Rotor Dynamics & Balancing Flashcards

What is the Campbell diagram used for in rotating machinery?

Answer: Plotting rotor natural frequencies and excitation order lines against shaft speed to identify resonance intersections

A Campbell diagram plots rotor natural frequencies (horizontal lines) and engine order excitation lines (diagonal lines) versus speed, allowing engineers to identify where resonances may occur during operation.

What does 'balance in-situ' (field balancing) mean?

Answer: Correcting rotor unbalance while the rotor remains installed in its operational bearings and casing

Field balancing (in-situ balancing) corrects rotor unbalance without disassembling the machine, using vibration measurements and trial weights while the rotor runs in its own bearings under normal operating conditions.

What is a 'heavy spot' on a rotor?

Answer: The angular location of the net unbalance mass concentration on the rotor

The heavy spot is the angular position of the effective unbalance mass on the rotor; it is located by measuring vibration phase and applying the appropriate phase lag correction for the measurement system.

What characteristic vibration pattern is associated with shaft misalignment?

Answer: Elevated 2× running speed, often with high axial vibration at 1× and 2×

Angular misalignment typically produces elevated 1× and 2× radial vibration along with strong axial vibration at 1×, while parallel misalignment tends to produce a strong 2× radial component.

What is the 'high spot' in rotor vibration analysis?

Answer: The angular location on the rotor that passes closest to the proximity probe at maximum vibration amplitude

The high spot is the rotor position that comes nearest to the proximity probe when the shaft is at peak vibration displacement; it lags the heavy spot by an angle determined by the system damping.

Which type of coupling misalignment causes predominantly axial vibration at 1× running speed?

Answer: Angular misalignment

Angular misalignment (where the shaft centerlines meet at an angle) causes the coupling to flex through one cycle per revolution, producing strong axial vibration at 1×.