By Nick Basta, Contributing EditorEconomic pressures and regulatory uncertainties are forcing many drug manufacturers today to operate in “hurry up and wait” mode. “Capital expenditures have to be made as late as possible in the drug-manufacturing process, yet companies must be ready to implement them once drugs meet regulatory approval,” says Lou Pillai, IT team leader at Pfizer, Inc. (New York, N.Y.).“Process design and specification used to be a somewhat unstructured process; now there’s a language and a methodology that allows everyone involved in design and process control to communicate with each other.” Modular construction (see Pharmaceutical Manufacturing, September 2004, p. 36) is helping drug makers manage these pressures in new plant construction. But for plant design, specification and validation, standards developed in the process control field are having a far-reaching impact on drug manufacturing. S88 (see sidebar, below), which originated as a way to write control logic for batch processes, has become a preferred route for designing and specifying all the production equipment in a pharmaceutical plant.The standard, first established in the 1990s by the World Batch Forum under the imprimatur of ISA International (Raleigh, N.C.), began as an approach to process control for batch manufacturing. It has also influenced a broader, parallel program, S95, “Enterprise Control System Integration,” designed to rationalize how information leaves the plant floor and is transferred to enterprise IT systems.Simple structure, significant benefitsS88 is grounded on three principles:
Historically, batch processing has suffered from a wide divergence in how control engineers dealt with their tasks. “Designing” a control system for a batch process could range from scribbling instructions on a sheet of paper to let an operator know which status lights to watch, to implementing elaborate control processes often run by programmable logic controllers. Batch automation systems from control vendors can tie these disparate elements together, but the reality has always been that other, separate process units had to be tied to the batch system in some fashion.The batch automation “movement,” if that term can be used, aimed to set some standards. It kicked off with the formation of the World Batch Forum (www.wbf.org; Phoenix, Ariz.) in the early 1990s. The forum brought together control engineers in batch-intensive industries, equipment vendors, and software developers who were exploiting the new capabilities of PC-based control. Members began a multi-year effort to establish a new standard, now known as ANSI/ISA S88 (and IEC 61512-1 in the international arena). Much of Forum’s work was to define a common language—concepts that meant the same thing from project to project, or control system to control system.S88 requires the use of object-oriented programming to conceptualize batch control, and specifies that the recipe be separated from the process unit or control system where that recipe would be executed. It then shows how to do this in such a way that the same recipe could be run on different process units, as long as those process units had comparable processing capabilities. The reusability also means that once a “library” of process and recipe models was defined, writing the actual control code could proceed rapidly from those generic models. Although there are numerous subclassifications, the basic elements of S88 are as follows:
- Batch functions should be modular sequences of such actions as filling, heating or drying;
- The “recipe,” or procedural steps, should be written independently of the equipment in which the actions are performed;
- The “logic,” or capabilities, of the equipment should be captured in a data file.
- Rockwell Software (Milwaukee, Wis.) employs S88 methods in RSBatch, for developing control programs, and RSView, its human-machine interface (HMI) software for displaying production activities. Without S88, the company says, writing batch code for its programmable-logic controllers can consume 50-60% of an automation project’s time; S88-based software allows this time to be cut to 15%.
- Honeywell (Phoenix, Ariz.) offers its POMS manufacturing execution software with S95 compliant features.
- Invensys’ (London) Wonderware subsidiary features InBatch software for manufacturing execution.
- ABB’s (Zurich) Industrial IT division offers Produce IT, claiming as much as a 50% reduction in implementation costs through S88 methods.
- Siemens Energy and Automation (Alpharetta, Ga.) deploys both its APACS+ batch control software and SIMATIC IT manufacturing execution technology with S88/95. The company claims that the largest “paperless” biotech plant in the world, Genentech’s Vacaville, Calif., facility, saved nearly $5 million in implementation costs by going this route.
- Emerson Process Management (Austin, Tex.) incorporates S88 standards into its DeltaV automation software; in addition, its project services organization has a “Project Builder Library” of predefined models that are used to define control system structures and components according to S88 definitions.
Historically, batch processing has suffered from a wide divergence in how control engineers dealt with their tasks. “Designing” a control system for a batch process could range from scribbling instructions on a sheet of paper to let an operator know which status lights to watch, to implementing elaborate control processes often run by programmable logic controllers. Batch automation systems from control vendors can tie these disparate elements together, but the reality has always been that other, separate process units had to be tied to the batch system in some fashion.The batch automation “movement,” if that term can be used, aimed to set some standards. It kicked off with the formation of the World Batch Forum (www.wbf.org; Phoenix, Ariz.) in the early 1990s. The forum brought together control engineers in batch-intensive industries, equipment vendors, and software developers who were exploiting the new capabilities of PC-based control. Members began a multi-year effort to establish a new standard, now known as ANSI/ISA S88 (and IEC 61512-1 in the international arena). Much of Forum’s work was to define a common language—concepts that meant the same thing from project to project, or control system to control system.S88 requires the use of object-oriented programming to conceptualize batch control, and specifies that the recipe be separated from the process unit or control system where that recipe would be executed. It then shows how to do this in such a way that the same recipe could be run on different process units, as long as those process units had comparable processing capabilities. The reusability also means that once a “library” of process and recipe models was defined, writing the actual control code could proceed rapidly from those generic models. Although there are numerous subclassifications, the basic elements of S88 are as follows:
- a physical model of a manufacturing process, which is a description of what the process does, and what its capabilities are.
- a recipe, which describes the formula (the physical ingredients of a batch) and what actions are to be taken in what order. The recipe is written as a procedural model, which can be subdivided into unit procedures, the unit procedures into operations, and the operations into phases.
- the equipment logic, which is the description of how the procedure is implemented.