How this video processing method can identify problems caused by vibration.
by Jeff Hay
November 8, 2018

Motion amplification is a video-processing method that detects subtle motion and amplifies that motion to a level visible to the naked eye. The process decodes light to pull out information that is indicative of motion, even if that motion is too small for the camera to detect with normal methods. The process involves the use of a proprietary camera—a high definition and high dynamic range video camera where every pixel becomes an independent sensor creating millions of data points in an instant.

Overview

The motion amplification system comprises a camera capable of operating at 120 frames per second (fps) at full frame resolution and 1,300 fps sub-frame offering an upper frequency range of 60 hertz (Hz) and 650 Hz respectively. Data is collected on the order of seconds (3 to 10 seconds is typical), and analysis can be performed in the field.

Analysis times to produce a motion amplified video range from 10 to 20 seconds. Many parameters can be determined from a data set. Displacement can be calculated from anywhere within the video by clicking and drawing a box on the screen where the desired displacement reading is to be determined. A time waveform and frequency spectrum are returned for that location in both the X and Y direction as viewed from the camera. More advanced techniques can be found such as frequency based filtering (FBF) where the user can use the graphical user interface (GUI) along with a frequency spectrum derived from the video to filter the video and generate a motion amplified video showing that frequency. The system can automatically stabilize the video in the event of ambient vibration to remove the excess vibration from the video.

Uses

Motion amplification has many uses. Vibration issues such as misalignment, imbalance and looseness are common issues diagnosed with motion amplification. Other issues such as structural cracks, resonance and soft foot can also be easily diagnosed with motion amplification. Additional uses include mechanical seals, metal press applications, pumps and assets behind glass.

The fundamental measurement motion amplification makes is displacement. For that reason, motion amplification is also well-suited for low speed applications in addition to traditional vibration faults. Displacement is most pronounced at low frequency, with displacements diminishing as the frequency increases. Motion amplification complements traditional vibration monitoring techniques that often use accelerometers as the data collection sensor.

Accelerometers are less sensitive in the low frequency regime and often have trouble detecting faults in the low frequency portion of the spectrum. Motion amplification can see motions down to 0.0 Hz. Applications at low speed include kilns, wind turbines and low frequency resonance.

For a closer look at motion amplification, watch the video below.

Workflows

Motion amplification is often used in conjunction with traditional vibrational and predictive maintenance tools. End users often integrate it into their route-based data collection as a device that is leveraged when an alarm level is indicating excessive vibration. The comprehensive view the tool gives allows the user to look at the asset in its entirety to see the big picture. The user can often hone in on the problem and move to the motion they see in the video to get a closer look, as the data often draws them to the problem area. This closer look in a particular area might involve a higher frequency data collection or a different camera angle.

The system is also leveraged in the design and commissioning phase. Using the system at this phase of an asset’s life allows the user to see issues before they worsen or cause secondary issues. It allows the asset owner and original equipment manufacturer (OEM) to be on the same page during installation and gives a baseline data set that captures the behavior of the asset when it is initially commissioned. This can then be used as a reference when diagnosing the health of the asset later.

Surveying equipment is another way in which end users leverage the system. This is especially useful when motion amplification is being used in a facility for the first time. In a single data collection, the system can see multiple motors, pumps, a network of pipes or large sections of a structure. This gives the system the unique advantage of being able to be used in a walk around survey. Users can leverage the system’s capabilities for a quick analysis of equipment. With this analysis, gross offenders—those experiencing large displacement from vibration but are undiagnosed because they are not routinely or continuously monitored—are identified.

Pump Applications

The system allows the user to evaluate the foundation of a pump, which can have an insubstantial base, loose bolts, base cracks or poor welding. The system allows the user to get to the root cause of the problem by creating a motion amplified video of the overall asset. Another use is looking at complex piping issues where traditional vibration measurement methods use a trial and error process to find vibration anti-nodes, where motion amplification allows the user to look at the complete piping view at the same time and then focus in on the root cause of the vibration.

Other troubleshooting areas include the evaluation of small-bore piping and mechanical seals. Traditionally, vibration of small-bore piping is not performed because of the sheer number of vibration measurement points that would be required. With motion amplification, the user needs to simply video the complete asset and look for small-bore piping that is shaking. This easily finds those small-bore piping situations that can be excited because of a resonance and foil overtime. Finding these issues allows the situation to be rectified before a failure occurs.

Also, because the system is noncontact, motion amplification can be used to troubleshoot mechanical seals on pumps and systems. This is not possible using traditional vibration contact methods.

FBF allows the user to see the motion at specific frequencies. This assists with troubleshooting all failure modes of the pump system such as misalignment and poor foundations.

Conclusion

Motion amplification has a wide array of uses, including vibration analysis and predictive maintenance. Some of the more common faults that are detected are: imbalance, misalignment and looseness. In addition, it is a particularly useful tool for analyzing and diagnosing structural defects and issues. Often, these structural issues are the root cause failure mode that lead to other failure modes that are detected at a much later stage in the asset’s life. These other failures are often corrected, and the asset returns to normal vibration levels while the root cause still exists, ultimately leading to another failure.