Selection of Pipeline Corrosion Control Strategy and Impact on Economics of Water Conveyance

Abstract

Mining companies located in the arid regions of northern Chile have been encouraged to consider new sources of water supply for their activities, motivated mainly by measured reductions in the phreatic surface and recent government regulations introduced to preserve a quota of groundwater and surface water for the local community and agricultural users. The Pacific Ocean represents an obvious water supply alternative, capable of satisfying the demand associated with the current mining operations and future expansions. This option requires the conveyance of desalinated seawater (or untreated seawater) from the coast to the points of use, typically covering distances of 50 to 200 km and with elevation gains of up to 4,500 m. High pressure pumping stations and pipelines are involved. Several mines in the area currently obtain their water in this manner and, as the water demand from the mining industry in northern Chile increases, more and more similar systems will be installed. In this context, selection of the materials of construction and corrosion control strategy for the pipeline is a key design decision, not only having an impact on the capital cost for the project, but also a significant influence on the lifecycle operating costs. Considerable energy is expended in the transportation of the water over long distances with large changes in altitude. As corrosion occurs, the characteristic roughness of the pipeline interior changes, leading to increased energy consumption to overcome the frictional losses. The approach to corrosion control also dictates the operating life expectancy and maintenance requirements for the pipeline. This paper presents a comparative economic analysis of the impact of internal pipeline corrosion control strategies on water conveyance systems for mining projects in northern Chile.