Maintenance Using Vibration Analysis and Condition Monitoring

Vibration data will help you make informed maintenance decisions. However, you need to know how a machine typically vibrates, so it’s wise to start with an understanding of its vibration spectrum. The vibration spectrum shows expected vibration behaviour. Understanding how vibration should behave enables you to identify anomalies that may indicate a machinery problem. The typical vibration characteristics are known as the baseline.

Typically, vibrations are assessed by acceleration, displacement, and velocity. Measuring displacement, velocity, and acceleration shows the vibration severity, sometimes known as its amplitude. The amplitude is the first indicator of the machine’s condition. Larger vibration amplitudes tend to indicate higher defect levels.

These parameters target different characteristics of machine vibration and allow the engineer to uncover potential problems. For instance, displacement analysis looks at vibrations at low frequencies measuring the back-and-forth movement of a part usually read in micrometres. Irregularities in the rhythm of the displacement are indicators of problems with the part's motion. Meanwhile, acceleration and velocity measurements are used to analyse machines more generally. Vibration sensors monitor overall vibration patterns during machine use.

Measuring velocity is used as a vibration measurement for most condition monitoring applications because it provides an indication of destructive force and therefore overall machinery health. To measure vibration velocity and other parameters, vibration sensors can be installed on a machine.

Vibration analysis finds many faults. Sensors might monitor the vibration, speed, and turning speed of the rotational axis of a centrifuge to reveal potential problems. Alternatively, acceleration and displacement sensors might measure absolute vibrations at the cross and cylinder heads of a reciprocating compressor and any material wear, such as on the support ring.

Velocity is the best indicator of machinery health for low and intermediate-speed components. Velocity measurements capture the frequency range of common faults such as misalignment, looseness, or imbalance. Velocity amplitude changes occur later than acceleration changes but also increase over time. This enables a better picture of the equipment's condition. 

Other faults vibration analysis may reveal include:

• Bearing failures
• Faults with motor motion
• Bent shafts
• Gearbox failures

Adding sensors to machinery gives engineers the ability to constantly monitor its vibrational signature to pinpoint faults and make any necessary repairs or adjustments. This keeps the machinery running smoothly, thereby increasing its lifespan. Accelerometers in vibration sensors measure changes in the amplitude, frequency, and intensity of forces. When attached to the machine being monitored, the device generates a voltage signal corresponding to the frequency of the machine’s vibrations. This is usually how often the vibration occurs.

Piezoelectric accelerometers use the piezoelectric effect to measure acceleration changes. They have dominated vibration condition monitoring applications for years. 

To recap, for conditioning monitoring, you should install vibration sensors measuring parameters targeting different characteristics of machine vibration. Measuring displacement, velocity, and acceleration shows the vibration severity, known as its amplitude. The amplitude is the first indicator of machine condition. Larger vibration amplitudes tend to indicate higher levels of defects in a piece of equipment.

Displacement provides a general picture of machine health using low frequencies, while acceleration deals with high frequencies. Velocity is used as a vibration measurement for most condition monitoring applications because it indicates destructive force - and therefore overall machinery health.

Machine failures account for almost $1 trillion in manufacturer losses per year. Maintaining the health of our equipment through constant conditioning monitoring will help mitigate inefficiencies in machine operation, costly repairs, and machine downtime.

Are you looking to implement vibration analysis predictive maintenance for a proactive approach to maintenance? RS can help - find out more here.