Implementation of Integrity Management Programs (IMP) for pipelines has motivated the design of Fitness-For-Service methodologies to assess Stress Corrosion Cracking (SCC) and fatigue-dependent features reported by Ultrasonic Crack Detection (UTCD) In-Line Inspections. The philosophical approach defined by the API 579 [1] “Fitness-For-Service” from the petrochemical industry in conjunction with Risk-based standards and regulations (i.e. CSA-Z662-2003 [2] and US DOT 49 Parts 192 [3] and 195 [4]) and in-line inspection validation (i.e. API 1163 [5]) approaches from the pipeline industry have provided the engineering basis for ensuring the safety, reliability and continued service of the in-line inspected pipelines. This paper provides a methodology to develop short and long-term excavation and re-inspection programs through a four (4) phase-process: Pre-Assessment, Integrity Criticality Assessment, Remediation and Repair, Remaining Life Extension and In-Service Monitoring. In the first phase, Pre-assessment, areas susceptible to Stress Corrosion Cracking (SCC) and fatigue-dependent features are correlated to in-line inspection data, soil modeling, pipeline and operating conditions, and associated consequences in order to provide a risk-based prioritization of pipeline segments and technical understanding for performing the assessment. The second phase, Integrity Criticality Assessment, will develop a short-term maintenance program based on the remaining strength of the in-line inspection reported features previously correlated, overlaid and risk-ranked. In addition, sites may be identified in Phase 1 for further investigation. In the third phase, a Remediation and Repair program will undertake the field investigation in order to repair and mitigate the potential threats as well as validating the in-line inspection results and characterization made during the Pre-assessment and Integrity Criticality Assessment (Phases 1 & 2). With the acquired knowledge from the previous three (3) phases, a Remaining Life Extension and In-Service Monitoring program will be developed to outline the long-term excavation and re-inspection program through the use of SCC and Fatigue crack growth probabilistic modeling and cost benefit analysis. The support of multiple Canadian and US pipeline operating companies in the development, validation and implementation of this methodology made this contribution possible.
The ability to accurately determine the rate of corrosion growth along a pipeline is an essential input into a number of key integrity management decisions. For example, corrosion rates are needed to predict pipeline reliability (probability of failure and/or probability of exceedance) as a function of time, to identify the need for and timing of field investigations and/or repairs and to determine optimum re-inspection intervals to name just a few applications. As more and more pipelines are now being inspected using intelligent in-line inspection (ILI) tools for a second or even third or fourth time, pipeline operators require reliable guidelines for comparing repeat ILI data sets to obtain valid corrosion growth rates. Because of the measurement uncertainties associated with corrosion size estimated from a single ILI run, the corrosion growth rate calculated from consecutive ILI runs has a degree of uncertainty that needs to be considered in determining valid and accurate corrosion growth rates. The ratio between the measured corrosion growth and the measurement error is an important parameter in determining a meaningful distribution of the corrosion growth rate either when performing defect to defect comparisons or when comparing the defect populations in pipeline segments. When this ratio is small the associated uncertainty can be too large to make meaningful probabilistic inferences. As the ratio increases, the effect of measurement uncertainty becomes more manageable, allowing growth rate distributions to be calculated with reasonable confidence. This paper describes an approach to define the probability distribution of corrosion growth rates as a function of a simple parameter that characterizes the ratio between the ILI-observed corrosion growth and the ILI measurement error. This approach has been developed as part of an ongoing PRCI-sponsored research project to produce procedures for determining and validating corrosion growth rates from repeat ILI runs. The paper also provides examples using sample data from repeat ILI runs showing the application of these procedures, the treatment of measurement uncertainty, the resulting corrosion growth rate information that can be obtained and the associated level of confidence in the results.
Over the past 12 years, as directed by federal and provincial regulations, Canadian pipeline companies have been formally developing and implementing Integrity Management Programs (IMPs). Since 1999, IMPs have been a requirement in the Canadian consensus industry standard CSA Z662. Furthermore, since the release of CSA Z662 Annex N in 2005, both the BC OGC and the Alberta Energy Resources Conservation Board (ERCB) (Canadian provincial regulators) have made CSA Z662 Annex N mandatory for their regulated companies. Annex N incorporates key management system (MS) elements such as a company’s policy and commitment, responsibilities, competency, planning, management of change, review and evaluation. This paper presents the findings of IMP audits conducted by the NEB and BC OGC regulators during the period of 2001–2011. This paper also includes the findings of NEB’s analysis of pipeline incidents that occurred between 2005 and 2009 and how these incident findings correlate to the audit findings. This paper is structured as follows: • Integrity management regulatory frameworks • IMP and MS elements and their interconnection • Audit findings from the NEB and the BC OGC • Incident findings from the NEB • Analysis of the audit findings and their correlation to incidents • Trends on IMP and MS audit and incident findings The paper provides a general understanding of the findings and their trends on pipeline integrity management and on incidents in terms of IMP/MS elements as described in Table 1. The results from this study may help stakeholders to determine strategies to increase the adequacy, implementation and effectiveness of pipeline integrity management. This paper does not include any company-specific information nor results and conclusions from any particular audit report or incident.
Industry standards (i.e. API 1160, ASME B31.4 and B31.8S-2001, CSA-Z662-2003) and regulations (i.e. US DOT 49 Parts 195-2002 and 192-2003, and NEB On-shore 99) have delineated the risk-based elements of oil and gas pipeline integrity management programs. A Fitness-For-Service Assessment is part of an overall Integrity Management Program that is implemented for the pipeline system depending on the required pipeline operational conditions, severity of integrity threats, and their impact or consequences to the public, environment and employees. This paper provides guidelines for pipeline operators of oil pipeline systems exposed to corrosive and geotechnical sensitive environments and high consequence areas to develop long term integrity plans. In this case, the pipeline integrity plans were prepared based on the integration of data and assessments such as metal loss, geometry and strain in-line inspections, product corrositivity, cathodic protection, geotechnical hazard identification, and pipe class location/high consequence areas. Guidelines for developing near-term integrity plans are herein provided based on best industry practices and regulations. In 2002, Oleoducto Central S.A. (Ocensa) and CC Technologies initiated the Phase 1 of the Fitness-for-Service assessment of 698 km of NPS 16/30 crude oil pipeline from Cupiagua to Coven˜as. Phase 1 was comprised of an internal corrosion study to assess the corrosivity of the product and its impact in the future. Corrosivity of the crude oil was determined from laboratory testing and correlated to the pipeline operational and topographical conditions. In 2003, the Phase 2 of the Fitness-for-Service assessment was comprised of a review of the near-term maintenance program and the development of the long-term maintenance program. The long-term integrity plan program for corrosion features was developed using a deterministic and probabilistic corrosion growth modeling to determine excavation/repair and re-inspection interval alternatives. The corrosion growth modeling took into account the in-line inspection tool accuracy based on the field validation program. The most cost effective alternative was identified by using a cost benefit analysis technique. This implemented approach contributed to timely schedule maintenance activities. In addition, the selected excavations confirmed with high confidence the results from the Ocensa-CC Technologies Canada predictability model. Geometry features reported by the geometry/inertial in-line inspection were initially evaluated, and correlated to the corrosion in-line inspection data, and the geotechnical hazard study to identify potential locations of slope instability, river-crossing scouring for assessing internal corrosion criticality. Strain areas were also assessed and correlated to pipe wall deformation and potential areas of land movement. Pipe class location limits were determined based on latest dwelling locations and distribution, and then correlated to the reported corrosion features for verifying minimum safety factors. The long-term maintenance program was integrated from all assessments performed on the identified integrity threats. As a result, guidelines were prepared for implementing technically sound and economically-optimized long-term inline inspection, excavation and repair plans.
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