Arc Furnace Failure Illustrated / by Jeff Drake

An electric arc furnace containment failed when a load of molten steel breached the insulating brick and melted through the exterior steel shell.

The Scope of the Litigation Graphics Presentation

The first step in explaining a catastrophic failure like this one is to orient and educate the viewer about the equipment involved and provide enough detail, so the failure is understood within this context. A series of 3D illustrations were prepared to show the materials and construction of the arc furnace shell which was designed to contain 230 tons of molten steel. The illustrations were also used to walk the viewer through the theory advanced by the experts retained by my client in terms of what precipitated the furnace failure and relate the photographic evidence to the failure scenario. The last task of the graphic presentation was to demonstrate the weaknesses and errors in the opposing expert’s theory of failure. 

Exhibit Development

A 3D computer model was created of the furnace shell, surrounding water-cooled panels, and brick refractory lining from the geometry and dimensions provided in the manufacturer’s engineering drawings. Camera views of the 3D model were created inside the CAD program and exported as individual illustrations.

My Client’s Expert Theory of the Failure Illustrated

The failure of the furnace was related to an area of the brick lining that was compromised due to a leak in a water-filled, steel cooling panel above the refractory lining. The leaking water penetrated through the refractory bricks causing the brick to hydrate. Hydration caused the brick to lose its structure and insulating qualities. The failure was initiated when the molten steel found its way through the compromised brick to the steel shell, melting through it immediately.

Putting the Evidence in Context

Photographs taken after the breach recorded the damage to the steel shell of the furnace. The geometry and position of the breached opening showed the maximum height the molten steel reached when it broke out through the shell. The breach was included in the 3D model to demonstrate the relationship of the breach to the body of the arc furnace shell.

Proving the Case

The volume of molten steel the furnace contained at the time of the breakout was disputed. The opposing expert theorized the shell was overfilled allowing the molten steel to flow over the refractory and contact the steel shell. Since the 3D model was created to scale it was possible to calculate and determine how full the shell could be before the molten steel would run out the “slag door” at the right of the furnace. Using this hypothetical overfilled volume, the cross-section was calculated and applied to each position the furnace could be oriented in during operation. Even with the furnace tipping the maximum full six degrees toward the tap hole, our analysis established that the overfilled cross-section would not run over the refractory brick and contact the steel shell. 

Conclusions

The reliable reconstruction of the arc furnace from the engineering plans, along with the post-loss photographs and remaining physical evidence, provided a fair and accurate representation of the furnace which served as the basis for a solid visual presentation strategy of this complex matter. The accuracy of the 3D model also empowered my client’s expert witnesses to authoritatively refute the opposing expert opinions. 

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