Limit States Design and Assessment of Onshore Pipelines

2012 ◽  
Author(s):  
Maher Nessim
Keyword(s):  
Natural Gas ◽  
Development Stage ◽  
Simple Design ◽  
Safety Factors ◽  
Limit States ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Wide Range ◽  
Assessment Standard ◽  
Expected Outcomes

In 2005, guidelines for the application of reliability-based design and assessment (RBDA) to natural gas pipelines were developed under PRCI sponsorship. The methodology underlying these guidelines has since been adopted as a non-mandatory Annex in the CSA Z662 standard (Annex O). The benefits of reliability-based methods include consistent safety levels, optimized solutions that make best use of available resources and flexibility in addressing non-standard problems. The key limitations of the methodology are that it requires specialized expertise, good data and a significant analysis effort. One approach that has been successfully used to simplify the application of reliability-based methods is to develop simple design and assessment rules that are designed to meet specified safety levels. In this approach, which is referred to here as limit states design and assessment, the checking rules incorporate safety factors that are “calibrated” to meet pre-selected reliability targets, within a specified tolerance, over a wide range of possible design and assessment cases. Probabilistic analyses are performed as part of the development stage, but the resulting checks are deterministic. The basic elements required to calibrate limit states design and assessment checks have been developed as part of the RBDA methodology, making the development of a limit states approach feasible. This paper provides an overview of an ongoing Joint Industry Project to develop a limit states design and assessment standard that addresses the key threats to the safety of onshore pipelines. The benefits and limitations of this approach are discussed in comparison to the full RBDA approach, and the expected outcomes of the project are described.

Reliability Based Design and Assessment for Location-Specific Failure Threats With Application to Natural Gas Pipelines

2006 ◽  
Author(s):  
Maher Nessim ◽  
Wenxing Zhou ◽  
Joe Zhou ◽  
Brian Rothwell
Keyword(s):  
Natural Gas ◽  
Individual Risk ◽  
Gas Pipelines ◽  
Limit States ◽  
Integrity Assessment ◽  
Natural Gas Pipelines ◽  
Risk Criteria ◽  
Reliability Based Design ◽  
Unstable Slope ◽  
The Individual

The acceptance criteria used in Reliability Based Design and Assessment (RBDA) are defined as a set of reliability targets (where reliability is defined as 1.0 minus the probability of failure). Because of the linear nature of pipeline systems, reliability targets are defined on a per km-year basis. Such targets are directly applicable to failure causes (or limit states) that are equally likely to occur anywhere along a segment of the pipeline (e.g. equipment impact or yielding/rupture of defect-free pipe under internal pressure). They are, however, not directly applicable for design and assessment situations involving limit states that apply at known specific locations. Examples include design for geotechnical loads on a particular unstable slope or integrity assessment of specific corrosion defects based on in-line inspection data. In previous work, reliability targets for natural gas pipelines have been developed on the basis of appropriate societal and individual risk criteria. This paper describes an approach to adapt these targets, and demonstrate compliance with them, for location-specific limit states. The approach is based on using separate checks to ensure that the individual and societal risk criteria underlying the targets are met. An example is included to demonstrate application of the approach to design a pipeline on an unstable slope.

Reliability Based Design and Assessment for Location-Specific Failure Threats With Application to Natural Gas Pipelines

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Maher Nessim ◽  
Wenxing Zhou ◽  
Joe Zhou ◽  
Brian Rothwell
Keyword(s):  
Natural Gas ◽  
Individual Risk ◽  
Gas Pipelines ◽  
Limit States ◽  
Integrity Assessment ◽  
Natural Gas Pipelines ◽  
Risk Criteria ◽  
Reliability Based Design ◽  
Unstable Slope ◽  
The Individual

The acceptance criteria used in reliability based design and assessment are defined as a set of reliability targets (where reliability is defined as 1.0 minus the probability of failure). Because of the linear nature of pipeline systems, reliability targets are defined on a per kilometer-year basis. Such targets are directly applicable to failure causes (or limit states) that are equally likely to occur anywhere along a segment of the pipeline (e.g., equipment impact or yielding/rupture of defect-free pipe under internal pressure). They are, however, not directly applicable for design and assessment situations involving limit states that apply at known specific locations. Examples include design for geotechnical loads on a particular unstable slope or integrity assessment of a corrosion defect at a specific location (as determined by in-line inspection). In previous work, reliability targets for natural gas pipelines have been developed on the basis of appropriate societal and individual risk criteria. This paper describes an approach to adapt these targets and demonstrate compliance with them, for location-specific limit states. The approach is based on using separate checks to ensure that the individual and societal risk criteria underlying the targets are met. An example is included to demonstrate application of the approach to design a pipeline on an unstable slope.

Probability Calculation of Equipment Impact Based on Reliability Method

2014 ◽  
Author(s):  
Jiang Lu ◽  
Wen Wu ◽  
Zhenyong Zhang ◽  
Jinyuan Zhang
Keyword(s):  
Natural Gas ◽  
Survey Data ◽  
Fault Tree ◽  
Gas Pipelines ◽  
Impact Frequency ◽  
Dense Population ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Probability Calculation ◽  
The Impact

In order to apply the Reliability Based Design and Assessment (RBDA) methodology to evaluate the equipment impact on the onshore natural gas transmission pipelines in China, a research project was undertaken by China Petroleum Pipeline Engineering Corporation (CPPE) based on the framework developed by C-FER Technologies (C-FER) in “Guidelines for Reliability Based Design and Assessment of Onshore Natural Gas Pipelines” (sponsored by PRCI). The objective of the project was to collect native data and calibrate the probability models[1] in order to make it suitable for the situations in China where there is dense population and many newly-built high pressure and large diameter pipelines. The equipment impact model consists of two components: a) the impact probability model which calculates the frequency of mechanical interference by excavation equipment; and b) the failure model which calculates the probability of failure in a given impact. A detailed survey was undertaken in 2012 in order to collect the data required to calculate the impact frequency and the load applied by an excavator to a pipeline. The survey data for impact frequency calculation was gathered based on 19,300km of transmission pipelines from 4 operating companies in China. They reflect current prevention practices and their effectiveness. The frequencies of basic events summarized in this survey used to calculate the probabilities of the fault tree are generally agreement with the data summarized in PRCI’s report. The impact frequencies calculated by the fault tree under typical prevention measures are 400%, 200%, 20% and 0% higher than that in PR-244-9910 report for class 1, class 2, class 3 and class 4 areas respectively, which is due to dense population and more construction activities. Bucket digging forces of 321 types of excavators from 20 manufacturers were gathered. The survey data of the forces are slightly higher than that in the PR-244-9729 report as a whole due to the increase in mechanical efficiency of excavators in recent years. The excavator maximum quasi-static load model was calibrated correspondingly. Equipment impact probability calculation and model sensitivity analysis results are described to present several characteristics of onshore transmission natural gas pipelines in China.

Application of Reliability Based Design and Assessment to Maintenance and Protection Decisions for Natural Gas Pipelines

2010 ◽  
Author(s):  
Maher Nessim ◽  
Howard Yue ◽  
Joe Zhou
Keyword(s):  
Public Awareness ◽  
Test Cases ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Wide Range ◽  
Awareness Programs ◽  
Detailed Assessment ◽  
Pipeline Failure ◽  
The Impact ◽  
Practical Implications

This paper describes a detailed assessment that was carried out to investigate the practical implications of using the Reliability Based Design and Assessment (RBDA) methodology, as described in Annex O of CSA Z662, as a basis for evaluating existing pipelines and making decisions on maintenance planning and damage prevention strategies. Two key pipeline failure threats are addressed, namely corrosion and equipment impact. The assessment was based on a number of test cases covering a wide range of diameters, grades, pressures, location classes and corrosion severities. The reliability levels associated with these cases were calculated as a function of time and compared to the reliability targets. Cases that did not meet the targets were re-analyzed with increasingly enhanced maintenance measures until the targets were met. Maintenance actions considered included higher maintenance frequencies and more stringent repair criteria for corrosion, and enhancements to such parameters as right-of-way patrol frequency and condition, public awareness programs and dig notification response for equipment impact. The results demonstrate that the reliability targets can be met through the implementation of reasonable and practical maintenance measures for the cases considered. The impact of using RBDA on the expected failure rates is discussed. In addition, the diameter and class ranges of pipelines requiring enhanced maintenance over the current norm are identified.

scholarly journals An Investigation into the Volumetric Flow Rate Requirement of Hydrogen Transportation in Existing Natural Gas Pipelines and Its Safety Implications

Gases ◽  
2021 ◽  
Vol 1 (4) ◽  
pp. 156-179
Author(s):  
Abubakar Jibrin Abbas ◽  
Hossein Hassani ◽  
Martin Burby ◽  
Idoko Job John
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Compressibility Factor ◽  
Volumetric Flow Rate ◽  
Gas Pipeline ◽  
Internal Erosion ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Natural Gas Pipeline ◽  
Wide Range

As an alternative to the construction of new infrastructure, repurposing existing natural gas pipelines for hydrogen transportation has been identified as a low-cost strategy for substituting natural gas with hydrogen in the wake of the energy transition. In line with that, a 342 km, 36″ natural gas pipeline was used in this study to simulate some technical implications of delivering the same amount of energy with different blends of natural gas and hydrogen, and with 100% hydrogen. Preliminary findings from the study confirmed that a three-fold increase in volumetric flow rate would be required of hydrogen to deliver an equivalent amount of energy as natural gas. The effects of flowing hydrogen at this rate in an existing natural gas pipeline on two flow parameters (the compressibility factor and the velocity gradient) which are crucial to the safety of the pipeline were investigated. The compressibility factor behaviour revealed the presence of a wide range of values as the proportions of hydrogen and natural gas in the blends changed, signifying disparate flow behaviours and consequent varying flow challenges. The velocity profiles showed that hydrogen can be transported in natural gas pipelines via blending with natural gas by up to 40% of hydrogen in the blend without exceeding the erosional velocity limits of the pipeline. However, when the proportion of hydrogen reached 60%, the erosional velocity limit was reached at 290 km, so that beyond this distance, the pipeline would be subject to internal erosion. The use of compressor stations was shown to be effective in remedying this challenge. This study provides more insights into the volumetric and safety considerations of adopting existing natural gas pipelines for the transportation of hydrogen and blends of hydrogen and natural gas.

scholarly journals Application of Higher-Order TVD Resolution for Investigation of Transients Problems in Natural Gas Pipelines

1996 ◽  
Author(s):  
Sarafa O. Ibraheem ◽  
Michael A. Adewumi
Keyword(s):  
Natural Gas ◽  
Hyperbolic Equations ◽  
Numerical Procedure ◽  
Higher Order ◽  
Transient Phenomena ◽  
Natural Gas Pipelines ◽  
Tvd Method ◽  
Base Solution ◽  
Wide Range ◽  
Upwind Methods

A higher-order numerical procedure is applied to simulate typical transient phenomena in natural gas transportation. Reliable modeling and prediction of transients features in transmission pipelines are desirable for optimal control of gas deliverability, design and implementation of active controls, and modeling of operational behavior of network peripheral equipment (e.g., chokes, valves, compressors, etc.). As an alternative to the Method of Characteristics (MOC) that is widely used presently, a higher-order Total Variation Diminishing (TVD) method is used to model some transient problems. This, class of methods has the capability to capture fine-scale phenomena and provides a better resolution of frontal discontinuities. In this study, the TVD method is utilized in conjunction with upwind methods. Also, in order to ensure a stable time-stepping scheme over a wide range of Courant-Friedrich-Lewy (CFL) number, a special Runge-Kutta method is employed as the base solution algorithm to integrate the highly non-linear, hyperbolic equations which govern the transportation of natural gas in pipelines. The overall procedure is stable, robust and accurate when applied to solve practical problems with simulated pressure waves.

Application of Reliability Based Design and Assessment to Seismic Evaluations

2010 ◽  
Author(s):  
Maher Nessim ◽  
Nader Yoosef-Ghodsi ◽  
Doug Honegger ◽  
Joe Zhou ◽  
Shanshan Wang
Keyword(s):  
Finite Element ◽  
Probability Distribution ◽  
Natural Gas ◽  
Finite Element Model ◽  
Element Model ◽  
Soil Liquefaction ◽  
Simplified Approach ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Ground Deformations

The application of reliability based design and assessment (RBDA) as a basis for seismic evaluations of natural gas pipelines is explored through analysis of a number of representative pipeline examples. To accomplish this, a simplified approach was developed to generate a representative probability distribution of permanent ground deformations due to soil liquefaction. An idealized pipeline alignment through a liquefiable layer under a river was defined, and a number of cases representing NPS12 and NPS36 pipelines in classes 1, 2 and 3 were analyzed using a finite element model. The probability of exceeding the strain limits for pipe body and girth weld were calculated and compared to the reliability targets. The results were used to identify diameter and class combinations that can meet the reliability targets, and to make preliminary conclusions regarding the viability of using RBDA for seismic evaluations.

Assessment on Design Factors of China’s Natural Gas Pipeline Based on Reliability-Based Design Method

2016 ◽  
Author(s):  
Zhenyong Zhang ◽  
Yawei Zhou ◽  
Jinyuan Zhang
Keyword(s):  
Natural Gas ◽  
Design Method ◽  
Large Diameter ◽  
Small Diameter ◽  
Research Report ◽  
Design Code ◽  
Limit States ◽  
Reliability Based Design ◽  
Location Class ◽  
Design Factors

Although the traditional method based on stress analysis is simple and convenient, the main limitation is that it does not reflect the actual failure mechanisms (or limit states). A pipeline network database of about 40 thousand kilometers comprising 258 design cases that represent combinations of steel grade, diameter, pressure, and location class is established, in order to evaluate and improve the design factors specified in the Chinese standard “Code for design of gas transmission pipeline engineering” (GB 50251). Referring to the research report “Target Reliability Levels for the Design and Assessment of Onshore Natural Gas Pipelines” accomplished by C-FER in 2005, the critical wall thicknesses and corresponding equivalent design factors are calculated by using reliability-based method to meet specified reliability targets. The research shows that the equivalent design factors obtained by Reliability-Based Design (RBD) method tend to increase as the pipe diameters get larger. The new design factors are smaller than those specified in the design code for pipelines with small diameter in location class 1 and 2, and larger than those in the design code for the other pipelines. Therefore, design factors are modified in each location class. The new factors are specific to pipes with small diameter (D ≤ 508mm), medium diameter (508mm < D < 711mm), and large diameter (711mm ≤ D ≤ 1219mm), thus enhancing the rationality and practicability of design factors.

Limit States Design—An Innovation in Design Standards for Steel Structures

1974 ◽  
Vol 1 (1) ◽  
pp. 1-13 ◽  
Author(s):  
D. J. Laurie Kennedy
Keyword(s):  
Design Method ◽  
Steel Structures ◽  
Probability Of Failure ◽  
Simple Design ◽  
Design Standards ◽  
Limit States ◽  
Working Stress ◽  
Wide Range ◽  
Ultimate Resistance ◽  
Two Sides

The greater rationality of limit states design as compared to working stress design is developed to show that limit states design leads to a more consistent probability of failure and that neither overly safe and therefore uneconomic structures nor structures with insufficient safety should result from this design methodology.This rationality is extended in the limit states design method in that the performance of the structure and its components is checked against the various limit states at the appropriate load levels. Thus the limit states of serviceability are checked at specified load levels and of strength and stability at the factored load levels.Functions are presented for the two sides of the inequality:[Formula: see text]A comparative design of a 20-storey structure selected to provide a wide range of variables shows that limit states design as proposed results in a structure comparable to that designed by working stress method with a moderate saving in the weight of steel. Some simple design examples are worked out to show the basic similarities between working stress design and limit states design and that the two methods are of about equal complexity or simplicity. It is believed, because the designer will have to check the ultimate resistance against the effect of the factored loads, that he will develop a greater awareness of the behavior of the material and members with which he is working.

Limit states and reliability-based design for a non-codified problem of aqueduct buoyancy

2006 ◽  
Vol 43 (8) ◽  
pp. 869-883
Author(s):  
Gil Robinson ◽  
James Graham ◽  
Ken Skaftfeld ◽  
Ron Sorokowski
Keyword(s):  
Design Methods ◽  
Model Parameters ◽  
Safety Factors ◽  
Design Code ◽  
Limit States ◽  
Reliability Based Design ◽  
Simulation Techniques ◽  
Working Stress ◽  
Engineering Problems ◽  
Partial Safety Factors

Limit states design methods and engineering judgement have been used to assess buoyancy issues for remediation of the 85 year old Shoal Lake Aqueduct in Manitoba. The study demonstrates how these methods can be applied to non-codified engineering problems. Four separate buoyancy analyses were completed using (i) partial safety factors from the Ontario Highway Bridge Design Code, (ii) project-specific partial safety factors, (iii) Monte Carlo simulation techniques, and (iv) working stress design (WSD) methods. Engineering judgement was required to develop a buoyancy model, interpret data for modeling parameters, and provide meaningful values for parameters that could not be measured. Results from the analyses show that more uniform reliability is provided when measured variability of the model parameters is accounted for. The reliability is not quantifiable when working stress design methods are used. Key words: limit states, probability, non-codified problem, aqueduct, buoyancy.

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