Case study 3: Inadequate welding - weld seam defects in metal construction

Inadequate welding - defects, causes and assessment according to DIN EN 1090

Mission and initial situation

As part of a private appraisal, I was commissioned to assess the quality of several welded joints on a steel balcony. The client had noticed cracks and deformations at the joints of the railing. The structure was only two years old and there were no inspection reports from the metal construction company.

Damage pattern detected

  • Visible cracks at fillet weld connections in the railing area
  • Uneven seam thicknesses and pore formation
  • Insufficient penetration welding on load-bearing connections
  • Splashes and tarnishing due to lack of post-treatment
  • Incomplete seam formation at corner joints

Some joints were already showing flaking in the coating area and signs of corrosion.

This case study shows typical damage to weld seams caused by faulty workmanship or poor quality assurance.

Root cause analysis

After visual inspection and documentation of the weld seams according to DIN EN ISO 5817 („Assessment groups for irregularities in fusion-welded joints“), several execution errors were detected:

  1. Inadequate preparation of the welding edges - No cleaning of scale and grease, insufficient joint gap.
  2. Incorrect welding parameters - too low current, low energy input → lack of fusion.
  3. Unqualified welding personnel - no proven welding qualification according to DIN EN ISO 9606-1.
  4. Missing workshop approval to DIN EN 1090-2 - Execution without supervision by a welding supervisor (IWE/IWT/IWS).

Normative evaluation

According to DIN EN 1090-2, Chapter 7.6 - Welding work, load-bearing components may only be manufactured by qualified personnel using tested procedures.
The valuation was based on Evaluation group B (DIN EN ISO 5817) for load-bearing constructions.

The majority of seam defects exceeded the permissible limits for pores, notches and seam irregularities.

In addition, a welding procedure qualification (WPQR) to DIN EN ISO 15614-1. This means that the entire design does not comply with the rules.

Consequences of the shortage

  • Reduced load-bearing capacity of the connections
  • Risk of cracking and breakage under continuous load
  • Start of corrosion due to open seams
  • Risk of injury from railings and stairs
  • No CE conformity according to DIN EN 1090

The expert opinion came to the conclusion that the welded joints did not meet the safety requirements and that renovation was necessary.

Recommended measures

  1. Complete dismantling the defective welded joints.
  2. New design according to DIN EN 1090-2, under the supervision of a certified welding supervisor (IWE/IWT).
  3. Welding procedure qualification (WPQR) before the start of production.
  4. Non-destructive testing (Seam testing according to DIN EN ISO 17638 / ultrasonic testing according to 17640).
  5. Surface treatment after welding - pickling, grinding and coating according to ISO 12944.
  6. Documentation in the quality assurance plan (QSP) and acceptance protocol.

Summary

Inadequate weld seams are one of the most common defects in metal construction. Incorrect seam formation, inadequate welding and a lack of qualification lead to structural risks and do not comply with standard requirements DIN EN 1090, ISO 5817 and ISO 9606.

Professional welding under the supervision of a welding engineer is essential to avoid safety and liability risks.

Note from the expert

As a publicly appointed and sworn expert and welding engineer (IWE), I prepare expert reports on welded joints and their evaluation in accordance with DIN and EN standards. My analyses are independent and court-proof.

Further information

Overview of the case studies:

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