Plant Services - February 2008 - (Page 27)

ASSET MANAGER Why Six Sigma? Because three isn’t enough popular methodology that companies of all sizes and industries are using is Six Sigma. The technique is best known for its ability to reduce product and service quality problems. Although Six Sigma shares objectives with Lean (improved processes, waste reduction, increased productivity and greater customer satisfaction), the methodology is more data-driven, quantitative and statistically based than Lean. Be assured that maintenance departments can benefit from Six Sigma programs. A Statistics reflect reality Six Sigma provides systematic problem-solving using a variety of statistical tools and analysis. The term “six sigma” comes from the statistics measure of deviation from the mean. For normal distributions, 68% of the population should fall within one standard deviation – one sigma – from the mean. Similarly, 95% and 99.7% fall within two and three sigma, respectively. Six Sigma Assume a specification calls for a part 1.00 methodologies. DMAIC – define, measure, analyze, iminch in length, with 3 sigma being equal to This version 0.01 inch. With 3-sigma quality, you’d expect prove and control – is applied to existing parts to be within spec 99.73% of the time (a substandard business processes. Define estabdefect rate of 2.7 per 1,000 parts). This was the accepted lishes goals for improvement in line with customer demands quality benchmark in manufacturing before the emergence and overall business strategy. This might be hierarchical, of Six Sigma. such as improved return on capital employed (ROCE) at the However, some companies felt that a 3-sigma standard overall business strategy level, increased asset performance wasn’t good enough. Motorola, for example, observed that at the Operations and Maintenance departmental level, and a process could drift by about 1.5 sigma over time. In the reduced defects at the improvement project level. example above, this would cause the process mean to range Measure refers to tracking data related to the process usfrom 0.995 to 1.005, which might represent a significant ing reliable metrics relevant to the goals established in the shift for some customers. first step. Analyze involves using statistical tools and root Thus, keeping the data points within an acceptable range cause analyses to identify ways to minimize the gap between required a counterbalancing tightening of tolerance. For a current metrics and the desired goal. Improve means opti1.5-sigma drift in the mean (half of 3 sigma), the sigma levmizing processes based on analysis, using project manageel tolerance would need to be half, or plus/minus 6 sigma. ment and change-management techniques to ensure effecThe acceptable Six Sigma tolerance level is 3.4 defects tiveness. Control refers to process monitoring and control to per million opportunities (DPMO), that is to say at least correct variances before defects appear. It requires adjusting 99.9996599% of data points should fall within plus or minus policies and procedures, budgets, compensation and incen6 sigma from the mean. Although this really represents 4.5 tives, information systems, organizational structure and so sigma in a normal distribution in which the mean doesn’t on to ensure results sustainability. February 2008 www.PLANTSERVICES.com 27 drift, it’s considered Six Sigma because of the expected 1.5sigma process shift. Some experts argue that the 1.5-sigma process shift is more empirical than theoretical. In fact, any process mean that changes as much as 1.5 sigma should be considered statistically out of control, unpredictable and, therefore, at risk of producing defects, regardless of the customer’s specification limits. The good news is that with modern technology such as condition-based monitoring and control software, trends can be tracked for detection and correction of any significant process drift. Even with countless variations on the Even with theme, there are really two fundamental Six Sigma methodologies: DMAIC and countless DMADV. Both strive to achieve predictable, variations on performance, and are the theme, there defect-free “Plan-Do-Check-Act” similar to Deming’s approach. are really two Although the two frameworks have similarities, there are significant differences. fundamental http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - February 2008

Plant Services - February 2008 Contents From the Editor Letters The PS Files Up and Running Crisis Corner What Works Asset Manager: Why Six Sigma? Technology Toolbox: Ensuring a Calm Response Cover Story: Best Practices Awards Lubricants: A Slick Success Story Motors: Reliable Torque Compressors: Before You Call for Help Web Hunter: Exploiting Intellectual Capital In the Trenches Product Picks Classifieds Fast Facts Energy Expert: Energy, Climate and Food

Plant Services - February 2008

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