Vibration - What to Look For, Most of the Time

Practical Solutions to Machinery and Maintenance Vibration Problems

Chapter 1, Basic Information

Section 1 What to Look For, Most of the Time

Only the most common vibration trouble sources are on this list. Compare with "Guide For Possible Sources Of Vibration Based On Frequency Only."

Main Vibration Trouble Source	Approximate % of Time it Occurs
Resonance magnification from pipes, pedestals, covers, steel bases, skids, beams, decks, etc.	20, usually partially resonant
"Foot/Frame Resonance"	30-40, more often in flexible frames
Unbalance	30-40, most often due to assembly errors
Misalignment (couplings and sheaves)	50-70, depending on craft training
Gearmesh frequency or rpm x # of blades	Less than 3
Loose iron (a-c motors and transformers)	Less than 1
Motors with loose or cracked rotor bar	Less than 1. May increase to approximately 5% for processes with more starts and stops.
Eccentric armature or non-uniform airgap	Less than 1. May increase to approximately 5% in high efficiency motors.
Oil whirl (journal bearings only)	Less than 1
Bent shaft	Less than 1
Loose base or loose part	Less than 1
Rub	Less than 1
Poorly counterbalanced reciprocating parts	10
Defective rolling element bearings	Less than 2*

* The number refers to situations when the bearing itself is the primary source for excessive vibration due to poor installation or manufacturing defects. When periodically monitoring vibration, bearing vibration occurs considerably more often. However, it is usually the result of wear due to an uncorrected other vibration source, such as unbalance or misalignment. For those programs that focus mostly on detecting bearing deterioration (rather than main vibration source), this number easily reaches 50 percent or more.

Textbook Index

This textbook contains only part of the information in our Practical Vibration Analysis seminar.

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