The selection of pipeline materials requires consideration of design, construction, operations, maintenance, threats, hazards, risks, safety and economics. Codes and standards provide mandatory and optional requirements and guidelines for the selection of materials. Experience and industry practice help to develop and implement requirements beyond mandatory and code minima, and to augment the achievement of safety and realization of the value of pipeline assets. Both codes and experience get updated over time. When selecting and using materials for pipeline systems, it becomes important to meet with code essentials, while simultaneously recognizing the recommendations of design engineers, materials specialists, manufacturers, installers and operators.
There is a wide gamut of materials that can be considered for pipeline systems. These include metallic and non-metallic materials. While steels are still used as the workhorse material in the industry, several non-metallic materials are gaining prominence. These include thermoset materials, for example, reinforced plastics, and thermoplastic materials, such as high-density polyethylene.
In addition to pipe, there have been significant developments in other pipeline component materials, such as for valves, fittings, flanges, gaskets, seals, adhesives, bolts and nuts. Considerable advancements have also taken place in the realm of joining and repair methods, for metallic and non-metallic materials. Many of these materials and methodologies are of a proprietary nature, with limits on how much information is divulged by the manufacturers and producers, and what is subject to information that is shared based on confidentialities. Proprietary materials, especially non-metallic products, and some corrosion resistant alloys, are generally not extensively addressed in codes and standards, especially in comparison with steel-based materials that are of the commodity type. Some internationally recognized specifications and standards address the requirements for the qualification of pipeline components, including pipe, fittings, flanges and valves, based on non-metallic materials. Other internationally recognized standards and specifications address the requirements for apparently commodity type materials and materials that are considered to be generally corrosion resistant and relatively long lasting, however, can be susceptible to failure when subjected to specific threats.
This paper provides an overview of the process of selection of pipeline materials addressing the above considerations and gives an outline for the implementation of such a process. It describes ways in which a balanced approach to the use of codes and standards that are necessary for regulatory and mandatory compliance, and the application of the benefits of proprietary materials that are available for commercial purposes can be achieved. Thereby, the optimization of asset life cycle and augmentation of safety and reliability during pipeline operations can be enabled.