bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Methods to Determine Stress Intensity Factors for 2D and 3D Cracks
Authors: Zhu Xian-Kui , Leis Brian N.
Published: December 2014

Increasing concern for crack assessment in the pipeline industry motivates analysis to quantify the crack driving force, with the linear-elastic fracture mechanics stress intensity factor, denoted K, viable for many vintage pipeline applications. This paper presents a brief review of numerical methods developed for calculating K via the finite element analysis (FEA) as a background to identify the “best” approaches for such purposes. The existing methods can be categorized into three groups: the displacement-based methods, the stress-based methods, and the energy-based methods. The first group involves the displacement extrapolation method, the quarter-point displacement method, and the displacement correction method. The second group involves the stress extrapolation method and the force method. The third group includes the J-integral method, the stiffness derivative method, the virtual crack extension method, the virtual crack closure technique (VCCT) and ABAQUS direct K output method. Based on the review, four methods were selected and evaluated for a central-cracked plate (CCP) specimen based on the FEA calculations via ABAQUS. The “best” methods are then applied in an analysis of K for through-wall cracks in a line pipe — important reference geometry for leak-versus-rupture analysis.
Fiber Optic Monitoring of Pipeline Subsidence: Analysis of Effective Sensor Cable Deployments
Authors: DuToit Dana , Ryan Kent , Rice John , Bay James , Peralta Jorge
Published: December 2014

Long range, distributed fiber optic sensing systems have been an available tool for more than a decade to monitor pipeline subsidence integrity challenges. Effective deployment scenarios are an important decision to be factored into the selection of this monitoring equipment and typologies relative to specific project needs. In an effort to analyze the effectiveness of various fiber optic deployment conditions, a controlled field experiment was conducted. Within this field experiment, a variety of distributed fiber optic sensors and point sensors were deployed in predefined positions. These positions relative to the pipeline were selected to support a range of deployment needs including new construction or retrofitting of existing pipelines. A 16-inch diameter by 60-meter long epoxy coated pipeline that was capable of being pressurized to mimic operating conditions was utilized. This test pipe was installed in a typical trench setting. Conventional point gauges were installed at key locations on the pipeline. Fiber optic sensor cables were installed at key locations providing 14 alternative scenarios in terms of sensitivity, accuracy, and cost.

After construction of the test pipeline, real time continuous monitoring via the array of conventional and fiber optic sensors commenced. A deep trench was excavated adjacent and parallel to the central portion of the pipeline which began to induce subsidence in the test pipeline. Continued monitoring of the various sensors produced real time visualization of the evolving subsidence. A comparison of the reaction of the sensors is compiled to provide an intelligent selection criteria for integrity managers in terms of accuracy, deployment, and costs for pipeline subsidence monitoring projects. In addition, further analysis of this sensor data should provide more insight into pipeline/soil interaction models and behaviors.
Prevention of Pipeline Dent Failure Under Fatigue Loading Conditions
Authors: Fontanabona Julien , Van Ky Dang , Gaffard Vincent , Moumni Zied , Wiet Paul
Published: December 2014

Pipeline dents fatigue life prediction is a subject of high interest for pipelines operating companies.

Empreinte is an in-house developed pre and post processor to ABAQUS Finite Element Calculations dedicated to pipeline integrity assessment. Empreinte was first developed and experimentally validated for dents assessments under static loading conditions.

As oil but also gas transmission pipelines are submitted to cyclic loading conditions (internal pressure variations, shutdowns, temperature variations …), it was decided to introduce a fatigue life criterion in Empreinte based on the Dang Van theory assuming that local mesoscopic stresses drive fatigue crack initiation.

Full scale tests performed for PRCI projects PR-201-927, PR-201-9324 and MD-4-2 were used to validate the proposed fatigue assessment methodology:

- the first full scale fatigue test was performed in 1994 on an X52 pipe. For this test, limited material and test data were available.

- the second full scale fatigue test was performed in 2007 on an X52 pipe. For this test, material characterization (in particular tensile tests with full stress strain curves) and test data (strain gages measurements, indenter geometry …) were available.

Fatigue life assessments were performed following three main steps:

1. using available data: non linear kinematic hardening constitutive laws were identified for the two pipes materials;

2. finite elements elastic-plastic modeling of the denting processes were carried out;

3. fatigue calculations were performed following a new approach using Dang Van criterion for which the parameters were determined from literature data.

The elastic shakedown assumption allowed the determination of the local stress cycle from the macroscopic stress cycle. The fatigue criterion integrating the combined influences of shear and hydrostatic stresses was checked on all points of the pipe.

Good agreement between experimental and calculated fatigue lives and fatigue crack initiation points was reached. This opens a promising way to assess pipeline defects fatigue life.

Efforts are now focused on the standardization of a testing method to identify the Dang Van criterion of a pipeline material at least in air environment.
Accuracy of the Double-Clip on Gauge Method for Evaluating CTOD of SE(T) Specimens
Authors: Yan Zijian , Huang Yifan , Zhou Wenxing
Published: December 2014

The crack tip opening displacement (CTOD)-based fracture toughness has been widely used for structural integrity assessment and strain-based design of oil and gas pipelines. The double-clip on gauge method has been used to experimentally determine CTOD. In this study, three-dimensional (3D) finite element analyses of clamped single-edge tension (SE(T)) specimens are carried out to investigate the accuracy of the CTOD evaluation equation associated with the double-clip on gauge method. The analysis considers SE(T) specimens with ranges of crack lengths (0.3 ≤ a/W ≤ 0.7) and specimen thickness (B/W = 0.5, 1 and 2). Based on the analysis results, a modified CTOD evaluation equation based on the double-clip on gauge method is developed to improve the accuracy of the CTOD evaluation. This study will facilitate the application of the fracture toughness determined from the SE(T) specimen in the strain-based design of pipelines.
In Line Inspection of Geotechnical Hazards
Authors: Westwood Stephen , Jungwirth Dan , Nickle Randy , Dewar Doug , Martens Michael
Published: December 2014

Four North American pipeline operators and a pipeline inspection company have been working together on a research project assessing the feasibility of using an electromagnetic non-contacting strain measurement tool capable of being deployed during ILI inspection to measure axial strain in pipelines. The axial strain sensor is the TSC StressProbe. It is an electromagnetic technique which makes use of the fact that when a steel structure is loaded, its electromagnetic properties change. Monitoring the changes in magnetic properties allows one to measure changes in strain.

The use of in-line inspection high resolution inertial survey tool data in the determination of bending strain in operating pipelines is well developed and understood. The missing component in determining the total strain in the pipeline is to understand the component of axial strain that the pipeline is experiencing without the need to expose the pipeline for the installation of surficial pipe monitoring (primarily strain gauges) or destructive testing (such as cut-outs). Many current methods of stress/strain measurement including the installation of strain gauges only allows for the determination of change in strain going forward from the date of install; whereas, the StressProbe responds to total strain at the time of inspection.

This paper will present the technology implementation, inspection feasibility and discuss preliminary results from case studies in determining the ability of the in-line inspection axial strain measurement to correlate with known changes in strain in pipelines being influenced by ground movements.
Development of API Grade Pipeline Steel With Improved Toughness on a Compact Strip Production (CSP) Line
Authors: Kendrick Vance , Frye Brian , McClure Jake , Holtman Mark , Stalheim Douglas G.
Published: December 2014

Oil and gas exploration around the world continues at a rapid pace. This rapid pace of oil and gas exploration in North America has been fueled primarily thorough the development of horizontal drilling and the “fracking” process of underground shale formations. The demand for various grades and dimensions of API casing and pipe has and will continue to increase in the foreseeable future as these shale formations are exploited.

To support this demand in North America, Gallatin Steel has embarked on a program to develop API casing and pipe coil skelp via their Compact Strip Plant (CSP). A key characteristic of API grade pipeline steels is excellent fracture toughness. This is one area where historically CSP facilities have struggled, especially in gauges greater than 8.8 mm (0.350″) due to overall lack of reduction from the thin slab design of a CSP facility. In addition, utilizing the typical Thermomechanical Control Processing (TMCP) separating recrystallized and non-recrystallized rolling used in API coil skelp production for strength and toughness of a traditional HSM or plate mill is difficult to achieve in the continuous CSP facility. Gallatin Steel has successfully developed, through a controlled combination of slab quality, alloy design, process modifications and process control, excellent toughness in both charpy and DWTT performance from a 65 mm (2.56″) slab in final coil thicknesses up to 12.7 mm (0.500″).

This paper will describe the results achieved to date on various thicknesses from 7.6 mm to 12.7 mm API skelp development at Gallatin Steel. Mechanical property performance along with microstructures/grain size will be presented. In addition, future work that Gallatin Steel will undertake to further improve the capability to produce quality API coil skelp will be discussed.
Topology Analysis and Optimization Design of Coal Bed Methane Gathering System in China
Authors: Zhou Jun , Li XiaoPing , Cheng Mengya , Deng Tao , Gong Jing
Published: December 2014

China is abundant in coalbed methane (CBM) resource. The unconventional natural gas reserves has reached 36.81*1012 m3. The Qinshui Basin in Shanxi Province is the largest gas field among CBM gas fields in China which are commercially exploited since the year 2003. In order to solve some typical problems in CBM production, this article considered the geographical characteristics of the fields, introduced and analyzed the low pressure gathering and transporting process and facilities, as well as the important techniques. Respectively, this article introduced the surface gathering and transporting procedure, analyzed the characteristics and topological structure; it also proposed the optimization scheme of combining steel pipes with PE pipes in processing system. The gathering and transporting processes of remote areas should be flexible and able to solve the problems during gas recovery from both largely exploited CBM blocks and remote blocks with low production. Thus a more reasonable system design should be proposed. To carry out the scheme, it first defined the topological structure of the system with graph theory, then established the economic model of the combined scheme. The article calculated the critical length of pipeline between two methods and defined the concept of “remote” well area. With the analysis of the actual conditions in a certain block in Qinshui Shanxi, the conclusion shows that: the scheme of laying pipelines can make more profit, which is consistent with the actual field situation., At the same time, we chose a phased optimization method, which divided the optimization of entire system into several sub-problems, including well group division, nodes connection relationship, determination of plant’s optimal position, and optimization of pipe diameter. Then we established optimization model that takes the investment costs of each stage as objective functions. The example shows that compared with the artificial design result, the total length of pipeline was reduced by 4.576 km, pipeline investment by 7.35×104 US$, with the respective rates of returns of 19.57% and 4.89%. The number of valve sets in the system fell from 16 to 11 (31%). By analyzing the investment and construction scale of the existing pipe network and optimal pipe network we have proved that the method has an ideal optimization effect. These techniques and schemes can give reasonable instructions in CBM surface gathering system design, powerfully promoting the development of the Chinese CBM industry.
Depressurization-Induced Crack Growth Enhancement for Pipeline Steels Exposed to Near-Neutral pH Environments
Authors: Yu Mengshan , Chen Weixing , Kania Richard , Van Boven Greg , Been Jenny
Published: December 2014

Pressure fluctuations are recognized as the driving force for the crack growth of pipeline steels in near-neutral pH environments; however, the crack growth mechanisms are still not fully understood. Difficulty in understanding the crack growth mechanisms is present due to two dilemmas between laboratory testing and field findings: high frequency study in the laboratory versus low frequency pressure fluctuations in the field; constant amplitude cyclic laboratory tests versus random pressure fluctuations in the actual spectra. To bridge the dilemmas, the crack growth behavior of X60 pipeline steel was investigated in near-neutral pH solution at frequencies as low as 1×10−5 Hz under variable amplitude cyclic loading. Special attention was given to the loading scheme consisting of minor cycles with R ratios (minimum stress/maximum stress) as high as 0.9 and underloads with a relatively lower R ratio of 0.5. It was found that the constant amplitude crack growth rate in near-neutral pH solution in the frequency region below 1×10−3 Hz decreases with decreasing loading frequency, and it reaches a constant value at very low frequencies. This crack growth rate-frequency relation is opposite of that found in the high loading-frequency regime, where crack growth rate was found to increase with decreasing loading frequency. Crack growth rate was observed to increase by a factor of up to 10 when the underload plus minor cycle loading scheme, as mentioned previously, was applied. Based on the findings obtained from the investigation, recommendations of pressure control were also made to minimize the crack growth during pipeline operation.
A Combined Leak Detection Method Using Pattern Recognition Techniques
Authors: Geiger Gerhard , Vogt Daniel
Published: December 2014

Due to the vast mileage of pipelines throughout the world, it is important that dependable leak detection systems (LDSs) are used to promptly identify when a leak has occurred so that appropriate response actions are initiated quickly. The swiftness of these actions can help reduce the consequences of accidents or incidents to the public, environment, and property. Internal systems [4] such as volume balance, mass balance or real-time transient model (RTTM) based methods are used successfully for that purpose. RTTM based methods offer excellent performance but more field sensors are needed than for simpler methods such as volume balancing, and therefore these methods are less robust because of their greater dependence on sensors which could fail. This paper describes a new leak detection methodology which uses pattern recognition techniques to combine two or more internal methods seamlessly into one scheme hence improving performance, robustness and applicability.
Pipelining Fengcheng Extra Heavy Oil Over Long Distance by Dilution and Heating
Authors: Deng Daoming , Sun Jiangang , Liu Xia , Zeng Dechun , Wan Yufei
Published: December 2014

Fengcheng Heavy Oil Block in Xinjiang Oilfield is located on the northeastern part of northwestern Junggar basin in China, and approximately 120 km and 400 km off Karamay City and Urumqi City respectively. In this Block there is conventional heavy oil, extra heavy oil and bitumen in the shallow formation, which are extracted by CSS and SAGD operations. Now heavy oil output of Fengcheng Block exceeds 2 million tons annually, and in the near future the output will attain 4 million tons per year. The highly viscous Fengcheng heavy oil, a part of which is now as thick as over 910,000 mPa s at 50 degree celsius, is being transported to Karamay and Urumqi Petrochemical Co. via the newly-built FK pipeline (design pressure 8.0 MPa) and 34-year-old KW pipeline (MOP 4.3 MPa) over distances of about 100 km and 430 km respectively. Diluent was selected by the petrochemical company. Gas-oil or/and light-crude-oil diluted Fengcheng heavy oil cannot be pipelined isothermally, and heating the diluted heavy oil to a temperature of about 93 degree celsius or 55 degree celsius was carried out corresponding to different diluents. Herein based on the measurement of viscosity of oil mixtures, capacity of the pipeline network for pipelining the different dilution-ratio Fengcheng heavy oil is investigated, and the bottleneck to pipeline the diluted Fengcheng heavy oil is pointed out. Maximum and minimum throughputs of different dilution ratio heavy oil for each pipeline are determined. Field experiment on maximum throughputs of KW pipeline transporting the mixed oil validated the prediction. FK line transporting gas-oil-diluted heavy oil shows unstable operating zones. The simple facilities-revamp scheme for KW line, reasonable dilution-ratio and some key process parameters were recommended for rehabilitations and operations.
Under Pressure Operations on Dense Phase CO2 Pipelines: Issues for the Operator
Authors: Barnett Julian , Wilkinson Richard , Kirkham Alan , Armstrong Keith
Published: December 2014

National Grid, in the United Kingdom (UK), has extensive experience in the management and execution of under pressure operations on its natural gas pipelines. These under pressure operations include welding, ‘hot tap’ and ‘stopple’ operations, and the installation of sleeve repairs.

National Grid Carbon is pursuing plans to develop a pipeline network in the Humber and North Yorkshire areas of the UK to transport dense phase Carbon Dioxide (CO2) from major industrial emitters in the area to saline aquifers off the Yorkshire coast. One of the issues that needed to be resolved is the requirement to modify and/or repair dense phase CO2 pipeline system.

Existing under pressure experience and procedures for natural gas systems have been proven to be applicable for gaseous phase CO2 pipelines; however, dense phase CO2 pipeline systems require further consideration due to their higher pressures and different phase behaviour. Consequently, there is a need to develop procedures and define requirements for dense phase CO2 pipelines. This development required an experimental programme of under pressure welding trials using a flow loop to simulate real dense phase CO2 pipeline operating conditions.

This paper describes the experiments which involved:

• Heat decay trials which demonstrated that the practical limitation for under pressure welding on dense phase CO2 systems will be maintaining a sufficient level of heat to achieve the cooling time from 250 °C to 150 °C (T250–150) above the generally accepted 40 second limit.

• A successful welding qualification trial with a welded full encirclement split sleeve arrangement.

The work found that for the same pipe wall thickness, flow velocity and pressure, dense phase CO2 has the fastest cooling time when compared with gaseous phase CO2 and natural gas.

The major practical conclusion of the study is that for dense phase CO2 pipelines with a wall thickness of 19.0 mm or above, safe and practical under pressure welding is possible in accordance with the existing National Grid specification (i.e. T/SP/P/9) up to a flow velocity of around 0.9 m/s.

The paper also outlines the work conducted into the use of the Manual Phased Array (MPA) inspection technique on under pressure welding applications.

Finally, the paper identifies and considers the additional development work needed to ensure that a comprehensive suite of under pressure operations and procedures are available for the pipeline operator.
Development of Distributed Fiber Optic Sensors for Offshore Pipeline Leak Detection
Authors: Kulkarni Mohan G. , Shafrova Svetlana , Rinehart Adam J.
Published: December 2014

Distributed fiber optic (FO) sensors have been used for onshore pipeline monitoring and leak detection applications. The use of FO sensors for offshore pipeline leak detection is still very new and requires developments to adapt the technology to such applications. This includes progressing the understanding of FO sensor performance for offshore leak detection, the need to develop requirements and procedures for offshore installation of pipeline and FO cable, and the need to design and develop sensor technology to cover long underwater pipelines.

ExxonMobil Upstream Research Company (EMURC) has undertaken an extensive offshore pipeline leak detection research and development program. One of the key goals of the program is to develop FO sensor technology for offshore use. This paper summarizes the key findings from several technology development studies.
Structural Performance of Buried Steel Pipelines Crossing Strike-Slip Faults
Authors: Vazouras Polynikis , Dakoulas Panos , Karamanos Spyros A.
Published: December 2014

The performance of pipelines subjected to permanent strike-slip fault movement is investigated by combining detailed numerical simulations and closed-form solutions. A closed-form solution for the force-displacement relationship of a buried pipeline subjected to tension is presented and used in the form of nonlinear springs at the two ends of the pipeline in a refined finite element model, allowing an efficient nonlinear analysis of the pipe-soil system at large strike-slip fault movements. The analysis accounts for large deformations, inelastic material behaviour of the pipeline and the surrounding soil, as well as contact and friction conditions on the soil-pipe interface. Appropriate performance criteria of the steel pipeline are adopted and monitored throughout the analysis. It is shown that the end conditions of the pipeline have a significant influence on pipeline performance. For a strike-slip fault normal to the pipeline axis, local buckling occurs at relatively small fault displacements. As the angle between the fault normal and the pipeline axis increases, local buckling can be avoided due to longitudinal stretching, but the pipeline may fail due to excessive axial tensile strains or cross sectional flattening.
Internal Corrosion Management of Crude Pipelines
Authors: Prakash S. Surya , Al-Shamari Abdul Razzaq , Safri Shabbir , Jaragh Amer Abdullah
Published: December 2014

Kuwait currently produces about 3 million barrels of crude oil per day and has a large pipeline network system for handling its oil and associated products (condensate, low pressure and high pressure gas, as well as produced and effluent waters). The total length of the pipeline network is about 4790 Km consisting of API 5L Grade-B carbon steel ranging in diameter from 100 mm to 1830 mm. The Kuwait Oil Company (KOC) is responsible for the corrosion and integrity management of the pipeline network system which involves: Internal Corrosion Monitoring to assess the internal corrosion status of the pipelines including the occurrence of microbial influenced corrosion; external corrosion protection with the help of coatings and cathodic protection, and periodic intelligent and cleaning pigging operations for internal corrosion assessment and cleaning.

The present paper focuses on the internal corrosion management of the export crude segment of the pipeline network system which is very important for a healthy economy. The internal corrosion monitoring protocol includes, online corrosion monitoring, cleaning pigging and intelligent pigging. Bacteria counts’ trending is also included as part of protocol. Some anomalies between the results obtained from corrosion trends, cleaning pigging results and intelligent pigging are highlighted and a sound engineering explanation is attempted to explain these apparent anomalies.
Development of Pipeline Regulations in the Norwegian Petroleum Industry and Examples of Follow Up
Authors: Sundby Trond , Anfinsen Kjell Arild
Published: December 2014

The Petroleum Safety Authority Norway (PSA) is an independent government regulator responsible for safety, emergency preparedness and the working environment in the Norwegian petroleum industry. Norway’s regulations for petroleum operations offshore and on land are risk-based, and give great emphasis to principles for reducing health, safety and environmental (HSE) risk. They have been developed over more than 40 years, changing from detailed prescriptive regulations in the early days to the present requirements, which are largely formulated in performance-based (functional) terms. They specify requirements for the various aspects, characteristics or qualities which a product, process or service must possess. These requirements express the performance or result which the product, process or service is to yield — in other words, what the government wishes to achieve through them. The Norwegian petroleum industry embraces 15 500 km of pipelines, about half of which are large trunk lines for gas transport.

This paper will summarise the development of the regulations and give examples from the pipeline regulations and the way the PSA follows up the industry today. We will also present statistical data for incidents involving pipelines and risers over the past decade, and highlight areas where we think the industry has a potential for improvement.
Computational Model Based Method for Defining an Improved Criterion for Dent Fatigue Assessment
Authors: Lecchi Maxime , Hertz Clemens Stéphane , Notarianni Philippe , Polo Magali
Published: December 2014

In the field of defects assessment, mechanical damage severity analysis is an issue of interest for many pipelines operators [1]. Indeed, common literature fatigue criteria [2] [3] [4] [5] often give underestimated dent lifetimes compared with experimental results. This causes repairs which could be avoided, therefore more predictive criteria would generate a significant maintenance costs saving.

This paper presents an improved method developed at CRIGEN (GDF SUEZ research center dedicated to gas and new energies) to assess dent defects subject to fatigue loadings. A realistic computational model based on the finite elements method has thus been developed. An analytic formulation of the stress concentration factor (SCF) giving more realistic results has then been set, allowing a classical fatigue analysis with S-N curves to be performed.

A specific software plug-in has been developed to automate the creation of the finite elements models. In these models dents are created at a realistic pressure with regard to the pipe characteristics. Then damaged pipe is exposed to a pressure variation to determine the maximal SCF.

After validation based on tests results, a simulated experimental design which covers diameters from 8 inches to 36 inches and steels from A37 to X70 has been set. Different indentation tools and different strokes have also been defined, resulting in 1080 simulations.

As a conclusion, this paper shows the method leading to the analytic formulation of the SCF allowing the fatigue assessment.
Comparison Between Standard and Modified Back-Slotted DWTT Specimens
Authors: Shim Do-Jun , Uddin Mohammed , Wilkowski Gery , Duan Da-Ming , Ferguson James
Published: December 2014

The effect of fracture speed on the ductile fracture resistance of line-pipe steels can have an important effect in the basic understanding of the toughness requirements for crack arrest. Recently, the authors have extended the drop-weight tear test (DWTT) work and developed a modified back-slot (MBS) DWTT specimen to obtain higher fracture speeds. The initial experimental observations demonstrated that this type of specimen can be used to obtain higher fracture speeds. Furthermore, the experimental results clearly showed the effect of fracture speed on the ductile fracture resistance.

In this paper, an in-depth study was carried out to further investigate why higher fracture speeds are obtained in the MBS-DWTT specimens. For this purpose, quasi-static and dynamic/impact DWTT experiments were conducted for both standard DWTT and MBS-DWTT specimens. In addition, finite element analyses using cohesive zone model were carried out to investigate the fracture behavior in these tests. In summary, the higher fracture speeds in the MBS-DWTT come from two major factors. First, as demonstrated by the quasi-static test results, the natural unloading characteristics of the MBS-DWTT specimen (even under pure displacement-controlled loading) leads to higher fracture speeds. Second, the steep unloading curve of the MBS-DWTT specimen produces a higher possibility of an unstable ductile fracture even during the impact event, which will result in higher fracture speeds.
Systematic Approach to Measuring ILI Tool Performance
Authors: Keane Sean , Cheng Karmun , Korol Kaitlyn
Published: December 2014

In-line inspection (ILI) tools play an important role within integrity management and substantial investment is made to continuously advance performance of the existing technologies and, where necessary, to develop new technologies. Performance measurement is typically focused for the purpose of understanding the measured performance in relation to the ILI vendor specification and for the determination of residual uncertainty regarding pipeline integrity. These performance measures may not provide the necessary insight into what type of investment into a technology is necessary to further reduce residual uncertainty regarding pipeline integrity, and beyond that, what investment, as an operator, results in an effective and efficient reduction in uncertainty.

The paper proposes a reliability based approach for investigating uncertainty associated with ultrasonic crack ILI technology for the purpose of identifying efficient investment into the technology that results in an effective and measurable improvement. Typical performance measures and novel performance measurement methods are presented and reviewed with respect to what information they can provide to assist in investment decisions. Finally, general observations are made regarding Enbridge’s experience using ultrasonic crack ILI technology and areas currently being investigated.
Development of X80M Line Pipe Steel for Spiral Welded Pipes With Low Temperature Toughness and Excellent Weldability
Authors: Sanchez Nuria , Güngör Özlem E. , Liebeherr Martin , Ilić Nenad
Published: December 2014

The unique combination of high strength and low temperature toughness on heavy wall thickness coils allows higher operating pressures in large diameter spiral welded pipes and could represent a 10% reduction in life cycle cost on long distance gas pipe lines. One of the current processing routes for these high thickness grades is the thermo-mechanical controlled processing (TMCP) route, which critically depends on the austenite conditioning during hot forming at specific temperature in relation to the aimed metallurgical mechanisms (recrystallization, strain accumulation, phase transformation). Detailed mechanical and microstructural characterization on selected coils and pipes corresponding to the X80M grade in 24 mm thickness reveals that effective grain size and distribution together with the through thickness gradient are key parameters to control in order to ensure the adequate toughness of the material. Studies on the softening behavior revealed that the grain coarsening in the mid-thickness is related to a decrease of strain accumulation during hot rolling. It was also observed a toughness detrimental effect with the increment of the volume fraction of M/A (martensite/retained austenite) in the middle thickness of the coils, related to the cooling practice. Finally, submerged arc weldability for spiral welded pipe manufacturing was evaluated on coil skelp in 24 mm thickness. The investigations revealed the suitability of the material for spiral welded pipe production, preserving the tensile properties and maintaining acceptable toughness values in the heat-affected zone.

The present study revealed that the adequate chemical alloying selection and processing control provide enhanced low temperature toughness on pipes with excellent weldability formed from hot rolled coils X80 grade in 24 mm thickness produced at ArcelorMittal Bremen.
Measurement of Mechanical Properties on Line Pipe: Comparison of Different Methodologies
Authors: Cooreman Steven , Van Hoecke Dennis , Liebeherr Martin , Thibaux Philippe , Enderlin Mary Yamaguti
Published: December 2014

Line pipe manufacturers always have to verify the mechanical properties on pipe to make sure that the pipe meets the requirements specified by the standard and/or customer. This involves measurement of mechanical properties along the hoop direction. The most accurate way to do so is by performing a ring expansion test, which, however, requires dedicated tools. The two other methodologies consist of standard tensile tests on either non-flattened round bar samples or so called ‘flattened tensile samples’. Round bar samples have the disadvantage that only part of the pipe’s wall thickness is considered. Furthermore they can only be used in case of larger OD/t ratios. Tests on flattened samples, on the other hand, require a flattening operation, which induces additional plastic deformation. However, this flattening operation is not standardized. Moreover, it was observed that the mechanical properties — especially the yield strength — resulting from tensile tests on flattened samples largely depend on test parameters such as residual deflection, extensometer position, flattening procedure, etc. Most manufacturers prefer to test flattened samples, because sample preparation is straightforward and cheap. Moreover it only requires a standard tensile bench.

An extensive FEA (Finite Element Analysis) study was launched to investigate the influence of those parameters on the measured yield strength. The applied FEA methodology consists of three steps. First the complete pipe forming process is modeled (in a simplified way). Next a pipe sample is flattened. Finally a tensile sample is cut from the flattened pipe sample and loaded in tension. The mechanical material behaviour is described by a combined kinematic-isotropic hardening model, which allows taking into account the Bauschinger effect. The results are also compared to simulations of ring expansion tests and tests on round bar samples.

Next a dedicated experimental test campaign was performed to verify the results of FEA. Results of ring expansion tests are compared to results obtained on round bar samples and flattened tensile samples.

The results of this study have shown that the applied methodology significantly affects the measured yield strength. Moreover tests on insufficiently flattened samples could considerably underestimate the actual yield strength on pipe. Finally some guidelines are provided to improve the reproducibility of the measured yield strength when using flattened samples.
Performance Monitoring and Modeling of Small Diameter MDPE Natural Gas Pipelines Subject to Ground Movement
Authors: Dinovitzer Aaron , Fredj Abdelfettah , Weerasekara Lalinda , Rahman Mujib , Wijewickreme Dharma
Published: December 2014

Considering the need to undertake pipeline replacement in a cost-effective manner while ensuring the public safety interest, evaluating the performance of pipelines subject to soil loading from landslides is a key concern in some of the natural gas distribution systems operated by FortisBC Inc. As it is typically uneconomical and impractical to relieve stresses in distribution pipe systems by excavating or instrumenting the pipelines to measure the highly localized strains, undertaking numerical and/or analytical modeling combined with experimentation is a key aspect in attempting to relate the measured ground movement to performance of pipe. For this purpose, capturing the fundamental soil-pipe interaction in small-diameter extensible plastic pipes and undertaking field monitoring to validate the numerical model are critically important. With this background, this paper presents field measurement and numerical modeling undertaken to model the performance of 115 mm diameter medium density polyethylene (MDPE) pipes buried in West Quesnel, BC, Canada. Using field survey data, the active landslides occurring perpendicular to the pipe axis at these two sites have been periodically characterized since 2000/2001.

Materials removed from the pipe system were tested to characterize the pipeline material behavior and limit strains. The data derived from these tests along with a range of soil behaviors are used to support pipe-soil interaction numerical simulation and thus characterize the strains accumulated in the pipeline in service. This paper discusses the limitations, challenges and recommendations for numerical modeling of soil-pipe interaction in small-diameter plastic pipes.
Qualification of a Combined Ultrasonic Inspection Tool for Detection and Sizing of Circumferential Weld Cracks in Offshore Pipelines
Authors: Willems Herbert , Bjørgen Hans Petter , Kristiansen Thor-Ståle , Wieme Guus
Published: December 2014

The target of inline crack inspection is normally related to the detection of axial cracks (weld cracks, SCC etc.) as axial cracks are usually expected under typical loading conditions in pressurized pipe. Ultrasonic crack inspection tools for this type of cracks have been available for over 20 years and have become a standard application in the ILI business. However, under certain conditions circumferential cracking may occur and the inspection technique needs to be modified accordingly. Especially under offshore conditions with limited pipeline accessibility not only the early detection of crack-like defects is required but also a precise depth sizing is important in order to minimize the risk of crack-related pipeline failure. In order to ensure a high probability of detection together with state-of-the-art depth sizing, a 10″ inline inspection tool was developed for the detection of circumferentially orientated weld cracks. The tool combines the advantages of the pulse-echo technique on the detection side with the excellent capabilities of the TOFD (time-of-flight-diffraction) technique for accurate sizing. Both techniques are implemented into a tethered tool where the pulse-echo unit serves for fast screening while the relatively slow TOFD-unit is used for sizing of any detected crack-like features.

In order to qualify the new tool for a special offshore application (inspection of circumferential cracking at welded anode pads) extensive testing was performed using a 10″ test pipeline prepared by Statoil. The test line contained 64 artificial weld defects for reference purposes as well as an unknown number of fatigue cracks in the weld area which were generated by fatigue testing of the corresponding pipes. The tests were full blind tests with no advance knowledge on locations and sizes of the cracks. The sizes of the fatigue cracks (length, depth) were determined by destructive examinations carried out after inline testing. The subsequent comparison of the destructive results with the non-destructive results showed that the specification of the tool with regard to detection and sizing was fully met. In the paper, the inspection concept and the setup of the new tool are described, and the results of the qualification tests are presented.
Considerations on the Use of the Pneumatic Hammer for HDD Pullback Assistance
Authors: Zhou Honggang , Liu Ming , Wang Yong-Yi , D’Eletto Daniel
Published: December 2014

Horizontal directional drilling (HDD) is a trenchless technique which has been frequently used to install underground pipelines due to its minimal impact on surrounding areas. In some circumstances, pneumatic hammers (or pipe rammers) are needed to assist HDD pull-back. The repeated impacts from the hammer can free a stuck pipeline during HDD pull back and facilitate the HDD installation. However, the operation of the hammer may plastically deform the pipe and/or induce fatigue flaw growth in girth welds which can negatively affect the integrity of the installed pipeline.

Compared with the relatively large number of studies and guidelines on HDD, there are few studies on the application of the pneumatic hammer for the pull-back assistance. This paper describes the key considerations for using the pneumatic hammer in the HDD pull-back. The topic covered in the paper includes: (1) identification of key issues for integrity assessment; (2) realistic estimation of impact loads; (3) assessment of potential integrity threats; and (4) operation monitoring and documentation.
Development of Selective Seam Weld Corrosion Test Method
Authors: Beavers J. A. , Brossia C. S. , Denzine R. A.
Published: December 2014

Selective seam weld corrosion (SSWC) of electric resistance welded (ERW) pipelines has been identified as a potential risk to pipeline safety. Due to recent pipeline failures, where seam weld defects may have played a significant role, the National Transportation Safety Board called upon the Pipeline and Hazardous Materials Safety Administration (PHMSA) to conduct a comprehensive study to identify actions that can be used by operators to eliminate catastrophic longitudinal seam failures in pipelines. Battelle contracted Kiefner and Associates, Inc. and Det Norse Veritas (U.S.A.) Inc. (DNV GL) with the objective to assist PHMSA in addressing this issue.

The objective of one of the tasks performed by DNV GL was to develop a reliable, rapid, non-destructive, field-deployable test method that can quantify SSWC susceptibility on operating pipelines containing ERW seams. For this effort, two different, field deployable, non-destructive methods were evaluated in laboratory testing. The methods were validated using a standard destructive test for assessing SSWC susceptibility. One method was based on measurement of the local potential difference between the seam weld and the adjacent base metal while the second was based on differences in the corrosion kinetics between the seam weld and the base metal. The method that is based on corrosion kinetics was found to be most effective in identifying SSWC susceptible pipe steels. It utilizes a barnacle cell to conduct linear polarization resistance measurements on small, selected areas of the pipe (e.g., the weldment or base metal). Additional laboratory as well as field-testing is planned to further validate the test method.
Determination of CTOD Resistance Curves in SENT Specimens With a Tilted Notch
Authors: Van Minnebruggen Koen , Verstraete Matthias , Denys Rudi , Thibaux Philippe , De Waele Wim
Published: December 2014

The Single Edge Notched Tension (SENT) specimen is a common tool for the determination of tearing resistance in pipeline steels and welds. However, it assumes pure mode I crack tip loading, which is unrepresentative for the evaluation of spiral seam weld flaws. To this purpose, the authors have performed SENT tests using specimens with a tilted notch. This paper evaluates experimental techniques to obtain the tearing resistance of such specimens. Mixed-mode crack opening displacement and ductile tearing are successfully measured using digital image correlation and direct current potential drop, respectively. The latter technique involves a calibration on the basis of a thermo-electric finite element model. Tearing resistance tends to increase with increasing notch tilt angle. Based on the limited number of tests performed, tilted notch SENT testing appears to be a promising tool for the assessment of spiral seam weld flaws.
If You Build It, Will They Come? Caribou Habitat Restoration for Pipeline Projects
Authors: Coupal Brian , Bentham Paula
Published: December 2014

The federal Recovery Strategy for the Woodland Caribou (Rangifer tarandus caribou), Boreal Population in Canada, identifies coordinated actions to reclaim woodland caribou habitat as a key step to meeting current and future caribou population objectives. Actions include restoring industrial landscape features such as roads, seismic lines, pipelines, cut-lines, and cleared areas in an effort to reduce landscape fragmentation and the changes in caribou population dynamics associated with changing predator-prey dynamics in highly fragmented landscapes. Reliance on habitat restoration as a recovery action within the federal Recovery Strategy is high, identifying 65% undisturbed habitat in a caribou range as the threshold to providing a 60% chance that a local population will be self-sustaining. In alignment with the federal Recovery Strategy, Alberta’s Provincial Woodland Caribou Policy identifies habitat restoration as a critical component of long-term caribou habitat management.

Habitat restoration initiatives of Alberta’s historical industrial footprint within caribou ranges began in 2001 and have largely focused on linear corridors, including pipelines. Initiatives include revegetation treatments, access control programs and studies, and restricting the growth of plant species that are favourable to moose and deer, the primary prey for wolves. Habitat restoration for pipelines also includes pre-construction planning to reduce disturbance and create line-of-sight breaks, and construction techniques that promote natural vegetation recovery. Lessons learned from habitat restoration programs implemented on pipeline projects in northeastern Alberta will be shared as an opportunity to improve common understanding of restoration techniques, the barriers to implementation, and potential outcomes.