API High Speed Balancing Acceptance Criteria and Pedestal Dynamics
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Acceptance criteria for high-speed balancing of turbomachinery are specified in API standards based on either pedestal velocity or shaft displacement. In addition to performing balancing, the measured displacements can also be used for verification of the unbalance response analysis. Since the pedestals are relatively soft, their dynamics need to be considered in the analysis. In this paper, multiple modal tests were conducted on 3 different pedestals. Different torques on the pedestal bolts were used to study the effect on the measured FRFs. The added-mass method was applied to DH7 pedestals. The calculated modal mass and stiffness were compared to values identified from the measured FRFs. Unbalance verification of some shop orders is compared to the predictions with different ways of characterizing the pedestal dynamics: rigid, mass and stiffness, and the FRFs.
Pettinato, Brian; Hantz, Brian; Wang, Qingyu (2018). API High Speed Balancing Acceptance Criteria and Pedestal Dynamics. Turbomachinery Laboratory, Texas A&M Engineering Experiment Station. Available electronically from