Offshore Pipelines
Written primarily for engineers and management personnel working on offshore and deepwater oil and gas pipelines, this text sets forth guidelines that can be employed to optimize pipeline development projects.
TABLE OF CONTENTS Offshore Pipelines
Chapter 6: Operating Stresses
6.1 Introduction
This chapter addresses the calculation of operation stresses and end movements (expansion) for trenched and non-trenched, single well pipelines. Operating stresses are those which result from a combination of internal pressure and thermal stresses that occur during operation. Equations of operating stresses and expansion are provided. Only single well pipe internal pressure is addressed. In the case of relatively thin-wall pipe ( D/ t > 20), the equations presented can be used with P representing the difference between the internal and external pressure. This is not the case with thick-wall cylinders ( D/ t < 20).
6.2 Operating Forces
When in operation, pressure and thermal forces exist, which act to expand the pipeline both rapidly and longitudinally. These are due to internal pressure and temperature difference between the pipe and surrounding fluid. The magnitude of these stresses is dependent upon forces opposing the above conditions, and boundary conditions, namely, soil friction acting longitudinally, end constraints, and end cap effect.
6.2.1 Internal Pressure Stresses
A pipeline is a pressure vessel in the form of a cylinder, and, for this reason, some of the most detailed information available is obtained in the literature for pressure vessel design. Pipes with D/t greater than 20 are referred to as thin-wall pipes, and that with D/t less than 20 are called thick-wall pipes.
6.2.1.1 Thin-Wall Pipe
If a thin-wall pipe is subjected to internal pressure, P, the action of radial force distributed around the circumference will produce...
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