Applying S88

By Jim Parshall and Larry Lamb

Reviewer: Nick Sands

Making batches of Chubby Hubby and Cherry Garcia is a great way to explain the practical side of automating a process using the ISA 88 series of standards on batch control (ANSI/ISA-88.01-1995 and ANSI/ISA-88.00.02-195). The authors were the control engineers at a Ben and Jerry's plant in Vermont. Their story starts with their old system and takes us through the whole automation project.

I am aware of the 88 series of standards, but honestly I have never read them (Who reads standards unless they have to?). Applying S88 strikes a nice balance between presenting the concepts of the standard and explaining the application of these concepts in a simple but interesting process (Who doesn't like ice cream?).

The key to the application of 88 appears to be the models; the procedural model, the physical model, the process model, and the control activity model. The models do get somewhat confusing, but here is where a real life example helps. There is also a discussion on states of operation and the transitions between states. The authors show the implementation of some of the batch logic in SFC (sequential function charts) and ladder logic.

I recommend Applying S88 for anyone who is not already an expert on the batch standard. The concepts are good to know even for those who work with continuous processes. It’s a quick read at 149 pages and not expensive at $49 for ISA members at www.isa.org.