ISO 18081:2024

Overview

ISO 18081:2024 - "Non-destructive testing - Acoustic emission testing (AT) - Leak detection by means of acoustic emission" defines the general principles and practical guidance for detecting leaks using acoustic emission (AE) testing. Published July 2024, this second edition updates the 2016 version and provides methods for applying AE leak detection to structures and components where leak flows (driven by pressure differences) generate measurable acoustic signals. The standard addresses AE generation phenomena, influences of fluid type and leak geometry, wave propagation, instrumentation, data presentation, and test documentation. Annex A gives example procedures for specific leak-testing applications.

Key technical topics and requirements

• Principle of AE leak detection: how leak flows produce continuous or burst AE and appear as increased background noise correlated with pressure.
• Influence factors: effects of fluid properties, multiphase flow, pressure differentials, and leak-path geometry on AE generation and detectability.
• Wave propagation and environment: considerations for signal attenuation, coupling, and environmental noise that affect sensor placement and interpretation.
• Instrumentation and sensors:
  • Requirements for AE instruments (portable and fixed), single- and multi-channel setups.
  • Sensor mounting, temperature/immersion considerations, intrinsic safety, and integral electronics.
  • Feature determination methods (RMS, ASL, hits, continuous vs. burst AE).
• Verification and calibration: use of artificial leak noise sources and system verification procedures.
• Test and location procedures:
  • Mounting and data acquisition best practices.
  • Single-sensor attenuation-based location and multi-sensor Δt/time-difference or cross-correlation techniques.
• Data presentation and interpretation: numerical level meters, frequency spectra, validation steps, rejection of false indications, and leakage-rate estimation.
• Quality and documentation: requirements for test procedures, instructions, reporting, and personnel qualification (recommended per ISO 9712).

Practical applications and who uses it

ISO 18081:2024 is intended for professionals performing leak detection with AE in-service or during testing. Typical users include:

• NDT engineers and technicians
• Inspection bodies and asset integrity teams
• Operators in oil & gas, petrochemical, power generation, aerospace, and pipeline industries
• Manufacturers of pressure equipment, valves, tanks, and piping

Practical benefits include early leak detection without intrusive methods, localization of leak paths, guidance for estimating leakage rates, and standardized reporting to support maintenance and safety decisions.

Related standards

• ISO 9712 - Qualification and certification of NDT personnel
• ISO 12716 - AE vocabulary
• ISO/TS 18173 - NDT terms and definitions
• EN 1330 series and EN 13477 series - AE terminology and equipment characterization
• EN 13554 - AE general principles
• ISO 20484 - Definitions of leak, leakage rate, leak tightness

This standard helps integrate AE leak detection into quality-managed inspection programs and aligns methods across industries for reliable, non-destructive leak assessment.