Vibration analysis and ultrasound work together

New applications of PdM technologies strengthen asset healthcare.

By J. Stanton McGroarty CMRP, CMfgE, senior technical editor

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Variable frequency drives

Applying both vibration and acoustical ultrasound for assessing the health of bearings hits the largest range of potential lifecycle anomalies, says Allied’s Garten. “Beyond just the routine bearing failure modes associated with lubrication and wear, effects of electrical transients and VFD-related anomalies have been identified with both technologies, leading to corrective action to the power circuit. This solved root causes rather than allowing repeat failures. There are slight differences in the data collected via vibration and ultrasound. This supports not just varying failure detection for trending and mitigation, but also the addition of varying alarm banding for anomalies beyond the normal mechanical focus. These anomalies are becoming more prevalent in the field.”

Allied has found value in applying acoustical ultrasound for assessment of several of the internal components for VFDs, as well, says Garten. “Utilizing acoustical ultrasound on these components has added value in assessing failures of these components prior to their normal end of lifecycle. Failures of iGBT assemblies, internal and external fans, and DC buss chargers all result in audible and spectral changes that trigger additional testing such as power quality assessment, motor current signature analysis, and field technical checks, to isolate and identify failures.”

A little vibration

Vibration2
Figure 2. Companies are requesting tablet apps for vibration monitoring.

Tom Hoenig, president of GTI Spindle Technology, describes an unusual shale processing application. “In most cases with vibration analysis we are looking to minimize vibration of machinery to prevent failures,” he says. “As the vibration increases at certain frequencies, we start planning for failures. In one case we were approached by a company who services shale shakers in the oil and gas industry. These are giant machines that sift large amounts of earth as their daily function. They only work well when they vibrate enough in the correct direction, frequency, and amplitude. So in other words less vibration means poor performance.”

The shale processor asked GTI to write an app that could run on GTI’s iPad vibration analyzer to inspect the peak performance of the vibration for its machines (Figure 2). The company needed to know how many Gs of vibration acceleration occurred at each mapped point on the machine, along with the frequency of that vibration. “They also needed to measure in two axes and show the vibration in an orbit plot,” explains Hoenig. “This way they could see the shake of the machine with two axis points of measure at each corner. The screen shots and reports generated by the iPad show the machine and all the points needed to be measured.”

Through the project, GTI learned not all equipment and assets are designed to minimize vibration, continues Hoenig. “Some equipment is made to vibrate to get the job done,” he explains. “Either way, vibration analysis again gives us the visual window to see the vibration and tell us if it is too much or not enough.”

Get the signal

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Figure 3. The interest in using ultrasound for monitoring critical assets remotely and continuously is on the increase.

Getting to equipment to take readings can be a major challenge. “Critical equipment can be located on a train, ship, or a remote site that is difficult or dangerous to access by employees,” says Ludeca’s Phillips. “Unfortunately, in the past it was very difficult or impossible to apply vibration analysis on equipment under these circumstances. We have done a lot of work to make vibration analysis in these environments possible, and the process has been very exciting. The condition monitoring system continually monitors the health of the equipment under normal operating conditions. Operators, mechanics, and management can be actively alerted via email or text message when conditional changes occur on a monitored machine. The data is automatically transferred back to a centralized location for routine analysis so that corrective action can be taken before unwanted consequences occur. In addition, capabilities such as wireless vibration monitoring, cloud computing, remote monitoring capabilities, and services are now available. In the past two years we have released new multichannel real time vibration monitoring systems. Routine access to cranes and other types of equipment can be very difficult or impossible for routine condition monitoring. We have also installed wireless monitoring systems in these applications to overcome access and safety concerns and ensure that equipment health monitoring is provided.”

lead-Stanton-McGroarty.jpgJ. Stanton McGroarty, CMfgE, CMRP, is senior technical editor of Plant Services. He was formerly consulting manager for Strategic Asset Management International (SAMI), where he focused on project management and training for manufacturing, maintenance and reliability engineering. He has more than 30 years of manufacturing and maintenance experience in the automotive, defense, consumer products and process manufacturing industries. He holds a bachelor of science degree in mechanical engineering from the Detroit Institute of Technology and a master’s degree in management from Central Michigan University. He can be reached at smcgroarty@putman.net or check out his .

The interest in using ultrasound for monitoring critical assets remotely and continuously is on the increase, says UE’s Messer (Figure 3). “Junction boxes can now be used in conjunction with the handheld ultrasound instrument and remote-mounted ultrasound sensors to collect data on multiple points from one central location,” he says. “Other sensors are available that can be connected to PLCs and other online data monitoring systems to monitor both mechanical and electrical equipment. Examples of assets that can be monitored remotely with ultrasound include overhead cranes, enclosed electrical switchgear, robots, and remote pumping stations.”

Impact demodulation is a new wrinkle for vibration analysis installations. “By applying impact demodulation to vibration data, we are able to identify impact vibrations, which decay or ring down very rapidly, and lift them out of the steady background vibration for analysis,” says Steven Hudson, senior analyst at Azima DLI. “Picture separating cymbal crashes from a steady drum beat. The impact sounds typically begin to be emitted long before actual failures in elements like bearings. Adjustments to sample durations and sampling rates may be required to support precise analysis and avoid aliasing or shadow data, but the payoff is better long-term forecasting. This new capability is particularly useful for slower turning equipment that used to make impact data difficult to obtain.” A white paper on impact demodulation is available at www.plantservices.com/whitepapers/2014/impact-demodulation-identification/.

To introduce and grow vibration monitoring and ultrasound technologies in an organization, a starter application can help to break into an industrial setting. “Even though it has become common knowledge that ultrasound can be used for compressed air or gas leak detection, it never gets old to see someone who finds a compressed air or gas leak with ultrasound for the first time,” says Messer. “It’s even more satisfying when a facility begins to use ultrasound to find and then repair the leaks and the savings and benefits that are then associated with those efforts. Being able to quantify compressed air and gas leaks using ultrasound is always exciting and is typically a good start for someone who is implementing the technology into a reliability program. Being able to document savings associated with compressed air or gas leak detection with ultrasound typically leads to investments in additional training and other predictive technologies. Benefits also include reduced compressor demand, increased capacity on the overall compressed air system, and a reduction in the facility's carbon footprint by reducing the greenhouse gas emissions.”

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