Keep Your Motors Running

A vibration-analysis program is the most effective way of monitoring motor mechanical health and performance.

Consider a wireless or hybrid vibration-analysis program to increase reliability and maximize personnel time.

By Alex Fillo, Motion

Motors are some of the most critical components in any facility. Equally critical is establishing the best maintenance strategy. This usually leads to a discussion of how to integrate predictive maintenance into a plan for critical and specialty motors. Motor-circuit and vibration analyses are the two most common technologies considered. Each is helpful in different ways: Motor-circuit analysis is used to evaluate electrical circuit health. Vibration analysis is best for monitoring mechanical health.

Vibration analysis

At its most basic level, vibration analysis studies movement within an asset. At a more technical level, it uses specialty sensors and equipment to record the frequencies generated by equipment movement. Vibration analysis uses a mathematical manipulation called a fast Fourier transform (FFT) to plot the spectrum of frequencies the equipment generates. An analyst reviews the FFT data plot to identify frequency amplitudes that match potential failure modes, such as bearing fault frequencies, structural looseness, imbalance, and misalignment. Accurate data collection, followed by a skilled analyst’s evaluation, is an extremely dependable and repeatable way to characterize an asset’s health. 

Some examples of faults in motors that are easily detected by vibration analysis include:

• lack of lubrication
• excessive internal bearing clearances
• loose hold-down hardware
• imbalance of fans and pumps
• cavitation and water hammer in pumps
• misalignment of couplings and sheave pulleys.

Half of all motors fail from bearing-related issues, and 95% that fail do so prematurely (Bloch & Budris, Pump User’s Handbook: Life Extension, 2014, The Fairmont Press Inc.). These statistics reveal significant opportunities to increase motor life by implementing a vibration-analysis program. Many of these faults are easily fixed, lengthening bearing life and, by extension, motor life. 

Collecting vibration data

Data-acquisition technology has moved from route-based measurements to wired data transmission. Today, wireless data collection has become rather common. Most sensors operate similarly, acquiring data in one, two, or three axes. Some sensors collect a complete time waveform and FFT spectrum. Others collect a simple, overall value (cumulative sum of all the frequencies shown in the FFT). These sensors then connect to a central hub (often known as a gateway) through a Bluetooth or radio-frequency system. The hub transmits the data to the cloud, where it can be accessed by plant maintenance staff and analysts. Some vendors are using advances in AI and machine-learning technology to develop programs that automate some of the analysis process, making better use of a highly skilled analyst’s time. 

Establishing a program

Designing a vibration-analysis program can be especially challenging without minimum knowledge of technology on management’s part, if not a strong background in the field. A route-based vibration-analysis program requires notable up-front investment and considerable ongoing use of manpower. It typically requires at least one vibration analyst certified to at least ISO Category level II (CAT II) by a certification organization. This process usually takes at least 18 months to ensure the analyst has real-world experience and practice applying the concepts from classroom training. Once implemented, collecting the data on 250 assets takes one person an average of 8 hours.

Another option for route-based programs involves outsourcing this work to a contractor who would come into the plant to collect and analyze data. The industry best practice for this program is to collect asset data monthly.  

A cloud-based wired or wireless system requires installing sensors on all critical assets and using a central dashboard to review asset health and determine what requires attention. This allows 24/7 data collection, and most systems have alarms that can automatically contact staff when an asset is in critical condition. 

Wireless-system benefits:

• Systems can use either site or remote resources for data analysis if sending data to the cloud.

• Most wireless vibration sensors also collect temperature data, which can be trended in the same system. 

• Some systems can also collect ultrasound data on slow-moving equipment. 

• Wireless systems do not depend on site resources to collect data. 

• Constant asset monitoring is possible (the data collection rate depends on the system).

• Alerts can be sent by phone or email, depending on the system.

• Some systems can pull data into an existing historian or distributed control systems (DCS). 

• Cellular connections can avoid connecting to local IT resources.

There are drawbacks:

• Initial costs can be significant.

• Typically, importing data into route-based vibration-analysis programs is not possible.

• Comparing total life-cycle costs is difficult because each plan is structured differently, with significant pricing variance.

• Comparing systems is difficult and many vendors keep details out of the public eye. 

• Users must be aware of sensor limitations regarding plant requirements (temperature, washdown resistance, data type, and software capabilities for complex systems). 

Hybrid approach

Consider a hybrid approach if a route-based system is desired or already in place. As with other methods, this would include, for all plant assets, a thorough criticality assessment and a work-study of the data-collection requirements.

The ideal hybrid system combines a cloud-based wireless (or wired) system to collect data from critical or hard-to-access assets with a route-based data collector for any required follow-up. A hybrid system could allow a sensor to collect a lower level of data, serving as a “check-engine light” that would indicate the need for additional follow-up with a handheld data collector. Many plants with well-developed, route-based vibration-analysis programs are now considering this hybrid approach to mitigate issues caused by turnover and labor shortages.

Choosing a vibration-analysis method can be daunting for those with limited exposure to the field. Whether you select a route-based program, a wired or wireless online program, or a hybrid approach, a well-executed system will extend the life of your motors. Partnering with a trusted, qualified, brand-agnostic third party, who can advise on a system to meet a facility’s needs, may be the best path for those with limited resources. EP

Alex Fillo is an Industry 4.0 Application Specialist on Motion’s P2MRO Team. Before joining Motion, Birmingham, AL (motion.com), she spent 10 years in maintenance, reliability, and operations management roles in the pulp and paper industry. Her experience includes vibration program design and optimization. Visit motion.com/efficientplant or learn more at P2MRO (motion.com/knowledgelinks/p2mro).