Julius Caesar usually gets the credit for "divide and conquer," but there's evidence he was just the most famous in a long line of ancient rulers to use it. That's the way with any great idea—everybody wants to make it work for them. Of course, breaking up a huge challenge into manageable chunks goes beyond beating armies and governing empires. For regular folks, it's terrific for homework and all kinds of personal and professional projects, too.
The version that's been sweeping the discrete and process industries for more than 15 years is the ANSI/ISA-88 standard, which has been getting a major boost from increasingly capable software and ever-faster microprocessors. They make control much simpler to apply in regular batch applications and enable S88's logical, flowchart-based principles to migrate to new settings more quickly and successfully.
Separation, simplicity and speed
One especially useful part of S88 is its decoupling of device control models from recipe control models, which makes it simpler and easier to reuse programming code and templates, adjust applications and build new systems (Figure 1).
“With model-based control, one controller program can be configured to control a wide variety of process cells—similar to how Microsoft Excel is used to solve a wide variety of engineering or financial problems," says Tim Matheny, PE, president of system integrator ECS Solutions Inc. in Evansville, Indiana. ECS is a certified member of the Control System Integrators Association (CSIA). "The program doesn’t change, like Excel doesn’t change. The data model that represents the process cell changes like the data that represents the engineering or financial problem changes. Model-based control for the basic process control system is an exciting innovation in batch process automation because it's very agile—quick to develop and quick to change.”
For instance, when Monin's flavoring syrups plant in Clearwater, Florida., reached capacity twice as fast as expected, its process engineers and managers knew they had to update their manual batching procedures and automate their numerous recipes in compliance with S88. Monin worked with system integrator Altra Systems in Orlando, Florida., to integrate plant-floor and enterprise data, improve recipe formation and management, and integrate with its Navision enterprise resource planning (ERP) system. As a result, Monin implemented FactoryTalk (FT) Batch, PhaseManager, PlantPAx Process Objects software library and other solutions from Rockwell Automation.
"The future for Monin is completely integrated manufacturing, so IT and process control must be joined together," says Armando Di Francesco, technical manager at Altra Systems. "Plant PAx software objects gave us many tools we needed, gave us control modules for our process and still saved 30 to 50% on the engineering and programming hours we would have been required to spend otherwise. We used PhaseManager to integrate the ControlLogix PLCs with FactoryTalk, and it simplified our phase programming and also reduced the time needed to develop phase templates for common tasks, such as agitating, mixing and adding ingredients.
"These six or seven templates are stored in FT Batch Server, where they can be filled with data from our 200 recipes. Also, if we need to change recipes or add new ones, it's easy, and we even have eSignatures for different operations to check who did what and comply with electronic batch record (EBR) requirements."
Switching skills to S88
Perhaps because batch control started out in discrete manufacturing, some potential users have been reluctant to adopt batch techniques in their process applications. This attitude has been shifting as they understand that continuous processes can be divided and organized into the stages, operations and actions in S88's process model, but many users still need to learn some new abilities.