Vibration analysis helps you monitor and detect issues using vibration data. Read about vibration analysis methodology, tools and techniques, vibration analysis measurement methods, and more.

Vibration analysis is defined as a process for measuring the vibration levels and frequencies of machinery and then using that information to analyze how healthy the machines and their components are. While the inner-workings and formulas used to calculate various forms of vibration can get complicated, it all starts with using an accelerometer to measure vibration. Anytime a piece of machinery is running, it is making vibrations. An accelerometer attached to the machine generates a voltage signal that corresponds to the amount of vibration and the frequency of vibration the machine is producing, usually how many times per second or minute the vibration occurs.

All data collected from the accelerometer goes directly into a data collector (software), which records the signal as either amplitude vs. time (known as time waveform), amplitude vs. frequency (known as fast Fourier transform), or both. All of this data is analyzed by computer program algorithms, which in turn is analyzed by engineers or trained vibration analysts to determine the health of the machine and identify possible impending problems like looseness, unbalance, misalignment, lubrication issues and more. Vibration analysis can detect problems such as:

Distributor and alignment and maintenance training provider VibrAlign uses the example of taking an industrial fan, removing a fan blade and starting it up. As expected, the fan vibrates due to an unbalanced fan wheel. This unbalanced force will occur one time per revolution of the fan. Another example would be a damaged bearing track causing a bearing roller to generate vibration each time it contacts the spall (similar to a pothole on a highway). If three bearing rollers hit the spall per revolution, you should see a vibration signal of three times the fan's running speed.

While accelerometers are still the most common tool used to collect vibration data, modern technology and improved sensor technology have allowed for non-contact, high-speed laser sensors that can detect issues accelerometers can't. This allows for a more accurate and more localized analysis, and opens up vibration analysis to more methodology. Vibration analysis is generally broken down into four principles, and each principle gives you specific information on the working conditions and features of the vibrating parts.

Outside of these four basic principles lie numerous forms of analysis, calculations and algorithms used to determine different aspects of vibration analysis. These include:

All of these vibration analysis techniques help to identify three major parameters: acceleration, velocity (RMS) and displacement. Each of these parameters emphasizes certain frequency ranges in their own way and can be analyzed together to diagnose issues. Let's take a look at each parameter.

Below is an example of what acceleration, displacement and velocity look like on the same signal. You can see some peaks at the same frequencies, but each has different amplitudes. This is a good visual of how each parameter assigns different importance to frequency ranges.

Advanced technology, particularly advances in wireless technology, has greatly improved how vibration analysts collect, interpret and share data. Today, vibration analyzers are extremely portable, communicate with smartphones and tablets in real time, and can generate FFT in extremely high resolution. Many vibration instrument companies develop their own apps to communicate with each other.

Another form of advanced technology you'll see with vibration analysis interpretation instruments is operating deflection shapes (ODS) 3D simulations of machinery vibrations. In a nutshell, this type of software exaggerates vibration-induced movements in a 3D model so you can visualize the forces impacting your machine while it's running.

Some vibration analysis instrument companies offer databases with thousands of bearing fault frequencies preloaded to help you identify certain fault frequencies for your bearings. Some software can continuously monitor the geometry of your rolling elements and warn you when possible premature failures may occur.

As with most advanced technology, the majority of vibration analysis data is automatically uploaded to the cloud and is available on your mobile device, computer or directly from your browser. This is especially useful if you're performing vibration analysis as a third-party consultant, so you can freely share spectra with your clients.

The methods and tools discussed in this article not only are great for determining what's wrong with a piece of equipment or machinery (reactive), but they also can be used to catch issues before they cause significant downtime (proactive). Using vibration analysis and monitoring enables you to look quantitatively into structural weakness or looseness, rotating component looseness and whether resonance is present.

If implemented properly, continuous vibration monitoring helps you optimize machinery performance. With the use of modern technology, you can take continuous vibration readings on various equipment in real time and have the data sent directly to your smartphone, tablet or desktop via the cloud.

The tools and techniques used in the vibration analysis process can be a bit confusing on paper, so let's take a look at a real-world example from IVC Technologies. This particular case study examines the testing of an air-handling unit in a pharmaceutical facility. The unit is needed to run two supply fans at capacity to meet enclosed air-flow requirements. The air-handling unit has two direct-coupled fans, each equipped with a 150-horspower motor. The initial assessment of the fan unit showed the unit to run normally when one fan was running, but once the second fan was turned on, vibration issues presented themselves at certain set points.

Vibration analysis revealed that once fan No. 2 was turned on, a slight increase in vibration amplitude across all three points of measurement occurred, while fan No. 1 remained the same. Testing showed the highest amplitude appeared in the motor outboard vertical at 0.456 inches per second, with a dominant peak at 841 cycles per minute, according to IVC Technologies. This indicated the problem might be a structural resonance vibration, since spectral data showed no other signs of mechanical issues.

As the consultant, IVC Technologies recommended the company inspect the frame's structure and the dynamic absorber of fan No. 2. A bump test was also recommended to further locate and analyze the resonance vibration.