HSE has identified inconsistencies in the application and supervision of welding of safety-critical metallic components. Such shortcomings have led to failures with high consequences such as fatalities. A study was carried out to identify common causes of these and to highlight priority areas for improvement of weld quality in industry.
Cases were assessed from within HSE’s historical investigations and from those provided by external organizations. Forty-seven(47) individual incidents in which the weld quality was a contributory factor were identified. These were reviewed against a range of causal types. Root cause and frequency (Pareto) analyses were then conducted to determine the primary contributory factors. Case studies were developed to illustrate key findings, and a visual set of examples of welding defects was compiled.
The most common failure modes identified were fatigue and ductile or brittle failure due to overload of the welds. In 49% of cases, the result was a complete collapse of the structure, 21% of the incidents led to injuries, and 11% led to one or more fatalities. Crack-like or volumetric flaws in weldments and poor or undersized weld geometry were the commonest weld quality deficiencies.
The most prevalent causes were inadequate welder supervision, insufficient percentage coverage of inspection, and joints not designed for ease of fabrication. Priority areas to improve welding outcomes have been identified. HSE will use the findings to support their regulatory activity.