In simple terms, defect elimination is a continuous process of locating existing defects and eliminating or reducing their impact. Consider the difference between inherent and available reliability. Inherent reliability is a system’s reliability when operating under ideal conditions. The word “ideal” meaning from the proper engineering design, installation, commissioning, operation, and maintenance. All components work as intended, and no outside factors affect the system. Engineers and suppliers often label this value as the “design rate.”
From the Plant Floor is a new monthly column that explores reliability challenges faced by organizations and solutions to overcome them.
Available reliability is a system’s reliability when operating under actual conditions. This means that some components may not work as designed or intended, bottlenecks may be present, and there may be outside factors affecting the system. Different factors determine the defects that are already in your equipment, including conceptual and engineering design error, equipment fabrication errors, installation errors, and management errors. Here are some examples of how the errors manifest themselves and broaden the gap between the inherent and available reliability.
- Servo motor – six identical servo motors were used on a cartoner. After repeated failures over a multiyear period, a root cause analysis found that one motor location required a larger motor than initially designed based on the application. The time to troubleshoot and replace the motor was four hours for each occurrence. The design engineer standardized the motors to a single model to reduce the ordering and stocking requirements. Thankfully, the site developed the proper parent-child relationships in the asset hierarchy, and the technicians wrote work orders at the child level. It was easy to determine the motor replacements over the years were in one specific location.
- Bagger transfer – Randomly, the bagger transfer chute would vibrate free from the normal position, creating jams and product scrap from misalignment. While a nuisance to the operators, data analysis of the SCADA information determined that the error had driven $11k of downtime in the previous two years. Pinning the chute provided a permanent fix.
- Equipment bases and frames – Improper soil compaction testing and other geological faults significantly increased the building foundation costs at a new plant location. To cover expenses for the additional building/ soil reinforcements, carbon steel equipment supports and framing were used over stainless steel. After four years, the plant was forced to reduce capacity due to rusted equipment base and support failures.
You can undoubtedly come up with a list of opportunities within your facility. Interestingly, maintenance and operations personnel often know where the defects are. The problem is that no one asks them, and they don’t feel empowered to fix the issues themselves. That is one of the goals of a defect elimination program, to empower people to address the problems.
One place to start understanding the current defects in your systems is through critical event reporting. This approach to root cause analysis provides a threshold requirement such as two hours of downtime in a process area. Performing a level of root cause determines the potential roots, and the corrective actions are assigned for resolution.
A better approach is to create small teams focused on taking action within a specific boundary area. This small three- to six-person cross-functional team is empowered to identify and remove the defects. They can prevent the introduction of new defects too. As mentioned, often, the maintainers and operators already know many issues.
If your site already uses a root cause analysis software tool, odds are you can use the same system to track your defect elimination efforts. If not, a spreadsheet will work. Like a root cause effort, track the finds and resolutions to share with others. When documenting, list the required actions, who is responsible, the date to complete, reductions in downtime hours, labor costs, repair times, waste, and so on. Share the stories and their results frequently. These small wins build upon themselves to foster even more significant successes. What keeps you from getting started?
This story originally appeared in the July 2022 issue of Plant Services. Subscribe to Plant Services here.