Failure of an impeller blade of a first stage air compressor
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B. Fischer
Boromir Fischer completed a training as State Certified Technical Assistant for Metallography and Physical Material Analysis at Lette-Verein in Berlin. He has worked in the metallographic laboratory of the Siemens Gas Turbine Plant (Siemens-Gasturbinenwerk) Berlin for more than a decade. The key areas of his work are failure analysis and microstructural examinations using the field emission scanning electron microscope.Madeleine Giller Apprenticeship as a materials testing technician at the welding institute SLV Berlin-Brandenburg. After that, she studied materials science at the Berlin Institute of Technology. She graduated with a masters degree in materials science in 2012. Since November 2012 employment as engineer at the Metallography Laboratory of the Siemens Gas Turbine Works in Berlin. She has been appointed laboratory manager within the Berlin Testing Center of the Large Gas Turbine Engineering Group in 2014. Her main fields of expertise comprise failure analysis and microstructural investigations using the field emission scanning electron microscope.
Abstract
Recurring failures affected the impeller of a steam turbine-driven integrally geared centrifugal air compressor in an oil refinery. In both incidents, part of the main blade of the stage #1 impeller liberated. The first incident occurred three years ago, when the subject compressor tripped. The second event happened a year later and is the subject of this contribution, when again the subject compressor tripped from stage #1 impeller damage. The impeller failure was caused by the liberation of one main blade due to high cycle fatigue failure. The high cycle fatigue crack might have been initiated by bending loads from tip rubbing. Corrosion pits were found on the subject cracked blade and elsewhere on the impeller, despite its short time in service. Even though there is no direct evidence for crack initiation at corrosion pits, it is a distinct possibility that corrosion fatigue was the acting failure mechanism, i. e., that the main fatigue crack was induced at a corrosion pit acting as stress raiser. It follows that the cracking may or may not have been purely stress-driven. The electrically driven sister compressor did not fail. It is therefore perceived as possible that vibrations, induced by the steam turbine, are the underlying root cause of the failure or that the corrosive environment at the steam turbine-driven air compressor was somehow more aggressive.
Kurzfassung
In einer Ölraffinerie kam es wiederholt zu Ausfällen des Laufrades eines dampfturbinengetriebenen Radialverdichters mit integriertem Getriebe. Bei beiden Vorfällen löste sich ein Teil der Hauptschaufel des Laufrades der Stufe 1. Der erste Vorfall ereignete sich vor drei Jahren, als der betreffende Kompressor ausfiel. Der zweite Vorfall, der Gegenstand dieses Beitrags ist, ereignete sich ein Jahr später, als der betroffene Verdichter aufgrund eines Schadens am Laufrad der Stufe 1 erneut ausfiel. Das Laufradversagen wurde durch den Bruch einer Hauptschaufel infolge eines hochzyklischen Ermüdungsbruchs (HCF – high cycle fatigue) verursacht. Der HCF-Riss wurde möglicherweise durch Biegebelastung infolge von Anstreifen ausgelöst. An der gerissenen Schaufel und an anderen Stellen des Laufrads wurden trotz der kurzen Lebensdauer des Laufrads Korrosionsgrübchen gefunden. Obwohl es keinen direkten Beweis für die Rissentstehung an Korrosionsgrübchen gibt, ist es durchaus möglich, dass Korrosionsermüdung der wirkende Versagensmechanismus war, d. h. dass der Hauptermüdungsriss an einem Korrosionsgrübchen entstand, die eine spannungserhöhende Wirkung hatte. Daraus folgt, dass der Riss rein spannungsinduziert sein kann oder auch nicht. Der elektrisch angetriebene Schwesterkompressor fiel nicht aus. Es wird daher für möglich gehalten, dass die von der Dampfturbine induzierten Schwingungen die eigentliche Versagensursache waren oder dass die korrosive Umgebung am dampfturbinengetriebenen Luftverdichter in irgendeiner Weise aggressiver war.
About the authors
Boromir Fischer completed a training as State Certified Technical Assistant for Metallography and Physical Material Analysis at Lette-Verein in Berlin. He has worked in the metallographic laboratory of the Siemens Gas Turbine Plant (Siemens-Gasturbinenwerk) Berlin for more than a decade. The key areas of his work are failure analysis and microstructural examinations using the field emission scanning electron microscope.
Madeleine Giller Apprenticeship as a materials testing technician at the welding institute SLV Berlin-Brandenburg. After that, she studied materials science at the Berlin Institute of Technology. She graduated with a masters degree in materials science in 2012. Since November 2012 employment as engineer at the Metallography Laboratory of the Siemens Gas Turbine Works in Berlin. She has been appointed laboratory manager within the Berlin Testing Center of the Large Gas Turbine Engineering Group in 2014. Her main fields of expertise comprise failure analysis and microstructural investigations using the field emission scanning electron microscope.
References / Literatur
[1] Neidel, A.; Giller, M.; Fischer, B.: Metallurgical Failure Investigation of Fractured Impeller Blade of First Stage Air Compressor. Internal report BLN MT/2022/0235. Berlin, August 11, 2022.Suche in Google Scholar
[2] Langenhan, B.: Personal communication, August 4, 2022.Suche in Google Scholar
[3] https://www.stahlportal.com/fileadmin/user_upload/content/1.4542_1.4548_Werkstoff_Datenblatt_01.pdf accessed August 8, 2022.Suche in Google Scholar
[4] https://www.stahlportal.com/lagervorrat/14542-x5crnicunb16-4/?gclid=EAIaIQobChMI-bbn-7Mm3-QIVzJBoCR3yswMLEAAYBCAAEgKFqfD_BwE accessed August 8, 2022.Suche in Google Scholar
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[6] Langenfeld, B.: Personal communication, August 4, 2022.Suche in Google Scholar
[7] Burkardt, N.: Personal communication, August 4, 2022.Suche in Google Scholar
[8] Burkardt, N.: 32882 Woodside Impeller Evaluation. Dresser-Rand Report Number D16-9047, Issued 4/28/2017.Suche in Google Scholar
[9] Burkardt, N.: Personal communication, August 10, 2022.Suche in Google Scholar
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Artikel in diesem Heft
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- How can stainless CrNi steel be etched to clearly characterize the individual phases?
- Study on the microstructure and tensile properties of GH5188 high-temperature alloy laser welded joints
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Artikel in diesem Heft
- Inhalt
- Editorial
- Editorial
- How can stainless CrNi steel be etched to clearly characterize the individual phases?
- Study on the microstructure and tensile properties of GH5188 high-temperature alloy laser welded joints
- Characterization of an electric resistance welded steel plate
- Failure Analysis
- Failure of an impeller blade of a first stage air compressor
- Picture of the Month
- Picture of the Month
- News
- News
- Meeting Diary
- Meeting Diary
