Speaker
Description
In this contribution, the most interesting and educating failure cases are presented that the
author came across during thirty years of laboratory practice as Senior Key Expert on Failure
Analysis at the Berlin Gas Turbine Plant of Siemens Energy. These case studies, that are
also used in the author’s annual lecture at TU Berlin, are presented and categorized in
accordance with VDI Guideline 3822, the German-speaking failure analyst’s guide to how to
organize and run a root cause failure analysis. An effort was made to have each of the main
four categories of failure causes represented, namely failures due to mechanical loading, wet
corrosion failures, failures due to thermal loading, and tribological failures. As a nice
additional touch, a fifth failure category will be introduced, which is meant as a surprise for
the audience. Case studies include turbomachinery components that failed due to tensile
overload, stress corrosion cracking, intergranular corrosion, hydrogen embrittlement, hot
cracking, fretting, erosion, and galling. Affected components include valves, retaining rings,
tubing and piping, burners, rotor disks, lifting lugs, and casings. Most of the presented case
studies were published in the section “Failure Analysis” of Practical Metallography between
October 2011 and the present time. Others were oral presentations at the Metallography
conferences held during that time. The focus of discussion of the failure cases in this paper is
the metallurgical evaluation of failure causes. This is the approach taken in many small
industrial laboratories. A holistic approach to failure analysis, which includes calculation and
simulation methods such as finite element analysis, and which also implies a knowledge of
the service stresses intended by design as well as the actual loading situation of the failed
part, is not the aim of this contribution.