Asbestos-fabric-insulated wire leads and asbestos-tape lead wrap used inside Square D QO circuit breakers, panelboards, and load-center assemblies during Square D plant fabrication

Product Description

Square D Company’s QO circuit breaker was one of the most widely produced electrical distribution products of the mid-twentieth century, manufactured in a national plant network anchored by Cedar Rapids, Iowa; Columbia, Missouri; and Lincoln, Nebraska. Publicly filed asbestos litigation records document that the QO breaker relied on multiple asbestos-containing components — the asbestos-filled phenolic arc chute, the asbestos-filled phenolic molding compound casing (sourced from General Electric and other suppliers), and — the subject of this article — the internal wire-lead insulation.

Plaintiffs alleged that Square D used asbestos-cloth-insulated stranded copper wire and asbestos-tape wrap on the internal jumpers, magnetic-trip coil leads, and load-side output conductors of QO breakers and QO panelboard bus assemblies. Asbestos fabric was selected because it withstood the heat generated during high-current interruption events immediately adjacent to the arc chute, where thermoplastic wire insulation would have softened, charred, and failed.

The material worked in parallel with the asbestos-filled phenolic arc chutes that extinguished the arc, and with the asbestos-filled phenolic molding compound that formed the breaker case. All three asbestos-containing subsystems were assembled together on the same breaker at the same plant.

Workers Exposed

The primary exposure population documented in litigation records is Square D plant workers on the QO assembly lines at Cedar Rapids, Columbia, and Lincoln. Assemblers cut lengths of asbestos-cloth-insulated wire, stripped the fabric back from the copper conductor for termination, and wrapped asbestos tape around lead junctions. Cutting and stripping asbestos-cloth wire insulation is a mechanically abrasive operation that releases respirable fiber from the cut end.

Downstream, industrial electricians, motor-shop electricians, and maintenance electricians who serviced Square D QO panels in the field encountered the wire-lead insulation whenever a breaker was opened for internal repair, replacement of a burned lead, or bus-work maintenance. Field electricians alleged in litigation that they cut and stripped the asbestos-cloth wire during breaker replacement work at industrial plants across the country.

Plaintiffs alleged that this work was performed at Square D plants and at end-user facilities without respiratory protection and without warning labels identifying the wire insulation as asbestos-containing.