ISO 20764:2003

Overview

ISO 20764:2003 specifies the nitrogen purge method for preparing test portions of high‑boiling petroleum and related products (boiling > 200 °C) for the determination of total water content in the range 3 mg/kg to 1 000 mg/kg. The standard covers two extraction procedures (atmospheric and reduced pressure) that generate test portions suitable for Karl Fischer titration (potentiometric or coulometric).

Key topics and technical requirements

• Scope and materials: Applicable to unused and used lubricating oils, non‑aqueous hydraulic fluids and other high‑boiling solvents.
• Two procedures
  • Atmospheric pressure: Nitrogen purge at 120 °C ± 1 °C for 60 min ± 5 min; cooling to about −77 °C to condense water into dried methanol.
  • Reduced pressure (for water‑retaining/used oils): Nitrogen purge at 60 °C ± 1 °C under 0.30–0.65 kPa absolute pressure for 90 min ± 5 min.
• Reagents and consumables
  • Nitrogen: pure grade, oxygen < 500 mg/kg; nitrogen flow normally 3 L/h ± 0.3 L/h; target water content of nitrogen ~1 µg/L.
  • Methanol: dried to ≤ 100 mg/kg and protected from moisture.
  • Solid carbon dioxide and cooling medium (methanol/ethanol/acetone) to maintain −77 °C ± 3 °C.
• Apparatus: wash bottle (≈250 mL), borosilicate three‑neck titration vessel, heating bath, Dewar cooling vessel, vacuum source (for reduced‑pressure method), flowmeter and analytical balance (to 0.01 g).
• Sampling and handling: Laboratory samples per ISO 3170; dry dark‑glass containers with ground‑glass stoppers; begin preparation within 1 hour of sampling where possible.
• Calculation & reporting: Water content calculated using blank correction and a procedure time multiplier (x = 4 for atmospheric, x = 6 for reduced pressure). Report method used (“(A)” or “(V)”) and any sampling delays.
• Safety: Standard warns of hazardous operations and requires appropriate safety and health practices.

Applications and users

ISO 20764 is used by:

• Petroleum laboratories performing water determination in high‑boiling liquids.
• Quality control and R&D teams for lubricants, hydraulic fluids and high‑boiling solvents.
• Laboratories preparing samples for Karl Fischer titration (ISO 6296, ISO 12937). Practical benefits include reproducible extraction of bound/free water from viscous or contaminated oils, allowing accurate water-content analysis for product quality, condition monitoring and failure analysis.

Related standards

• ISO 6296:2000 - Karl Fischer potentiometric titration (water in petroleum)
• ISO 12937:2000 - Karl Fischer coulometric titration (water in petroleum)
• ISO 3170 - Petroleum liquids - Manual sampling
• ISO 383 - Laboratory glassware - Ground joints

Keywords: ISO 20764, nitrogen purge method, water content, petroleum, high‑boiling liquids, Karl Fischer, lubricating oils, hydraulic fluids, test portion preparation.