Pipe Fabrication Formula Full Pdf Download _HOT_
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As described above, modern construction projects are evolving to resort to modular and off-site prefabrication technologies for better quality and productivity benefits (Construction 2011; Eickmann and Fagerlund 1999). Due to the low labor cost and convenient procurement of basic materials like steel, the engineering and manufacturing for prefabrication components (i.e., pipe spools or steel structure) and modules is usually undertaken by overseas vendors in East Asia, such as South Korea, China (Choi and Song 2014). After the components or modules are manufactured, they will be shipped from the manufacturers in East Asia to the construction sites in North America such as Alberta, Canada. Thus, with more and more prefabricated materials and assemblies, the material supply chain becomes increasingly complicated and uncertain for industrial modular construction projects (Choi and Song 2014; Song et al. 2005). Material supply presents itself as a driver in planning crew installation operations on site, which is aimed to maximize the productivity of skilled labor and heavy equipment, keep schedule extension to the minimum while mitigating project budget overrun.
In the spool fabrication shop, a large amount of raw pipe and pipe fittings (e.g., elbow, tee, flanges) are fabricated into pipe spools through a series of operations such as cutting, fitting, welding, quality control checking, stress relief, hydro testing, painting and other surface finishing. The typical fabrication process of one pipe spool is illustrated in Fig. 2. After the engineering drawings are received and all required materials are available, cutting sheets will be released to the fabrication shop. Pipe, as the main component of spools, will first be cut to the desired length and the end surfaces of the pipe are beveled to the specification in the drawings. Then, the pipe sections and pipe fittings are fitted and welded. The fabricated subassembly often needs to be fitted and welded several times on the shop floor before the spool is completed. After that, the spools are checked for quality control, and stress relief, hydro test, painting or other surface finishing work are performed, if required.
The typical real-world scenario is that multiple pipe spools are fabricated simultaneously in one shop, sharing the same labor resources and drawing from the same inventory for most raw materials. And every spool has an expected delivery date to the module yard or to the construction site. As shown above, various types of raw materials (e.g., pipe sections of different sizes, elbows, olets and flanges) are connected in the spool fabrication process. Timely supply of all materials is critical to achieve the smooth execution of the fabrication process. Any delay in material supply processes would postpone start time on corresponding activities, potentially extending the project duration.
Another reason accounting for temporary material shortage in the spool fabrication practice is attributed to the fact that raw materials can be misused in fabrication of spools. For example, a 12-meter-long piece and two 6-meter-long pieces of pipe of the same size, thickness and material type are procured to fabricate Spools A and B. Note the two 6-meter-long pieces of raw pipe are intended for fabricating the two 5-meter-long pipe runs on Spool A. However, in the fabrication process, the 12-meter-long piece of raw pipe is cut into the two 5-meter-long pipe runs. This happens to cause material storage in fabricating the 10-meter-long pipe section on Spool B, which actually requires the 12-meter-long piece of raw pipe.
As one data source, ISO drawings provide the basis for performing work breakdown and defining all the fabrication activities. The technology-constrained relationships among all activities are also specified in order to properly sequence the execution of activities. In addition, the material supply information extracted from the material management system presents additional constraints. The availability of laborer resources and the preset deadline by which to complete a particular spool project are two other constraints. All these constraints are factored in mathematical programming formulation and entered into the optimization engine in search of the optimum solutions. The mathematical model underlying the proposed framework is shown in Eq. (1).
The three spools are different in design, but share the same labor resources (i.e., two fitters and one welder), the same workstations in the shop and draw on the same inventory of raw materials (i.e., raw pipe and pipe fittings). The proposed optimization approach is used to schedule the fabrication of the three spools in order to finish them in the shortest duration with the fixed labor resources (two fitters and one welder allocated); in the meantime, the material demand pattern dictated by the schedule must match the time-dependent material supply pattern. Note the unit of time for scheduling anlysis is minute (min) in order to be in line with the activity time available. As required by the contract, Spool 3 needs to be finished on Day 2, i.e., the 960th minutes after project starts (assume 8 working hours per day). Figure 9 shows the Gantt chart of the baseline schedule with the assumption that all materials are available when needed. It is worth mentioning that the output visulization is designed to be intuitive to users and also interactive with users. When the mouse cursor moves on activities, the detailed information of corresponding activities including spool identification, activity identification, duration, start time and required resources pops up as shown in Fig. 10, which makes the Gantt chart much easier to communicate, comprehend and execute by practitioners. As indicated by the baseline schedule, the three spools can be completed with 774 min, which is roughly 13 h with two fitters and one welder. And Spool 3 is completed at the 774th minute, which is less than the deadline of 960 min.
Abstract:In order to enhance the environmental adaptability of peristaltic soft-bodied pipe robots, based on the nonlinear and hyperelastic characteristics of silicone rubber combined with the biological structure and motion characteristics of worms, a hexagonal prism soft-bodied bionic actuator is proposed. The actuator adopts different inflation patterns to produce different deformations, so that the soft-bodied robot can realize different motion modes in the pipeline. Based on the Yeoh binomial parameter silicone rubber constitutive model, the deformation analysis model of the hexagonal prism soft-bodied bionic actuator is established, and the numerical simulation algorithm is used to ensure both that the drive structure and deformation mode are reasonable, and that the deformation analysis theoretical model is accurate. The motion and dynamic characteristics of the prepared hexagonal prism soft-bodied bionic actuator are tested and analyzed, the motion and dynamic characteristic curves of the actuator are obtained, and the empirical deformation formula of the actuator is fitted. The experimental results are consistent with the deformation analysis model and numerical simulation result, which shows that the deformation analysis model and numerical simulation method are accurate and can provide design methods and reference basis for the development of a pneumatic soft-bodied body bionic actuator. The above research results can also prove that the hexagonal prism soft-bodied bionic actuator is reasonable and feasible.Keywords: silicone rubber; pneumatic; pipeline robot; soft-bodied bionic actuator; soft-bodied robot 153554b96e
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