It’s easy to regard vibration analysis and ultrasound as competing technologies. As these technologies grow and mature, however, the experts in both fields are coming to agree that, for many applications, vibration analysis and ultrasound are at their best when they are used together. Vibration analysis and ultrasound are often viewed as complementary parts of a complete condition monitoring toolkit. Sophisticated users select their technologies on a very individual basis. The choice takes into consideration equipment criticality, typical failure modes, the cost of failures, the cost of monitoring, the practicality of redundancy, and other characteristics of the business, the site, and the individual assets within it.
“We use both vibration analysis and ultrasound to monitor bearing condition and trends over time to predict bearing failure,” says Paul Berberian, vice president of predictive technology at GTI Predictive. “While we are using our vibration tools to determine root cause analysis for unbalance, misalignment, bearing defects, and looseness, ultrasound is a very good tool for determining when and how much to lubricate. This prevents overlubrication which is one of the main causes of bearing failure. Financially, if you correct the root cause and you lubricate it properly, a bearing should easily operate throughout its expected life.”
Traditionally, vibration and ultrasound inspections have been most popular in bearing monitoring, explains Alan Bandes, vice president of marketing at UE Systems. “Since ultrasound senses friction, it has gained popularity in lubrication programs where users can identify bearings in need of lubrication quickly, and, by incorporating equipment such as the grease caddy, lube techs can apply just the right amount of grease to prevent overlubrication,” he says. “Another use of the two technologies is basic bearing route inspection. Since ultrasound relies on just one test point, the time of inspection is cut by at least a third. Yet another application in which ultrasound has assisted vibration programs is inspection of slow-speed bearings. Ultrasound will detect the slightest signs of increased friction or early stages of spalling in a relatively short time.”
Figure 1. Combined use of vibration analysis and ultrasound also improves equipment availability and wrench time.
Combined use of vibration analysis and ultrasound also improves equipment availability and wrench time (Figure 1). “Ultrasound and vibration analysis have unique capabilities,” says Trent Phillips, condition monitoring manager at Ludeca. “However, they’re companion technologies, as well. Using both together can provide very early detection and confirmation of bearing faults, lubrication issues, and more. Additionally, the combination of these tools can deliver optimal use of manpower through more efficient condition monitoring coverage of important assets. All of this leads to increased time to plan and schedule activities that will keep equipment running upon demand. The result is reduced downtime, reduced costs, reduced risk, reduced spare parts usage, improved safety, increased capacity, increased uptime, and increased profits.”
The evolution of condition monitoring tools has proceeded against the backdrop of changes to statutory and technical issues in the businesses themselves. New motor technology, notably the spread of variable frequency drives (VFDs), has created new failure modes that must be monitored. New extraction techniques have pushed mining and drilling equipment in new directions, creating unprecedented environmental and mechanical challenges. Arc flash prevention has prompted changes to OSHA, NFPA, and NEC standards. With all these changes come new monitoring requirements.
Change calls for fresh thinking regarding the use of vibration analysis and ultrasound, as well as other condition monitoring tools. Use these tools, individually and in combination, to meet the evolving monitoring needs of equipment and the environments in which it operates.
Arc flash in the box
Ultrasound can be used to keep arc flash danger away from employees, explains T.J. Garten, electrical and energy subject matter expert at Allied Reliability Group. “During routine infrared electrical surveys, we have utilized acoustical ultrasound to assist with failing part identification, as well as severity determinations,” he says. “Listening for chattering contacts, intermittent auxiliary contact operation, starter coil assembly chatter, and coil winding electrical hum assists the analyst in providing corrective work orders. This information changes the work from a search-and-find mission to a planned repair that eliminates hot-spot chasing.”
Electrical inspection is a fairly new application for ultrasound technology, says Adrian Messer, operations manager at UE Systems, but its use hasn’t increased much in the past few years. “The main driver of this application is safety because we can typically inspect energized electrical equipment without having to open the panels and doors on the equipment,” explains Messer. “So, there’s little fear of creating an arc flash because we aren’t changing the environment inside of the equipment and we aren’t exposing ourselves to the energized electrical connections. Additionally, when ultrasound is used in conjunction with traditional infrared inspection, the user can scan with ultrasound prior to opening up the electrical equipment for the infrared inspection.”