sediment is reported as percentage by mass.
- Apparatus and materials: 1 L wide-necked extraction flask, metal-coil condenser, refractory extraction thimble (porosity index P16; 25 mm × 70 mm; 15–17 g), corrosion-resistant thimble basket, water cup for samples >10% water, heater (hotplate preferred), oven (115–120 °C), analytical balance (accuracy 0.1 mg). Toluene must conform to ISO 5272 grade 2.
- Sample handling: Samples must be collected according to ISO 3170 or ISO 3171. Thorough mixing (non-aerating mixer) and temperature records (before and after mixing) are required; avoid excessive heating (>10 °C rise) during mixing to prevent sediment settling.
- Procedure specifics: Add 150–200 ml toluene, extract for 30 min after solvent runs clear, ensure solvent level in thimble stays below 20 mm of top, dry thimble 1 h at 115–120 °C, cool and weigh; repeat extractions until mass change between successive extractions ≤ 0.2 mg.
- Calculation: S = (m3 − m1) / (m2 − m1) × 100, where m1 = mass of empty thimble; m2 = thimble + test portion; m3 = thimble + sediment. Report to nearest 0.01% (m/m).
- Precision: Precision data are provided for the 0.01–0.40% range; reproducibility is expressed as R = 0.033 + 0.255 S (S in % m/m). The standard includes safety warnings about hazardous materials and operations.
Applications and users
This extraction method is used by:
- Petroleum testing laboratories and refinery QC teams for sediment determination in crude oils and fuel oils.
- Tank and ship inspectors, custody-transfer testing services, and regulatory or compliance laboratories that require standardized sediment measurements.
- Research and environmental laboratories assessing solid contamination in hydrocarbon samples.
Keywords: EN ISO 3735:1999, ISO 3735:1999, sediment determination, crude oil sediment, toluene extraction, fuel oils, petroleum testing, laboratory sediment test.
Related standards
- ISO 3170, ISO 3171 - sampling of petroleum liquids
- ISO 4793 - laboratory sintered (fritted) filters / thimble porosity grading
- ISO 5272 - toluene specifications
- ISO 1773 - laboratory glassware (boiling flasks)
For safe and accurate use, follow the standard’s safety notes and report mixing procedures and sample temperatures as required.