Critical Speeds And The Importance Of Stiffness - A Case Study In The Design And Testing Of A Large Mechanical Drive Steam Turbine To API Standard 612.
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Rotordynamics has long been one of the major considerations in the design of variable speed rotating equipment. Bearing support stiffness is a significant factor in the designer's ability to predict critical speeds and response to unbalance. This case study is used to describe the influence of support stiffness on the rotordynamics performance of a large variable speed mechanical drive steam turbine. This joint effort by the user and machinery vendor identifies several practical issues in meeting the intent of API Standard 612, Third Edition. Modem analytical techniques can be used to predict bearing support stiffness in both the horizontal and vertical directions. When the stiffness in the two directions are dissimilar, multiple critical speeds may occur, which complicate the interpretation of API 612 test results. Effects of critical speeds on response to unbalance are discussed. Also presented are some analytical and experimentally determined dynamic characteristics obtained during the design and test.
Bethel, Lawrence L.; Gans, Bruce E.; Brown, Royce N.; Lewis, Richard A. (1993). Critical Speeds And The Importance Of Stiffness - A Case Study In The Design And Testing Of A Large Mechanical Drive Steam Turbine To API Standard 612.. Texas A&M University. Turbomachinery Laboratories. Available electronically from