O'Reilly logo

Statistics for Process Control Engineers by Myke King

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

2Application to Process Control

Perhaps more than any other engineering discipline, process control engineers make extensive use of statistical methods. Embedded in proprietary control design and monitoring software, the engineer may not even be aware of them. The purpose of this chapter is to draw attention to the relevance of statistics throughout all stages of implementation of improved controls – from estimation of the economic benefits, throughout the design phase, ongoing performance monitoring and fault diagnosis. Those that have read the author’s first book Process Control: A Practical Approach will be aware of the detail behind all the examples and so most of this has been omitted here.

2.1 Benefit Estimation

The assumption that the variability or standard deviation (σ) is halved by the implementation of improved regulatory control has become a de facto standard in the process industry. It has no theoretical background; indeed it would be difficult to develop a value theoretically that is any more credible. It is accepted because post‐improvement audits generally confirm that it has been achieved. But results can be misleading because the methodology is being applied, as we will show, without a full appreciation of the underlying statistics.

There are a variety of ways in which the benefit of reducing the standard deviation is commonly assessed. The Same Percentage Rule[1,2] is based on the principle that if a certain percentage of results already violate a specification, ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required