Overview
ISO 9030:1990 - "Crude petroleum - Determination of water and sediment - Centrifuge method" specifies a laboratory centrifuge procedure to determine the water and sediment content of crude oil. The standard defines the principle, apparatus, reagents, sampling and sample handling (Annex A), step‑by‑step procedure, result expression, precision data (determined up to 1% (V/V) water content) and test reporting requirements. This method is intended for custody transfer checks, refinery quality control and routine laboratory analysis where a centrifuge method is appropriate.
Key topics and technical requirements
- Principle: Equal volumes of crude oil and water‑saturated toluene are mixed in cone‑shaped centrifuge tubes; after centrifugation the volume of the denser water + sediment layer is read.
- Apparatus: Requires a heated centrifuge capable of maintaining sample temperature and delivering a minimum relative centrifugal force (rcf) at the tube tip (document specifies rcf at least 600 at the tip). Centrifuge tubes must be 203 mm cone‑shaped, made of annealed glass, and volumetrically calibrated.
- Reagents: Use water‑saturated toluene (ISO 5272 grade) and an appropriate demulsifier (recommended stock: 25% demulsifier / 75% toluene, adjusted by agreement).
- Temperature control: Samples and solvent must be maintained at 60 °C ± 3 °C during mixing and centrifuging (49 °C ± 3 °C may be used by agreement, with possible impact on precision).
- Procedure highlights: Fill tubes to 50 ml with sample, add 50 ml water‑saturated toluene, add 0.2 ml demulsifier, invert to mix, centrifuge (typically 10 minutes), read water + sediment volume to specified reading precision and repeat spin(s) until readings stabilize.
- Measurement accuracy: Graduations must be verified (ISO 4787) and readings taken to defined increments (e.g., nearest 0.05 ml for sub‑1 ml graduations; see standard for full tolerances).
- Precision and reporting: Precision data are provided for water/sediment contents up to 1% (V/V). The test report must include product ID, reference to ISO 9030, test results, any deviations and test date.
Applications and users
- Who uses ISO 9030: Petroleum laboratories, refinery QC teams, custody transfer inspectors, crude sampling organizations, and analytical service providers.
- Typical applications: Determining free water and sediment for quality control, custody transfer correction, troubleshooting emulsions or separation issues, and validating sampling and sample handling procedures.
Related standards
Use ISO 9030:1990 when a standardized centrifuge method is required to quantify low levels of free water and sediment in crude petroleum and when laboratory conditions (heated centrifuge, calibrated tubes, controlled reagents) can be met.