Welding quality hinges on stringent control of the process environment, where even trace amounts of moisture in shielding gases or on metal surfaces can severely compromise weld integrity. Moisture ingress results in hydrogen evolution during welding, leading to porosity, hydrogen induced cracking (HIC) and embrittlement defects that undermine joint strength and durability.
Industrial welding processes such as MIG, MAG, TIG, orbital, plasma and oxy-fuel welding rely on carefully selected and controlled gas mixtures to stabilise arcs and protect the weld pool. However, moisture contamination can originate from multiple sources, including residual water vapour in gas cylinders, permeation through hoses and seals, leaks during cylinder changes and condensation in pipelines.
To mitigate the risks caused by trace moisture in welding, it is critical to implement moisture measurement strategies using trace moisture analysers capable of detecting moisture at ppm (or ppb) levels. Integration points include:
- Gas cylinder/manifold outlets – inline trace moisture analysers verify bulk gas dryness before delivery
- Shielding gas supply lines – portable or inline sensors ensure there is no moisture ingress en route to the weld torch
- Purge gas flows – moisture sensors monitor inert gas purging in pipe or vessel welding, validating effective moisture removal
Sensor technologies such as aluminium oxide sensors deliver real time, continuous moisture monitoring with rapid response times and low maintenance, enabling early detection of moisture spikes.
Complimentary moisture monitoring measures include purging with dry inert gases (argon, nitrogen), installation of desiccant dryers or gas purifiers, optimised gas flow rates to avoid turbulence induced air ingress and rigorous maintenance schedules to prevent leaks and component degradation.
Adherence to industry standards such as ISO 14175 and certifications like NADCAP in aerospace provides a framework for acceptable moisture limits and validation protocols, essential for ensuring weld quality in safety critical applications. Incorporating trace moisture measurement and monitoring throughout the gas supply chain is indispensable for preventing hydrogen related defects, ensuring mechanical performance and achieving reproducible, defect free welds critical to high reliability industries.
