# Productivity Analysis of Documentation Based on 3D Model in Plant Facility Construction Project
## 4 Productivity Analysis of 3D-Model-Based Documentation  
### Case Study  
#### 4.1.1 Project Description  
The case of this study is a plant facility consisting of four modules as the Engineering Procurement Construction (EPC) project as shown in Figure 2. 3D modeling was performed based on the design documents provided by the client, and the drawings needed for the fabrication were made using the 3D model. The whole module consists of four modules. Module A (180.96 Ton) consists of 1965 production drawings, Module B (120.06 Ton) consists of 1216 production drawings, Module C (114.06 Ton) consists of 939 drawings, and Module D (120.94 Ton) consists of 1175 drawings. A total of 5295 production drawings were delivered. The case project was conducted from December 2014 to September 2015. The detailed process is as shown in Figure 3. 3D modeling proceeds after the process of reviewing and inquiring design drawings from the client. Fabrication drawings (e.g., general arrangement drawings, assembly drawings, single part drawings, single plate drawings) and reports (e.g., information including drawing number, part number/type/quantity/size/weight, painted area, bolt type/quantity, etc.) are generated after completion of 3D modeling. These documents are submitted for approval of client. The drawing productivity comparison data presented in the case project is based on the first drawing delivery. Correction and re-delivery of drawings are repeated due to design changes and various factors after delivery, and factory production starts when the final production approval is obtained from the client. Figure 1: 3D-model-based collaborative documentation process. Design changes may occur even after the final production approval, and the drawings must be immediately modified. In general, all personnel or some will be put into a new project because the time spent on the project is reduced after the final production approval. The prefabricated members are installed on site, and factory production and field installation take place simultaneously. If an issue occurs at this time, the drawing may need to be modified. When this process is completed, the project is closed. The 2D-drawing-based documentation method is the same as described above except for the presence of a 3D model. Drawing modifications and deliveries are repeated many times during the project. If this process is based on 2D drawing, it takes a lot of time and frequently causes design errors. However, in case projects using 3D-model-based documentation, modification time, and design errors were reduced. In addition, an accurate 3D model that reflected design and engineering changes was able to automatically calculate the data (e.g., drawing number, part number/type/quantity/size/weight, painted area, bolt type/quantity) needed for manufacturing. In addition, the 3D model made it easy to identify whether the modifications were reflected. As shown in Figure 3, the documentation process, which is a unit of work, is iterative and complex. Therefore, detailed time measurement of all tasks is not possible for case analysis. Therefore, in this study, working hours were collected according to the types of fabrication drawings through expert interviews with engineers who participated in actual work. This study was conducted by interviewing the staff in charge of the design office who performed the project to collect productivity comparison analysis data of 3D-model-based documentation method and 2D-drawing-based documentation method. The 2D-drawing-based documentation method is based on the case of using AutoCAD, and the 3D-model-based documentation method is based on the case of using TEKLA. A total of four people were used for the documentation work of the case project, and it was assumed that 8 h were worked per day. The engineer's experience is more than 5-10 years of experience, and they are familiar with both methods of documentation.