A Short History of the World…of Batch
“Batch manufacturing has been around for a long time,” says Lynn Craig, batch guru and Process Automation Hall of Fame inductee. “Most societies since prehistoric times have found a way to make beer.” That’s a batch process. It’s one of the oldest batch processes. Food processing and the making of poultices and simples (early pharmaceutical manufacturing) are so old that there is no record of who did it first.
“The process consisted of putting the right stuff in the pot, and then keeping the pot just warm enough, without letting it get too warm. Without control, beer can happen, but don’t count on it. Ten years ago, or a little more,” Craig continues, “batch was a process that generally speaking didn’t have a whole lot of instrumentation and control, and all of the procedures were done manually. It just didn’t fit into the high tech world.”
In many cases, the way food is manufactured, and the way pharmaceuticals and nutraceuticals are made, differs hardly at all from the way they were made 100 years ago. In fact, this is true of many processes in many different industries.
What is different since the publication of the ISA S88 batch standard is that there’s now a language and a way of describing batch processes, so they can be repeated precisely and reliably, anywhere in the world.
The S88 model describes any process (including continuous processes) in terms of levels or blocks (See Figure 1 below). This is similar to the ISO’s Computer Integrated Manufacturing (CIM) standard, which uses a set of building blocks that conceptually allow any process to be clearly elaborated.
The highest three levels, Enterprise, Site and Area, aren’t, strictly speaking, controlled by the batch standard, but are included to explain how the batch standard’s language can interface with the business systems of the area, plant site, and business enterprise as a whole. The Enterprise is a common term for a complete business entity, while a Site is whatever the Enterprise defines it to be. A site is commonly a place where production occurs.
The second edition of Tom Fisher’s seminal book on the batch standard, Batch Control Systems, which was completely rewritten after Fisher’s death by William Hawkins, states that, “Areas are really political subdivisions of a plant, whose borders are subject to the whims of management…and so it (the area) joins Site and Enterprise as parts of the physical model that are defined by management, and not by control engineers.”
The next two levels, Process Cell and Unit, are the building blocks of the manufacturing process. Process Cell is used in a way intentionally similar to the widely used discrete manufacturing cell concept. One or more Units are contained in a Process Cell. A Unit is a collection or set of controlled equipment, such as a reactor vessel and the ancillary equipment necessary to operate it.
Within the Unit are the Equipment Module and the Control Module. The Equipment Module is the border around a minor group of equipment with a process function. An Equipment Module may contain Control Module(s) and even subsidiary Equipment Modules.
The Control Module contains the equipment and systems that perform the actual control of the process.
Since the introduction of the S88 batch standard, every major supplier of automation equipment and software has introduced hardware and software designed to work in accordance with the standard. Many of those suppliers are corporate members of WBF, which formerly was known as World Batch Forum (See Figure 2 below). WBF was founded by Michael Saucier, then at Honeywell, as a way to promulgate the use of the S88 standards worldwide. (See the sidebar accompanying this story for an interview with Maurice Wilkins, WBF’s chairman, and Lynn Craig, WBF’s director.
A Batch of Batteries
EaglePicher Technologies, in Joplin, Mo., is a manufacturer of battery technologies for defense, aerospace and commercial uses. Bruce Henne, an engineer at EaglePicher, uses Rockwell’s Batch and eProcedure software to control the batch processes he uses to make batteries and power supplies.
“We have a variety of operations,” Henne says, “from highly meticulous discrete processes that are entirely manual, to those that are ‘automatic’ but designed to have an operator in attendance 24 hours a day. Each of these operations is low volume, and that low volume and intense guidance equals both higher quality and good production.”
Henne uses the batch software for all of his processes. “I like the fact that I can use the same software for the whole gamut from our manual processes to our automated systems.”
Because much of EaglePicher’s output is destined for military and aerospace applications, its batch software needed to be robust, reliable, and able to be acceptable to the U.S. Department of Defense for its “track and trace” program. “There’s no tolerance for risk in the product,” Henne says.
“It is a very large task,” Henne continues, “to transfer a paper system to an automated software system, but it’s easy to do using S88’s unit cell concept. We’re using eProcedure manual phase control for batch. eProcedure hooked into a batch engine would be a real boon to batch processing. eProcedure is like Lego blocks…everybody here is excited about it!”
EaglePicher is still in the beginning implementation stage of its project. “We’re still in the early stages, but the ‘aha!’ for engineers and operators is that the framework stays the same with S88 instead of an ISO procedure and a traveler,” adds Henne. “Doing things consistently will reduce variability, and the numbers will go up on throughput, and go down on waste. We expect it to be a principal tool in the future.”
Henne says that the structure of S88 is going to continue to drive process improvement at EaglePicher. “One of my operators wanted to just go all the way to the SPC control charts,” he says. “The batch system has added feedback at a higher trust level, and the operators want to start using eProcedure as ‘instructions,’ so we can capture data and put it right into the database, replacing paper logs.”
Henne says that acceptance of batch processing theory by his operators has been excellent. “When they see it, they want it. We haven’t yet extrapolated design into our fully automated PLC-based stuff, because we’re focusing on the discrete manual procedures. The operators want to go all out.”
Some Batch Mythology
Control columnist Greg McMillan says (with his tongue firmly in his cheek), “Process control doesn’t apply to batch processes. Use that time-tested fixed sequence. After all, that batch cycle time is a tradition, and the golden batch sure looks shiny.” He goes on to point out that simply following the process flow diagram (See Figure 3 below) will not guarantee the optimal outcome. “Process engineers don’t think in terms of changing state,” he says. “They are used to seeing a ‘snapshot’ of the process, and trying to control a continually changing process to a snapshot. This doesn’t work well.”
McMillan points out that most process descriptions don’t take into account the variability of time in the process. “The process industry,” he says, “has large and variable time delays and time lags from batch-cycle times, vessel-mixing times, volume-residence times, transportation delays, resolution limits, dead band, and measurements.” Each of these must be accounted for in the batch control system.
Batching the Enterprise
The ISA S95 standard, Enterprise/Control System Integration, was developed in parallel with ISA’s S88 batch standard, and was developed by some of the same people from some of the same antecedents, like Process Automation Hall of Famer Ted Williams’ Purdue manufacturing model. In the past two years, S95 has been granted wide acceptance and adoption, with both enterprise automation giants SAP and Microsoft having decided that optimizing manufacturing operations requires more than counting “goesintas” and “goesoutas,” and knowing the cost of raw materials and labor. In the meantime, it has become clear that much of the discussion of S88’s upper levels describe the same territory as S95, but with somewhat different terminology. Consequently, a working group has been formed by the two standards committees to regularize the terminology of the two standards, so they can be used simultaneously and interchangeably to describe manufacturing from the control loop to the annual report.
WBF CORPORATE MEMBERS/SPONSORS
Automated Control Inc.
Bachelor Controls Inc.
Complete Systems Automation
Dow Chemical Co.
Emerson Process Management
|Honewell Industrial Solutions
IDEAS Simulation & Control
Novo Nordisk Engineering A/S
Siemens Energy & Automation
Yokogawa Industrial Automation
Many companies support the batch standard. Most suppliers have batch standard-compatible systems and software.
To Learn More…
The new, second edition of Batch Control Systems (ISA Press, 2006) by William M. Hawkins and Thomas G. Fisher, is one of the best places to start.
Another good book to add to your batch library is Applying S88: Batch Control from a User’s Perspective (ISA Press, 2000) by Jim Parshall and L.B. Lamb.
One of the best reference libraries on batch processing and the batch standard is the “WBF Body of Knowledge.” This reference library will eventually house all of the papers given at every annual WBF Conference. WBF produces two conferences per year, one in the U.S. and one in Europe. The 2006 WBF Europe Conference will be in Mechelen, Belgium, Nov. 13-15, and the 2007 WBF North American Conference, “Meeting of the Minds,” will be in Baltimore, Md., on April 30-May 4. More information on both conferences can be found at www.wbf.org.
The State of the Batch
ON AUGUST 15, 2006, Lynn Craig, of WBF (formerly the World Batch Forum) and a founding member of the SP88 Batch Standard Committee, and Maurice Wilkins, chairman of WBF, sat down with Control’s editor-in-chief Walt Boyes and talked candidly about the state of batch control and the batch standard.
Craig: We’re well past the tipping point. What we need to do now is bring a lot more people along, and we haven’t been terribly successful at it. WBF has, I think, provided a lot of information and help for people who want to understand. But we have entirely too many people out there in the industry who don’t understand the nuances of S88 yet.
Wilkins: S88 needs to get out to the other people it was intended to get out to, which include the process engineers and the plant engineers. It’s still seen as an automation kind of thing, and it needs to get out to the other guys who need to embrace it, too. Industry tends to see it as an automation thing, but it isn’t intended to be an automation thing. It sits in the automation environment, and it shouldn’t.
Craig: S88 is a beautiful, beautiful toy, and I call it that on purpose. It’s the kind of thing that management can understand, operations can understand, and process engineering can understand. It’s a tool for understanding amongst disparate groups. You have the modularity, so you can look at some grouping of equipment. You can talk about it. Everyone can understand what the other is saying. Too many of us in the automation world have been seen as the kind of geeks that speak a language that nobody understands, so “I don’t want to talk to them anyway.” This is a way to come out of the cave, and talk about how this process is going to run.
S88 defines a structure that can be used to understand most any manufacturing process, and can be applied to controlling and communicating about an awful lot of industry out there today.
I don’t think you can apply S88 to all discrete automation, but you certainly can apply it to a lot. You can also apply it, I think, to continuous. There’s a lot more to it that what’s written down in the standard. You have to interpret it for continuous process, but it’s very effective there. All it is doing is providing a structure to apply internally consistent procedural control to a manufacturing process.
I think in terms of applying S88 to a continuous process more in terms of the state that the process is in. Let’s face it, a continuous process has states. It has states during startup, and it has a fixed state where you’d like to have it run and never vary. What S88 does is provide the procedural control to get from state to state to state, until you’ve reached the proper state to run in. It’s a way to provide a control process from one stable state to another, desired stable state. It’s more than just starting up or shutting down. A lot of continuous processes will change products or grades on the fly. That’s a place where S88 can help a lot by institutionalizing the best practices and procedures for going from one state to the next.
Wilkins: I can upset the refinery guys by saying that the refinery process is one large batch. Batch was always seen as what you got relegated to when you weren’t good at doing the other stuff. It’s interesting that I’ve been schooled in both sides, and I find batch much more interesting. So to tell a refinery guy that it’s a big batch is a good way of upsetting him.
Question: Is that why S88 usage is lower in the petrochemical industry?
Wilkins: Yes. Batch has always been seen as somewhat inferior to their wonderful optimizers and things like that. Don’t get me wrong; those are wonderful control tools, but there’s a lot that batch can offer. There are so many applications and operations in a refinery or a continuous petrochemical plant that the batch standards could help with, but they just don’t use it. Oil movements are a good example. Startup and shut down of any one of a major unit, and recognizing and reacting to any abnormal situation…there is no common way that they handle those, and abnormal situation handling is becoming a big deal now. That’s something we have taken for granted in batch since the year dot. So I think there’s a lot of scope for the future there.
Craig: I think batch has an image problem, mainly because 10 years ago or a little more, batch was a process that generally speaking didn’t have a whole lot of instrumentation and control, and all of the procedures were done manually. People did batch, and it just didn’t fit into the high tech world. We fixed that with S88, but a lot of people don’t know it yet. S95 is there to deal with management of the entire manufacturing process. Manufacturing operations management is what it’s really all about. There are many different kinds of processes, many of which S88 can deal with. I see structured procedural control of continuous and discrete processes emerging as separate views of the same standard.
I can tell you what I think ought to happen next. S88 was written at a time when the problem to be solved was batch control. It is written in unabashedly batch terminology. A lot of that gets in the way of people understanding how to apply it to other kinds of processes. It seems to me that we’re going to have to have guidelines, or perhaps even separate standards addressing the various kinds of manufacturing using S88’s principles. I think that’s needed because the terminology and the language turns people off. They have to interpret, and a lot of people don’t like interpreting.
Wilkins: I agree that there’s more work to be done with S88. Coming back to S88 and S95, there are some needs in some industries to combine the two together into some kind of modular automation standard. There are some industries that will get scared off by the word “batch.” It was more than 10 years ago now that S88 was brought out, and it does need refreshing. There’s a need to bring all of the parts together, and I do know that the SP88 committee is starting to talk again about a revision, and that’s coming along too.
Craig: There’s an active working group looking at revising S88.01, and there’s also an active working group trying to define how S88 and S95 work together. I think S88 and S95 will work well together, once we get all the bugs out and all the lines of communication clear. One of the things holding back process automation technology is that we didn’t have good communication with the business aspects of the company. One reason MESs haven’t been as productive as they should be is that, in the past, they haven’t had good connections to the manufacturing process. So I think the linkage of S88 and S95 helps both the quality of automation and the quality of the management of that process.
Wilkins: The state of the batch is good. It is going in the right direction. The standards are in place, and all of the suppliers have control systems that address the issues around batch. There’s a lot of activity still around the standards, which is a good thing. As I said earlier, they just need to get adopted in a broader sense and in a wider sense. They need to reach more of the people they were intended reach in first place. In an adoption sense, they’re getting out there, but the people who need to understand them are still not getting it.
Craig: There’s still a lot to learn. A lot of people have to learn a lot. I think we need to get two or three things going at the same time. WBF has been trying to address these things, and has been for its entire existence, but formal education on the theory and implementation of batch control is still needed. We need to learn how to use this stuff, from the real nuts and bolts things all the way back to the theory. Continuous processes have developed a good deal of theory on optimizers and so forth, probably spawning more Ph.D theses than any other topic. We could use some of that in the batch and process automation worlds.