Overview
ISO 4262:1993 specifies the Ramsbottom method for determining carbon residue in petroleum products. The procedure measures the carbonaceous (coke) residue left after evaporation and pyrolysis of a test portion heated rapidly in a glass coking bulb inside a metal furnace at approximately 550 °C. The method is applicable to relatively non‑volatile petroleum products and covers residues in the range 0.01 % (m/m) to 30.0 % (m/m). It provides a comparative indication of coke‑forming tendency useful in fuels, lubricants and related quality control.
Key topics and technical requirements
- Principle: weigh test portion into a glass coking bulb with a capillary opening; heat quickly to remove volatiles and induce pyrolysis/coking; cool and reweigh to obtain residue percentage.
- Temperature control: furnace nominally 550 °C; control bulb thermocouple should reach 547 °C in 4–6 minutes and remain within 550 °C ± 3 °C for the remainder of the standardization interval.
- Apparatus:
- Glass coking bulb with capillary diameter > 1.5 mm and ≤ 2.0 mm.
- Metal coking furnace with hemispherical bulb wells (specified internal dimensions) or molten bath variant; control bulb (stainless steel) with thermocouple for performance checks.
- Accurate temperature‑measuring device and a syringe (5 or 10 ml) for sample introduction.
- Performance verification: routine checks of furnace wells (fully and singly loaded) using a control bulb; thermocouple calibration recommended at least every 50 hours of control bulb use.
- Sample preparation: thorough shaking/warming if necessary, straining through a 150 µm sieve when required; special procedures for light products or after 90 % distillation (see Annex A).
- Weighing precision: bulbs weighed before and after test to 0.1 mg; bulbs cooled in a desiccator prior to weighing.
Applications and users
- Quality control in refineries and fuel laboratories to rank fuels by coke‑forming tendency.
- Lubricant formulators and testing labs for base‑oil characterization (finished oils with ash‑forming additives may give biased results).
- Engine, turbine and burner manufacturers assessing deposit propensity of fuels and oils.
- Regulatory and specification bodies requiring standardized carbon residue data for product classification.
Related standards
- ISO 3170 / ISO 3171 (sampling of petroleum liquids)
- ISO 3405 (distillation characteristics)
- ISO 683‑13 (referenced for materials)
- Annex A/B of ISO 4262 provide residue‑after‑distillation procedure and apparatus notes.
Keywords: ISO 4262, Ramsbottom method, carbon residue, petroleum testing, coking bulb, pyrolysis, carbonaceous residue, furnace calibration.
