Looking for a way to implement a flexible production strategy without breaking your budget or spending weeks or months writing new software code? The answer can be found in ANSI/ISA-88.00.03-2003, a control industry standard that establishes best practices for automating batch manufacturing plants and batch control.
Although originally designed for batch manufacturing processes, the ISA-88 standard is also helping users save time and money in automating continuous production processes.
Common Process Control Language
ISA-88 accomplishes this by defining a common language for process control to improve communication between the various players involved in controlling plants and production processes. It also creates a structure with consistent concepts and models for batch processes that provides a map for how developers should organize their software code.
The standard sets forth a set of building blocks for process control at all levels: enterprise, site, area, process cell, unit, equipment module and control module. The three highest levels explain how the standard’s language can interface with the business systems of the area, plant site and business enterprise as a whole.
The next two levels, process cell and unit, are the building blocks of the production process. One or more units are contained in each process cell. Each unit is a collection of controlled equipment.
Within the unit are the equipment and control modules. An equipment module defines a small group of equipment with a process function and can contain control modules and subsidiary equipment modules. The control module contains the equipment and systems that perform the actual process control.
Universal Structure
The standard can be applied to either simple or complex processes, so that one programming system can be used for all production processes in a plant. Using this methodology, users and programmers can:
- Identify the structure and format for recipes and procedures;
- Define levels of recipes and procedures;
- Recognize product-specific recipes and procedures that are separate from processoriented equipment and its direct control;
- Identify a hierarchy of manufacturing equipment and its dedicated control;
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Recognize equipment capabilities used during recipe and procedure driven
production; and - Recognize the need for modular and reusable control functionality.
Reusable software code blocks are central to the ISA-88 standard and are programmed using IEC 61131-3-compliant software, which is available from all major automation vendors. Code can be programmed in ladder diagram as well as structured text, function block diagram, instruction list or sequential function chart languages.
Each vendor includes libraries of reusable control modules and algorithms that define common machine functions and recipe steps in their software. Once the initial process or recipe has been programmed, modular code blocks can be reused for the same functions with minimal modifications. This eliminates the need to reinvent the wheel for different recipes, and allows future changes to be made almost dynamically.
According to industry experts, users typically achieve a 30 percent savings in programming time and costs for the first project, and as much as 70 percent savings on subsequent projects.
Broad Applicability
Industry experts say an estimated 50 percent of all U.S. manufacturing is now accomplished using techniques and technologies consistent with the ISA-88 standard, which has been proven in thousands of applications and can be applied in either DCS or PLC control environments.
The ISA-88 standard can be so widely applied because its central objectives are to:
- Reduce a user's time to reach full production levels for new products;
- Enable vendors to supply appropriate tools for implementing batch control;
- Enable users to better identify their needs;
- Make recipe development straightforward enough to be accomplished without the services of a control systems engineer;
- Reduce the cost of automating batch processes; and
- Reduce lifecycle engineering efforts.
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