3D modelling fosters collaboration

By AMEC's standards, it was a medium-sized project. An expansion to the processing capacity of an existing polymer processing plant, the work involved approximately 600 new lines of piping and 60 new pieces of equipment. But the main challenge on the job was that all the new items had to fit into existing buildings.

The AMEC engineers in charge of the project expected difficulty in getting pieces to fit through passageways and in interfacing new piping to the existing facility. Because they were so concerned about fit, they ruled out doing the design in 2D and began a search for a suitable 3D plant-modelling program.

'It is difficult to detect interferences when only two dimensions are visible', says Tim Rothwell, engineering systems development manager at AMEC's Design and Engineering arm in Manchester. 'Even when designers use plan, section, and elevation views to try to spot clashes, if heights on two drawings don't match perfectly, it is possible for an interference to go unnoticed. It is also difficult to detect interferences between disciplines because they typically do not share drawings early in the design phase.'

In its search for a suitable 3D modelling solution, AMEC ruled out the option of using high-end workstation-based systems, such as those used by its on- and offshore divisions, because of the high implementation costs and long learning curves. Also, knowing it would want to tailor the software, AMEC wanted a program that was easy enough for its own engineers to customise.

An additional requirement was that the software be based on AutoCAD, as over time there had been a considerable amount of investment in this industry-standard package and the majority of the design staff is trained in its use. Another major factor was that the majority of AMEC's clients required deliverables in an AutoCAD format.

The ease of setting up the software to handle a new project was also a major consideration. 'Sometimes a client comes to us and wants a project up and running in a day,' explains Rothwell. 'You can't do that with all programs.' Finally, AMEC wanted a suite of integrated applications that would allow the different disciplines to share data seamlessly.

Multidisciplinary

AMEC eventually opted for the AutoPLANT package from Macclesfield-based Rebis because, in addition to it being AutoCAD add-on software with full 3D modelling capabilities, it also included modules for each of the design disciplines.

AMEC's implementation included: the intelligent piping and instrumentation diagram (P&ID) module; the piping module; an equipment design module; structural 3D; the Isogen PLUS module, which produces isometric drawings automatically from the 3D mode; the Instrumentation Workgroup; and Explorer and Explorer/ID (Interference Detection) add-ons, which permit automatic interference detection and walk-through visualisation of a 3D model.

For the polymer plant expansion project, AMEC had two preliminary tasks. One was to take measurements of the existing facility so that it could be modelled in the Rebis 3D software. The other was to set up the software for the project, establishing the tag-numbering scheme in the database, for instance, and setting up a unique symbol library.

The actual design process began with marking up the existing paper P&IDs to reflect the new equipment and then transferring that information into the Rebis P&ID module. The software maintained an up-to-date database of the information on these drawings, such as tag numbers for lines, instruments and equipment.

After the P&IDs were done, datasheets and instrument lists were generated automatically. These documents and the drawings were given to mechanical, structural, and piping engineers who began using their respective modules to place items into the 3D model created from measurements of the existing facility. For example, mechanical engineers used the AutoPLANT Equipment module to design and place equipment and tanks. This module automated much of their work by providing a library of parametrically defined components. With the library, the designer simply entered a few values representing the specifications of the equipment and the software drew the model.

Structural engineers used the Structural 3D module, which also has a library of standard shapes. In a similar way, piping engineers used the piping module to route the pipe. To do this, they drew lines indicating where pipes should be placed, as they would in 2D. But rather than geometric representations of the pipes, each digital pipe model was actually an object containing additional information from the database such as performance and material specifications. And because the engineers were working in 3D, they were able to include the z dimension in the model. Having the z dimension visible was easier than trying to imagine elevations in 2D.

Early collaboration

One benefit of working this way was that it fostered early collaboration. For example, a structural engineer could import equipment models into his design and a piping designer could route pipes around the structural steel. This helped avoid clashes from the start. In addition, as individual designers worked, they used Explorer to perform periodic interference checks. 'We encourage the designers to do this themselves. The interference-checking tool is easy to use and runs on the same PC the designers are using. The items in the model are also intelligent, which means you can add or delete pieces of equipment rather than changing individual lines and circles,' explains Rothwell.

The ease of making changes encouraged engineers to experiment with different layouts to find the best way to integrate the expansion with the existing facility. Another benefit of 3D modelling was that since every item in the 3D model had a corresponding entry in the database, there was less chance for errors related to wrong part numbers.

When they had completed the 3D model, AMEC used the Explorer/ID module to perform a thorough evaluation of the entire design for interferences. Engineers fixed any problems that were detected. Once the process had been modelled accurately, instrumentation engineers designed the instrumentation.

They entered specifications for instruments directly into the project database.Then the various modules of the AutoPLANT Instrumentation Workgroup used that information, along with information entered previously during the creation of P&IDs, to generate loop diagrams, termination diagrams, and data sheets. At that point, all that was left was producing construction documents. These were generated automatically from the 3D model.

For piping isometrics, engineers simply selected the views they wanted and commanded the Isogen PLUS to create the drawings. Engineers could produce up to 40 isometrics in 20 minutes.

By modelling the polymer plant expansion in Rebis 3D, AMEC reduced design time by 25 percent compared with manual design methods. The work of customising the new software went smoothly and was done in-house with all the right materials ordered and all new pipes joining perfectly to existing ones.

'The software itself was affordable, but we experienced additional cost savings in not having to bring in applications specialists to do the programming,' says Rothwell. 'We knew this project could benefit from 3D modelling. The ability to create a digital representation of the entire expansion, with geometry linked to specification data, paid off in both design and construction.'