1980 to provide construction services to the energy sector, utility/government, and agri-business clients in the Idaho and Oregon area. Prather had previously worked in the irrigation systems field and saw an opportunity to provide services specific to this business. Environmental Considerations The unique surroundings of these projects require skilled planning and careful implementation of the plan. Limiting the environmental impact is important on these projects. It is important to the land owners that a small footprint be made upon the land and as little area as possible be disturbed during the pipeline installation. The right of way is often very narrow due to environmental concerns and the time to build and have the pipeline active is usually short. Governmental agencies perform routine checks to ensure the contractor does not exceed the space limitation requirements. Contracts are tightly monitored and failures are penalized. With all of these limitations, it is important to be efficient once the project starts. Since the pipeline cannot be welded in the standard fashion, in most cases, the runs must be welded in short, straight strings made up of six to eight pipe sections. A yard area is secured near the final pipeline location and multiple, parallel, short runs are built. These runs are then aligned and welded together to make longer runs that are eventually pulled and pushed into place, using dozers and trackhoes (Fig. 2), from the source to the output. This approach is very similar to the method often applied for directional bores and traditional straight bores under roadways and beneath other right of ways such as rivers, marsh lands, and populated areas. Evaluating the Traditional Welding Process In the past, each of the weld joints that make up these short strings was welded using the shielded metal arc welding (SMAW) process. Given the typical pipe wall thickness for the diameter, each weld joint usually requires a total of four passes, a root pass, two fill passes, and a cap pass. Welding of each joint from root to cap was expected to require three worker hours. The quality of each weld was subject to variation from welder to welder. While the specification requirement was not as stringent as that for petrochemical applications, the loads and strains placed upon the pipe during the installation process (Fig. 3) required high quality and uniformity. Any discontinuity that was present in a weld could result in a catastrophic failure during the process of pulling and pushing the pipe into place or a long-term failure once in operation. A limiting factor when using the SMAW process is the availability of capable and qualified welders and welders’ helpers. If a welder decided to move on to another job, the loss of his or her labor would detrimentally affect the project plan and schedule. In some Fig. 2 — Short runs are aligned and welded together to make longer runs that are pushed or pulled into place. NOVEMBER 2016 / WELDING JOURNAL 45
Welding Journal | November 2016
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