3D Modeling Lets Southern Company Design Power Plants with Fewer People

Modeling a power plant as a single 3D CAD model is allowing Southern Company Engineering to design power plants with fewer people than when 2D CAD was used. For example, in the mechanical design area, one large project that would have required five mechanical designers in the past is now being completed just as quickly with only two mechanical designers. Fewer people are needed because having all the components of the plant's mechanical, electrical, structural in a single 3D model improves communication between disciplines, prevents interference, and allows material take-offs and isometrics to be produced almost automatically.

Southern Company Engineering is a division of Southern Company, the largest producer of electricity in the United States. The engineering unit, with a staff of about 1,000 employees, designs and supports the company's power generation plants. About half of its work involves nuclear power plants while the remainder deals with fossil and hydro power plants.

Southern Company's traditional business supplies energy to a 120,000-square-mile U.S. service territory spanning most of Georgia and Alabama, southeastern Mississippi, and the panhandle region of Florida, an area with a population of about 11 million. Through its international subsidiaries and affiliates, Southern Company also has electric utility operations in Argentina, the Bahamas, Brazil, Chile, China, England, Germany, the Philippines, Trinidad and Tobago, and parts of the United States outside its traditional service territory. The company operates more than 36,000 megawatts of electric generating capacity in the United States, the most of any U.S. electric utility. It operates some 44,000 megawatts worldwide.

Problems with 2D

Southern Company Engineering has designed more than 275 electric generating units. Until recently, power plants were designed using AutoCAD in 2D and drawings were the primary means of communicating design information. The biggest drawback to this approach was that it still allowed each discipline involved in a project to proceed with design independently. Each discipline: electrical, mechanical, civil, and Instrumentation & Control (IC), had its own CAD files. It was up to individual designers and engineers to communicate with each other about aspects of their work that might affect other disciplines. To ensure that a mechanical engineer didn't route pipes through a piece of structural steel, for instance, he needed to track down the right civil engineer and take a look at his drawings. Although drawings were routed throughout the engineering offices for review, they quickly became outdated. In-spite of best coordination efforts, some interference still made it through to construction.

To improve communication between disciplines, Southern Company Engineering decided to try a different approach in which the entire plant would be represented in software as a single 3D CAD model. Since the staff had become familiar with AutoCAD, the company decided to adopt a personal computer-based system call AutoPLANT 97, from Rebis, Walnut Creek, CA that runs as an add-on to AutoCAD. Since the two programs use the same menus and modeling conventions, only minimal additional training in AutoPLANT 97 was required. Users needed about one week to learn the 3D aspect of the software and three days to learns its 2D functionality. At Southern Company Engineering, AutoPLANT 97 and AutoCAD typically operate on 300 MHz and 400 MHz PCs equipped with 128 megabytes of RAM, although there are a few PCs with dual 300 MHz processors and up to 512 megabytes of RAM.

Better communication

Now when Southern Company designs a new power plant, an individual solid model is created for each piece of equipment and every run of pipe. Mechanical engineers model pipes with AutoPLANT's spec-driven piping module. Civil engineers model structural steel using the software's Multi-Steel module. They use basic AutoCAD for concrete. Electrical components are modeled using either the piping module or with basic Auto CAD solids such as rectangles to represent components such as conduit banks. Instrumentation & Control uses AutoPLANT's 2D P&ID and Loops modules to document the plant's instrumentation.

Different sections of a power plant are represented within the software as different work areas. Solid models representing piping and equipment are placed into appropriate work areas using AutoCAD's xref feature. When a designer looks at a particular work area of the plant on his computer screen, he sees all its contents because CAD models from civil, mechanical, electrical, and I&C, the xref attachments, are all there. AutoPLANT also reads basic AutoCAD files that have been x-referenced.

With the entire plant available as a single 3D model, it is no longer necessary for designers from different disciplines to track each other down to communicate about a project. All the pertinent information that any designer needs is visible in the AutoPLANT model. It is always up-to-date because when the software displays xref files, it shows current versions. Having up-to-date information has nearly eliminated any interference caused by miscommunication between disciplines. The software's interference detection feature has also helped reduce any interference. It recognizes both AutoPLANT entities and solids, and highlights potential clashes. Having fewer interference to begin with and finding any that do exist before construction are a big source of the time savings Southern Company is experiencing with the new software in terms of both cost and schedule.

Faster material take-offs and ISOs

As CAD models are created, designers enter specifications and vendor information into the AutoPLANT database. The software includes a very complete catalog containing specifications for thousands of components. When Southern Company designers place a particular component into the AutoPLANT model, the software automatically brings all of the specifications from its catalog into a database that creates the intelligence of the model. Specifications for components not included in the catalog are entered by the designers. AutoPLANT simplifies this by asking questions about the component such as its size, rating, and so on. Having component information in a database yields a tremendous timesaving when it becomes time to produce bills of materials (BOMs). The user simply tells the software to create the document and it does so automatically using the information in the database. In addition to saving time over preparing BOMs by hand, the automatic approach is more accurate. It's easy to miss a gasket or bolt on a drawing when counting parts by hand, but AutoPLANT does not have this limitation. It counts every item in the database.

The 3D model also saves time in the production of isometrics, plan views, and sections. Rather than drawing each of these by hand, designers produce them from the 3D model. Drawings produced in this manner require minimal checking because the software ensures that they are consistent with the 3D model. To generate ISOs, designers use AutoPLANT?s auto-iso feature or a compatible third-party isometric generator called ISOGEN. With both approaches, ISOs have elevations and dimensions tagged and located, with materials for purchasing automatically derived from the database as mentioned above.

Good results

Southern Company Engineering's use of AutoPLANT 97 includes the recent design of two power plants. One, called the Olin project, is a co-generation plant that will produce 112 megawatts. Creation of a 3D model was particularly beneficial on this project because the plant had to fit onto a relatively small site. The plant included a combustion turbine connected to a heat recovery steam generator and a main steam turbine located on a separate turbine island. There was a great deal of interconnected piping and cable trays, as well as a large cooling tower and other auxiliary equipment such as pipe racks. A 3D model allowed designers to optimize their use of the available space while avoiding any interference. One mechanical engineer and one mechanical designer handled all the piping design, including the production of 250 isometric drawings. The ability to produce ISOs quickly the 3D model and component database provided significant time-savings on this project.

The second project is much larger. Called the Barry project, this is a combined cycle plant that will produce 532 megawatts. It has two combustion turbines, each with its own heat recovery steam generator, and one steam turbine. Heat from the combustion turbines runs through the heat recovery steam generators, which drive the steam turbine. This project has realized another benefit from the 3D-plant model. Images produced from the model are much easier for people to understand than drawings. Southern Company produced walk-through animations of the facility to show to clients. Color glossy pictures of the plant were used in place of an artist's rendition at the groundbreaking ceremony. Even designers and engineers prefer shaded 3D images larger than 2D drawings.

Southern Company Engineering managers are convinced that 3D modeling is the right approach to power plant design. The efficiencies of this approach save time, which translates into fewer dollars and fewer people devoted to a particular project and provides faster development cycles. The company believes that this technology will give them a competitive advantage as more plants are designed this way and much of the work will be applied to new projects.

For more information, contact Rebis, 1600 Riviera Ave. Suite 300, Walnut Creek, CA 94596. Telephone: 510-933-2525, Fax: 510-933-1920.