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PRCI PR-244-9910
- Pipeline Design for Mechanical Damage
- Report / Survey by Pipeline Research Council International, 01/01/2001
- Publisher: PRCI
$38.00$75.00
L51860e
C-FER Technologies, Inc
Need: Mechanical damage by third-party excavation is the leading cause of pipeline failures in North America and Europe, yet pipeline design standards are mainly based on resistance to internal pressure and do not explicitly address mechanical damage. Without a design method that takes into account the likelihood and consequences of mechanical damage, the risk (referring to the total risk to life safety herein) implied by current design practices is not uniform for different pipelines with respect to mechanical damage.
Result: A reliability-based method provides a means to ensure that risks implied by the design are acceptable and uniform. To achieve this goal, the design criteria presented in this report were calibrated to meet a set of target reliabilities that were selected by a two-step approach. In the first step, the average target reliability level was set to match the overall historical level, on the basis that gas pipelines in general have a satisfactory safety record. The second step involved varying the target reliability levels in inverse proportion to the severity of failure consequences so as to maintain consistency of risk. The consequences, and hence the target reliability levels, were functions of pipeline diameter, operating pressure and location class. The tool used to develop the design check is a probabilistic model that relates the probability of failure due to mechanical damage to the design parameters (e.g., diameter, wall thickness, steel grade, pressure and location class) and the preventative measures put in place (e.g., burial depth, response time to notification, level of site-supervision for excavation, and frequency of right-of-way patrol). The model has two essential components: a fault tree that estimates interference frequency based on land use type and preventative measures, and a structural reliability model that estimates the probability of puncture or burst due to a gouged dent for a given interference event. The overall probabilistic framework is based on the Monte-Carlo simulation method. In predicting failure probabilities, the uncertainties in load and resistance variables and model errors were taken into consideration.
Benefit: The objective of this project was to develop a design check for mechanical damage and assess its implication on wall thickness design. A reliability-based, limit states design method (also referred to as load and resistance factor design method) was chosen as a rational approach to meet the objectives. In addition, the benefit of preventive maintenance during pipeline operation (e.g., effects of one-call system and right-of-way patrol) was considered in developing the design check.
C-FER Technologies, Inc
Need: Mechanical damage by third-party excavation is the leading cause of pipeline failures in North America and Europe, yet pipeline design standards are mainly based on resistance to internal pressure and do not explicitly address mechanical damage. Without a design method that takes into account the likelihood and consequences of mechanical damage, the risk (referring to the total risk to life safety herein) implied by current design practices is not uniform for different pipelines with respect to mechanical damage.
Result: A reliability-based method provides a means to ensure that risks implied by the design are acceptable and uniform. To achieve this goal, the design criteria presented in this report were calibrated to meet a set of target reliabilities that were selected by a two-step approach. In the first step, the average target reliability level was set to match the overall historical level, on the basis that gas pipelines in general have a satisfactory safety record. The second step involved varying the target reliability levels in inverse proportion to the severity of failure consequences so as to maintain consistency of risk. The consequences, and hence the target reliability levels, were functions of pipeline diameter, operating pressure and location class. The tool used to develop the design check is a probabilistic model that relates the probability of failure due to mechanical damage to the design parameters (e.g., diameter, wall thickness, steel grade, pressure and location class) and the preventative measures put in place (e.g., burial depth, response time to notification, level of site-supervision for excavation, and frequency of right-of-way patrol). The model has two essential components: a fault tree that estimates interference frequency based on land use type and preventative measures, and a structural reliability model that estimates the probability of puncture or burst due to a gouged dent for a given interference event. The overall probabilistic framework is based on the Monte-Carlo simulation method. In predicting failure probabilities, the uncertainties in load and resistance variables and model errors were taken into consideration.
Benefit: The objective of this project was to develop a design check for mechanical damage and assess its implication on wall thickness design. A reliability-based, limit states design method (also referred to as load and resistance factor design method) was chosen as a rational approach to meet the objectives. In addition, the benefit of preventive maintenance during pipeline operation (e.g., effects of one-call system and right-of-way patrol) was considered in developing the design check.
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