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Penstock Failure at PG&E's Helms Creek Pumped Storage Hydroelectric Plant

A 30-foot diameter penstock failed catastrophically during "water-up" of the Helms Creek pumped storage hydroelectric plant in California. APTECH was hired by the supplier of the penstock to find the cause of the failure. The issues that APTECH investigated related to weld quality and workmanship, structural significance of welding defects, and the reliability of inspection techniques to locate critical flaws. Issues of material properties and fracture toughness, in particular, were evaluated. A structure integrity reconstruction of the accident was performed. This reconstruction of the existing conditions at the time of the accident led to the conclusion that significant additional stresses were imposed on the system by the foundation settlement. APTECH provided expert testimony to this effect in the subsequent trial. The jury verdict was in our client's favor.

Satish Almaula		Plant failure and root cause analysis; process and design engineering analysis; process technology development and testing; plant engineering, operations, maintenance and safety management; plant and process control system management.

Geoffrey Egan, Ph.D.		Engineering mechanics, welding engineering, stress and fatigue analysis, risk analysis, nondestructive examination, project management.

Steve Paterson		Metallurgy, welding, boiler pressure part and machinery failure analysis.

Eric Sullivan, P.E.		Metallurgy, welding, failure analysis, fire and explosion investigations, equipment, piping.

Jeffrey Grover, P.E.		Mechanical engineering, failure analysis, civil engineering.

Philip Lindsay, P.E.		Corrosion failure analysis, metallurgy, piping systems, corrosion mitigation, materials selection.