Choice of Pipeline Material: PVC or DI Using a Life Cycle Cost Analysis

Abstract

As the world's pipeline infrastructure continues to age and the demand for product delivery continues to grow, every utility has been required to make decisions about the condition and adequacy of their existing pipeline systems. When utilities find that the existing systems do not have adequate capacity or have become too costly or risky to operate to meet future needs, many times replacement is the only solution. As systems are being replaced, everyone is looking to reduce up-front capital, operational, and maintenance cost through detailed design. However, there are unconsidered environmental costs associated with these financial savings. This paper uses a Life Cycle Cost (LCC) approach to address the pros and cons of using Polyvinyl Chloride (PVC) or Ductile Iron (DI) pipeline material in design. The study considers the project life cycle and how each life cycle phase is impacted by standardized design approaches. For each pipeline material, the following life cycle phases have been evaluated: material production and pipeline fabrication, material transport, life cycle usage, and end of life. Each phase has been evaluated for both economic and environmental impacts. The results of this particular case study are directly impacted by the applicable design standards for the each pipeline materials. In this design example, the PVC pipeline internal diameter was significantly less than the DI pipeline internal diameter. This design consideration made the DI pipeline material hydraulically more efficient, which over the life cycle, made the DI pipeline the most fiscally and ecologically attractive alternative. This study demonstrates that specific design standards and specific system design characteristics (flow rate, pressure requirements) influence the LCC and total CO 2 emissions. The conclusion of this study demonstrates that a complete pipeline design should be considered in the LCC approach before a decision is made on what material is used in design.