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Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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Vibration <strong>and</strong> Noise in <strong>Pumps</strong> 427<br />

produce torsional or lateral vibrations. The forces in a typical industrial<br />

coupling are similar to those in a universal joint (Figure 18-2). When a<br />

small angular misalignment occurs, the velocity ratio across the joint is<br />

not constant. If one shaft spe<strong>ed</strong> is assum<strong>ed</strong> constant, then the other shaft<br />

has a faster rotational rate [6] for part of the revolution <strong>and</strong> a slower rotational<br />

rate for part of the revolution. This variation of rotating spe<strong>ed</strong> results<br />

in a second harmonic (twice shaft spe<strong>ed</strong>) vibrational component.<br />

Figure 18-2. Effects of angular misalignment in shaft couplings.

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