## 4 Data Analyses, Discussion and Findings
### Pattern and Route  
According to the survey, piping prefabrication is feasible in most cases, especially when using the threaded coupling, groove coupling, and flange coupling modes. Piping prefabrication is applicable for the most type of projects such as offices and hotels. However, the challenges and barriers that each contractor may face are different depending on the characteristics of projects. Under the promptings of successful cases, MEP contractors who want to adopt piping prefabrication in their projects need to validate and evaluate its feasibility again. Contractors should expand the prefabrication capacity incrementally in a keen competition environment. Based on the result of semi-structured interviews, case studies, site visits, as well as the questionnaire, a four-phase route is suggested for MEP contractors. In the first phase, the MEP contractors are suggested to learn to develop BIM model above LOD 300 based on the real size of the fittings and valves. BIM is beneficial to identify the prefabrication scope and to communicate the scope with supply chain participants. The virtual BIM model is useful to avoid conflicts with other MEP systems. BIM can provide rich data for prefabrication. Take the fire sprinkler system as an example, BIM provides the accurate length of pipes. To achieve this goal, a lot of components information need to be stored in the BIM software, for example, stored as families in Revit. This information needs to be reconfirmed and updated with the distributor and manufacturers. This is helpful to develop BIM model of high quality in a very short time. In this phase, the BIM model that contains accurate data can be used to produce the detailed drawings with dimensioning automatically for workers on site. The contractors need to evaluate the benefit of BIM in improving the productivity of piping installation through clear observations of the piping installation process. Figure 7: Challenges of piping prefabrication. In the second phase, piping contractors should collaborate with a local fabricator to implement prefabrication in a pilot project. Piping contractors provide detailed shop drawings to the fabricator, then the components are transported to site according to the installation plan. In this phase, the main question should be settled is how to manage these prefabricated components. The management includes components labeling, packaging, transportation, and installation to the right place. From the experience of the case, it is difficult to find the right one from a pile of components. The production productivity of fabricator is higher than installation productivity on site. Therefore, the more quantity of prefabricated components conveyed to the site, the less efficient when picking out the component one by one according to the installation sequence. Besides, the label posted on the component cannot reflect the accurate location of it. As shown in Figure 8, the prefabricated pipes laid in a disorderly pile. The information exported from the BIM model developed in Revit such as the pipe length, the pipe ID was marked on pipes. Meanwhile, the plans of sprinkler system developed in Revit automatically were printed to workers for installation on site. Although the ID of a pipe can distinguish this pipe from other pipes, the ID cannot explicitly infer the location of this pipe. In other words, the worker needs to analyze the location of the pipe manually in the drawing according to the information marked on the pipe. In order to integrate the prefabrication activity into the business process of the piping contractor, it is suggested for contractors in the third phase to set up a small prefabrication production line to produce standard components such as pipe spools. The production process and the management process in the facility shop should be planned carefully based on the experience obtained in the second phase.