Process Engineering: Batch control sets the standard

It has been nearly a decade since the Instrumentation, Systems and Automation Society (ISA) introduced S88, its first standard for batch control systems.  Its still integral in optimizing operations today.

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In 1995, the Instrumentation, Systems and Automation Society (ISA), Research Triangle Park, N.C., introduced its first standard for batch control systems, now known as S88. Since the standard was introduced, most, if not all, automation system vendors have designed the modular, S88 control philosophy into their systems, or now provide software that integrates with their systems.

The standard was created to provide a common language and models for the design and specification of control systems for batch processing. It has the added benefit of allowing users to more easily integrate products from different vendors.

“Batch control is where automation starts,” says Lynn Craig, chair of the ISA SP88 committee and president of consulting firm Manufacturing Automation Association Inc., Medford, N.J. “Not only do you have to control the equipment, but the procedure.” To-date, there is no correlating standard for control of continuous, discreet or staged processes.

 The SP88 committee was formed in the 1990s. In 1994, the World Batch Forum (WBF), Longwood, Fla., a nonprofit organization, was formed to support and publicize the S88 standard.

The first part of the standard, ANSI/ISA-88.01-1995 Batch Control Part I: Models and Terminology, was published in 1995. It defines models and terminology for the physical plant, procedures and recipes of a batch process. “It really defines what batch control is and its structure,” Craig says.

The second part of the standard, ANSI/ISA-88.00.02-2001 Batch Control Part II: Data Structure and Guidelines for Languages, was published in 2001; the third part, ANSI/ISA-88.00.03-2004 Batch Control Part III: General and Site Recipe Models and Representation, was published in 2004. Craig says two additional parts will be published, possibly in 2006, which will address production recordkeeping and connecting third-party equipment, such as packaging equipment, to plant control systems.

Another standard, S95, is an outgrowth of the S88 standard. The ISA S95 standard for Enterprise-Control System Integration establishes common terminology for the description and understanding of manufacturing information in an enterprise. It also defines the information exchange between the manufacturing control functions and other enterprise functions, including data models and exchange definitions.

 “S95 is intended to connect the automation definitions in S88 to the business,” Craig says, citing SAP, Newton Square, Pa., as and example of one software vendor that has announced it will base its products on the new standard. Craig says a technical report about the connections between the two standards should be published this year.

The standard with the mostest
Christie Dietz, project leader for Emerson Process Management, St. Louis, says the S88 standard defines both physical and procedural models that are written once and then used as templates. Physical models define the equipment used in the process, such as unit, equipment and control modules, whereas procedural models, which include procedure, operation and phase modules, define the control that enables the physical models to perform tasks.

“DeltaV is based on S88,” says Emerson’s Kim Conner, product manager. “So right out of the box, users have the capability to configure recipes and modules based on the standard.” The user can defines these recipes by making connections between the various models and modules. For example, you might have a vessel (physical model, unit module) that at some point in the procedure must undergo filling or heating (procedural model, phase), Dietz says.
“Since you can reuse models, the front-end costs of building a system will be lower,” says SP88’s Lynn Craig. He adds that this will also help reduce the amount of training needed by those who use an S88-aware system.

Joachim Ruhe, Batch - MES business development manager for ABB, in Wickliffe, Ohio, says manufacturers can use S88 concepts to integrate third-party controls, such as a programmable logic controller (PLC), into any open control system that supports S88, S95 and OPC standards, such as ABB’s 800xA automation system. “The ability to make online changes to recipe parameters, sequence or equipment assignments is a key advantage of 800xA,” he says. “You don’t have to have to stop the running process to make any of these changes.”

Ruhe says ABB’s 800xA Production Management suite provides MES functions that automate, monitor, control and document current Good Manufacturing
Practices (cGMP) compliance for highly regulated industries in accordance to FDA’s 21 CFR Part 11. Components of the Production Management suite also can provide benefits in manufacturing processes of less stringently regulated industries to meet specific requirements of good automated manufacturing practice (GAMP) guidelines.

Emerson’s Conner says its DeltaV Batch automation system also helps manufacturers maintain documentation for 21 CFR Part 11 compliance, and it has the tools to design and implement Process Analytical Technologies (PAT) framework (PAT is an initiative supported by FDA to ensure quality in the pharmaceutical industry). “Chemicals may come under more regulation,” Dietz says, and a way to document compliance is already in place with S88.
Another benefit is that users can more easily compare proposals between S88-aware systems because they use a common vocabulary, says Mark Wheeler, vice president of manufacturing execution for Aspen Technology Inc., Cambridge, Mass.

“When we talk to a customer, or they talk to another company, everyone knows the language,” Emerson’s Conner says. “Everyone is on the same page.”

Whereas Emerson and ABB have worked the S88 principles into their automation systems, AspenTech markets separate software that integrates with an existing automation system. However, Wheeler says many of those who have implemented the Batch Plus software are using it for product development or scale-up, so it is not connected to an automation system.

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