Case Study: Investigation of Chair Failure - Heiberg Engineering & Forensic Services

Manufacturing Defect: Plaintiff Side

Multi-Disciplinary Investigation of a Chair Failure

A plaintiff was leaning back on his office chair when he heard a loud snapping noise and fell backwards off the chair. Through x-rays we were able to determine a that a torsion rod intended to provide stability to the chair back had broken.

With the opposing side’s cooperation, we performed a destructive inspection together with a metallurgical examination that revealed a manufacturing defect in the torsion rod that caused it to fail.

The plaintiff, who was a fireman, was unable to work due to his injuries. Plaintiff received a seven figure settlement.

Forensic Investigation of Chair Failure

The subject chair after the incident (note that it does not return to the upright position).

Forensic Investigation

The underside of an exemplar chair that was disassembled to learn the construction of the subject chair.

An X-Ray showing a break in the torsion bar, within the seat base assembly.

The fracture surface of the torsion rod, during agreed upon destructive inspection.

These micro-cracks are a manufacturing defect and the cause of the torsion bar/chair failure.

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