CVA Machinery and Equipment Troubleshooting 2

Question 1

An overhung fan shows high 1X in both radial and axial directions, with axial phase readings in phase across both bearings. What is the most likely cause?

Accepted Answer

Overhung rotor unbalance

Answer

Overhung unbalance typically produces high 1X radial and axial vibration with in-phase axial readings.

Question 2

Across a flexible coupling, axial 1X phase readings differ by about 180 degrees and axial amplitude is high. What does this indicate?

Accepted Answer

Angular misalignment

Answer

Angular misalignment produces strong axial 1X with roughly 180-degree axial phase shift across the coupling.

Question 3

A shaft shows dominant 1X axial vibration, and axial phase measured at the two bearings of the same rotor is about 180 degrees apart. Which fault is most likely?

Accepted Answer

Bent shaft

Answer

A bent shaft causes high axial 1X with opposing axial phase at each end of the rotor.

Question 4

A spectrum shows many running-speed harmonics plus half-order harmonics (0.5X, 1.5X, 2.5X), and phase readings are unstable. What is the most likely fault?

Accepted Answer

Rotating looseness (Type C)

Answer

Rotating looseness, such as a loose bearing fit, produces many harmonics, often with half-order components and erratic phase.

Question 5

During a soft foot check, which procedure is typically used?

Accepted Answer

Loosen one hold-down bolt at a time and measure foot movement with a dial indicator

Answer

Loosening each bolt in turn while watching a dial indicator shows how much each foot lifts.

CVA - Certified Vibration Analyst Practice Test

CVA - Certified Vibration Analyst Practice Test

CVA Machinery and Equipment Troubleshooting 2