Abstract

Maintaining the integrity of a high pressure flexible pipe field system requires a systematic approach towards ensuring pipe integrity over the entire field life. While risk-based approaches have existed towards steel structures and pipelines for many years, no widely accepted approach has, until recently, been proposed for flexible pipes. This paper describes industry Guidelines for the Integrity Monitoring of Unbonded Flexible Pipes, which define a systematic riskbased approach towards managing the integrity of flexible pipes. Also described is the practical implementation of these guidelines on two offshore flexible pipe field systems.

The integrity management guidelines have been applied to BP's Atlantic Margins Foinaven and Schiehallion flexible pipe field systems. Integrity management strategy is based on an identification of potential failure modes and an evaluation of the risk and consequence of failure from each mode. The program has also provided a systematic approach to managing the risks associated with damage that occurred to some of the flexible pipes. A series of inspection, monitoring, testing, analysis and offshore procedures have been put in place to implement the integrity management strategy.

The flexible pipe integrity program has effectively managed in-service pipe integrity and implemented solutions relating to pipe damage using the same risk-based process. The inspection and monitoring program provides for the periodic evaluation and review of in-service inspection and monitoring results and the revision of management strategy in light of these results.

A structured risk-based approach to the integrity management of flexible pipe field systems provides confidence in the operator's ability to manage their in-service performance. Thedevelopment of industry guidelines for flexible pipe integrity management and their practical implementation is an important step in demonstrating that this confidence can be achieved.

Introduction

The purpose of the integrity management process is to identify potential causes of failure and to implement a risk-consistent monitoring and inspection strategy to avoid failure during the service life of the system.

Based on the results of collaborative joint industry project effort [1][2], a risk-based approach has been developed to identifying potential failure modes of a flexible pipe field system and then evaluating the probability and consequence of failure for all relevant modes. This methodology has been refined by the authors following its application to several key flexible pipe field systems, two of which are presented in this paper.

The development of integrity management strategy, and the maintenance of an integrity management program specifically addressing the flexible pipe field system, has by now been implemented for operators on a significant number of new and existing systems. This approach is consistent with recent industry practice for the integrity management of safety-critical or environmentally critical offshore systems, whereby integrity monitoring methods are related to the identified risk level in the system.

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