Overview
EN ISO 13757:1996 - Liquefied petroleum gases - Determination of oily residues - High‑temperature method specifies a laboratory method to determine oily residues in LPG (liquefied petroleum gases) remaining after evaporation at 105 °C. The procedure concentrates a filtered LPG sample by evaporation into dichloromethane (methylene chloride), removes solvent by rotary evaporation, dries the residue in an oven at 105 °C, and reports the oily residue as mg/kg LPG. The standard includes safety cautions for hazardous materials and equipment.
Key topics and technical requirements
- Sample collection and mass: Typical sampled mass is 800–1 200 g LPG taken from a stainless steel sample cylinder with dip tube.
- Solvent and reagents: Dichloromethane (analytical grade) is used as primary solvent (pentane may be substituted if regulatory/health restrictions apply, provided comparable residue performance). Other reagents include acetone, ammonium peroxodisulfate/sulfuric acid (for cleaning) and grade 3 water (ISO 3696).
- Apparatus: stainless steel sampling lines and in-line filter; 5 dm3 shallow glass beaker; stainless steel cooling coil (coiled 3 mm tube); rotary evaporator (bath 65 °C ± 5 °C); evaporation flask (tare ≤ 130 g); oven at 105 °C ± 5 °C; cooling bath capable of −60 °C.
- Procedure highlights:
- Filter and collect LPG into a beaker containing ~50 cm3 dichloromethane.
- Evaporate LPG, concentrate the soluble fraction, rinse and combine solvent washes into an evaporation flask.
- Use rotary evaporation (no vacuum) to remove solvent, then oven‑dry residue at 105 °C for 1 hour, cool in a desiccator and weigh to nearest 0.1 mg.
- Perform a blank test and apply blank correction to results.
- Safety: Work in an explosion‑proof hood, ventilated fume hood for dichloromethane, earth equipment to prevent static ignition, wear appropriate PPE.
- Performance: Interlaboratory precision reported for 70–100 mg/kg oily residues - repeatability r = 15 mg/kg; reproducibility R = 50 mg/kg.
Applications and users
- Applications:
- Quality control of LPG batches for downstream equipment (vaporizers, burners) where oily deposits can interfere with heat transfer or combustion.
- Acceptance testing in LPG production, storage and distribution.
- Investigations of deposit problems in vaporizer systems and safety/maintenance audits.
- Who uses it:
- Petroleum and LPG laboratories, quality assurance teams, refinery and distribution technical staff, standards laboratories, and independent test laboratories.
Related standards
- ISO 3696:1987 - Water for analytical laboratory use (grade 3 water).
- ISO 4257:1988 - LPG sampling methods.
- The standard was prepared by ISO/TC 28 (Petroleum products and lubricants) and includes an informative annex.
Keywords: EN ISO 13757:1996, liquefied petroleum gases, LPG oily residues, high‑temperature method, dichloromethane, rotary evaporator, oven drying, sampling, test precision.
