This paper outlines methodologies and analytical tools for the Risk Based Inspection and Integrity Management (RBIM) of pipeline systems. The objective of a risk based integrity management (asset management) approach is to ensure and maintain the required confidence in the pipelines integrity and hence maximise its operating availability, whilst optimising the resources used to ensure the pipeline integrity e.g. the planning of inspection intervals and methods, repairs etc.

ABSTRACT

This paper outlines methodologies and analytical tools for the Risk Based Inspection
and Integrity Management (RBIM) of
pipeline systems. The objective of a risk based integrity management (asset
management) approach is to ensure and
maintain the required confidence in the pipelines integrity and hence maximise
its operating availability, whilst optimising the
resources used to ensure the pipeline integrity e.g. the planning of inspection
intervals and methods, repairs etc.

The basic steps of a pipeline system RBIM are:

  1. Establish and define the required levels of confidence in the pipeline’s integrity.
  2. Develop as detailed knowledge as possible of the pipelines past, present and future operating condition and
    environment.
  3. Systematically evaluate and rank the risks of each potential failure mode specific to the particular pipeline, accounting
    for and highlighting the uncertainties. This is largely performed at a qualitative level.
  4. Time-dependent degradation failure modes (e.g. internal corrosion) considered to be a risk to the pipeline are
    assessed using spreadsheet based semi-probabilistic structural reliability assessment tools. These are quick and
    simple to use, predicting the period in which the confidence in pipeline’s integrity against a particular failure mode
    falls below specified levels. A risk based inspection (RBI) planning approach is developed mixing the structural
    reliability approach with a generic database approach of risk analysis in c) above.
  5. A total production maintenance (TPM) approach is considered linking it with risk-based maintenance (RBM).
    f) Solutions are then considered to reduce / eliminate the risks considered to be unacceptable and the uncertainties in the
    integrity management, and to maintain confidence in the pipeline integrity.

KEYWORDS: Risk Based Inspection, Integrity Management, Total
Production Maintenance and Pipeline Systems.

INTRODUCTION

The design of Pipeline systems is increasingly being optimised through use
of advanced design methods, primarily to minimise the CAPEX (particularly on
high CAPEX projects such as major trunk lines). This generally results in less
redundancy to extreme loads, reduced toleration to corrosion, third-party defects
and fatigue damage, with the expectation that these loads will be monitored
and controlled during operation, thus the monitoring and control requirements
need to be well defined. Also many pipeline systems are ageing beyond their
design life, with an increasing risk of failure and hence need to be inspected
and repaired or verified as fit for purpose. Further, the operation of pipeline
systems is characterised by fewer multiple-tasked employees supported with more
expensive inspection tools.

These industry environments require tools for the application of risk and
reliability methods to identify and prioritise among project tasks where the
risks are highest from both safety and business view points. For successful
operation and maintenance of pipeline systems, it is important to select technologies
and methods such that risks are managed in the most cost-effective manner. A
good understanding and management of risks is of vital importance in ensuring
the integrity of the pipeline.

The development of risk and reliability tools requires the integration of
risk analysis, materials technology and structural
analysis. Risk analysis is increasingly used for decision making in detailed
design, as most risks can be identified and controlled in the design process
or requirements for future controls identified. For planning of risk based inspection
of pipelines in operation, it is necessary to combine our knowledge of risk
analysis, prediction of corrosion and third-party defects and remaining structural
strength.

Some of the risk based inspection methods in literatures tend to be too complicated,
and can not be practically applied due to a lack of databases for the determination
of the variables used in the risk estimation. It is therefore important that
simplified methods of risk estimation are developed.

The purpose of this study is to apply risk-based inspection planning methodologies
to pipeline systems, by developing a set of methods and tools for the estimation
of risks using structural reliability approach and incidental databases, and
to illustrate our risk based inspection and management approach through a few
examples. Focus will be on the development of simplified methods and analysis
tools for practical applications.

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