A data framework for environmental assessment of metal arc welding processes and welded structures during the design phase

Abstract

Welding is a widely used technology that allows the joining of thick metal plates for the development of large structures (e.g. piping, tanks, vessels). Many industries are intensively using welding for manufacturing and assembly activities. Sustainability assessment of welded structures is currently performed with misleading information in terms of data heterogeneity (nature) and quality (source). The data required to carry out a robust environmental analysis are spread among different documents and become available only when the project is finalized. This paper aims to define a data framework for a life cycle inventory of metal arc welding processes to preventively assess the environmental performances of different processes for comparison and decision-making analysis. The framework is presented as innovative solutions for life cycle inventory that provide (i) a common data structure (model), (ii) necessary data (input/output), and (iii) physical allocation/placement of data (project design documents). This study was performed in accordance with the international standard organization ISO 14040/14044 by using an attributional life cycle assessment (aLCA). Two structures (an oil and gas riser and a ship hull) were investigated considering the same functional unit: the manufacturing, use, and disposal of a welded structure able to guarantee the engineering requirements (according to a specific standard) in terms of strain, stress, and corrosion allowance over the expected lifetime of 20 years. In both cases, the share of welding process in respect to an overall product/structure life cycle impact assessment is strictly dependant on the project design choice and can be negligible for high-corrosion-resistance materials (e.g., Inconel alloy). On the other hand, the use of traditional metals (e.g., carbon steel) allows a large decrease of the environmental load, and the influence of the welding process becomes significant in a life cycle perspective.