Failure Analysis of Studs on an Electric Turbine Outer Head Cover

Failure analysis on studs connecting the outer head cover to the stay ring of an electric-generating turbine – in use at a Canadian Power station.

The analysis was performed by evaluating the finite element model of another engineering firm. The finite element method is a numerical technique that is used to predict the behavior of complex structures. Finite element methods were originally developed and used by large corporations and research companies during the mid-1960s. Although finite element analysis programs became commercially available in the early 1970’s, they did not become a commonly used design tool until the personal computer became commonplace in the 1980’s.

In general, the accuracy of finite element results is dependent on how well the finite element model and its applied loading represent the actual part and loading conditions. Simplifications in geometry and how the mechanical interaction between connecting parts (such as bolted joints and weldments) represented in a finite element model can have a significant effect on the results.

Likewise, how the boundaries of a FEA model are constrained (translation and/or rotation) can greatly affect the analysis results. Additionally, the accuracy of finite element results is dependent on applied loads which may be complex and not easily defined.

It was determined that due to the number of errors and assumptions in the original FEA model, the combined or “net” effect is not easily quantified without correcting all of these errors.

O’Donnell Consulting Engineers Performs Failure Analysis on Equipment including Shafts, Bearings, Vessels, Heat Exchangers, Cyclones, and Welded Structures.