What is Vibration?
Most of us are familiar with vibration; a vibrating object moves to and fro, back and forth. A vibrating object oscillates. We experience many examples of vibration in our daily lives. A pendulum set in motion vibrates. A plucked guitar string vibrates. Vehicles driven on rough terrain vibrate, and geological activity can cause massive vibrations in the form of earthquakes.
There are various ways we can tell that something is vibrate: we can touch a object and feel the vibration, we may also see the back-and-forth movement of a vibrating object… Sometimes vibration creates sounds that we can hear or heat that we can sense.
But, what is vibration? In simplest terms, vibration in motorized equipments is merely the back and forth movement or oscillation of machines and components, such as drive motors, driven devices (pumps, compressors and so on) and the bearings, shafts, gears, belts and other elements that make up mechanical systems. The unexpected breakdown of rotating machinery is the single largest cause of emergency downtime in industries.
A broad range of complex vibration problems can occur on industrial machines. These include roller-bearing wear-out, problems with roll drive systems, and structural issues (including resonance). Successful analysis and resolution of machine vibration problems requires a thorough understanding of the equipment, and the ability to apply various diagnostic and damping techniques.
Causes of machine vibration
Vibration can result from a number of conditions, acting alone or in combination. Keep in mind that vibration problems might be caused by auxiliary equipment, not just the primary equipment.
Misalignment/shaft run-out — Vibration can result when machine shafts are out of line. Angular misalignment occurs when the axes of (for example) a motor and pump are not parallel. When the axes are parallel but not exactly aligned, the condition is known as parallel misalignment. Misalignment can be caused during assembly or develop over time, due to thermal expansion, components shifting or improper reassembly after maintenance. The resulting vibration can be radial or axial (in line with the axis of the machine) or both.
Wear—As components such as ball or roller bearings, drive belts or gears become worn, they might cause vibration. When a roller bearing race becomes pitted, for instance, the bearing rollers will cause a vibration each time they travel over the damaged area. A gear tooth that is heavily chipped or worn, or a drive belt that is breaking down, can also produce vibration.
Looseness—Vibration that might otherwise go unnoticed can become obvious and destructive if the component that is vibrating has loose bearings or is loosely attached to its mounts. Such looseness might or might not be caused by the underlying vibration. Whatever its cause, looseness can allow any vibration present to cause damage, such as further bearing wear, wear and fatigue in equipment mounts and other components.
Imbalance — A ‘heavy spot’ in a rotating component will cause vibration when the unbalanced weight rotates around the machine’s axis, creating a centrifugal force. Imbalance could be caused by manufacturing defects (machining errors, casting flaws) or maintenance issues (deformed or dirty fan blades, missing balance weights). As machine speed increases the effects of imbalance become greater. Imbalance can severely reduce bearing life as well as cause undue machine vibration.
Effects of vibration
The effects of vibration can be severe. Unchecked machine vibration can :
- Accelerate rates of wear (i.e. reduce bearing life) and damage equipment.
- Vibrating machinery can create noise, cause safety problems and lead to degradation in plant working conditions.
- Vibration can cause machinery to consume excessive power and may damage product quality.
- Vibration can damage equipment so severely as to knock it out of service and halt plant production.
By using E&B rubber mounts and vibration damping mounts, we can control most of the effects of vibration and prolong machinery life and provide enhanced product quality and production rates.
