Best of Schadensanalyse an Turbomaschinen Reloaded – die Highlights aus 30 Jahren Laborpraxis

Abstract

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.