When it comes to sharing process data electronically, users confront a virtual Tower of Babel. Computers just don't communicate very well with other computers in matters like this. But chemical engineers have taken up the challenge through an initiative called the Process Data eXchange Institute (pdXi).
The exchange problem for process data is monumental, the equivalent of transferring written files between word processors as if there were no translators built into the word processing programs for importing such files. Essentially, the files have to be reentered manually.
To a large extent, that's just what happens in the process industries. Although a lot of process design data is in electronic form, large amounts of it are transferred between companies on paper.
In 1989, a proposal to address this problem drew the support of the Computers & Systems Technology Division of the American Institute of Chemical Engineers, and in 1991, pdXi was formed under AIChE auspices. Today, it has a roster of 23 sponsoring companies, which each contribute annual dues of $10,000.
The stated purpose of pdXi is to establish an ongoing institute to develop and maintain open approaches to electronically exchanged and managed process data between computer applications, databases, and organizations within the process engineering discipline and with other disciplines. "Process data" are by definition stream and equipment data and other data used to support the process engineering activity over the entire life cycle of processing facilities.
"pdXi has accomplished a phenomenal amount of work, very effectively," says pdXi technical director John Baldwin, a senior lecturer teaching plant design in the chemical engineering department at Texas A&M University, College Station. It has been receiving a lot of international attention, he says, adding, though, that "we are nowhere near the end of this road."
The problem faced by pdXi is a large one, but the benefits also could be substantial. It has been estimated that engineers spend 40 to 70% of their time manipulating data and that 10 to 20% of a project's cost could be saved if data could be exchanged electronically.
To get started, pdXi issued a request for proposals to develop the methods and tools needed. In late 1991, pdXi selected a contractor from among 10 competing bids. A seven-member multidisciplinary project team includes members from academic, commercial, and standards organizations and is headed by Neil L. Book, a chemical engineering professor at the University of Missouri, Rolla.
Early on, the team settled on an approach that adopts a neutral exchange format - namely an ASCII text file, common to all systems. This strategy makes data exchange independent of any of the systems involved.
Addressing the problem of data exchange is not as simple as it might first appear. For example, an early consideration for the team was to decide which stage in the plant life cycle to make the initial focus. For this, it chose the conceptual process design stage, leaving other stages such as engineering design, construction and commissioning, and operations and maintenance for attention in the future.
Three models have been developed to aid in the description of process data: a planning-level model that provides a means for relating other pdXi models, an equipment model that describes installed equipment with key process data found on specification sheets, and a simulation model that provides a description of components and physical properties, streams, and unit operations data used by simulators. Among other models are ones tailored for unit operations and for physical properties.
A significant effort has been development of a data model as a way to define protocols for storing data. Such a model encapsulates all relevant conceptual design information from operating companies, software vendors, engineering contractors, and equipment design manufacturers. All told, the current data model roster consists of more than 500 objects with more than 1,300 attributes.
pdXi has issued its specifications to a number of software vendors, according to Baldwin. "If there are other people who think they would be interested in providing software by the pdXi approach," he says, "we're interested in hearing from them."
Attention is now being given by pdXi to generating a practical demonstration of data exchange. The institute is also establishing a liaison with other standards groups to harmonize its work with and incorporate it into that of such organizations as the International Standards Organization and the National Institute of Standards & Technology. For the future, pdXi is looking to further extend the demonstration prototype and to extend models to other areas of the plant life cycle.
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