Don’t Let a Trickle Turn Into a Waterfall: The Importance of Vibration

A member of the Mobil Connect community recently asked why their machine was vibrating and what that might mean.

To be honest, my immediate reaction was that disaster is on the horizon, as I’ve always known vibration to be a precursor to failure. But, then I began to think, what do we really know about vibration and how can we use it to enhance rotating machinery performance?

So, this tip will focus on vibration and vibration analysis. It will consider the characteristics and how we may use vibration analysis as a tool to enhance rotating machinery performance.

What is vibration?

Vibration is defined as the motion a machine makes from its normal center position while at rest. It is caused by a force that is changing direction, and all machines demonstrate some degree of vibration. Three machine properties affecting vibration are:

  • Stiffness: the force required to bend a machine part.
  • Mass: the weight of the component decided by acceleration.
  • Damping: the tendency to slow down the vibratory motion.

The sum of these properties equals the “excitation force” and vibration results from forces beyond excitation equilibrium.

Vibration is measured in amplitude, or the amount of movement from neutral to the upper limit, back through neutral, and then to the lower limit.

spring diagram

The greater the vibration amplitude, the more severe the vibration. Vibration is an important sign, because the more abnormal the vibration, the closer you are to equipment failure.

What is vibration analysis?

Vibration analysis is a method of detecting and determining the mechanical condition of rotating equipment. This is accomplished through the measurement and interpretation of data. Specifically, vibration analysis measures five vibration characteristics:

  • Frequency: the period of vibration in one sine wave cycle.
  • Amplitude: the total displacement from peak to peak.
  • Velocity: maximum speed from peak to peak
  • Acceleration: the rate of change of velocity from extreme to center point.
  • Phase: measurement of angles of the vibrating part to another fixed point on the machine.

When a piece of rotating machinery vibrates, it produces a sound. Some vibration is normal, and so it’s important to be able to distinguish between normal sounds and those that indicate a concern.

Vibration analysis is done through the use of a variety of meters, analyzers, and monitors. These instruments read both vibration and the associated noise. They may be hand held (meters), remote (monitors) and complex (analyzer).

Vibration techs collect and compare a combination of vibration amplitude and noise frequency data to determine if there has been a change in machine condition.

Why vibration analysis?

The answer is simple – real time vibration analysis will catch a minor problem before it becomes a major issue or failure. It will identify such issues as:

  • Shaft imbalance
  • Misalignment
  • Mechanical looseness or excess clearance
  • Housing distortion
  • Bearing damage
  • Excessive surface roughness gears
  • Poor design or installation, etc.

Vibration analysis is a core pillar of maintenance and reliability programs for most plants. It is typically conducted in stages and requires dedicated personnel. At a minimum, critical equipment should be measured on a regular basis.

Vibration analysis and lubrication

At this point, you may be wondering what has vibration analysis to do with lubrication. The truth is that vibration analysis goes hand-in-hand with a proactive lubrication program.

Vibration analysis can help detect issues like bearing wear or particles in the oil. While these results would have to be further validated through techniques like oil analysis, vibration can indicate lubrication-related issues.

We hope this was a good primer on vibration analysis, and if you have any further questions, don’t hesitate to reach out via the comments section below!