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4:47 pm
May 15, 2017
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Beware Self-Inflicted Reliability Problems

modern manufacturing industry and mechanization concept, abstrac

Think of this expert advice as a reality check for your operations and take action accordingly.

By Jane Alexander, Managing Editor

The root cause of poor reliability can come from many sources, including aging plant assets, poor design decisions, even disregard for reliability by those who built and/or installed the equipment. Then, there are the many other reasons outside of your control that could be contributing to the reliability problems your site is experiencing today. While any reliability-improvement initiative will require that all of those issues be addressed, according to Jason Tranter of Mobius Institute (mobiusinstitute.com, Bainbridge Island, WA), operations must first deal with those of the “self-inflicted” variety.

Don’t think you have self-inflicted reliability problems? Tranter begs to differ. It’s a bitter pill to swallow, but yes, you do,” he said. “That’s good news, though, since it is much easier to deal with the self-inflicted root causes than the inherent reliability problems you adopted.”

What does Tranter mean by self-inflicted? To determine why equipment fails prematurely and/or why you experience slowdowns, safety incidences, or quality problems, he explained that personnel could go through a detailed reliability-centered maintenance (RCM) analysis process, or perform root-cause failure analysis (RCFA) after each failure occurs. “Better yet”, he said, “they can learn from the experience gained at thousands of plants around the world and consider some of the most common root causes of equipment failure.”

Focusing on rotating equipment, Tranter outlined those types of problems as follows, starting with the most obvious and working backward to their root causes.

#3. Cause of Reliability Problems: Imperfect operating and maintenance practices

Most of the equipment in a plant or facility, i.e. motors, pumps, fans, compressors, and turbines, is designed to run for many, many years without unplanned downtime. While those types of assets may incorporate some components that wear out, many items, such as bearings and gears, are designed to provide years of trouble-free operation. This, however, assumes that all of the parts were installed correctly, the components are precision aligned, the bearings and gears are correctly lubricated, all fasteners are tightened to the correct torque, there is no resonance, belts are tightened to the correct tension, and the rotors are precision balanced.

It also assumes that the equipment is operated as designed. Pumps, for example, should be operated at their best efficiency points (BEPs). “If you are unsure these types of situations are occurring,” Tranter cautioned, “then they almost certainly are.” He pointed to several areas where seemingly minor issues could be causing serious problems:

1705fvibration2

Just 5/60th of a degree of angular misalignment can cut bearing life in half. (Reference: Harris, Tedric A., A Rolling Bearing Analysis, John Wiley & Sons, New York, 1984.)

Shaft alignment. When two shafts are “collinear” (no angle or offset between their centerlines) it reduces stress on the bearings, couplings, shafts, and the rest of the machine components. Research has revealed that just 5/60th of a degree of angular misalignment can cut bearing life in half (see Fig. 1).

If you use laser alignment with appropriate tolerances, and you remove soft foot, then this will not be a source of poor reliability. By the way, just because your vibration analyst does not detect misalignment does not mean that your machines are precision aligned.

The life of a bearing is inversely proportional to the cube of the load.

The life of a bearing is inversely proportional to the cube of the load.

Balancing. When you balance to ISO 1940 grade G 1.0, the cyclical forces on the bearings, shaft, and structure are minimized and you gain reliability. If you do not have a balancing standard, then unbalance will be a root cause of failure. If you wait until the unbalance generates “high” vibration, then you will have reduced the life of the equipment and supporting structure. That’s because the life of a bearing is inversely proportional to the cube of the load (see Fig. 2). Tranter noted that, while this calculation sounds very complicated, it basically means that if you double the load, a bearing’s life will be reduced to an eighth (23).

Tiny 3-µm particles cause more damage than 40-µm and 10-µm particles (Reference: A Study by Dr. P. B. McPherson)

Tiny 3-µm particles cause more damage than 40-µm and 10-µm particles (Reference: A Study by Dr. P. B. McPherson)

Lubrication. When you correctly lubricate bearings and gears, whether with grease or oil, and that lubricant is free of contaminants, you will achieve maximum life. But if bearings are not adequately greased, their life will be reduced. If the oil is contaminated, the viscosity is incorrect, or additives are depleted, then the life of gears and bearings will be greatly reduced.

Research was performed to determine which particles caused the greatest damage. It wasn’t the 40-µm particles or the 10-µm particles, it was the tiny 3-µm particles (see Fig. 3).

By the time you can see water in oil, the life of the bearing has been halved.

By the time you can see water in oil, the life of the bearing has been halved.

According to Tranter, personnel may think that if they can’t see water in oil then the oil must be fine. Sadly, that is not correct (see Fig. 4). By the time water can be seen in the oil, the life of the bearing has been halved. “We could continue the discussion,” he said, “but suffice it to say that there is a great deal we can do to avoid problems that arise due to imperfect maintenance and operating practices.”

#2. Cause of Reliability Problems: Desire and organizational culture

It’s one thing to understand all of the above root causes. “It’s another,” Tranter observed, “to obtain approval to establish standards and purchase all of the tools, such as laser-alignment systems, that enable technicians and operators to do their jobs correctly. But owning the tools and having standard operating procedures won’t solve the problem.” As he put it, the problem will only be solved when technicians and operators want to use those tools properly and are given the time and encouragement to do so.

Thus, the issue of “desire” and its link to organizational culture must be considered as a root cause of self-inflicted reliability problems and addressed accordingly.

#1. Cause of Reliability Problems: Inadequate management support

Tranter believes a strong case could be made that the root cause of all failures derives from lack of senior-management support for a culture of reliability. Without their support it will be impossible to change the culture and thus change behavior.

“Think about initiatives to improve safety at your plant,” he said. “If senior management didn’t support them, would those initiatives have been successful? Senior-management support leads to people being employed in safety roles, investment in training and tools, and posting of signage that provides warning and feedback on progress, among other things. It also keeps sites from cutting corners that would risk safety, and it makes it clear how important safety is to the future of the organization.”

According to Tranter, the type of management support that drives safety at a site needs to be leveraged to drive reliability improvement. “Everyone within the organization,” he said, “needs to understand that reliability is critically important to the organization and that senior management will stand strong when shortcuts that compromise reliability are available.” Without adequate senior management support, he concluded, meaningful culture change won’t occur, and reliability-improvement initiatives won’t be able to eliminate self-inflicted root causes of problems. MT

Jason Tranter, BE (Hons), CMRP, VA-IV is CEO and founder of Mobius Institute (Balnarring, Victoria, Australia, and Bainbridge Island, WA). For more information on this topic and other reliability issues, including vibration monitoring and training and certification of vibration analysts, contact him at jason@mobiusinstitute.com, or visit mobiusinstitute.com.

Where Does Condition Monitoring Fit?

By Jason Tranter, Mobius Institute

Condition monitoring plays several crucial roles in the battle against self-inflicted reliability problems. For example, providing an early warning of impending problems minimizes the impact of premature failure, and detecting and eliminating the root causes ensures that we achieve the greatest life and value from our precious assets.

Many plant personnel, however, believe that if they have a condition-monitoring program in place, equipment reliability will be optimized. That, unfortunately, is not true.

Most detected faults are avoidable. While it is important to get an early warning, it is much more important to avoid the problem in the first place. Condition monitoring can help by detecting the root causes of failure, including misalignment, unbalance, lubrication issues, and looseness, among others. If those problems are cost-effectively nipped in the bud, then we avoid future failures.

Another way condition monitoring plays a role in plants is in acceptance testing. As part of the purchase agreement, condition-monitoring specialists can perform tests to ensure the new or overhauled equipment is “fit for purpose.”

You may be surprised at how many problems you actually bring into your plant.

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