Root cause analysis identifies and stops problems at their source

July 15, 2004
A garden with a dose of root cause analysis produces a bumper crop of long-term profit
American industry prefers quick, simple solutions. The problem is that they only address symptoms of problems, rather resolving the root causes of the problems. Instead, we ignore these problems or simply swap parts or implement random changes until the symptoms go away. Asset reliability and optimum life-cycle cost are essential in a worldwide economy. Historically, problems can be classified by their primary functional source.A difference of one word
The terms root cause analysis and root cause failure analysis are often confused. Both use identical methodologies. The only difference is the reason for the analysis , the trigger. Deviation from an acceptable norm may justify root cause analysis, but only equipment or system failure results in a root cause failure analysis.Root cause analysis provides a cost-effective way to isolate factors that result in problems. It can be used to resolve any problem that has a serious, negative effect on management, operations, maintenance and support of plants and facilities. It can identify incipient problems, isolate the problem's actual cause or forcing function as well as identify the factors that contributed to the problem.Digging deeper
Based on historical data, 15% of asset reliability and life-cycle cost problems can be attributed directly to the plant's sales function. Like other facets of business, sales seems to have lost sight of proven methods designed to load our plants with high-volume orders for standard products, which would promote effective asset utilization and support reliability and optimum life-cycle cost.Instead, plants are loaded with small orders, accelerated-delivery requirements and, in many cases, non-standard products. As a result of the plant having to forego best practices in production planning and scheduling, and with maintenance foregoing its preventive maintenance, profits disappear. In effect, the entire plant becomes reactive, captured by the demands imposed by the sales function.Because of the way sales operates, 22% of reliability and life-cycle cost problems are from failures within the production or manufacturing function. In addition to the restrictions that improper loading and backlog impose, there can be failures in planning and scheduling. This, and the resulting suboptimal procedures and practices used in production, generate problems that could be resolved using root cause analysis. This includes:  Failure to use the installed assets or plant capacity properly.  Outdated or ineffective standard operating procedures  Production practices that run contrary to best practices.  Operator errors caused by lack of proper training, supervision or morale.  Improperly adjusted and calibrated production or manufacturing systems.Maintenance failures contribute 17% to historic reliability and life-cycle cost problems. While the above limitations account for some of the maintenance deficiencies, most result from failure to follow best practices in the planning, management, execution and evaluation of maintenance activities.The plant and maintenance engineering function is responsible for 27% of reliability and life-cycle cost problems. The predominant failures include:  Improper design, selection and procurement of new capital assets.  Uncontrolled modifications and changes to existing assets.  Failure to apply root cause analysis universally to recurring problems in capacity, quality, cost and reliability.The procurement or purchasing function contributes an additional 11% to reliability and life-cycle cost problems. The predominant failures here include:  Buying capital assets and major replacements based solely on low-bid instead of life-cycle cost analysis.  Substitution of cheaper parts for MRO spares.  Lack of vendor qualification and assessment process.  Improper maintenance on MRO materials.The final 8% can be attributed directly to a plant management function that is driven by monthly and quarterly profitability, not optimum life-cycle benefits.The harvestThe following is an example of the effective use of root cause analysis, and it took place in a large, integrated steel mill. The plant was struggling with a substantial increase in the quantity and cost of rolling-element bearings. During a six-year period, the annual replacement cost rose from $2.7 million to $14.1 million. Root cause analysis revealed the reason was misapplication of predictive maintenance.When the plant established its predictive maintenance program, the mission was to eliminate unscheduled downtime. Therefore, as soon as a bearing exhibited any abnormality, it was replaced. The obvious result was excessive, premature replacement of every bearing in the plant.The root cause analysis didn't stop with the obvious , the maintenance program , but determined the underlying reason that bearings were exhibiting abnormal behavior. The result indicated the root causes of the bearing problems.  Misapplication accounted for 27% of the bearings. The underlying reasons included failure to specify bearings properly and electing to substitute less expensive, often light-duty, bearings.  Improper installation caused 22% of the bearing failures. The failure source was improper craft skills, lack of instructions and the absence of supervision.  Lubrication-related problems contributed 18% to the failure rate. This was a combination of improper lubricants, wrong methods and incorrect frequency.  Abnormal bearing loading accounted for 17% of the bearing wear. The root causes included improper operating practices and operator errors.  A variety of other factors, such as electrical arcing, caused 11% of the premature bearing wear. The root cause varied from poor maintenance practices to environmental and corrosive attack.   The final 5% was the result of bearings that had reached the end of their normal life.Of the $14.1 million spent, only $705,000 was for bearings that had reached or exceeded their rated design life. The remaining $13.4 million was an unnecessary cost. Armed with the knowledge gained through the root cause analysis process, corrective actions eliminated each of the identified root causes, as well as contributing factors. Crafts received training in proper installation and lubrication of rolling element bearings; rewritten procedures ensured proper bearings operation and maintenance; upgraded specifications and procurement practices ensured the purchase of proper replacement bearings; and increased first-line supervision ensured universal adherence to best practices. As a result of these changes, the annual replacement cost for rolling element bearings dropped to $750,000 and has remained constant, within $50,000, for more than 10 years.The bottom line is that we no longer can afford to put Band-Aids on the visible symptoms of the myriad problems that plague our plants. Instead, we must use root cause analysis systematically to resolve them once and for all.  Contributing Editor R. Keith Mobley is principal consultant at Life Cycle Engineering in Charleston, S.C. Contact him at [email protected].

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