ISA-88.01
International industrial standard
The ISA-88.01 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 ISA-88 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 continuous 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 ISA-88 standard can be applied.
Before ISA-88.01: ‘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 executes 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.
ISA-88.01: Models and terminology
ISA-88 consists of models and terminology for structuring the production process. The main idea of ISA-88 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
ISA-88.01 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. ISA-88.01 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. Process engineers, without any detailed knowledge of equipment control, can develop ISA-88 recipes.
Recipes command equipment
When all equipment possibilities 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 instructs the equipment what function to execute, and in which sequence. That is how raw materials are processed into a certain end product. By applying ISA- 88 it becomes easier to put new products into the market, due to the elimination of programming new functions.
Control activity model
When producing a batch, equipment and recipes definitions are required. Batch process control is also equally important as well. For example scheduling, recipe management, process control need to be defined. ISA-88 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 ISA-88.01
The standard was published in 1995. Since then it has been applied all over the world. It is known that the application of ISA-88 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.