Pipeline Integrity: Program Develpoment, Risk Assessment and Data Management
IMP Approach
Gas industry organizations have researched and identified two paths for operators to collect and effectively use data for
risk assessment. The two paths are Prescriptive-Based or Performance-Based. MDU will use both the Prescriptive and
Performance based methods depending on the pipeline segment. Based on the knowledge of our system, Performance-
Based will be the primary method used. The two methods are:
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Prescriptive-Based: limited, and no flexibility, but easier to implement. All of the specified data elements must be
available in order to perform risk assessment. Elements include pipe attributes, construction, operational, and
inspection.
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Performance-Based – more options for: inspection intervals, inspection methods, mitigation and prevention
activities. Requires more knowledge and data intensive, risk assessments and analysis to perform integrity
assessment. Performance-Based IMP’s require the following:
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Description of risk analysis methods
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Documentation of all applicable data
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Documentation analysis for integrity assessment intervals, mitigation and prevention methods
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Documentation performance matrix that will effectively evaluate intervals, mitigation and prevention methods
chosen.
IMP for Performance Process
Montana-Dakota’s IMP is based on the following six facets:
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Identify Pipeline Integrity Threats
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Data Identification, Collection and Integration
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Risk and Integrity Assessment
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Develop Integrity Management Plan
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Mitigation Strategy
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Continuing Assessment
A. Identify Pipeline Integrity Threats
The identification, management and assessment of threats to a pipeline are key components of an Integrity Management
Plan. Therefore, identification of threats becomes the first step in the process. These threats are numerous, with
significant threats to particular pipeline segments, and the commensurate risk they impose, being considered in
determining an overall approach to integrity management.
In the threat phase, pipeline segments are identified. We defined operating pipeline segments as a pipeline system that
connects a primary gas source to a primary gas delivery point or from major pipeline facilities such as valve – valve or
pig launcher – pig receiver, etc. This differentiates operating segments from High Consequence Areas (HCA) segments.
After identifying each pipe segment, High Consequence Areas are located, based on OPS’s HCA rule. It is essential to
recognize the impacts of threats that exist in a HCA segment versus elsewhere on the operating segment. This is
particularly critical in the mitigation step, where it is imperative to understand the condition of the pipeline segment
extending beyond the HCA, but within the specific operating pipeline segment.
A High Consequence Area or HCA is defined as areas where the potential consequences of a gas pipeline accident may
be significant or may do considerable harm to people or their property.
The OPS definition includes:
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All class 3 & 4 locations, and
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Areas where the pipeline is within 300, 660 or 1000 feet of a building occupied by person who are confined, or
are of impaired mobility, or would be difficult to evacuate, and
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Areas where the pipeline is within 300, 600 or 1000 feet of a building or outside area where 20 or more persons
congregate at least 50 days in any 12-month period.
OPS’s HCA definition takes into consideration the area potentially affected by a pipeline rupture and subsequent
ignition and fire. This heat affected zone is based on GRI Report: GRI-00/0189. The C-FER model equation is:
MDU’s case study is an eight-inch pipeline, operating at 500 psig and in a Class 3 area. Therefore, the segment falls
within the 300 foot HCA rule criteria.
Once the HCA’s are identified, we focus on threats. The demands on the pipeline system and threats to pipeline integrity
are constantly changing. The types of threats to a pipeline are numerous and the mechanics of failure may be time
dependent, stable and time independent. Time dependent is external and internal corrosion, and stress corrosion
cracking. Stable is manufacturing related defects, welding/fabrication defects and equipment. Time independent threats
include items such as third party damage, incorrect operations, weather related and outside force.
