CSA Z662 Research Articles

Comparison of tensile strain capacity models of oil and gas pipelines

In the field of strain-based pipeline design, the widely used pipeline tensile strain capacity models mainly include CSA Z662, PRCI-CRES, and EXXON MOBIL. In this paper, the methods for calculating the ultimate tensile strain, toughness, and other key parameters of various models are emphatically introduced, and their applicable ranges are compared. Ninety-six sets of full-scale test and curved wide plate test data are collected in this paper. The prediction accuracy of various tensile strain capacity models under different steel grades is compared and verified by the test results. The CSA Z662 model has few parameters to consider, the TSC prediction value is relatively low, and EXXON MOBIL has more nonconservative situations when the strain is less than 4%. The PRCI-CRES model has the highest prediction accuracy.

Reliability analysis of intact and defected pipes for internal pressure related limit states specified in CSA Z622:19

The importance of reliability-based design and assessment has been widely recognized by the pipeline industry. Thus, this paper aims at providing comprehensive reliability assessment of intact and defected pipes subjected to internal pressure based on the CSA Z662:19. Various limit states related the pipe design, pre-commission hydrostatic testing, and operation are studied. Specifically, both corrosion and crack defects are considered for pipeline integrity assessment based on different defect scenarios. Reliability results, or probabilities of failure, are reported with respect to design factors, hydrostatic test pressure factors, and safety factors, which can be used in designing new pipes, determining the applied pressure in hydrostatic tests, and operation pressure control of defected pipes, respectively. The effects of pipe grade, pipe dimensions (i.e., diameter and wall thickness), corrosion or crack defect sizes (e.g., length and depth), and internal pressure on POFs for different limit states are also investigated.

Model for optimal sectioning of hydrocarbon transportation pipelines by minimization of the expected economic losses

Pipelines are the safest and most cost-effective alternative for transporting oil and refined products. Nevertheless, accidental losses of containment (LOCs) may occur, thus posing significant threats to people and the surrounding environment. These LOCs also lead to substantial economic losses due to remediation, commodity loss, emergency response, and property damage. The effects of an LOC might be mitigated by implementing proper maintenance plans and installing sectioning valves (i.e., blocking). The location and number of sectioning valves depend on the type of pipeline (underground or non-underground), the commodity being transported, the neighboring population density, and altimetry. Therefore, defining the optimal location and number of valves in a pipeline is a challenging decision that goes beyond the static distances suggested by recognized standards such as CSA Z662. In this paper, a model is proposed to determine the optimal number and location of sectioning valves, which minimize the expected economic losses in terms of the amount of volume spilled and the costs of remediation, emergency response efforts, repair, and commodity loss. The model is applied to a real oil pipeline with significant changes in altimetry. The results indicate a reduction between 10 and 18% of the expected economic losses compared with a static distance reported by CSA Z662.

Local Buckling Behavior and Plastic Deformation Capacity of High-Strength Pipe at Strike-Slip Fault Crossing

As a typical hazard threat for buried pipelines, an active fault can induce large plastic deformation in a pipe, leading to rupture failure. The mechanical behavior of high-strength X80 pipeline subjected to strike-slip fault displacements was investigated in detail in the presented study with parametric analysis performed by the finite element model, which simulates pipe and soil constraints on pipe by shell and nonlinear spring elements respectively. Accuracy of the numerical model was validated by previous full-scale experimental results. Insight of local buckling response of high-strength pipe under compressive strike-slip fault was revealed. Effects of the pipe-fault intersection angle, pipe operation pressure, pipe wall thickness, soil parameters and pipe buried depth on critical section axial force in buckled area, critical fault displacement, critical compressive strain and post buckling response were elucidated comprehensively. In addition, feasibility of some common buckling failure criteria (i.e., the CSA Z662 model proposed by Canadian Standard association, the UOA model proposed by University of Alberta and the CRES-GB50470 model proposed by Center of Reliable Energy System) was discussed by comparing with numerical results. This study can be referenced for performance-based design and assessment of buried high-strength pipe in geo-hazard areas.

Analysis of buried pipelines subjected to reverse fault motion using the vector form intrinsic finite element method

Buried pipelines crossing reverse faults is a common case in practice, while their mechanical responses are not very clear. To analyze buried pipelines subjected to reverse faults, a beam-shell coupling scheme is proposed based on the Vector Form Intrinsic Finite Element (VFIFE or V-5) method. Particular emphasis is given to identifying pipeline failure with three performance based limit states: the local buckling, the tensile strain limit and the flattening parameter limit. The critical fault displacements, at which the specified performance criteria are reached, are presented in diagram form. Effects of fault displacement, crossing angle, as well as fault dip angle on critical fault displacements are examined. This study shows that when the fault dip angle is 40°, the critical fault displacements of local buckling and pipe-wall rupture are the largest when a pipeline is oriented approximately parallel to a reverse fault plane. And for a perpendicularly crossing pipeline, the smaller the dip angle is, the more severe the cross-section distortion will be. Moreover, the critical strain of local buckling are obtained and compared with the recommendation of CSA Z662.

Parametric study of buried steel and high density polyethylene gas pipelines due to oblique-reverse faulting

A numerical study is carried out on buried steel and high density polyethylene (HDPE) pipelines subjected to oblique-reverse faulting. The components of the oblique-reverse offset along the horizontal and normal directions in the fault plane are determined using well-known empirical equations. The numerical model is validated using the experimental results and detailed finite element model of a 114.3 mm (4″) steel gas pipe subjected to a reverse fault offset up to 0.6 m along the faulting direction. Different parameters such as the pipe material, the burial depth to the pipe diameter ratio (H/D), the pipe diameter to wall thickness ratio (D/t), and the fault–pipe crossing angle are considered and their effects on the response parameters are discussed. The maximum and minimum compressive strains are observed at crossing angles of 30° and 90°, respectively. It is found that the dimensionless parameters alone are not sufficient for comparison purposes. Comparing steel and HDPE pipes, it is observed that HDPE pipes show larger compressive strains due to their lower strength and stiffness. For both steel and HDPE pipes, peak strains increase with increasing D/t and H/D ratio for a constant pipe diameter and fault offset. For a given H/D ratio, compressive strains increase with increasing D/t ratio in HDPE pipes, while in steel pipes considered in this study, this effect is negligible. Finally, the peak strains of the pipes are compared to those suggested by Canadian Standard Association for Oil and Gas Pipeline System, CSA Z662.

Potential Benefits of Data Integration for Pipeline Integrity Management Programs

Abstract Pipeline integrity management programs are a requirement under Annex N of CSA Z662.07. Annex N requires that data from many sources and details be collected, integrated and analyzed on a continuous basis. The stated goal is to provide guidance for developing, documenting and implementing pipeline integrity management programs, which provide safe, environmentally responsible and reliable service(1). If executed properly, there should be improved pipeline integrity with measurable improvements and benefits. An important step in reaching this goal is risk assessment, which requires continuous data input to maintain valid integrity assessments. This dynamic process of data collection and integration enables continuous analysis and potentially leads to a more proactive integrity management system. The biggest problem for most operating companies in creating a dynamic and proactive integrity management program (IMP), compliant with Annex N, is in handling the significant data issues. Indeed, the data collection, integration and analysis are the most daunting tasks of the program. A software solution that accepts data from the many activities involved in the lifecycle of a pipeline system would be potentially beneficial. Application of integrated software tools in the oil and gas industry will result in improved integrity management, greater confidence in our pipeline infrastructure and economic benefits. We will review some of the data requirements of Annex N of CSA Z662.07 and identify the components of the program that may differ from your existing management plan. The nature and detail of data to be managed will be presented. Finally, we will provide an example of the role that software tools can play to assist in meeting the requirements of this challenging regulatory initiative.