Most likely, you’re familiar with S88, shorthand for ANSI/ISA-88, the standard that addresses batch process control. You probably also understand that S88 offers a lot more than just a standard.
S88 is a design philosophy for describing equipment and procedures that defines the physical model, procedures and recipes. In the context of recipe design, S88 helps to organize responsibilities and to clarify and simplify design.
For decades, Electronic Batch Records (EBR) have been designed through various modelling approaches including word processing, proprietary workflow charts and programming-like sequence definition.
Why not apply the elegance of a standard to design EBR recipes? More specifically, why not apply the S88 approach to the mysterious world of EBR recipe design?
Let me propose seven good reasons why manufacturers should.
- Lack of ambiguity. The EBR design process involves cross-functional teams. Basing the design process on a common, agreed-upon, standard that defines what the main building blocks of a recipe (procedure, unit procedure, operation and phase) look like and how they interact can save a lot of time.
- Common terminology. Manufacturers can ease requirement definition by using common terminology. As mentioned in number 1, EBR design involves cross-functional teamwork. Using identical words with identical meanings helps.
- Reusability. Lower design effort by ensuring reusability of already designed and tested sub-parts of a recipe. S88 features a modular recipe design based on clearly specified functional blocks with defined inputs and outputs. This provides the capability to reuse defined recipe elements as frequently as possible.
- Design clarity. S88 supports a highly structured approach for modelling recipes, but EBRs can be complex. It’s critical to have a clear and easy-to-understand way to describe the intended behavior of a recipe. In essence, an EBR is a workflow and many different modelling languages exist to describe workflows. S88 recommends the use of Sequential Function Charts (SFCs) for modelling and graphical representation. The beauty of using SFCs is that they show, in an easy digestible way, the WHAT, HOW and WHY aspects of a recipe, i.e., WHAT are all the main states of the recipe; HOW can the recipe progress to the next state, and WHY those changes would occur.
- Simplify integration with DCS. S88 design is dominant in DCS environments. The S88 approach to EBR recipes feels like a natural extension. Consider how much easier it would be collaborate successfully with automation engineering teams if both sides are using a common language and, more importantly, a common model.
- Validation. Because recipes are verifiable throughout the S88 design process, the testing phase is expedited. S88 recipe design includes a clear definition of rules and structures, which allows verification during the design process and provides early feedback to recipe authors. Of course, manufacturers can accomplish this using other modelling approaches as well, but the effort won’t be rooted in a common and agreed-upon way to do things.
- Simplicity on the shop floor. When it comes to executing an EBR recipe, perhaps the most important aspect is to minimize the intrusiveness of the EBR for operators. Execution should be as simple as intuitive as possible. The S88 recipe model provides an easy-to-understand, clearly guided method to execute even highly sophisticated recipes.
There are probably many more than seven good reasons to think about using the S88 recipe standard in the context of EBRs. In my mind, probably the strongest is #4, clarity. EBRs can be as complex as the process for which they are designed. Shouldn’t the recipe model be as simple as possible?
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