Despite batchs growing acceptance, some potential users are still hesitant about trying it, especially if theyd only been considering a simpler type of automation. Ladder logic is still the king in terms of comfort. I think 80s% of the code we see is ladder, and the remaining 20% is IEC formats like sequential function block and standard text, says Craig Bransfield, engineering manager at Automated Control and Technical Services, a CSIA-certified system integrator in Bakersfield, Calif. When I pipe up and tell customers there are ISA-88 programs and models they can use, most get that deer-in-the-headlights look. But once we get them to try ISA-88, they say, Wow! This is great! It just takes awhile to get them to that point.
Bransfield adds that users are initially worried about new batch methods because they dont know if their staffs will be able to respond appropriately. Theyre concerned that the guy who has to come in at 2 a.m. on Sunday will be able to respond quickly and safely, and ladder still gives that warm fuzzy feeling that they can do it, adds Bransfield. Were very sympathetic to these worries, and so well spend half a day showing people on a laptop how well batch programs work until the concept sinks in, and theyre willing to rely on it.
Once batch is adopted, Bransfield reports that ISA-88s common jargon and handshake protocols can help increase users comfort level. If I walked into an application that someone else built years ago, and they used ISA-88, I would know just what to look for, he says. Its very comforting for customers to know that we can respond that well.
Experienced users say knowing how ISA-88 originated can help rookies understand it better and enable them to develop future solutions to meet the unique needs of their own applications.
AstraZenecas Ann Lindholtz uses ABBs System 800xA to increase vessel pressure, continuing a drug process and recipe in its batch protocol.
Bransfield adds that, When I first ran into ISA-88 years ago, it was what Id been trying to do by hand for years. I knew then that it would think like I do and that I wouldnt have to reinvent the wheel with every project.
Rob Purvy, senior consultant with Siemens E&As process automation division, explains, Batch approaches have changed along with technological advances. Were now living in a more Windows-based society, so thats meant changes for batch too. Before the mid-1990s, we did inflexible, monolithic batch code programming. This situation shifted when users began defining recipes in their PLCs or controllers. Then ISA-88 was able to separate equipment-control from recipe-development definitions. ISA-88 also gave everyone a common, flexible language for batch applications. Now chemical engineers can make flexible recipe changes and push through new products more quickly. As a result, ISA-88 is widely accepted, and users want to put in ISA-88 systems.
For example, Air Products plant in Wichita, Kan., recently completed the first of two phases of a migration from a 20-year-old continuous process control system to a Siemens PCS 7 (DCS) with Simatic Batch management software. The first phase was at the facilitys South Plant, a hydrogen reaction facility, specializing in polyurethane curing agents and additives (Figure 3). It normally produces 35 products, but can make up to 250 products.
The project team needed only 18 days to complete the new installation, which controls 75 unit vessels and 50 equipment modules. During the outage, the team installed the new PCS 7 system, made sure more than 2,500 I/O points were transitioned and tested the Simatic Batch configuration for production sequencing. Plant manager Ramon Lopez reports the new software will increase his plants capacity and improve visibility of its processes.
We now have a more precise way of making our chemicals, and it will be consistent, shift after shift, hour after hour, says Lopez. This reduces raw material costs. Being able to operate the equipment consistently all the time also will reduce maintenance. Reducing downtime by 5% is a big improvement. The Wichita plant has reduced material, labor and field installation costs by about 30% after one year of operation.
Branching Out and Up
Batch applications are evolving rapidly, moving into some new and unexpected areas, such as packaging, and even beginning to form links with the enterprise level, thanks to a working group combining ISA-88 and ISA-95 committee members. In fact, Dawn Marruchella, batch product manager at Emerson Process Management says efforts are underway by several non-batch industries to come up with ways to apply ISA-88 and ISA-95 methods to their own applications.
Other industries are finding that they must find standard ways to communicate, and then integrate with higher levels, says Marruchella.
Some companies are even building standards for their own software based on how ISA-88 does it, and then building a library of standard modules to reduce project work.
For instance, A-CTS Bransfield reports that he applied an ISA-88 batch design to help rebuild the co-generation engine at small, 500-kilowatt power plant operated by Crimson Resource Management in Castaic, Calif. The plant uses natural gas from its oilfield to produce electricity. I chose to arrange the generator and its engine as a batch design, but the one difference was that this application keeps the batch in a running state. Usually a running state has an endpoint, but this does not. It just makes power until the operator tells it to stop. This application has nothing to do with a traditional batch, but it was still highly adaptable to it.