Draw to a CONCLUSION

It's often been said that the latest advances in information technology are inventions waiting for an application. However, designers of process plants are finding that systems such as electronic mail and the Internet, by removing the barriers to information transfer, are becoming invaluable tools.

For companies based in high-cost regions, some of these ITtechniques have allowed design to become a truly international process, with large savings in both time and money, and improvements in quality.

One of the key factors here is the development of intelligent piping and instrumentation diagrams (P&IDs) - electronic documents that contain equipment specifications, engineering information and other data. Once the intelligent P&ID is developed, it is easy to transfer it around the world electronically, and update it whenever needed, so that all designers are working from the same database.

Saving time

This approach has many advantages, as Toyo Engineering has discovered. The company, founded in 1961 as a subsidiary company of Mitsui Toatsu Chemicals, designs and builds plants for gas processing, oil refining, petrochemicals, fertilisers, nuclear power and discrete part manufacturing. Working with many engineering contractors and process designers, including MW Kellogg, ABB Lummus and UOP, involves a great deal of information transfer and co-working between departments. Toyo's switch to an intelligent P&ID system dramatically cut detailed design costs by distributing its workload around the world based on cost and skill factors.

Labour costs in Japan have risen so high that engineering companies based there cannot compete without distributing their workload globally. The problem that this raises is being able to share complete and error-free engineering data between all of the different disciplines involved. The greatest difficulty is keeping designers, who might be thousands of miles apart, synchronised with the latest information about the process.

Toyo is currently on its third generation of computer aided plant engineering systems. The first generation was a 2D CAD system running on a mainframe-based central engineering system. In the mid-1980s, the mainframe was scaled down to engineering workstations and personal computers, and design calculation programs and spreadsheet applications were developed. The third generation, begun in the early 1990s, uses PC networks and client-server technology.

separate schedules

In the traditional working procedure, companies would create separate schedule sheets from P&ID documents and related design documents, such as line lists, instrument data sheets and valve takeoff lists, to transfer these design data. But this creates such a mass of different technical documents that it's impossible to keep them fully synchronised. Intelligent P&IDs incorporate all this information into a single electronic data file that can be updated in seconds over a wide area network.

An important requirement of developing an intelligent P&ID was finding a software package that would maintain a multi-drawing external relational database that can be used to manage project-wide P&ID data. Toyo selected AutoPLANT P&ID from a Californian software house, Rebis, because the structure of its external database seemed to be ideally suited to the company's needs.

In process engineering, the information on required basic processing equipment and its operating conditions is generated by the process simulation package. These data, mainly operating pressure, temperature, flow-rate, and physical properties, are used to develop the process flow diagram.

transfer time

The next step is creating the equipment data sheet. This requires definitions of the size of equipment, design conditions, equipment type and material of construction. In the new procedure, all of these data are carried over into the intelligent P&ID. Also, during the development of the P&ID, engineers determine line sizes using a hydraulic calculation program (Figure 1). Data sharing avoids the need to re-input calculation data and results.

The intelligent P&ID, with its database table, is transferred downstream to the appropriate engineering department. Instrument data is sent to the index system, and to the design program from which data sheets are generated. Likewise, the line table is transferred to a line design program, which generates the line schedule by calculating test pressure, insulation thickness and other factors. These conditions are finally sent to the piping isometric system. For instrumentation, process data is transferred with the instrument table and back to the P&ID application after the instrument engineer selects the type and size of each piece of equipment.

Creating instrument indexes, line lists and valve lists has also led to major time savings. Traditionally, these reports are created by looking at the P&ID and typing in the data. Then, additional design data are input by the engineer to refer to other documents such as the equipment data sheet. The new approach makes it possible to generate the list simply by typing the commands in the P&ID program.

Each component appears on the P&ID with its particular associated factors, including design condition, pressure, temperature and base material of construction. Toyo engineers developed a search macro in the AutoPLANT P&ID package that helps engineers maintain consistency. The routine changes the colour of graphical objects that match the search condition. It allows engineers to identify all items in a drawing which do not meet the specified criteria. This makes achieving system-wide consistency easy; for example, by making sure the components on the pump discharge line have pump shut-off design capability (Figure 2).

Keeping consistency with other engineering documents is also important. Project engineers have to do checking work, such as equipment tag and name check with equipment lists and nozzle data with vessel engineering drawings. All the tags for instruments and lines can be used for an index of related engineering documents, which can be used to measure the progress of engineering work.

quality improvements

The switch to P&IDs has also helped Toyo to achieve substantial quality improvements. In the traditional approach, the definition of instrument tags and limits of lines are not clear enough for everyone to understand.

A certain number of mistakes always occur during the detailed engineering stage, but the clearer definition afforded by the intelligent P&ID significantly reduces these errors. Another factor is that design changes can be instantly communicated to designers working around the globe, eliminating the potential for mistakes caused by outdated information.

However, the benefits of the intelligent P&ID must be weighed against the additional input load. An intelligent P&ID takes 20-30 per cent longer to prepare than a conventional P&ID. For Toyo's own licence process work, the extra input time is far outweighed by the time savings downstream. But for licensed work, in which basic design packages are provided by other companies, almost all data for the intelligent P&ID is provided as paper documents. Also, P&IDs are provided as dumb CAD drawings. In these cases, it's not as easy to justify the use of the new method.

Overall, Toyo management is very pleased with the initial results of the intelligent P&ID concept. These have shown that the new system pays off by saving engineering time downstream and improving process data quality. The P&ID becomes a powerful document for coordination and transfer of process data to detailed engineering disciplines. It seems clear that the more engineering disciplines use the intelligent P&ID, the greater the overall quality improvement that can be achieved.

Yoichi Nishi is process CAD systems manager at Toyo Engineering