Comparative Analysis Four Different Ways of Calculating Yield Index SSS_pk Based on Information of Control Chart, and Six Sigma, to Measuring the Process Performance in Industries: Case Study in Aden’s Oil Refinery, Yemen

Abstract

Process capability index PCIs have long been used to assess process efficiency in the manufacturing. While PCIs assess the process stability and efficiency, real measurements of product quality depended on estimate the standard deviation for a short-term variance was calculated as the base approach in several previous studies for measuring PCIs. Studies in recent years seek to estimate shift of the process mean from target. In today's smart manufacturing production climate, manufacturers keep track of production performance. Since the deviance of process mean comparative to the target is different. This allows a more robust norm to be implemented by estimate the relative shift to describe the variance of process in Six Sigma (SS). For that purpose, this paper suggests an evaluation method by comparative analysis to four different ways of calculating yield indexes Spk based on six sigma and control information, of S X chart. Moreover, this paper extends the univariate process index yield SSSpk to a multi-generalized yield index is called SSMSpk. An established an updated approach to assess univariate and multi-characteristic, based on understanding variation which is critical to quality (CTQ) and focusing on the position and actions of natural process tolerance between defined tolerances limits. To demonstrate the trueness verification proficiency of this approach, this paper includes an industrial case study to assess the process efficiency in Aden's oil refinery, Yemen. The findings of this study indicated that the indexes which are calculating based on six sigma outperformed existing indices and that this study has important implications for industrial practitioners, researchers and quality control experts interested in the evaluation of process performance.

Monitoring, Evaluation, and Improvement Model for Process Precision and Accuracy

“…It is obvious that accuracy index δ and precision index γ are two important parameters of the process capability index, as well as two important indices for evaluating the process quality level. For example, when |δ| ≤ 1.5/k and γ ≤ 1/k, then the process quality reaches the k-sigma quality level [20]. Raising the process precision and process accuracy can increase the values of process capability indices as well.…”

“…As the process was statistically controlled, this study used the statistical testing method as well as applied the control chart data in statistical process control, in order to propose a model to evaluate process precision and accuracy. Plenty of studies have suggested that as the process quality attains the k-sigma quality level, the required conditions are (1) |δ| ≤ 1.5/k and (2) γ ≤ 1/k [20]. That is, when the accuracy index is bigger than 1.5/k (δ > 1.5/k), it is learned that the process is excessively shifted to the right of tolerance, so the process must be improved.…”

“…Apart from process capability indices, the six sigma method, initiated by Motorola in 1986 [15][16][17], is also applied by this study. The six sigma method is also a tool prevalently employed by the industry to assess and enhance process quality [18][19][20]. According to the research of Chen and Chang [14], when the standard deviation of the process is σ = d/k and the process mean shifted from the target value falls within 1.5σ, it means that the process has reached the k-sigma quality level.…”

X-bar Chart Based on Six Sigma to Continual Quality Improvement: Implementation on Oil Vapor Pressure Characteristic, at Yemen's Aden Oil Refinery

“…We plan to use 4.5 sigma to estimate the upper and lower control limits of the oil refining process in this study because 3 sigma estimation is inadequate. Despite the fact that there are a number of estimation approaches, studies have shown that 4.5 sigma is efficient at reducing variance and thus improving process efficiency (Chakraborti et al 2008;Schoonhoven et al 2009 ;Ravichandran 2016;Ali, Ghaffar, Al-Swidi, & Ahmad, 2021;and Almazah, Ali, Eltayeb, & Atta, 2021). Control limits can be determined using the following mathematical expression, given k as the sample size of n and 4 items with means the (d) is set according to this equation; as the constant (𝑘)…”

Construct the Optimum Process Model for Transistor Gaskets with Six-Sigma DMAIC

“…Not only can this process capability analysis chart measure the process quality, but it also can analyze whether the process defect is caused by excessive process variation or process deviation, providing engineers with suggestions and directions for process improvement [11,12]. Therefore, many studies have applied the process capability index to the process capability analysis chart as one of the tools which promote the improvement process of the six-sigma DMAIC method [13][14][15].…”