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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> 465<br />

Figure 18-26. interference diagram of torsiona! resonances of six-stage pump<br />

train,<br />

tions. Identification of all possible sources of dynamic energy is an important<br />

step in diagnosing an existing vibration problem or avoiding<br />

problems at the design stage.<br />

The most likely sources of dynamic torques include the following:<br />

« <strong>Pumps</strong>, turbines, <strong>and</strong> compressors<br />

• Motors (synchronous <strong>and</strong> induction)<br />

• Couplings<br />

• Gears<br />

» Fluid interaction (pulsations)<br />

• Load variations<br />

The transient torques of a synchronous motor were measur<strong>ed</strong> during<br />

startup (Figure 18-27) by attaching a strain gauge to the motor shaft <strong>and</strong><br />

obtaining the signal with an FM telemetry system. A synchronous motor<br />

produces a pulsating torque [39] that varies from twice line frequency as

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