difficult and discouraging for ladder-logic programmers to document their programs.”

MES brews better beer

Software for managing revisions to PLC algorithms and HMIs are not the only tools available for this task. Often, the MESs that operate above PLCs and below the enterprise resource planning (ERP) system have this ability built into them. “Tools built into our infrastructure let you manage the HMI graphical code, alarm-and-event detection, and the integration with devices and other software, such as databases and ERP applications,” says Steve Garbrecht, program manager for infrastructure and platforms at Wonderware, a Lake Forest, Calif.-based software unit of Invensys.

SABMiller Plc, the world’s second-largest brewing conglomerate, decided to exploit this fact when it built its Ibahyi brewery near Port Elizabeth, South Africa. As it went about building a showcase facility, it tested a number of technologies, including Wonderware’s ArchestrA architecture. The company learned to use it to synchronize changes both locally and globally so the company could improve the efficiency of its operations, yet ensure that its beers taste the same everywhere in the world.

ArchestrA’s interoperability was crucial “because of the variety of different platforms and systems we use in each brewery,” explains Thinus van Schoor, automation manager at SABMiller. Built on Microsoft’s .Net infrastructure, the architecture ties disparate systems together and propagates revisions in a controlled manner.

Software developers can define standards and create templates that allow reusing common sets of code for the next set of applications. “If you had several batch reactors, for example, you would create standards for monitoring and controlling a batch reactor,” says Garbrecht. This would include such things as defining feedback mechanisms, reports and overall management of the operation. As users create these standards, they write the documentation, which becomes embedded in the application’s code.

As is the case with systems used at Sanofi-Aventis and NEC, the software requires users to log in before they check an object out. Each object has a set of permissions associated with it, giving only certain people access to specific chunks of code. “Only some developers will be able to modify the base template, which is the source of the application,” says Garbrecht. “The others may only be able to modify objects that are derived from that standard.” In each case, the software asks for comments on whatever changes were made when the developer checks the changes back in. The historical archive keeps track of when changes were made and who made them.

Creating the standards and templates took a little extra time, but the company reaped significant dividends from the investment. After testing and refining them at a couple of breweries, the company was able to install them in what Garbrecht calls a cookie-cutter approach that cut installation time by as much as 70 percent in some plants.

For more information, search keywords “version control” at www.automationworld.com.