Human Reliability: More Than Half the Answer

By Dr. Klaus M. Blache, Univ. of Tennessee, Reliability & Maintainability Center

My prescription for achieving reliability incorporates human reliability. This human element consists of people, processes (engineering and machinery/equipment), and products that lead to best practices and customer deliverables. In short, the better you do things, the more availability and throughput you get.

Reliability is about dependable engineering processes that support designing-in and sustaining machinery/equipment (M&E), maintenance practices to enable early detection of issues, and specifications that guide the purchase of maintainable M&E. Aspects to consider include:

• Accessibility
  • easing access in performing maintenance
  • eliminating the need for special tools to gain access
  • designing out the need to remove components and other items that haven’t failed to get to those that often do fail.
• Modularity
  • making each equipment module easy to handle by one person
  • ensuring that disposable modules are easy to reach
  • designing out the need to dispose of long-life parts by using disposable parts.
• Diagnostics
  • capturing enough data for problem analysis
  • analyzing faults and issues down to the component level
  • ensuring that performance data is captured and stored for analysis, supplier feedback, and internal continuous-improvement teams.

To me, maintainability refers to the “ease and speed of maintenance to return the system (people, process, machinery/equipment, and product) back to its original operating condition.” Maintenance is the repairing or servicing of a product or machinery/equipment. Maintainability is a design parameter (like the preceding examples) to minimize or optimize repair time.

Unfortunately, research shows that human error is still occurring at a high rate. Failure-rate studies have found that more than 50% of all equipment fails prematurely after maintenance work has been performed on it. This has been evidenced in many types of equipment systems and organizations. To better understand how human performance influences risk associated with nuclear power plant operations, the U.S. Nuclear Regulatory Commission (NRC) requested a study (INEEL/EXT-01-01166) that showed the average human-error contribution to the increase in risk was 62%. In the same study, maintenance practices and maintenance-work control errors were evident in 76% of the events, and operations errors were present in 54%.

What can be done? For new M&E, there’s an opportunity to design-in numerous maintainability concepts. More opportunity, however, is in existing facilities. A good first step would be to perform a PM Optimization (PMO) to eliminate any unnecessary tasks and related interventions.

A PMO will pinpoint if the M&E requires further design review, changes, and frequency in how those reviews are performed, or if they should be eliminated. Mature operations have lots of mistake-proofing and visual controls for operations. This technique should be expanded to include maintenance to support maintainability needs and reduce availability risk.

Human reliability is related to the field of human factors (ergonomics), which refers to designing work areas, work practices, and workflow to accommodate the capabilities of people (operators and maintainers). These factors can’t be ignored. This applies to all types of industries. According to the Occupational Safety & Health Administration (OSHA), 30% to 50% of your recordable injuries are somehow related to ergonomics.

Understanding and instilling human reliability, in turn, is the key in interconnecting the daily functional links to reliability and maintenance that drive real-world outcomes in availability. And it’s more than half of the answer. MT

Based in Knoxville, Klaus M. Blache is director of the Reliability & Maintainability Center at the Univ. of Tennessee, and a research professor in the College of Engineering. Contact him at kblache@utk.edu.