Free span design is generally comprehensive, and pipelines can expect to have thousands of free spans after installation. Erosive processes, support failures, variations in operational conditions and axial force redistribution will alter span configurations over time, resulting in new free span assessments after every survey cycle. Therefore, free span design is a continuing assessment throughout the design life.
Typically for each survey cycle, an engineer will assess necessity of free span rectification. Historically, as demonstrated through three case examples in this presentation, up to hundreds of unnecessary free span interventions have been performed on single existing pipelines, with costs in the range of tens of million Norwegian kroner, due to low quality analyses, poor data management, lack of reasonable account of free span history or combinations thereof.
This presentation demonstrates background for and benefits of digitalization of free span analyses, improved data management techniques and systematic treatment of free span history between survey cycles. Case studies, based on existing pipelines and their design, operations management and intervention histories will be applied to illustrate typical pitfalls and benefits with new and improved calculation methods and digital data management and interpretation.
Authors: Knut Vedeld, Einar Stiansen, Kjetil Bergseng and Olav Fyrileiv, DNV GL