ISO 8943:2025

Overview

ISO 8943:2025 - Refrigerated light hydrocarbon fluids - Sampling of liquefied natural gas - Continuous and intermittent methods - specifies standardized methods for collecting representative samples of liquefied natural gas (LNG) while it is being transferred through an LNG transfer line. The standard covers both continuous sampling (constant flow into a gas sample holder) and intermittent sampling (grab samples at predetermined time or flow intervals) and is intended to ensure accurate composition data needed for density and calorific-value calculations in custody transfer and quality control.

Notable updates in the 2025 (third) edition include:

• an overview of gasified LNG sampling,
• introduction of CP/FP (constant pressure / floating piston) sample holders and cylinders,
• provisions for multiple shore-transfer pipelines,
• specification of a stable flow rate for continuous sampling,
• guidance to detect outliers in online analysis,
• an example sampling report.

Key technical topics and requirements

• Scope and definitions: Clear terminology for LNG sampling components (e.g., sampling probe, LNG sample vaporizer, gas sample holder, gas sample cylinder, CP/FP cylinder).
• Sampling system outline: Direct vs. indirect sampling methods; spot and incremental composite approaches for indirect sampling; handling multiple transfer lines.
• Precautions: Safe handling of LNG, risks of partial fractionation of samples, and requirements for supervision during sampling operations.
• Apparatus specifications: Materials, sampling probes, vaporizers to gasify LNG samples, compressors for transfer, pressure regulators, sample filters, and technical details for CP/FP cylinders and holders.
• Procedures: Step-by-step sampling workflows for continuous and intermittent methods, filling and purging of sample cylinders, suspension of sampling, and interface options for online gas chromatograph systems.
• Reporting and quality control: Requirements for a sampling report and examples, plus annexes such as sub-cooling calculations and CP/FP technical specs.

Practical applications and who uses this standard

ISO 8943:2025 is used where accurate LNG composition is essential:

• Terminal and berth operators performing custody transfer and invoicing based on calorific content.
• Pipeline and transfer-line engineers designing sampling tap points and vaporizers.
• Laboratories and analysts conducting offline or online gas chromatography and compositional analysis.
• Quality assurance / metrology teams ensuring representative sampling and traceability.
• Safety and operations personnel implementing safe handling and sampling procedures during LNG transfer.

Typical applications include custody transfer verification, product quality control, regulatory compliance, and calibration/validation of online analytical systems.

Related standards

• ISO 10715 (sampling concepts: direct and indirect sampling references)
• Earlier ISO documents referenced for definitions (e.g., ISO 1998 series)
• National and industry LNG guidance used alongside ISO 8943 for implementation details

Keywords: ISO 8943, LNG sampling, liquefied natural gas, continuous sampling, intermittent sampling, CP/FP sample cylinder, LNG vaporizer, online gas chromatograph, transfer line.