Process Monitoring with Multiple Product Grades

Abstract

In the continuous process industries, multiple grades of the same product are often made on the same production equipment. Key product properties for each grade are usually monitored separately because of inherent differences among grades. Although highly effective in detecting changes that affect individual grades such as changes in grade-specific raw material properties, this approach is usually slow in detecting changes common to all grades such as a drift caused by production equipment or changes in common raw materials. The case study of this paper illustrates a simple method of combining and monitoring data from multiple grades allowing speedy detection of changes affecting all grades and yet still permitting differentiation of overall process shifts from grade-specific shifts.

• Average Run Length
• Exponentially Weighted Moving Average
• Statistical Process Control

Additional information

Notes on contributors

Necip Doganaksoy

Dr. Doganaksoy is a Statistician in the Applied Statistics Program. He is a Member of ASQC.

Josef Schmee

Dr. Schmee is the Sharpe Professor of Management in the Graduate Management Institute. He is a Member of ASQC.

Mark Vandeven

Mr. Vandeven is a doctoral candidate in the Decision Science and Engineering Systems. He is a Member of ASQC.