ISO 15970:2008

Overview

ISO 15970:2008 - Natural gas - Measurement of properties - Volumetric properties: density, pressure, temperature and compression factor - specifies requirements and field procedures for measuring the volumetric properties of natural gas used mainly for volume calculation and conversion. The standard covers density at reference and operating conditions, pressure (differential, gauge, absolute), temperature and the compression factor (Z). It focuses on instruments and methods suitable for in-line or on-line field operation in transmission and distribution systems and on techniques that do not require gas composition analysis.

Key Topics and Requirements

• Density measurement
  • Defines density at reference (standard/base) and operating conditions for volume conversion and mass-flow calculations.
  • Covers density transducers based on vibrating elements, typically for ranges ~5 kg/m3 to 250 kg/m3.
  • Includes guidance on installation, sampling, calibration, verification, maintenance and quality control.
• Pressure measurement
  • Addresses differential, gauge and absolute pressure transmitters, both analogue and smart (microprocessor-based).
  • Sets requirements for performance assessment, installation and calibration.
• Temperature measurement
  • Focuses on conditions typical for transmission and distribution (253 K < T < 338 K).
  • Recommends use of RTDs (resistance thermometer detectors) and covers installation and verification.
• Compression factor (Z)
  • Describes the role of compressibility (Z) in volumetric metering and volume conversion between metering and reference conditions.
  • Provides measurement/estimation guidance where compositional analysis is not used.
• Traceability and safety
  • Requires calibration traceable to national or international standards.
  • Notes compliance with hazardous-area electrical standards (IEC 60079 series).
• Supporting material
  • Informative Annex A (instrument selection, testing, operational procedures) and Annex B (instrument documentation).

Applications and Who Uses It

ISO 15970 is intended for:

• Gas transmission and distribution operators for accurate custody transfer and invoicing.
• Metering and instrumentation engineers specifying or commissioning field devices.
• Manufacturers of density, pressure and temperature transmitters seeking compliance and performance benchmarks.
• Calibration laboratories and service providers ensuring traceability and verification procedures.
• Regulators and auditors evaluating measurement systems and metering accuracy.

Practical benefits include consistent volume conversion, improved mass-flow measurement, reduced disputes in custody transfer, and standardized installation/calibration practices for field instrumentation.

Related Standards

Key referenced standards include:

• ISO 2186; ISO 5167-1; ISO 6976; ISO 10715; ISO 12213-1
• IEC 60079 series (explosive atmospheres); IEC 60751 (RTDs); IEC 60770-1 (transmitter performance)

Keywords: ISO 15970, natural gas measurement, density, pressure, temperature, compression factor, compressibility factor, volumetric metering, field instrumentation, calibration, custody transfer.