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.

“Users can simulate their process using Batch Plus without making a big investment in materials or equipment,” he says.

Systems built around the S88 standard are more accepted in regulated industries, Wheeler says. He estimates that about half of Batch Plus users are specialty or fine chemicals producers, and the other half are pharmaceutical manufacturers.

The Batch Plus program allows the user to build recipes, and the Batch.21 historian supports 21 CFR Part 11 compliance needs. “Batch.21 collects data from control systems or other platforms and uses the same hierarchy as S88,” Wheeler says.

ABB’s Ruhe has been involved with the SP88 committee since shortly after its inception. He says that S88-aware systems can provide a seamless and complete integration of computer and control systems. If a control algorithm is changed in the control system, the recipe in the computer system can be automatically updated.

“With an integrated system, you don’t have the nightmare of managing multiple databases,” he says. “There are no data concordance issues since the data is entered once – the ‘single source of truth’.”

Much to gain, little to lose
Better control of any process will contribute to improved operations. Craig says one of the main operational benefits of the standard is reduced variation. “S88 makes processes more schedulable,” he says. “If the schedule is optimized, then you can make more product more predictably.” This could result in 10% to 15% more throughput, he estimates.

Leo Charpentier, Columbia, Md.-based product marketing director for NovaTech LLC, says the modularity of the software makes it easier for a supervisor or engineer to make process changes, including during the night shift. This can reduce downtime and emergency trips to the plant during the night. “The plant is less dependent on control engineers,” he says.

Charpentier, who has been a member of the SP88 committee since the beginning, says S88-aware products, such as NovaTech’s FlexBatch software, allow batch processors to run shorter cycle times. Since the recipes are automated, equipment can be used for the next step as soon as it is available. “This allows operators to spend time addressing problems, rather than closely monitoring the progress of the batch,” he says.

FlexBatch runs on a Windows-based system, and integrates with NovaTech’s D3 automation system. After users install the software, they go through a configuration step and can then build their application.

Eastman Chemical produces several batch intermediate chemicals at its Kingsport, Tenn., site, where it uses FlexBatch, says Mike Eads, systems technical associate. He says implementing the S88-aware software required about three man-years to build the applications (defining accurate operating procedures for making the chemicals, writing sequence and batch language (SABL) programs, and developing the Master Recipes).

Eads says the biggest benefit of the system is standardization. “Each batch is produced using a Master Recipe for each product embedded in FlexBatch,” he says. “The result is products that are made in the same manner batch after batch.” Eastman uses FlexBatch on two batch processing lines that produce a variety of products.

Although Eastman’s control system requires permission from operators to proceed to certain steps, about 75% of the process is now run by the software, providing reduced batch cycle times. Eads says operators have to give permission to perform certain operations where the DCS cannot determine the necessary information, such as a tank level, visual inspection of certain intermediate products, or steps that require action by an operator for safety reasons.

Bob Fink, Croydon, Pa.-based senior process control engineer for Rohm and Haas, says the company has been upgrading plants without recipe-level automation and those that have an older in-house legacy system to Emerson’s DeltaV Batch. Additionally, plants built in the past several years have the automation system. He says about a dozen sites now use the S88-aware system.

Fink says it took engineers about a year to build a library of modules that they now connect to create recipes. “You don’t need someone with control expertise,” he says. “A process engineer can develop or make changes to a recipe in the new system.”

Fink counts quality and productivity improvements among the benefits of a system based on S88 principles. Product quality is more consistent on a batch-to-batch basis, whereas the system can coordinate different operations at the same time. “The main benefit is the flexibility,” he says. “We can now make changes easily to a system that makes a lot of different products.”

“S88 recommends a modular approach to automation, but gives no guidance about how to go about it,” says Dave Chappell, section manager for Procter & Gamble (P&G), West Chester, Ohio. “It’s a high-level standard.”

Since a large number of P&G’s products are made by batch processing, it was important to develop a method to automate as many of its batch production systems as possible. Chappell says P&G licensed a recipe-management system and then developed an in-house automation approach that would direct a truly automated engineering process for the design and automation of the company’s batch processes. P&G then licensed this system to ATR Systems Inc., now known as Siempelkamp, Cambridge, Ontario, in 2001.

Andrew Weatherhead, manager of the batch and process systems group for Siempelkamp, says it began marketing P&G’s system as Batch.Objects in September 2003. The company provides automation systems to various industries, however the clients that operate in batch mode are mainly in the consumer-products and pharmaceutical sectors.

Siempelkamp’s Batch.Objects allows users to build their systems by working from a library of standard templates and PLC control modules to construct a project within a development environment. “The system is more plug-and-play,” Weatherhead says. He estimates a three-to-one reduction in development time using Batch.Objects, as well as reduced cost of ownership.

Weatherhead says the main benefit of using Batch.Objects is standardization. “A project that is built around standards, such as ISA’s S88 standard, is a great step towards simplifying development and providing a solid framework which will improve long term maintenance” he says. “Our system also makes use of the ISA S95 standard.”

SP88’s Craig says S88-aware systems can also improve operator training because the modules work the same way every time. This results in better procedural control, which can boost throughput – and possibly yield.

Fink says Rohm and Haas uses Mimic simulation software from Mynah Technologies, Chesterfield, Mo., in conjunction with the DeltaV Batch automation system to train operators. The training can be done on the actual system hardware, or on dedicated hardware.

A standard for the future
“S88 is more broadly used than we originally guessed,” Craig says. He says makers of specialty chemical and consumer products were the first to embrace the control standard. But pharmaceutical manufacturers might now be the biggest proponents, he says.

 “Most any control system introduced or upgraded in the last 10 years is, to some degree, compatible with S88,” Craig says. “Nearly all of the batch control systems are based on the standard.”

Although the S88 standard will effectively be complete in the next year or two, Craig says a corresponding standard might be written for continuous process control. “You can think of a continuous process as a very long batch process,” he says. “Start-up procedures can get you into trouble.” It might be easier for manufacturers to avoid such trouble if start-up and shutdown procedures were automated.

P&G’s Chappell is a charter member of the SP88 committee. He also is chair of the SP88 Make2Pack working group, which is sponsored by the WBF, SP88 and Open Modular Architecture Controls (OMAC). The Make2Pack project will develop conceptual models and terminology for industrial automation that can be applied to the total manufacturing process. The initial focus will be on packaging and converting machinery, and batch processing equipment.

“The group will develop a standard way to do automation,” Chappell says. “I expect the effort will apply to all manufacturing automation,” such as continuous processes, not just batch.

In the mean time, Craig says several papers have been written about applying S88 to continuous processes, especially in the food and beverage industry.

“It’s all in there,” Emerson’s Conner says of the DeltaV Batch. “Continuous processors also have the capability to configure recipes and use the modules.”

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