(I believe an oil pipeline leak is a good example of how easy it can be to initially figure out the cause of a failure. Civil litigators and insurance claims consultants like to know early on where the technical issues in a case might be heading)
An oil pipeline has got to be one of the simplest structures in the built environment, “…a line of connected pipes that are used for carrying liquids and gases over a long distance”. (Ref. 1)
The pipes are connected by welding the ends together. The pipeline is often supported at the connections on simple foundations. This would be the case in terrain underlain by permafrost – permanently frozen ground – or where it’s more economical to build above the ground rather than bury the pipeline. Welding and building foundations are the two main tasks on-site in pipeline construction.
Such a simple, linear structure is susceptible to pressure to build it fast. Fast work can be a threat to the quality of the welded connection and the foundations.
Pipeline planners and designers estimate cost in part on how fast it can be built.
Pipeline contractors make money by building it fast. “Excavate the ground, construct the foundations, lift a length of pipe in place, weld the connection. Next please.”
The adequacy of the ground to support foundations is investigated by engineers along the pipeline route at the design stage – but not at the location of every pipe connection. Foundation soils vary even in the most uniform of natural deposits. The soils will be weaker at some locations and stronger at others. Too weak a soil will cause a foundation to subside and possibly over stress the welded connection and cause it to fail and leak – oil.
The adequacy of the welded connections and the foundations are inspected, ideally by an independent materials testing and inspection firm – but not likely at every connection. A grossly inadequate weld while unlikely that is missed during inspection might leak oil regardless the adequacy of the foundation. A less than adequate weld combined with the stress from a subsiding foundation might break and leak oil. A low probability perhaps but still.
An initial hypothesis as to the cause of a leak would be easy for a forensic engineer. S/he’s got three main choices for a simple structure like a pipeline:
- A poorly welded connection,
- A subsiding foundation over stressing a properly welded connection, or
- A subsiding foundation over stressing a poorly welded connection.
Depending on specific conditions at the failure site, the expert would pick one of the possibilities for their initial thought on the cause of the oil leak.
- Merriam-Webster, Dictionary 2017