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Getting Started

Background

If needed, here are some links for background info or other places to start.

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Beginning Risk Assessment/Management

Excerpts taken and modified from Chapter 1

Let’s not overlook the always-first task:

Fix the Obvious

Once that’s done, let’s see next steps:

The Risk Assessment Process

Robust pipeline risk assessment generates a risk profile, showing changes in risk along a pipeline route. Risk management uses that profile to identify ways to effectively minimize the risk. Risk assessment is always the beginning point for risk management. Risk estimates can be generated with varying levels of rigor.

Quickly getting answers

Focus Point
A good risk assessment framework supports all levels of rigor: from rapid, ‘ballpark’ estimates to detailed, robust analyses.

Formal pipeline risk assessment does not have to be highly complex or expensive. A savvy risk manager can, in a relatively short time, have a fairly detailed pipeline risk assessment system set up, functioning and producing useful results. Simple computer tools such as a spreadsheet or desktop database can efficiently and completely support even the most robust of assessments. Then, by establishing some administrative protocols around the processes, the quick-start applicator now has a complete system to fully support risk management.

The underlying ideas are straightforward, and rapid establishment of a very useful decision support system is certainly possible. Initial information and processes may not be of sufficient rigor for full decision-support, but the user will nonetheless immediately have a formal structure from which to better ensure decisions of consistency and completeness of information.

Both a rudimentary, quick assessment and a robust, detailed assessment will follow the same procedure. This provides for the assessment to grow—getting more accurate with the inclusion of more and more details. The difference between the simple assessment and the robust lies only in the depth of investigation. Before examining this in more detail, consider also that a risk conceptualization exercise is also available to ‘get answers quick’.

Risk Conceptualization—Getting ‘In the Ballpark’

There exists a type of risk analysis that is even more preliminary than the rudimentary assessment to be presented in a following section. This might be termed more of a risk conceptualization rather than assessment and is based solely on basic deductive reasoning.

Illustrated by an example, an analyst may posit that a pipeline’s future risks will mirror the losses shown by recent historical annual US gas transmission pipeline experience. He assumes that the subject pipeline ‘behaves’ as an average[2] US gas transmission pipeline (see Stats). Under this assumption, he deduces that future risks on the subject pipeline are 1.2 significant leak/ruptures per 2,000 mile-years that generate $1,200/mile-year of losses. He scales these values to the length of his subject pipeline and uses results in decision-making.

A similar approach is the use of historical leak/break rates to predict future behavior of sections of distribution pipeline systems. With larger counts of leak/break events, these produce more statistically valid summaries and are sometimes used to understand system deterioration rates.

These generalized, deductive-reasoning approaches obviously are limited, especially when applied to a particular pipeline segment (see numerous discussions later in this text regarding pitfalls associated with use of general statistics in this way). They do, however offer useful risk context, providing insights into behaviors of populations of components over long periods of time. In the absence of any other information, this approach provides estimates that may often be a close approximation—perhaps within an order of magnitude or so—of average future performance of many pipelines.

Risk Assessment Steps

Beyond the conceptualized risk estimate noted above, true risk assessment must consider the specifics of the asset being assessed and not be unduly influenced by historical data from other assets, even if similar. The following minimum steps are required for assessment of pipeline risk, regardless of level of rigor. While seemingly detailed, these steps can be completed very quickly when only approximate solutions are sufficient.

  1. Segmentation: Identify the components that comprise the pipeline being assessed
    • A new component is needed for every significant change in the pipeline’s current and historical construction/operating/maintenance practice and every significant[3] change in the pipeline’s surroundings.
  2. Estimate Probability of Failure for each plausible failure mechanism.
    • Exposure: Estimate each component’s unmitigated exposure from each threat, recognizing the two types of exposure
      • Degradation rate from time-dependent failure mechanisms
      • Event rate from time-independent failure mechanisms.
    • Mitigation: Estimate effect of each mitigation measure for each component’s threats
      • Identify all mitigation measures
      • Rate effectiveness of each
      • Combine and apply estimates to appropriate exposures.
    • Resistance: Estimate each component’s resistance to failure from each mitigate exposure
      • Theorize amount of resistance available in the absence of defects
      • Estimate the role of possible defects present in each component, considering rates of defect emergence and age and accuracy of all inspections and integrity assessments.
  3. PoF: Calculate PoF from each threat
    • Risk Triad: combine Exposure, Mitigation, Resistance
    • Estimate TTF and then PoF for time-dependent failure mechanisms
    • Estimate PoF for time-independent failure mechanisms
    • Combine all PoF’s.
  4. Calculate CoF for each component, based on desired level of conservatism and
    • Possible failure scenarios
    • Possible damages from each scenario.
  5. Combine PoF and CoF into a risk estimate for each component. Combine component risk estimates as needed.

These steps show the inputs and analyses necessary to produce plausible estimates of risk along a pipeline. Varying levels of rigor are possible at each step.

Experience has shown that any threat can independently dominate the actual risk. Therefore, each plausible threat warrants consideration and should be documented in the assessment, even if only a cursory level of effort can be applied to generate initial estimates.

Implicit in these steps is the initial recognition that a pipeline (or pipeline station or any other portion of a pipeline system) is a collection of components. Each component will contribute to the risk associated with the whole collection. Each component is exposed to threats from its immediate surroundings. These normally include corrosion, external forces, and others. Each component also generates some amount of consequence potential to its surroundings. This is the reality that should be captured in any risk assessment. See segmentation discussions.

Even the most rudimentary risk assessment needs to acknowledge the individual components that comprise the pipeline system and their individual surroundings. To do this, a list of components is needed. This can be very detailed or, at the other extreme, very generalized.

As described above, for each component, three inputs are needed to characterize each plausible threat (failure mechanism). Each component also requires one input for consequence potential. These four component-specific inputs are best obtained by examination of all of the pertinent underlying features but can be simply assigned a preliminary general estimate, pending the deeper analyses. In a very rudimentary assessment, the four ingredients are directly input for each component based perhaps solely on SME judgment.

Published inBeginners CornerRisk AssessmentRisk Modeling