Maintenance Q&As

What Is a Vibration Sensor: How to Measure Vibration to Minimize Failures

Answered October 02 2019

One of the technologies used to track equipment health is vibration monitoring. Vibration sensors can be used to give maintenance teams insight into conditions within key assets that might lead to equipment failure, allowing them to head off the need for major repairs.

Vibration sound wave

What is a vibration sensor?

A vibration sensor is a device that measures the amount and frequency of vibration in a given system, machine, or piece of equipment. Those measurements can be used to detect imbalances or other issues in the asset and predict future breakdowns.

Why you need to monitor vibrations

Any business that uses heavy equipment in their daily operations can benefit from monitoring vibrations. The advantages of doing so include the following:

Understand causes of damage

When a piece of equipment starts showing signs of wear, vibration analysis can help with root cause analysis (RCA). By monitoring vibrations within the asset, you can track down the root source of the vibrations and subsequent damage.

Monitor repair needs

While vibration monitoring can help with RCA, it truly shines when used in predictive maintenance. When connected to a CMMS or similar system, you’re able to track vibration data in real time. When you see dangerously high levels of vibration reflected in the data, you’ll know that you need to perform repair work on the connected asset.

Keep an overall health check on equipment

Condition monitoring relies heavily on sensors, including vibration sensors. By monitoring vibration data from key assets, you’re able to see how they’re performing during specific time periods.

For instance, if you’re currently adapting your system to process new materials, vibration monitoring can help you see whether specific pieces of equipment are able to handle it without undue wear.

How do vibration sensors work?

A vibration sensor either connects directly to an asset or monitors it wirelessly. Once placed, it will detect vibrations from the asset through various means, depending on the type of sensor (more on that below). Over time, you’ll get two types of data from the device:

Frequency

The first type of data is the frequency, or how often the vibration occurs. By tracking when spikes in vibration happen in a given asset, you’ll be able to pinpoint root causes.

Intensity

The second point of data you’ll get is the intensity of the vibration as it occurs. The more vibration you have from a piece of equipment, the higher the intensity measurements will be.

Tip: The word “frequency” is used in different ways depending on the context. Here, it’s how often peaks in vibration occur. In other contexts, it can refer to the wavelength of the vibration itself (which might reflect in intensity measurements).

As these two types of data are collected, your CMMS will log them into the asset’s history, which can then be used as a point of comparison. As malfunctions occur, they’ll reflect in the data, and your system will be able to predict future failures and malfunctions by comparing the current data with past trends.

7 types of vibration sensors

Vibration sensors come in various forms. Each of the following has its own applications within an industrial setting.

1. Strain Gauges

One type of vibration sensor is the strain gauge, which is a foil that’s applied directly to the surface of the machine being monitored. The foil contains an electrically conductive grid. As the grid is stretched or compressed—such as when that piece of equipment is vibrating—it changes the electrical resistance of the grid. By reading changes in the grid’s resistance, an electric current passing through it will take more or less time to get through.

Those readings can be used to measure the vibration of an object based on how much the material is “straining.” In order to work properly, strain gauges need to be perfectly bonded to the surface, meaning installation can be a bit time consuming.

Use: Strain gauges are inexpensive on their own, and they’re best used on uneven or curved surfaces. However, you do need special equipment to amplify and read the signals produced by the gauge, which can get expensive.

2. Accelerometers

By far the most common types of vibration sensors, accelerometers measure the changes of velocity of a given component. When attached to a piece of equipment, any vibration will reflect a change in velocity, which will cause the accelerometer to produce an electrical signal. That signal is then interpreted to produce vibration data.

The most commonly used type of accelerometer is a piezoelectric accelerometer, which produces a strong, clear signal at most frequencies. However, piezoresistive accelerometers are becoming more popular due to the fact that they are better at high and low frequencies. The drawback is they cost up to five times as much as piezoelectric sensors.

Use: Accelerometers are commonly used for general vibration analysis. However, they do require supporting electronics in order to be useful.

3. Eddy-Currents

An Eddy-Current sensor is a non-contact sensor that produces magnetic fields which are used to measure the relative movement of a given object. If the sensor is fixed in place and the object is vibrating, that movement will register in the magnetic field. Capacitive displacement sensors work in a similar way, but with strong electric fields instead of magnetic fields.

Since Eddy-Current sensors measure relative movement (i.e. movement relative to the sensor’s position), they must be fixed in place. The fact that they don’t need to make contact with the asset makes them ideal for delicate assets or setups.

Use: Eddy-Current sensors are frequently used in laboratories where fragile equipment is used and measurements need to be precise. Outside the lab, they don’t see much use.

4. Laser displacement

Like Eddy-Current sensors, laser displacement sensors are non-contact sensors, except instead of using magnetic fields and electric currents, they use a laser beam with triangulation. The beam is aimed at the asset and reflects back through a receiving lens into a receiving element. Any changes in the object’s position will cause the beam to hit a different part of the receiving element.

Use: Laser displacement sensors tend to work best with stationary objects in clean settings, and they won’t interfere with delicate instrumentation. However, they don’t tend to fare well in rugged environments, and they are very expensive.

5. Gyroscopes

A gyroscope is a contact sensor that measures angular velocity, which is how quickly something turns or rotates. They do this by using MEMS (microelectromechanical systems) technology, which provides accurate measurements of how many degrees an object rotates per second.

In vibration monitoring, gyroscopes aren’t typically used on their own. Instead, they’re used to supplement the data you’d get from an accelerometer with orientation data.

Use: Gyroscopes can be used together with accelerometers on rotating equipment, filling in gaps in the data provided. With MEMS technology, they’re fairly inexpensive, making them great for low-budget applications.

6. Microphone sensors

Vibrations create sound, and that sound is often beyond the range of human hearing. Microphone sensors—also called acoustic pressure sensors—can provide some basic information on changes that might occur in high-frequency vibrations that equipment operators wouldn’t normally be able to detect.

Microphone sensors have the benefit of being highly cost effective, though the information they provide is fairly limited.

Use: Microphone sensors can accurately detect changes in vibration frequency, but not absolute values. In addition, they aren’t very effective at pinpointing the exact source of vibrations, which means they’re typically used in conjunction with accelerometers.

7. Vibration Meters

A vibration meter is a handheld device used to analyze vibration data and put it into a readable format. They often include accelerometers, but models that do not can be connected to an installed accelerometer to give you a quick look at the current health of the asset.

Use: Vibration meters are used to perform quick checkups on assets, but aren’t good for continuous long-term data.

Machine types that use vibration sensing

Vibration sensors are highly effective at monitoring the health of a wide range of machines. In fact, 90 percent of machines can benefit from vibration monitoring. Following are a few examples.

Water pumps

Water pumps are important pieces of equipment in the water and wastewater industry. If water pumps and condensers stop working, they can leave thousands of people without access to clean water and cause extensive damage to the environment.

Vibration sensors help make sure the bearings, motors, and fans in water pumps and condensers operate smoothly, providing advanced warning of potential issues if readings start to get a bit rough.

Motors, gearboxes, and belts

Any asset with a motor, gearbox, or belt system relies on rotating components, which means vibration monitoring can play a vital role in condition monitoring for those machines.

Monitoring vibrations in these types of systems can prevent minor imbalances in individual machines from developing into major disruptions in the entire system. For instance, the food and beverage industry makes use of chillers with motors. If the motor goes down, the chiller can’t do its job, and thousands of dollars worth of food product is lost.

Fans and compressors

Fans and compressors—such as those used in most industrial machines and ventilation systems—make use of rotating equipment that must run smoothly. If a fan or compressor system starts showing signs of imbalance or wear, that will reflect in any vibration data collected, allowing maintenance teams to detect issues in the system early enough to minimize repair costs.

Wind turbines

Perhaps the largest pieces of rotating equipment are wind turbines, which rotate anywhere between 5 rpm and 30rpm. Making routine checks on wind turbines can be time consuming and dangerous, given the heights—in excess of 300 feet—and rotor movements involved.

To cut down on the costs of monitoring wind turbines and preserve the safety of technicians, vibration monitoring can provide consistent, accurate data on the current health of each turbine in a wind farm. If an imbalance shows up, that’s a signal to send a technician out to fix it.

Rolling bearings

Most pieces of rotating equipment use rolling bearings to keep parts moving. Mixers, turbines, motors, and wheel axles make use of bearings to keep everything spinning smoothly.

To keep doing their job, rolling bearings need lubrication. If they go too long without it, they grind and wear out, causing extra vibration in the asset. By the time that grinding becomes audible to human ears, it’s often too late—the bearing system likely needs replacement.

Tracking the vibration caused by bearing systems can alert maintenance teams to a machine’s need for oiling, preventing the cost of more expensive repairs later on.

Combining vibration sensors with UpKeep CMMS

In order to get the most out of vibration sensors, you need a system that can collect and analyze the results. Otherwise, all that instrumentation won’t do you much good.

A CMMS can log and manage vibration data you collect from your sensors, allowing you to make intelligent maintenance decisions and even automatically create work orders when things get out of balance.

Real-time alerts

As your sensors collect data, your CMMS will log that information and use it to anticipate when future problems may arise. When vibration data crosses certain limits, you’ll get an alert as soon as it happens.

Failure reports

Reports generated from the data help you see how your equipment is faring, track when failures occur, and make informed decisions about future maintenance procedures. You’re able to plan maintenance exactly when it’s needed instead of performing it too soon or too late.

Easy monitoring

Using a CMMS together with vibration monitoring allows you to keep a close eye on your machines, making it easy to watch for potential issues and schedule needed maintenance tasks.

In order to get started tracking your facility’s equipment, try UpKeep for free.

Key Takeaways

Vibration sensors are an excellent way to monitor the health of key assets. They provide precise information on how individual pieces of equipment are doing, and the data they provide can help you anticipate when future maintenance needs may occur. The end result is a more streamlined maintenance process and improved machine health.

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