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5 OFFSHORE PIPELINES
During the sixties, offshore pipeline design saw the vigour
and strength for a young structured engineering field, as solutions
to the practical problems demanded innovation and vision. Such
initial vigour and strength is documented in numerous scientific
papers and research reports of this era. For example, in the 1960s
Shell Research and Development carefully studied and advanced
the water depth of pipeline. Dixon and Rutledge (1968) published
the stiffened catenary solution for offshore pipelines. In the mid
1960s, a straight stinger was used to lay pipe in the North Sea
[Berry, 19681. A patent for the articulated stinger was issued in
1969 [Broussard, et a1 19691. The articulated stinger provided
major technology advancement in the feasibility of laying pipe in
ever-deeper waters. For the historically inclined reader,
Timmermans (2000) presents an interesting overview of the
development and achievements of the offshore pipeline design and
construction discipline worldwide.
The objective of this chapter is to serve as a reference and
guide to the offshore pipeline engineer during the design process.
The following aspects of offshore pipeline design are discussed:
the establishment of a design basis, aspects of route selection,
guidance in sizing the pipe diameter, wall thickness requirements,
on-bottom pipeline stability, bottom roughness analysis, external
corrosion protection, crossing design and construction feasibility.
These topics encompass the majority of issues regarding offshore
pipelines.
Some issues not covered herein are expansion analysis,
curve stability, risers and steel catenary risers (SCRs), analysis of
the installation of in-line appurtenances, fracture analysis of
weldments and subsea connections.
5.1 Design Basis
The first step in offshore pipeline design is establishing a
concise design basis document (DBD). For consistency, every
project requires, in its early phase, the establishment of the DBD.
This is to be used as a reference by the design team for the
different aspects of offshore pipeline design. The DBD provides
basic project-dependent information, and enables consistency and
correctness of project calculations, reports, bid specifications,
contract documents, installation procedures, etc, with respect to the
fundamental parameters of the project.

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