ISO 1998-2:1998

Overview

ISO 1998-2:1998 - Petroleum industry: Terminology - Part 2: Properties and tests is the second part of a multi‑part ISO terminology standard for the petroleum sector. Published in 1998 as the second edition, it provides equivalent English and French terms with definitions used to describe physical and chemical properties of crude oils and petroleum products and the common test concepts related to those properties. The edition reorganized the terminology with a new classification and numbering system and complements the other parts of ISO 1998 (Parts 1–7 and 99).

Key topics

This part focuses on standardized wording and definitions for properties and test concepts, including (but not limited to):

• Density and relative density (reference temperatures such as 15 °C are noted; ISO 5024 referenced)
• API gravity (relation to relative density; API scale usage)
• Water and sediment (definition covering solids and aqueous phase)
• Vapour pressure concepts:
  • Reid vapour pressure (RVP) - defined for 37.8 °C (100 °F) and vapour/liquid ratio 4:1, with notes about water saturation effects
  • Air‑saturated vapour pressure (ASVP) - defined in vacuo for air‑containing liquids and typical test conditions
• Viscosity family of terms:
  • Dynamic (absolute) viscosity
  • Kinematic viscosity
  • Apparent viscosity (for non‑Newtonian fluids)
  • Newtonian fluid definition
• Distillation curve and initial boiling point (graphical/measurement concepts for boiling/distillation behaviour)
• Terminology numbering and classification (format x.yy.zzz; Part 2 subcategories listed, e.g., physical/chemical properties, fuels/distillates, lubricants)

Applications and users

ISO 1998-2:1998 is intended for consistent usage of terms across the petroleum value chain - from field production to the final user. Practical applications include:

• Harmonizing vocabulary in laboratory test methods, quality control and analytical reports
• Supporting specification documents, product data sheets and trade contracts where precise property definitions (density, RVP, viscosity) matter
• Aiding regulators, legal metrology and standards bodies when reference temperatures or test concepts must be unambiguous
• Assisting technical writers, translators and terminologists who prepare bilingual documents

Primary users: petroleum engineers, laboratory analysts, QC/QA personnel, standards committees, regulators, and technical documentation teams.

Related standards

• ISO 1998 (other parts: Part 1, 3–7 and 99)
• Normative reference: ISO 1998‑99 (General and index)
• Other referenced material: ISO 5024 (reference temperature guidance for density)

Keywords: ISO 1998-2, petroleum terminology, properties and tests, density, vapour pressure, Reid vapour pressure, viscosity, distillation curve, API gravity.