Engineering Analysis of Welding Failures: Lessons from HSE Report RR1215

Introduction

The integrity of welded structures is paramount in industries where safety and operational reliability are critical. Welding failures can lead to catastrophic structural collapses, serious injuries, and even fatalities. The recent HSE Research Report RR1215 (2024) provides a comprehensive investigation into 47 cases of welding-related failures, identifying key causes and the systemic weaknesses contributing to these incidents. This analysis reviews the report's findings, drawing out significant lessons that engineers and industry professionals must consider to enhance welding practices, quality control, and regulatory compliance.

Overview of Welding Failures

The HSE report examines 47 cases from various high-risk industries, including offshore and onshore oil and gas, chemical processing, power generation, lifting equipment, and mobile structures.

Consequences of Welding Failures

Nearly half of all incidents resulted in total structural collapse. Over 20% led to injuries, with 11% causing fatalities. Other failures resulted in containment breaches, production downtime, and hazardous safety events. Failures predominantly resulted from fatigue cracking and overload fractures, exacerbated by defects such as crack-like flaws in welds and poor weld geometry.

Root Cause Analysis

A systematic root cause analysis and Pareto assessment were conducted to isolate the principal contributors to these failures. The study categorises failures under seven key areas:

Deficiencies in Weld Quality

74% of cases were attributed to this category.

Key issues included:

- Crack-like or volumetric flaws (49%), including hydrogen cracking, lack of fusion, and porosity.

- Undersized welds (45%), which compromised load-bearing capacity.

Design Errors

45% of failures of cases were attributed to this category.

Key issues included:

- Inadequate joint configuration leading to stress concentration.

- Poorly designed fit-ups that reduced the effectiveness of the weld.

Training and Knowledge Gaps

38% of incidents were attributed to this category.

Key issues included:

- Lack of understanding of welding parameters and fatigue cycles.

- Inadequate appreciation of weld criticality in structural performance.

Inspection and Quality Control Failures

32% of failures of cases were attributed to this category.

Key issues included:

- Insufficient weld coverage during inspections.

- Poor selection of non-destructive testing (NDT) methods.

Inadequate Supervision and Oversight

28% of cases were attributed to this category.

Key issues included:

- Insufficient oversight by qualified welding engineers.

- Poorly defined acceptance criteria for weld quality.

Incorrect Welding Procedures

26% of failures of cases were attributed to this category.

Key issues included:

- Incorrect application of heat input and preheating.

- Excessive repair welding causing material degradation.

Material Selection and Handling Issues

15% of failures of cases were attributed to this category.

Key issues included:

- Use of unsuitable base metals or filler materials.

- Contamination due to improper storage and handling.

Case Studies of Notable Failures

- LPG Vessel Joggle Weld Failures: Multiple LPG vessels failed hydrotesting due to brittle fracture from lack of weld penetration. Weak procedural controls and inadequate inspections were key factors.

- Alkyd Reactor Pipe Fracture: A stainless-steel pipe failed due to fatigue at an improperly designed weld toe. Poor understanding of cyclic loading and weld geometry contributed to the failure.

- Offshore Caisson Failure: A major offshore caisson section detached due to missing corrosion-resistant alloy (CRA) cladding, leading to galvanic corrosion. The fabrication team failed to recognise its criticality, and inspection protocols missed the omission.

- School Truss Collapse: A 57-meter steel truss collapsed before commissioning due to undersized welds at load-bearing joints. Self-certification of welds and lack of independent inspections contributed to the failure.

- FPSO Bridle Spool Failure: A methanol storage pipe spool failed due to stress corrosion cracking at a high-residual-stress weld root. The issue was exacerbated by excessive weld penetration and lack of post-weld heat treatment.

Key Engineering Lessons and Recommendations

Enhancing Quality Assurance

Strict adherence to established welding procedures, such as those outlined in BS EN ISO 3834 and ASME IX, is necessary to maintain weld integrity and performance.

Strengthening Inspection and Testing Protocols

Expanding non-destructive testing (NDT) coverage beyond regulatory minimums is crucial for identifying defects before failures occur.

Improving Supervision and Competency

Greater oversight from welding engineers and improved welder qualifications can significantly reduce fabrication errors.

Incorporating Design Considerations

Structural engineers should consider welding constraints when designing joints, ensuring accessibility and durability under operational stresses.

Better Material Selection and Handling

A more rigorous approach to selecting, storing, and handling materials can prevent hydrogen embrittlement, cracking, and corrosion-related failures.

Conclusion

The HSE RR1215 report underscores critical shortcomings in welding practices across various industries. Analysing historical failures provides valuable insights into weld quality, design, inspection, supervision, and training deficiencies. Implementing the recommendations outlined in this study will help engineering teams prevent future failures and maintain industry best practices.

For further reading, the full HSE Research Report RR1215 is available at: https://doi.org/10.69730/hse.24rr1215