1 February 2006
Batch Standards Boost Sophistication
Smart manufacturers leverage standards, like tried-and-true ISA-88, to evolve into a more integrated system
By Jarrad Reif, Gavan Hood, and Ralph Kappelhoff
Batch manufacturers are under increasing pressure to enhance efficiency and agility, while maintaining or increasing flexibility in manufacturing across global systems—whether existing products and processes or new ones. It's a tough challenge. The ability to refine production processes is an art that requires a combination of expertise in process engineering and production information. For every achievement made in collecting and processing information, a new requirement arises.
Among manufacturers' typical challenges:
- Deploying systems across all plant areas with consistent operating philosophies that minimize operator training and facilitate moving operators between roles. (Systems should lead operators through the process and present clear information for decision-making.)
- Deploying systems across all plant areas with standard coding formats to minimize training requirements for maintainers and to reduce engineering and commissioning time.
- Developing systems that expose diagnostics information to eliminate the need for programming tools to troubleshoot operational problems.
- Capturing and aggregating process information from the control system and rendering that information so accurate, real-time decision making can occur based on quantitative data.
The best companies convert these challenges to opportunities to differentiate their systems from the pack. By taking advantage of emerging capabilities in the standards communities and the vendors supporting these standards, smart manufactures are armed with tools to make the transition to a holistic (raw material to end product, ERP to control system) integrated manufacturing system based on industry standards. New developments in standards are making the process easier and more effective.
Collaboration supports consistency
With so many standards in existence, standards committees must resist the temptation to create new standards and extensions without prior investigation of existing representations. In many cases, refinement of existing implementations or convergence with an existing standard can avoid duplication of effort and enable synergy among standards, leading to well-understood representations of manufacturing.
Over the years, ISA-88 has withstood the tests of adoption, support, and time with a substantial percentage of implementations in the batch processing industry. Products within the batch industry have evolved to represent implementations consistent with the standard as represented within ISA-88 Parts 1, 2, and 3.
A number of standards and guidelines exist in the industry. OMAC, ISA-88, and ISA-95 are converging to a consistent representation of manufacturing. A number of groups have formed to take the standard to new levels, including valuable work on ISA-88 Part 4 Production Records representation and ISA-95 Part 3 Activity Models of Manufacturing Operations Management.
Members of these organizations are actively coordinating activities to identify overlaps and promote consistency in the standards efforts. In some cases, these efforts have formal recognition with groups such as the ISA 88/95 Joint Working Group (JWG), focusing on identifying overlaps and improving consistency between ISA-88 and ISA-95 initiatives.
Another collaborative effort, the Make2Pack joint workgroup sponsored by WBF, OMAC, and ISA, has the charter for better integrating making and packing. These activities are representative of a trend in major standards groups toward consistency among the standards, which will open new opportunities for those that adopt standards in their organizations and will allow companies to take their organizations to new levels based on a consistent standards base.
ERP vendors are realizing the value of industry standards in integration with manufacturing. For example, SAP is integrating support for the Business to Manufacturing Markup Language (B2MML) WBF implementation of ISA-95 Parts 1 and 2 into their systems.
Control elements gain attention
An integrated ISA-88/95 representation allows consistent use of components across batch, packaging, and warehousing. This common representation allows consistent standards-based integration from batch to higher-level and adjacent systems. An end-to-end system representation will provide a holistic system-wide representation of manufacturing with no boundaries between production areas.
This holistic representation enables the goal of end-to-end tracking and tracing from raw material to product (as indicated by the red line) to transition from fiction to reality.
For many years, software products based on the ISA-88 batch control standard have been available to the batch industry. These products are now popular, but like any system, there are limits in terms of communications via phase logic interface with controllers.
The next generation of process controllers is representing equipment control elements, like equipment phases and ISA-88 state machines for example, explicitly within the controller.
The availability of these ISA-88 features out of the box in controllers enables practitioners to more readily utilize ISA-88 modular control concepts across the manufacturing plant beyond the process cell.
The ability to code complex equipment sequencing actions direction into ISA-88 state machine interfaces shipped in the controller exists and is important. This provides enhanced stability and the ability to execute time sensitive actions easier. The capacity to extend this capability to higher-level functions in controllers will provide more options for batch processing.
Modular control concepts studied
For many years, proponents of batch manufacturing contended ISA-88 modular control concepts are applicable outside the batch process cell.
The representation of control modules and equipment modules across industry segments is something worth pursuing. OMAC has taken batch concepts into the packaging domain.
A formalization of the adoption of modular control concepts across industry segments by ISA-95 and ISA-88 remains an active engagement.
Breaking down the plant into modules as defined in the ISA-88 models allows standard control modules to develop independently as long as the interfaces are standardized.
As a result, we are able to develop and share different modules at different sites. The sharing of standard code modules allows numerous reviewers to incorporate improvements that can then slot into all plants. This is similar to the philosophy in the Linux world of open source initiatives.
Having a consistent equipment hierarchy enables code reuse across manufacturers' facilities. Adoption of an industry standard model for modular control such as ISA-88 equipment and control modules enables vendors to better communicate with vendors and reviewers to provide input into improvements for the system.
Promises of tomorrow's systems
The plant of the future will incorporate a global view of all processes within the plant via the corporate intranet/portal; access to plant Key Performance Indicators (KPIs) real time via the corporate intranet/portal; use of expert systems to monitor plant performance and highlight poor performance in real-time and to optimize plant scheduling; use of real-time KPIs by operators to improve decision making; increased use of plant floor data to update corporate Manufacturing Execution Systems (MES) in real time, allowing MES to provide real-time insight of supply chain; and extension of tracking and tracing from transactional data at Material Requirements Planning (MRP) level down to time series data at plant floor.
The consistent models presented by the convergence of standards and availability of standards-based products in new form factors open many doors, including reuse of advanced batch modular control skills across the enterprise; dynamic systems that can be downloaded and configured in standard modules; new vendor-integrator-manufacturer relationships based on open systems; and original equipment manufacturers (OEMs) presenting systems in standard pre-tested and understood configuration to manufacturers.
The production record initiatives identified within ISA-88 Part 4 provide an opportunity to provide more auditable representations of production information.
To achieve this advanced level of tracking and tracing, production data should be stored in a manner that associates the data with context including products in fabrication, locations within a production facility, and the time at which the data came to be.
This transforms and elevates opaque production data into a valuable production information resource. The establishment of these associations often spans the entire system and multiple vendors.
The integration of the ISA-88 Part 4 standard with ISA-95 will enable the integration of production records with higher-level systems more consistently than is currently possible. The support of vendors for ISA-88 Part 4 will provide products from multiple vendors that share a common base for representation of production records and auditing of systems.
Move to more manageable systems
Standardization of control system coding around known state machine representations allows the development of consistent implementations in all production areas including batch and packaging areas:
- Leads to lower total cost of ownership (TCO) due to reduced training needs. Common skills applied across the manufacturing plant.
- Allows systems to be developed that will support all areas of the plant without customization to fit individual process areas therefore minimizing implementation time and spreading the benefit of the development time.
- Allows minimalist change and validation; modular systems capable of being managed at the component level resulting in better application of change management.
This new range of standards-based interoperability and convergence capabilities are nearing reality. The ability to move standardization of core batch processing capabilities directly into process controllers introduces a new technology to the batch industry.
These capabilities provide valuable tools for batch processors to leverage proven standards-based technologies into other areas of the manufacturing plant, reducing TCO of manufacturing through improved modularity and consistency across the manufacturing process.
The challenge tothe batch processing industry is to review batch-processing activities in light of these emerging and available capabilities and take their processing system to new levels of efficiency, manageability, and flexibility.
About the Authors
Jarrad Reif (email@example.com) is technology and systems manager at Carlton and United Beverages in Victoria, Australia. Gavan Hood (firstname.lastname@example.org) is senior systems architect at Rockwell Software in Queensland, Australia. Ralph Kappelhoff (email@example.com) is general manager at Rockwell Software in Milwaukee. The article is based on the authors' presentation at the World Batch Forum (www.wbf.org) in Atlantic City, N.J., in 2005.
EM: Equipment module
KPI: Key performance indicators are factors that directly and indirectly influence the effectiveness of a product or process.
Linux: An open source computer operating system that because of its robustness and availability has won popularity in the open source community and among commercial application developers.
MES: Manufacturing execution systems use network computing to automate production control and process. By downloading recipes and work schedules and uploading production results, MESs bridge the gap between business and plant-floor or process-control systems.
MRP and MRP II (material requirements planning): Phases in developing computerized methods to plan the use of company resources, such as raw materials, vendors, production equipment, and processes.
OEM: Original equipment manufacturer is a company that manufactures a given piece of hardware and sells it to a value-added reseller, which changes and repackages the hardware.
OMAC: Open Modular Architecture Control Users Group (www.omac.org).
TCO: Total cost of ownership is the cost to purchase and maintain software over time.
Application Example: Conveyors
Conveyors work in numerous industries to move everything from cartons and bottles to car bodies from one place to another. In some cases, conveyors space items on a line so another machine can perform the next process step on the product efficiently.
Here's an example of a spacer system. Within the spacer system are three conveyors:
Gap conveyor ensures each item has a minimum gap between them required by light sensors in the system. To achieve this gap, the conveyor must run at a faster speed than the in-feed conveyor so that gaps can generate.
Out-feed conveyor moves gapped items to the next location.
The out-feed conveyor speed must be at the same speed or faster than the gap conveyor, which runs at a speed faster than the in-feed conveyor. Thus, one can infer the out-feed conveyor must be running faster than the in-feed conveyor.
A user can manage this system using equipment modules (EM) and controls.
Control modules manage the control of drive devices for startup and speed changes of the conveyors. The equipment modules coordinate the drive control modules for each conveyor and in turn, the higher-level spacer equipment module coordinates everything.
The requirement of this conveyor system to coordinate the speeds of the three conveyors fits well with the application of equipment modules. Equipment module EM-Spacer is responsible for coordination of the three conveyors and their associated equipment modules—EM-Infeed, EM-Gap, and EM-Outfeed.
External systems can control the conveyor system via the exposed phases on EM-Spacer such as Start, Jog, Hold, and the rest.
S88 Stays Aware and Flexible
S88 is more than a standard for software, equipment, or procedures; it's a way of thinking, a design philosophy. Understanding S88 helps one to better design processes and manufacture products.
Leveraging the knowledge and experience contained in the standard enables you and your customers to identify your needs better, make recipe development easier, and reduce the time it takes to reach full production levels with a new system or for each new product.
By following the concepts explained in S88, you can improve the reliability of operations and reduce the automation life-cycle cost of ones batch processes, including lowering the initial cost of automating operations.
One very important way S88 does this is by isolating equipment from recipes.
When the code to run equipment and the code that defines a product recipe are in the same device, such as a programmable logic controller (PLC) or a distributed control system (DCS), the two different sets of code eventually become indistinguishable and in some cases inseparable. Every additional ingredient and process improvement can require many person-hours to modify the software.
Documenting such a system is difficult, which makes recipes tough, if not impossible, to maintain. Altering the process is even that much more complicated.
If recipes are at a higher level, as in S88-aware system, they are more flexible.
The person who knows what process changes are required—process engineers or lead operators—can make the changes directly. Control systems experts are not necessary.
Source: Applying S88: Batch Control from a User's Perspective, Parshall and Lamb, ISA Press 2005.
Defining the ISA-88 and ISA-95 Overlaps
The ISA-SP95 enterprise control system integration committee has been working with the ISA-SP88 committee to get experts together to ensure there's no disconnect between the two standards.
"There is a difference in audience between the two standards," said Dennis Brandl, president of BR&L Consulting in Cary, N.C., and chair of ISA-SP88. Some terminology can be confusing.
The ISA-88 standards deal with the control engineer's view and the process engineer's view of production and focuses on batch industry. The ISA-95 standards deal with the next levels up: the operational views, the plant supervisors, and production managers or operators.
ISA-95 also covers a broader range of industries. Therefore, standards writers expand on some words used in ISA-88 in the ISA-95 standards. "That was what led to confusion," Brandl said. "We're just trying to make sure there is no conflict."
Process management, a term in ISA-88, deals with controlling resources in a process cell. Inside ISA-95, there's an activity set called production execution management that includes process management, but it also covers more than process cells, such as production lines and storage areas.
"So all we're trying to do is clarify that with a technical report, here's where some of these words might be confusing. They appear to overlap, but they're really different concepts," Brandl said.
While there's no real plan to merge the two, he said, Brandl does point to an upcoming technical report that advises professionals to be aware that there are some of the same concepts in ISA-88 and ISA-95.
The committee members in ISA-SP95 want to point out the models manufacturers apply to batch can also apply to continuous and discrete manufacturing. "The names aren't quite right for those industries, but the concepts and the design patterns, the patterns included inside the standards, are the same," Brandl said.
In some industries are requirements for nonstop production, which means it flows all the way through the production facility. "You don't want breaks in production even as you switch from one product or grade to the next grade," he said. "To do that, we found we could apply the concept of product switchover recipes, and we could use the ISA-88 concept of equipment modules and control modules in this discrete manufacturing project."
With these models, any engineer looking at these systems will come up with the same solution. The SP95 committee has done the same thing in electronic assembly and the same in chemical production.
"Take food manufacturing," Brandl said. "You always have more products than production lines, so you're always doing switchovers. You want a minimum break between the times you're doing those switchovers. If we apply the ISA-88 pattern of equipment modules and control modules in how we program the PLC code, it will allow us to use recipes to do the switchovers, to do them in a consistent manner. You get repeatability. You don't get variability based on the operator's skill." —Ellen Fussell Policastro
ISA-SP88 Batch Control committee
ISA-SP95, Enterprise-Control System Integration committee
Batch babble begone: Standard interface builds common language
Applying S88: Batch Control from a User's Perspective by Jim Parshall and L.B. Lamb
The World Batch Forum: The forum for automation and manufacturing professionals