Condition monitoring and predictive maintenance are certainly worthy of buzzword status in the modern-day world of industry, as these terms are bandied about to tout the latest and greatest solutions for reducing maintenance downtime and unplanned equipment failure. That said, in looking at the evolution and underlying concepts that serve as the foundation of these, as some might say, overused terms, one can see how condition monitoring and predictive maintenance can provide tangible benefits. To leverage these advantages, most experts agree it is important to establish concrete goals and a quantifiable method of measuring and documenting results.
The Difference Between Condition Monitoring & Predictive Maintenance
Depending on whom you talk to, the definitions of condition monitoring and predictive maintenance may range from very specific to pretty vague. In most discussions, however, condition monitoring is viewed as a subset of a larger predictive maintenance program. Ultimately, condition monitoring and predictive maintenance aim to move plant systems maintenance from a reactive position to a proactive one.
|Emerson’s CSI 2130 Machinery Health Analyzer is designed to quickly and accurately identify developing faults in rotating machinery. The route application shown here uses pre-defined settings to provide instant feedback in a bar graph format. (Photo courtesy of Emerson Process Management)|
In looking at the history and evolution of condition monitoring and predictive maintenance, it could be said that electronic vibration measurement begat vibration frequency analysis, which begat condition monitoring, which begat predictive maintenance.
The beginning of industrial vibration measurement can be traced back T.C. Rathbone. Rathbone established the first guidelines for judging machine condition from vibration measurement in a 1939 paper, titled “Vibration Tolerance” (Power Plant Engineering). Following Rathbone’s publication, it soon became apparent that while amplitude measurement was necessary for effective vibration analysis, monitoring frequency and frequency patterns could provide more information on the root cause of machinery vibration. A device called the vibrograph—a primitive version of today’s vibration analyzer—was used to aid in the measurement of frequency vibration.*
The modern era of vibration analysis can be traced back to Art Crawford’s graduate research on methods for reliably balancing high-speed spindles. Crawford’s work ultimately resulted in the formation of a company, International Research & Development Inc., which made significant strides in the areas of dynamic balancing, frequency analysis, and condition assessment.*
Predictive maintenance can be viewed as an umbrella under which any process that aims to logically and efficiently organize plant systems maintenance resides. Condition monitoring is the most established of these processes, but with the preponderance of technologies available today for organizing and automating the maintenance process, a need arose for a more broad-based terminology that extends beyond the traditional roots of vibration analysis and condition monitoring. Likewise, the term condition monitoring has expanded to include not only machinery vibration, but also other process variables, such as lubrication, heat buildup, and contaminant monitoring and analysis.
“The goal in any manufacturing environment is more up time,” says Jim Wiles, director of application consulting for Software Toolbox, a provider of industrial automation software systems. “In the ’80s, we adopted programs, such as TPM (Total Productive Maintenance), which allowed for planned downtime to do maintenance—the cost of the downtime offset the cost of unplanned breakdowns.” However, he says this approach inherently meant that certain healthy components were replaced prematurely. “With proper condition monitoring, we can now monitor a piece of equipment and schedule the maintenance outage for when we actually need it—prior to a known failure,” says Wiles. “This inevitably reduces the amount of planned maintenance outages, subsequently increasing equipment availability.”
Deane Horn, product line manager for Online Monitors in Emerson Process Management’s Machinery Health business unit, says the focus at Emerson is to structure the maintenance activity within the context of a whole program aimed at detecting, analyzing and taking action based on concrete information. He says predictive technologies should be viewed as tools for achieving the end result of optimizing the maintenance of plant equipment.
Ultimately, Horn says the success of a maintenance program relies on having clear goals and gathering the necessary data to show those goals are being met. He says this is important because this data will be required to make the case for the ongoing investment that is required to effectively build out a maintenance program. “Make the case for the strategy by defining a clear goal, and determine a way to measure the progress,” says Horn. “It’s so important to define how you’re going to measure and continue to track [maintenance results].”
Horn encourages a cultural mindset on predictive maintenance where technical team members, finance, and general management are all involved in defining goals for the maintenance program. He says that doing this will ensure that “everybody’s bosses, bosses, bosses have bought into [the maintenance program.]”
While the roots of condition monitoring can be found in vibration analysis, other process variables such as lubrication, heat buildup, contaminants, and power train alignment are now commonly monitored.
“Heat buildup in bearings, gear boxes, electrical panels, etc., is an indicator that something is going wrong,” says Wiles. Infrared thermography can be used to benchmark and monitor heat buildup in equipment components on a scheduled or real-time basis.
Contamination can also provide key data to help indicate when equipment failure might occur. Lubricants and coolants can cause substance breakdown in process equipment and introduce contaminants into the process, leading to premature component failure. “Metal particles in oil are never good for the equipment you are trying to lubricate,” says Wiles. He says oil and wear particle analysis can be employed to test lubricants/coolants to determine the level of contaminants. “The analysis can also determine what type of contaminant it is, often times leading to the source of the problem,” says Wiles. For example, he says a high level of brass may indicate a bushing is starting to break down; a high level of carbon may indicate the oil itself is breaking down. On one occasion, Wiles says an oil analysis actually discovered the wrong oil was being used for the application. He says the discovery enabled the end-user to change the oil before it had a significant negative impact on the process, thus eliminating a potentially catastrophic failure.
Alignment monitoring can help identify the root cause of vibration. Laser alignment testing can be used to ensure proper alignment of power trains and couplings. Misalignment often indicates component failure in the making, such as a worn coupling, bushing, bearing block, mount, etc. “Discovering [misalignment] before a major failure of any components will both prevent the failure and prevent additional equipment damage had the failure occurred,” says Wiles. For example, he says a worn coupling will cause vibration in a drive shaft, prematurely wearing the bearings supporting the shaft and increasing vibration, causing subsequent failure to components related to the drive train—a chain reaction that only gets worse as it goes unattended.
Horn says process instruments also play an important role. “The instrumentation provides valuable information to assist in the condition monitoring/predictive maintenance program,” says Horn. In particular, he says fluid temperature and pressure measurement can be informative. “A rise in temperature can change the mechanical behavior of the machine—not only bearing temperatures, but it might also be process fluid temperatures,” says Horn. He cites pressure, temperature, flow, start/stop, running conditions, and even weather conditions as key pieces of information that can inform the larger condition monitoring/predictive maintenance program.
Over the past decade, technology advancements in vibration analysis have helped increase the reliability of the data being captured, while manufacturers have gained a better understanding of the life cycles of their products, particularly regarding materials used and how they react in different conditions, types of lubricants to use in what situations, etc. Wiles says these two trends, along with advances in oil and other liquid analysis techniques, allow end-users to more effectively determine what mechanical part in a piece of equipment may be starting to degrade. “Using new technologies to move data, users can be alerted immediately on an upcoming failure,” says Wiles. “This allows them to be proactive to an issue, plan around it, and hopefully not interrupt production.”
Looking ahead, Wiles says he believes data collected by condition monitoring systems will give equipment manufacturers the feedback they need to produce better products that will allow manufacturing facilities to run longer and more efficiently with reduced MTBF (mean time between failure)/MTBR (mean time between replacement).
Horn says he sees two clear market trends that will play a role in the condition monitoring/predictive maintenance going forward—wireless and diagnostics. He says the powerful diagnostics that are now available through modern process instruments and the ability to efficiently communicate that information anywhere/anytime via wireless transmitters will enable end-users to more effectively respond to process conditions and limit unplanned downtime. “Wireless is at the point where it is really starting to hit mainstream in the vibration world,” says Horn.
Horn says he sees “ease-of-use” as another trend going forward in the vibration space. He says Emerson has launched a company-wide Human Centered Design initiative that aims to put the user and useability at the forefront of its product development cycle. He says vibration analysis, which has traditionally been a challenging task that requires a lot of expertise, is a prime candidate for an ease-of-use push that makes it easier to use the tools to more effectively diagnose vibration issues.
Matt Migliore is the executive director of content for Flow Control magazine and FlowControlNetwork.com. He can be reached at Matt@GrandViewMedia.com.
* “From Vibration Measurements to Condition Based Maintenance,” Sound and Vibration, January 2007, Mitchell, John S.