S88

S88.01

International industrial standard

The S88.01 standard is titled ANSI/ISA-88.01-1995, Batch Control Part 1: Models and Terminology. The standard has been accepted internationally. It was developed especially for the batch processing industry.

Batch processes

You will find batch processes in the chemical and pharmaceutical industries as well as food, beverages and paper industries. One characteristic of batch processing is that it is hard to preserve the batch identity if a batch is stored together with another batch. Another characteristic is that it is possible to make different end products with the same equipment. That is why a high amount of flexibility is required. The S88 standard provides a way to bring flexibility into batch control.

Continuous and discrete processes

Although the standard was developed for batch processes, it can also be applied to continuous and discrete processes. Examples of contiuous processes are water purifying and gas winning. An example of a discrete process is the production of cars. If in such processes a certain amount of flexibility is required, the S88 standard can be applied.

Before S88.01:
‘Equipment’ with hard coded procedures

In batch industries, equipment is used to process raw materials in a predefined sequence. Usually this sequence is programmed hard coded, for example in PLCs. The equipment is physically capable of executing other functions or execute existing functions in different sequences, but, because the sequence is hard coded, not all the possibilities are used. If you want to make a different end product with the same equipment, you will need the help of a control system engineer. This will cost time and money.

S88.01: Models and terminology

S88 consists of models and terminology for structuring the production process. The main idea of S88 is to separate equipment control from the procedure that describes how to make the end product. This is how it becomes possible to execute different procedures for different end products, using the same equipment.

Physical model

S88.01 provides a hierarchical model for structuring the physical equipment, which is called the Physical model. Based on this model the control system engineer programs all the possible functions of the equipment.

Recipes

The product knowledge is described in recipes.

S88.01 defines 4 different kinds of recipes: General, Site, Master and Control Recipes. Every recipe consists of different levels. The highest level defines the process described in the recipe. The lowest level shows what has to be done, step by step, to make the end product. S88 recipes can be developed by process engineers, without any detailed knowledge of equipment control.

Recipes command equipment

When all the possibilities of the equipment have been programmed, the process engineer can choose phases (basic equipment functions like mixing, heating, adding raw materials). The process engineer develops a recipe by putting these phases in the right sequence. The recipe will tell the equipment what function to execute, and in which sequence. That is how raw materials are processed into a certain end product. By applying S88 it becomes easier to put new products into the market, because often it won’t be necessary to program new functions.

Control activity model

When you produce a batch, you will need equipment and recipes. But there are also a lot of activities that are important in the control of batch processes. For example scheduling, recipe management, process control. S88 provides a model for these activities: the Control Activity Model. By using this model you can develop a flexible control system, in order to realize a flexible production process.

Results of S88.01

The standard was published in 1995. Since then it has been applied all over the world. It is known that the application of S88 can lead to a lot of advantages.

For example:

Improved flexibility
Improved through put
Improved use of capacity
Higher process quality
Improvement of production yields
Less operator actions needed
Improved conformance to functional specifications
Improved communication between suppliers, end users, consultants, system integrators
It becomes easier to integrate solutions of different suppliers
Reduction of time to market
… and so on.

Do you want to know the exact contents of the models and terminology of S88.01? Then attend the official ISA seminar.

Do you want to learn how to apply S88.01 in practice? Then attend the official ISA Training course.