MODELING A POWER plant as a single 3D CAD model is allowing Southern Company Engineering to design power plants with fewer people. For example, in the mechanical design area, one large project that would have required five mechanical designers is now being completed just as quickly with only two. Fewer people are needed because all the components of the plant-mechanical, electrical and structural-are included in a single model improving communication between disciplines, preventing interference, and allowing material take-offs and isometrics to be produced almost automatically.
The Southern Co. division has designed more than 275 electric generating units. Until recently, the power plants were designed using AutoCAD in 2D and drawings were the primary means of communicating design information. Each discipline involved in a project tended to design independently, and each discipline had its own CAD files. It was up to individual designers and engineers to communicate aspects of their work that might affect other areas.
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 in an attempt to improve communication.
Because the staff was familiar with AutoCAD, the company decided to adopt a personal computer-based system called AutoPLANT that runs as an add-on to AutoCAD. The two programs use the same menus and modeling conventions, so only minimal additional training was needed.
Now, a single solid model is created for each piece of equipment and every run of pipe. Mechanical engineers model pipes with a specification-driven piping module. Civil engineers model structural steel using another special module. Basic AutoCAD is used for concrete.
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 pertinent information any designer needs is visible in the model.
Having up-to-date information has nearly eliminated interference caused by miscommunication between disciplines, said Grady Luster, Southern Company Services Engineering Automation manager. The software also recognizes interference and highlights potential clashes. Having fewer interferences to begin with and finding any that do exist before construction are a big source of time savings in terms of both cost and schedule.
In one recent plant design, one mechanical engineer and one mechanical designer handled all the piping design, including the production of 250 isometric drawings. This project is a 112 MW cogeneration plant. The 3D model was particularly beneficial on the project, Luster said, 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. The 3D model allowed designers to optimize their use of the available space while avoiding interferences.
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.