Offshore Pipeline Free Spanning Analysis Based On DNV Design Code

Offshore pipeline has proven the most economical means of large scale
transportation method for crude oil, natural gas, and their products for oil and gas
exploration. Problems faced during pipeline mechanical design is free span
formation due to seabed unevenness, scouring action, and exposure to current and
wave flow. 1bis work presents proper free span assessment to avoid excessive loads
and deformation as pipeline could undergo oscillatory force, excessive bending
stresses, and buckling. Analysis spreadsheets were created for free span analysis
according to latest Det Norske Veritas (DNV) design codes; DNV-RP-Fl05 "Free
Spanning Pipelines, February 2006". Results obtained were presented in graphs and
tables. Parametric studies were performed to determine the span length for different
outside diameter, safety factor and boundary condition. Results indicated that
pipeline failure occurred if span length is longer than the permitted length. 1bis can
be solved by rerouting, span correction, installation of grout bag support or
mattresses.