Damage Assessment and Confinement in Offshore Pipelines

Overview

Main Objective

This report presents the results of research on four problems of the propogating buckle in marine pipelines.

Public Abstract

This report presents the results of research on four problems of the propogating buckle in marine pipelines. Simulated accidental damage was produced in the laboratory on model pipes with point type and knife (line) type indentors. These damaged pipes are subjected to external pressure and a propogating buckle initiated. It is found that the point type and line type damage produce similar initiation pressures when the damage is characterized by the ovality of the most damaged section.

A propogating buckle can also be initiated from a bending buckle. Using model pipes, it is shown experimentally that bending of the pipe beyond that needed to buckle it does not have a large influence on the initiation pressure.

A propogating buckle can be conveniently arrested by using the so-called slip-on arrestor. In practice, this arrestor has a gap between the arrestor and the pipe which can considerably degrade the arrestor performance. It is shown that the loss in efficiency can be somewhat mitigated by te use of groupt.

The propogating buckle can cause a fracture of the pipeline due to the large strains that occur in the flattened pipe. An analysis is developed to determine the shape of the collapsing pipe and the associated strains. Separate bend tests are conducted to determine the bend radius to produce fracture.

Status History

Final report submitted in 02/1982.

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