Abstract
Simplified design procedures for boiler feed pump shafts, based on a ‘stiffness criterion’ related to the first critical speed in air, have generally led to trouble-free shaft designs. An indication that this approach had shortcomings was the serious vibration experienced with a recent booster feed pump. The efforts to cure the vibration are fully described. A review is made of the various factors, both mechanical and hydraulic, that can influence the vibration of pump shafts and some of these are shown to have little effect on critical speed. Others, in particular the hydrostatic centering force associated with wearing rings, seem to be of undoubted importance and must be considered when designing large high-speed boiler feed pumps.
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