FactorsAffectingProductivityofPipeSpoolFabrication

1 International Journal of Architecture, Engineering and , No. 1, March 2012, Affecting Productivity of Pipe Spool FabricationSeyed Parham Mosayebi1, Aminah Robinson Fayek1, , Laury Yakemchuk2, Scott Waters21 Department of Civil & Environmental Engineering, University of Alberta,Edmonton, Alberta T6G 2W2, Canada2 Aecon Industrial Western Inc., 53367 Range Road 232, Sherwood Park, Alberta T8A 4V2, CanadaAbstract:Pipe spool fabrication is an early stage in industrial construction projects and is crucial for thesuccessful delivery of a project. Pipe spool fabrication is a complex and uncertain process due to the uniquenessof its products. The productivity of the fabrication process and the factors affecting productivity are thereforeof great importance to project managers and construction researchers alike.

2 Being able to identify all of the sig-nificant factors affecting productivity is critical to the ability to accurately estimate productivity and ultimatelyimprove the fabrication process. This paper introduces the factors that affect the productivity of the pipe spoolfabrication process that are not accounted for in the production unit of spools. In addition, the impact of eachfactor on productivity is illustrated, and different methods for modeling these factors are proposed. This paperprovides a framework for a more comprehensive approach to estimating the productivity using the productionunit of :Diameter inch, factors, pipe spool fabrication, spool fabrication falls under the category of in-dustrial construction processes.

3 The term industrialconstruction is used to describe a wide range of facil-ities for basic industries, such as petroleum refineries,petrochemical plants, nuclear power plants, and oil/gasproduction facilities (Barrie and Paulson 1992). Pipespools are normally built in a fabrication shop througha series of cutting, fitting, welding, and other processesaccording to the engineering designs (Song et al. 2006).Final products are either assembled, and form largemodules, or are shipped directly to a construction sitefor a higher level, the piping process can be dividedinto four phases: design, pipe spool fabrication, mod-ule assembly, and site installation. Pipe spool fabrica-tion directly affects module assembly and site installa-tion, therefore it is a critical stage not only in a pipingproject (Hu and Mohamed 2011), but also in an overallindustrial construction project.

4 As a result, the pro-ductivity of the spool fabrication shop has always beenof great interest to and Oduba (2008) introduced many factorsthat affect the productivity of field pipe rigging andwelding processes on an industrial construction factors can be categorized into three groups: at-tributes of the spool, attributes of the crew, and envi-ronmental conditions. In this study, Fayek and Odubadeveloped a fuzzy expert system to estimate labourproductivity, defined as manhours per unit quantity,using, as inputs, the introduced productivity models were developed to estimate the produc-tivity of pipe rigging, carbon steel butt welding, andalloy steel butt welding. These models had a numeri-cal accuracy of 38%, 49%, and 41%, respectively, and alinguistic accuracy of 86%, 75%, and 50% (2006) investigated the effects of usingstandardized spools, both in the fabrication shop andfor on-site installation processes.

5 According to her def-inition, a specific material refers to a material that isa one of a kind, which means the facility s design onlyhas one of it. In contrast, a standard material refersto materials that are identical and have been used morethan once in the facility. She used a simulation modelto measure the effect of using standard materials forpiping projects. Her model indicated a reduced cycletime in the fabrication of standard materials, in com-parison to specific and Fayek (2008) used a work breakdown*Corresponding Author. et Journal of Architecture, Engineering and Construction 1 (2012)30-36structure approach for modeling the pipe spool fabri-cation and assembly process. They developed a simula-tion model capable of both estimating the productivityof the fabrication shop and indicating potential bottle-necks in the fabrication process.

6 The results of thismodel were satisfactory, as it was capable of estimat-ing the productivity of the fabrication shop with lessthan 5% error. Also it used statistical analysis to de-termine resources with a high waiting time that createbottlenecks in the et al. (2009) studied the effects of shop layoutand their proposed Flow Production System (based onlean production practices) on the productivity of thefabrication shop. The study showed that changing theshop layout to a flow production layout resulted in asignificant reduction in spool cycle and Mohamed (2011) studied the effects of theassembly sequence ( , cutting, fitting, and welding)on the spool fabrication process. A simulation modelof the pipe spool fabrication shop was used to test theeffects of changing the sequence of steps.

7 There aremany alternatives approaches to build a spool from itsraw material. The spool can be fitted and roll weldedin various sequences to make the intermediate spoolassemblies and eventually the final spool. The simula-tion model demonstrated that changing the sequenceof activities can reduce the cycle time and amount ofhandling by an average of 10%.In this paper, first the processes of pipe spool fab-rication are briefly introduced, and the diameter inchstandard for measuring unit cost, production, and pro-ductivity is explained. Then, the important produc-tivity factors that are not considered in the diameterinch standard and their effect on the fabrication pro-cess are explained. In addition, methods for modelingthe effect of these factors on productivity of the fabri-cation process are presented.

8 This research is based ona case study in a major industrial fabrication facilityin Alberta, IN PIPE SPOOLFABRICATIONB efore a project is started, the required materials, suchas pipes, flanges, fittings, and valves are shipped tothe fabrication shop and stored in the designated all the material required for an isometric is avail-able, that isometric is released to the shop for fabrica-tion. Pipes, the main component of spools, must firstbe cut into pieces of the size required by the draw-ings. After pipes are cut, the cutting operators usedisk grinders to smooth the end surface of the pipesand bevel them if required. Then pipes are moved tofitting stations to be joined together. Once the pipesand other components of the spool, such as reducers,valves, and flanges, are fit, overhead cranes are usedto move the assemblies to the welding stations.

9 Fit-ters usually move assemblies that weigh less than 50pounds by is performed via two methods: roll weld-ing and position welding. In roll welding, the welderfixes one end of the pipe into a pipe turner and rotatesthe assemblies while welding them. Position weldingis used when the pipes cannot be rotated by a turner(the assembly has a branch longer than 5 feet), or whencomponents are not round in shape. Position welding isa difficult procedure, and takes longer to perform thanroll welding. Assemblies may move between fitting andFigure spool fabrication process31 Mosayebi et Journal of Architecture, Engineering and Construction 1 (2012)30-36welding stations several times before roll welding is fin-ished or the final spool is ready to be position spools are complete, they go through qualitycontrol.

10 Then, based on the drawing requirements,they may be hydrotested or undergo other processessuch as surface treatment and typical processes in pipe spool fabrication areillustrated in OF PIPE SPOOLFABRICATION PROCESSS pool fabrication jobs are usually unit-based projects,where contractors bid on the unit cost of the of the most common standards used for measuringspool fabrication unit cost, production, and productiv-ity is called a diameter inch ( ). Factoring, based ondiameter inches, is used to determine the quantity ofmanhours required to complete a specific task. Itemswith thicker material and/or higher material grades re-quire more time to complete and therefore receive morefactored diameter inches. The is a reliable factorfor cost estimation and scheduling that considers thephysical attributes of a spool and its required fabrica-tion processes.