Multiple Drive Shaft Fractures in Lift Oil Pumps
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A. Neidel
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.
Tobias Gädicke
was born in 1986 and joined the Siemens Energy Sector in 2005 as apprentice in the Berlin Gas Turbine Works. As materials testing technician, his main field of expertise is metallographic target preparation of laserdrilled holes in turbine blading. Also, he is expert in the field of portable metallography by means of the replica technique with both putty and replica foils which he regularly applies to microstructural analyses of large gas turbine casings made of ductile iron and steel castings. He is a lecturer in the DGM seminar on portable metallography. Metallurgical failure analysis of gas turbine engine hot gas path components are another field of of his.
Abstract
Several high-pressure lift oil pump failures were reported from the field. These assemblies are used to inject lubrication oil into the sliding bearings of heavy rotating turbomachinery equipment, such as steam and gas turbine rotors, often weighing in excess of a hundred tons. This ensures that the rotor shaft “floats” on a lube oil film even at low rotational speeds, when hydro-dynamic lubrication conditions have not yet been fully established. A fractured spline shaft, which was the driven shaft of one of the failed pumps, was received from the client for the determination of the metallurgical root cause of failure. The subject spline shaft failed due to torsional overload. This cracked the hardened case and initiated high cycle fatigue (HCF) cracking as secondary damage. The main fatigue cracks were nucleated at overload fractures in the hardened case, in the fillet radii at the base of the teeth of the spline shaft. No evidence of any material defects that could have contributed to the failure or could even have been causative for it was found.
Kurzfassung
Uns wurde vom Ausfall mehrerer Hochdruck-Anhebeölpumpen an ihrem Einsatzort berichtet. Diese Baugruppen dienen dazu, Schmieröl in die Gleitlager schwerer rotierender Turbomaschinen, beispielsweise Dampf- und Gasturbinenrotoren, einzuspritzen. Deren Gewicht liegt häufig bei über hundert Tonnen. So wird sichergestellt, dass die Rotorwelle auch bei geringen Drehzahlen auf dem Schmierölfilm „schwimmt“, wenn die Voraussetzungen für eine hydrodynamische Schmierung noch nicht vollständig gegeben sind. Zwecks Ermittlung der metallurgischen Grundursache des Versagens stellte der Kunde eine gebrochene Keilwelle zur Verfügung. Es handelte sich in diesem Fall um die Abtriebswelle einer der ausgefallenen Pumpen. Die Keilwelle versagte durch Torsionsüberlast, durch die es zur Rissbildung in der gehärteten Randschicht (Einsatzschicht) und als Sekundärschaden zur Rissbildung durch hochzyklische Ermüdung (High Cycle Fatigue, HCF) kam. Die Hauptermüdungsrisse in der Einsatzschicht bildeten sich an Gewaltbrüchen in den Übergangsradien am Fuß der Keilwellenzähne. Es konnten keine Hinweise auf Materialfehler gefunden werden, die zum Schaden hätten beitragen oder den Schaden verursacht haben könnten.
About the authors
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.
Tobias Gädicke 
was born in 1986 and joined the Siemens Energy Sector in 2005 as apprentice in the Berlin Gas Turbine Works. As materials testing technician, his main field of expertise is metallographic target preparation of laserdrilled holes in turbine blading. Also, he is expert in the field of portable metallography by means of the replica technique with both putty and replica foils which he regularly applies to microstructural analyses of large gas turbine casings made of ductile iron and steel castings. He is a lecturer in the DGM seminar on portable metallography. Metallurgical failure analysis of gas turbine engine hot gas path components are another field of of his.
References / Literatur
[1] Neidel, A.; Giller, M.; Fischer, B.; Gädicke, T.: Internal Report BLN MT/2017/0026_rev, Berlin,February 10, 2017Search in Google Scholar
[2] Dahmann, P.: Stellungnahme zu Problemen mit Pumpe High-pressure gear pump ZG 5 R. Aachen, January 25, 2017Search in Google Scholar
[3] Cherolis, N. E.; Benac, D. J.; Pridemore, W. D.: Fatigue in Rotating Equipment – Is it HCF or LCF? J Fail. Anal. and Preven. 16 (2016), pp. 828-84110.1007/s11668-016-0162-6Search in Google Scholar
[4] Pohl, M.: Personal communication, January 25, 2017Search in Google Scholar
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Articles in the same Issue
- Contents
- Editorial
- Editorial
- Challenges in the determination of the macroscopic degree of cleanliness determined by ultrasonic immersion testing of (ultra-clean) gear steels
- Determination of prior austenite grain-and martensitic substructure size from metallographic etchings using a multi-step image processing algorithm
- Failure Analysis
- Multiple Drive Shaft Fractures in Lift Oil Pumps
- Picture of the Month
- Picture of the month
- News
- News
- Meeting diary
- Meeting diary
Articles in the same Issue
- Contents
- Editorial
- Editorial
- Challenges in the determination of the macroscopic degree of cleanliness determined by ultrasonic immersion testing of (ultra-clean) gear steels
- Determination of prior austenite grain-and martensitic substructure size from metallographic etchings using a multi-step image processing algorithm
- Failure Analysis
- Multiple Drive Shaft Fractures in Lift Oil Pumps
- Picture of the Month
- Picture of the month
- News
- News
- Meeting diary
- Meeting diary
