Advancing hydrogen leak detection: Design and calibration of reference leaks

The introduction of hydrogen into the gas grid requires stricter safety measures due to its enhanced flammability compared to natural gas. Detecting small hydrogen leaks is crucial for meeting health and safety requirements, given hydrogen's potential for easy ignition and the hazards associated with its combustion. This paper presents an overview of the quantification of small hydrogen leaks, regarding conversions between common units of measurement, namely concentration and leak rate. In addition, the need for traceable assessments of hydrogen leakage was also considered, which included proposal of the design, calibration, and metrological evaluation of portable hydrogen reference leaks in the range of 10−6 to 10−4 Std cm3/s, the latter being considered as the lowest side of the range of interest for quantifying hydrogen leaks. Two methods of manufacturing leak artefacts, namely conductance and permeation, are explored, and the produced leaks were used to test two hydrogen leak detectors with different working principles. A calibration technique based on a constant pressure gas flowmeter is described together with the uncertainty budget. The study provides insights into the challenges of calibrating detectors for hydrogen leaks, highlighting the importance of traceability in ensuring safety and environmental protection in the context of hydrogen infrastructure. It was demonstrated that reference leaks are highly suitable to test hydrogen leak detectors in the mentioned flow range due to their simplicity, high reliability, low depletion rate and high portability.