Overview
EN ISO 20485:2018 (ISO 20485:2017) - Non‑destructive testing - Leak testing - Tracer gas method - specifies techniques for detecting leaks using a tracer gas and tracer‑gas‑specific detectors. Prepared by ISO/TC 135 and adopted by CEN, the standard describes principles, apparatus, object preparation, test procedures and reporting requirements for tracer‑gas leak testing.
Key topics and technical requirements
- Scope: Methods for detection of leaks by introducing or extracting a tracer gas and detecting its presence with chemical or physical detectors.
- Principles of detection: Creation of a partial‑pressure difference across the test boundary; tracer gas is revealed by chemical reactions (e.g., colour‑change reagents) or physical sensors that produce an electrical signal.
- Detectors and tracer gases:
- Mass spectrometers (commonly tuned for helium-4)
- Electron‑capture or alkali ion detectors (for SF6 or halogens)
- Pirani gauges (thermal‑conductivity based)
- Photometers (optical absorption/emission)
- Technique groups:
- Group A - tracer gas flows into the object (object evacuated or placed in pressurized chamber)
- Group B - tracer gas flows out of the object (object pressurized or placed in vacuum chamber)
- Standardized procedures: Includes vacuum techniques (total/partial/local), vacuum box, sniffing, accumulation, bombing (pressurize then vacuum for small internal volumes), vacuum chamber and carrier‑gas techniques, and ammonia/colour‑change tests.
- Test setup & reporting: Requirements for apparatus, object preparation, initial set‑up, selection/agreement of reference conditions, and mandatory information to include in the test report (test conditions must be stated and claimed).
Applications and users
EN ISO 20485:2018 is applied wherever nondestructive leak detection is required, including:
- Leak testing laboratories and NDT service providers
- Quality and reliability engineers in automotive, aerospace, medical device, HVAC, refrigeration, and pressure‑containing equipment manufacturing
- R&D and production testing for sealed components and assemblies
Common practical uses: helium leak detection, sniffing for localized leaks, vacuum‑box testing of welds and joints, accumulation testing for assemblies, and bombing for complex small‑volume components.
Related standards
- ISO 20484 - vocabulary for leak testing (referenced normative)
- EN 13185 (superseded by EN ISO 20485:2018)
Keywords: EN ISO 20485:2018, ISO 20485:2017, tracer gas method, non‑destructive testing, leak testing, helium leak detection, vacuum box, sniffing, accumulation technique.
