L03: High Speed Balancing: API Acceptance Criteria, Pedestal Dynamics, and Unbalance Response Correlation
Abstract
Acceptance criteria for high-speed balancing of turbomachinery are specified in API standards based on either pedestal velocity or shaft displacement, and these are discussed in detail Pedestal velocities are measured using velocimeters located at each pedestal whereas shaft displacements are measured using eddy-current probes adjacent to each bearingIn 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 are conducted on 3 different pedestals: DH4, DH7, and DH70 The FRFs are parameterized to be used in a rotordynamic model Different torques on the pedestal bolts are used to study the effect on the measured FRFs The added-mass method is applied to DH7 pedestals with a 100 kg plug in the pedestal bore The calculated modal mass and stiffness are 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 Minor improvements are observed using the measured data comparing to the original models and further areas of improvement are identified The effect of vacuum on the unbalance response is also studied
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Citation
Hantz, Brian; Pettinato, Brian; Wang, Qingyu (2021). L03: High Speed Balancing: API Acceptance Criteria, Pedestal Dynamics, and Unbalance Response Correlation. Turbomachinery Laboratory, Texas A&M Engineering Experiment Station. Available electronically from https : / /hdl .handle .net /1969 .1 /197454.