bluuebunny/crossref_metadata_2025 huggingface dataset:
NR198803 Evaluation of an X80 Pipe Fabricated from a Plate Processed using On-line Accelerated Cooling
Authors: Williams  , Maxey
Published: August 2023

In recent years a number of important developments in steel making, rolling, and heat treatment have been applied to the production of plate for API Grades X65 through X80 line pipe. Based on industry interest in the performance of these steels in line pipe, a research task was to investigate the characteristics of representative examples of these new pipes. The objectives of this task are to provide independent measurements of pipe properties and to examine the metallurgical characteristics that may affect their performance in service. It is anticipated that information from the task will aid users in the selection of pipe for future gas-transmission lines.

This report presents the results of an evaluation of an X80 pipe fabricated from a microalloyed, controlled-rolled steel processed using on-line accelerated cooling.
L51877 Crack Arrest Toughness to Avoid Dynamic Ductile Fracture in Gas Transmission Pipelines
Authors: Malik
Published: August 2023

Design against long ductile fracture propagation in gas pipelines involves an analysis of the balance between driving force, derived from the gas pressure, and the fracture resistance of the material. Initially, the shelf energy in the Charpy test was successfully used as a measure of fracture propagation resistance. As material strength, pipe diameter and operating pressures increased and required greater fracture propagation resistance, the limitations of the Charpy energy approach became increasingly apparent. This limitation for modern steels is due to the fact that the Charpy test involves significant energy absorption contributions from processes not related to fracture propagation. If an energy-balance approach is to be maintained, and if material resistance is to be measured in a fairly simple laboratory notch bend test (e.g. Charpy or drop-weight tear), the problem reduces to the isolation of the propagation energy absorption per unit of crack advance.

To resolve crack propagation energy, a novel modification was evaluated for both Charpy and DWTT specimens by employing a back-slot including a snug fitting shim to replace the removed material. In most cases, this modification was effective in curtailing the load-displacement trace when the propagating crack interacted with the slot on the backside of the specimen. It is also noted that this approach did not affect the initial portion of the load-displacement history and thus allowed crack propagation energies to be resolved.
L51397 Microseismic of a Gas Storage Reservoir - Volume 2
Authors: Hardy  , Mowrey
Published: August 2023

Underground gas storage involves the storage of natural gas within the pore structure of a large volume of suitably porous rock, termed the "reservoir rock," located at some depth below the surface. Strata of relatively low porosity and permeability, termed the cap rock, normally directly overlie the reservoir rock itself. In practice, natural gas is injected under pressure from the surface down a cased borehole into the reservoir rock. Due to the permeable nature of this rock, the gas eventually fills the available pore volume, but is prevented from leaving due to the impermeable nature of the cap rock. As a result, stresses develop within the reservoir rock, and these are transmitted to the cap rock and hence to the surrounding strata. From a rock mechanics point of view, it is these stresses and their effect on the reservoir structure as a whole, which determine the structural stability of the reservoir and the maximum level to which it may be pressurized. In order to more realistically evaluate the optimum pressure for a new or existing reservoir facility, an objective means for field evaluation of reservoir stability is required. Since field techniques were not available for the measurement of storage reservoir response directly in terms of such basic mechanics parameters as stress, strain or deformation, an indirect method involving the measurement of microseismic activity was utilized in the New Haven studies. Such microseismic techniques are based on the physical fact that many materials, including rocks, generate transient vibrations (microseismic activity) in the audible and sub-audible range when stressed and/or deformed.

This research represents Phase III of a study involving the rock mechanics aspects of optimization of gas storage pressures in reservoirs and involved the detailed microseismic study of an underground gas storage reservoir. The main objectives of the overall program have been the development of techniques for evaluating optimum pressures for underground gas storage reservoirs and the evaluation of the mechanical stability of such reservoirs under operating conditions.

Due to the detailed nature of the study, the associated monograph has been prepared as a two-volume set. The primary purpose of Volume 1 was to provide a detailed discussion of the microseismic technique and its application during studies at the New Haven site. The present volume (Volume II) deals almost exclusively with the acquisition and detailed processing of microseismic data from the New Haven site, and the analysis of this data in terms of various reservoir parameters. The two volumes, although complementary, were prepared to be utilized independently if desired.
L51506 Development of Improved Methods for Inspecting Gas Storage Well Downhole Casing
Authors: Swanson  , Kilman
Published: August 2023

Casing corrosion in storage wells is a matter of considerable concern to the gas storage industry. Such wells are typically flowed through the casing rather than through production tubing, to facilitate high flow capacities. When failures occur, gas leakage to surrounding formations, freshwater zones and to the surface can pose a sizable economic loss as well as a serious safety hazard. For these reasons, monitoring corrosion in down-hole casing in gas storage fields has become a major concern of many storage field operators, and the in situ detection and assessment of corrosion damage by means of logging instruments is a significant part of this effort.

The study reported in this document has sought to investigate in detail the objectives, methods and results of currently available commercial logging devices as a first step in determining whether down-hole corrosion damage can be more accurately characterized by improved logging methods. Of the several methods potentially capable of meeting the through-wall measurement requirement, only two form the basis for current commercial corrosion logs: the flux leakage, or magnetic perturbation technique, and the remote field eddy current approach. In seeking to provide reasonably short term performance improvements to the industry, it was decided in this project to pursue refinements of magnetic perturbation logs for two reasons: first, the shortcomings evidenced by present logs of this type appear to be amenable to relatively simple improvement, and second, the remote field eddy current approach, while useful as an adjunct to damage assessment, offers little promise of sizing individual corrosion flaws.
L51525 Sizing of Girth Weld Defects Using Focused Ultrasonic Beams
Authors: Hallett J. B.
Published: August 2023

This project was produced to evaluate the performance of focused beams in sizing and positioning defects in pipeline girth welds. The sound beams from standard flat transducers were focused using acoustic lenses. Two types of plastics, having different sound velocities are used in the design of these lenses. One is used for the lens and the other for the wedge. The profile of the lens/wedge boundary was designed to focus the sound at a selected depth. The design takes into account the beam angle, beam diameter, focal point and working range required. The effects of test surface curvature were also incorporated into the design. This project was conducted in three phases using sample welds containing real defects, such as root cracks, slag and lack of sidewall fusion. In Phase III the individual defect size predictions were compared to the actual defects found during destructive examination. Only the readings where the signal sources could be positively identified as defects by breaking open or sectioning were included. All measurements were made to the nearest 0.5 mm (0.02 inches).
PR-179-13202-R01 Field Evaluation of a Continental Controls Corp. NSCR NOx Sensor Control System
Authors: Bacon  , Olsen
Published: August 2023

Emissions compliance of stationary engines can be successful with the application of a non-selective catalytic reduction (NSCR) after treatment system. To accomplish this, the equivalence ratio (?) must be precisely controlled within a narrow range near stoichiometric conditions. The ability for Air Fuel Ratio (AFR) control systems to maintain the engine equivalence ratio in the required narrow operating range long term under field conditions has not been established. This project builds upon prior work at the Colorado State University (CSU) Engines and Energy Conversion Laboratory (EECL) to develop a NOx sensor minimization control algorithm utilizing an AFR controller manufactured by Continental Controls Corporation. Testing was performed on a Waukesha VGF-series L36GSI engine utilized for power generation.
L52293 Brine String Integrity Survey and Model Evaluation
Authors: Ratigan
Published: August 2023

Brine strings are essential components of both natural gas and liquid hydrocarbon storage caverns. Both the natural gas and liquid hydrocarbon storage industries are well aware that a limit exists for the fluid velocity in the injection tubulars in their storage caverns. If the brine injection or brine withdrawal velocity is gradually increased, eventually, the hanging tubular will experience flow-induced vibration, resulting in the potential for the hanging tubulars to bend and/or break. Additionally, in both types of hydrocarbon storage, salt falls can impact the brine string integrity.Result: The magnitude of the velocity limit for flow-induced vibration of the hanging tubulars in salt caverns is not known. In the absence of a clearly defined method for determining the maximum allowable fluid velocities in the hanging tubulars, much of industry has attempted to adopt a conservative maximum flow velocity based on "industry experience". Sometimes this works and sometimes it does not.

The objective of this project is to better define the causes of brine string failure and failure mitigation technologies. The project (1) compiled case histories of successful brine string installations as well as brine string failures in solution mining, liquid hydrocarbon storage, and gas cavern dewatering; (2) evaluated case histories with models (proposed in the literature) for brine strings that have not failed as well as brine strings that have experienced failure; and (3) developed recommendations for maximizing brine string integrity.
L51556 Pressure Loss in Compressor Yard Pipework
Authors: Beavers
Published: August 2023

This handbook enables designers to reliably predict pressure losses in natural gas compressor and meter station yard piping under steady state flow conditions. Pressure loss data are presented in the form of non-dimensional pressure loss coefficients for a wide range of components. Many example calculation sare provided. Recommendations are also made on the installation of compressors to reduce pressure losses and increase efficiency.

Also see related document, L51557.
L51699 Diverless Pipeline Repair Clamp Phase III
Authors: Miller
Published: August 2023

Offshore oil and gas developments are underway for water depths beyond which divers can function. The economic lifelines of these projects are the pipelines which will transport the products to shore. In preparation for the day when one of these pipelines will require repair because of a leak, the Pipeline Research Committee of Pipeline Research Council International, Inc. is funding research directed at developing diverless pipeline repair capabilities.

This Report summarizes the results of the third and final phase of this project. Phase III work included design, manufacture, and dry testing of 1) a one-half scale model of a 12"� repair clamp, 2) a full-scale bolt test fixture to demonstrate boltcontainment and startup under realistic misalignment of the clamp halves, and 3) a full-scale one-way cylinder for end seal activation. Engineering drawings for a 12" - 900# (324 mm, 15.3 mPa) diverless repair clamp package were also produced, and are provided with this report in Appendix B. Phase III also included a study commissioned from Oceaneering directed at defining the interfaces of the clamp package and the ROV, including suggested procedures for deployment and positioning of the clamp package on the pipeline. Issues regarding bolt make-up by the ROV were also studied in detail and limitations in bolting capability were outlined.
L51707 Factors Affecting Heat Affected Zone Root Strains in Pipeline Girth Welds and Repairs
Authors: Graville B. A.
Published: August 2023

A previous study on hydrogen cracking in the heat affected zone of pipeline girth welds and repairs found that large strains in the HAZ transverse to the weld played a major role in causing cracking. Large transverse strains were believed to arise from bending of the weld due to the thermal contraction of the weld around the pipe circumference. Large root strains were simulated in the laboratory using a bend test which enabled the effect of material composition and strength to be studied. In the bend test, the specimen deflection at the onset of cracking, indicated by a drop in load, was used as a measure of susceptibility to cracking. The study showed that increasing the base metal strength for the same HAZ (achieved experimentally by heat treating the same base metal) resulted in a decrease in the critical deflection. This suggested that considerable strain concentration was occuring in the HAZ which increased as the base metal strength increased. Although the study succeeded in quantifying the effects of base metal composition and strength on the sensitivity to cracking, the program did not attempt to address the factors that influence the degree of strain applied to the weld. Specifically, the study only considered a single weld metal strength, and only one pipe wall thickness was addressed. Thus it was not clear whether the move to higher strength pipes welded with higher strength electrodes or a change in the dimensions of the pipe might increase the exposure to cracking risks. Furthermore, if bend tests are used to screen materials, the question is raised as to whether the acceptance level of critical deflection should be changed for higher strength materials. Heat affected zone cracking was observed in both complete circumferential welds (tie-in welds) and in part-circumferential welds (repairs). Various procedural details, such as heat input and length of repair, could influence the root strain and might warrant specific controls to minimize risk of cracking.

This study assessed the effects of weld metal strength, pipe thickness, pipe diameter, heat input, and weld (repair) length on root strains in girth welds. A literature review was conducted and simple analysis methods were applied to identify areas with a high risk for cracking. The results show that high tensile stresses in the axial direction on the inside surface of the pipe result from the radial contraction of the weld and consequent bending of the pipe. Welding procedures with high heat inputs and few weld passes tend to have the greatest effect on stress. Multipass welds decrease the tensile stress, which becomes compressive after a certain thickness. Base metal and weld metal strength were shown to significantly impact strain in the heat-affect zone.
L52247 Human Factors Analysis of Leak Detection and Response Scoping Study
Authors: McCallum  , Richard
Published: August 2023

There has been a substantial level of effort over the past several decades to understand the role of the human controller/operator in process control industry accidents. This work received a substantial impetus from the Three Mile Island nuclear reactor accident in March 1979, which led to an increased focus on the role of the operator as a decision-maker within the process control system. In response to this focus, industry guidelines were developed to address human factors issues in control room design and plant maintainability, among other issues. During the same period that industry guidelines were being developed in the nuclear industry, the human factors community made significant progress in developing theoretical models of the role of the operator in process control. Models that recognized the importance of operators" cognitive capacities, tendencies, and errors provided additional analytic power in both reconstructing accidents and developing approaches toward new designs.

Two alternative near-term research plans were identified, along with the required funds, industry resources, and time. Expected products resulting from two alternative research efforts were outlined. An immediate benefit to industry in supporting the outlined research would be implementation of the Human Factors Operational Review Procedure. This would allow operators to come into compliance with key aspects of the Pipeline Integrity Management rules. More specifically, this guideline would be responsive to the requirement to identify and evaluate preventive and mitigative measures to protect High Consequence Areas, including emergency procedures for responding to spills and ruptures. Human factors critically affect operators" capability to detect and respond to spills, ruptures, and other emergency conditions; and the proposed guideline would directly support these requirements. More generally, it is anticipated that support of this research would result in significant improvement in operational safety, reliability, and efficiency.
L52286 Limit State Function Development for the Application of RBD and Assessment to Onshore Pipelines
Authors: Zhou
Published: August 2023

For pipelines that utilize high design factors, excessive plastic deformation may occur in the hoop direction under internal pressure applied during field hydrostatic testing. Excessive plastic deformation can lead to coating damage and subsequent corrosion. Therefore, a limit state function for excessive plastic deformation was established to address this condition. The limit state function was established as the allowable plastic strain minus the accumulated plastic hoop strain induced by hydrostatic test pressure.

The objective of this study was to expand the limit state function library to allow a wider range of conditions and threats to be explicitly considered in the application of RBDA. The new limit state functions developed in this study are applicable to situations involving excessive plastic deformation under hydrostatic testing pressure, restrained thermal expansion, seam-weld defects and stress-corrosion cracking (SCC). The basic assumptions and methodologies used to develop these limit state functions are described in this report. Probabilistic characteristics of the input parameters (including model uncertainties) associated with each limit state function are also summarized based on publicly available literature, studies funded by PRCI and data provided by PRCI members.
L52289 Use of Pipeline Geometry Monitoring to Assess Pipeline Condition
Authors: Hart James , Zulfiqar Nasir , Popelar Carl
Published: August 2023

Describes an algorithm is developed for deducing the longitudinal or axial strain from geometry pig measurements of a laterally displaced pipeline; often caused by geohazards. The development is limited to those lateral displacements of the pipeline that results in a predominantly transverse loading; i.e., the induced transverse component of the loading is much greater than its axial component. The emphasis is upon evaluating inelastic straining that accompanies large lateral displacement of the pipeline. The induced extensional strain is found to vary linearly with the change in curvature of the pipeline. The validity of the approach is established through favorable comparisons of the predictions for the extensional strains with those determined from buried pipeline finite element simulations of various displaced pipe configurations, pipe geometries, and loading amplitudes. Since the algorithm relies only upon measurements of the geometry of the displaced pipeline, it is independent of the pipe's and soil's material properties, pipe-soil interaction, and the loading conditions.

Benefit: The efficacy of the algorithm is demonstrated by performing a large matrix of finite element simulations of displaced pipelines of different geometries subjected to block subsidence, landslides intersecting the pipeline at varying angles, fault crossings at different angles and different loading states, and comparing the analytical strains with the strains deduced from digital pig measurements of the curvature of the deformed pipeline. In this regard, the finite element simulations serve the role of surrogate geometry pig measurements. These comparisons are used to establish the resolution of the change in curvature measurement required of a geometry pig to produce a reliable estimate for the longitudinal strain in a displaced pipeline. An error analysis is also performed to establish the relative error as a function of the curvature measurement gage length, a characteristic feature-length, and the abruptness of the displaced shape of the pipeline.
L51733 Noise Control Guidelines For Compressor Stations
Authors: Frank
Published: August 2023

A regulatory requirement exists for pipeline companies to maintain noise control policies and procedures for compressors and compressor stations. The Pipeline Industry requires guideline� to help individual companies to prepare such policies and procedures.

This report contains a series of standardized Guidelines that could be used by gas transmission companies to develop their own specifications for noise control, applicable for new compressor package design as well as existing compressor station retrofit. The context of the work is to identify each party's responsibilities towards achieving the intended results, which should inherently lead to more successful noise control projects. The specification strategy is to maintain traditional vendor/sub-vendor roles between compressor packagers and component manufacturers. The content of the Guidelines request guaranteed acoustical performance for compressor packages, supported by field performance testing for certification of compliance to guarantees. This can be achieved during the specification process by having the purchaser establish specific design criteria, and be pre-establishing field performance testing methods.
L41022 Flow of Natural Gas Through High-Pressure Transmission Lines
Authors: Johnson
Published: August 2023

Numerous data on gas flow through pipe lines under many conditions of operation were obtained from carefully conducted tests, and these data, together with other available information, were analyzed carefully to obtain practical information for the use of operators in designing pipe lines and determining the effects of different operating conditions on pipeline capacities. In other words, the investigation was primarily an engineering study of representative natural-gas transmission lines operating under numerous conditions of flow.

For the purpose of presentation the discussions in this bulletin have been arranged generally to include, first, a listing of pipeline formulas used by different investigators; second, a discussion of flow tests made by the writers on commercial and experimental pipelines, including methods of testing and of analyzing flow data; and third, a discussion of the application of flow data to commercial pipeline transmission problems. Detailed mathematical development of formulas is included in appendixes with appropriate references in the main text of the bulletin.
L51659 Diverless Pipeline Repair Clamp I
Authors: Miller
Published: August 2023

Offshore oil and gas developments are underway for water depths beyond which divers can function. The economic lifelines of these projects are the pipelines which will transport the products to shore. In preparation for the day when one of these pipelines will require repair because of a leak, the Pipeline Research Committee of Pipeline Research Council International, Inc. is funding research directed at developing diverless pipeline repair capabilities.

Several types of damage are possible, ranging from latent weld defects on one end of the spectrum to damage resulting in parting of the pipe at the other end. This study is specifically directed toward laying the groundwork for development of a diverless pipeline repair clamp for use in repair of leaks resulting from minor pipedefects. The incentive for a clamp type repair is costs. When compared to replacing a section of pipe, either by welding or by mechanical means, the clamp type repair requires much less disturbance of the pipe, less time, fewer operations and less equipment.
L51841 Compendium of Pipeline Girth Weld ECA Methodologies to Support Revisions to Existing Code Practices
Authors: Wang
Published: August 2023

Significant progress has been made since the mid-1980's in understanding the role of weld defects in pipeline integrity. Unfortunately, this new knowledge has not been incorporated into Appendix A. More significantly, new line pipe materials and welding processes since the mid-1980's have created conditions that were not anticipated in the original code, and that can lead to unsafe designs. This project was commissioned to produce a document to provide the technical basis for the revisions of Appendix A. The technical and historical background of several internationally recognized girth weld ECA (Engineering Critical Assessment) procedures are reviewed. Some recent developments in further refining the girth weld ECA procedures are described, with particular emphasis on the work funded by PRCI. These new developments lead to the recommended revisions to API 1104 Appendix A. The Canadian code, CSA Z662 Appendix K, is the process of adopting some of these developments.
L52060 Internal Repair of Gas Pipelines Survey of Operator Experience and Industry Needs Report
Authors: Harris
Published: August 2023

A repair method that can be applied from the inside of a gas transmission pipeline (i.e., a trenchless repair) is an attractive alternative to conventional repair methods since the need to excavate the pipeline is precluded. This is particularly true for pipelines in environmentally sensitive and highly populated areas.

This project was a survey and so did not involve an experimental procedure or equipment in the conventional sense. The objectives of the project were to evaluate, develop, demonstrate, and validate internal repair methods for pipelines; develop a functional specification for an internal pipeline repair system; and prepare a recommended practice for internal repair of pipelines. The purpose of this survey is to better understand the needs and performance requirements of the natural gas transmission industry regarding internal repair.
L51462 Sensitivity Verification for Acoustic Emission on Buried Pipelines
Authors: Robinson
Published: August 2023

The objective of this report was to develop a method of defining sensitivity of an installed acoustic emission system. The project was divided into five phases, which were designed to address specific tasks leading to development and evaluation of the sensitivity verification system. The five phases were: 1) Selection of a reference transducer with broadband characteristics. 2) Characterization of signals coming from defects when detected at various positions on a test pipe. 3) Development of a calibration system, which accurately simulates signals detected in the test pipe. 4) Field evaluation of equipment developed in Phase 3. 5) Documentation of the entire program.
L51482 Well Casing Response to Buried Explosive Detonations
Authors: Esparza  , Westine
Published: August 2023

Occasionally, buried explosives are used within proximity of producing oil and gas wells which increases the stresses in the casing near the explosion which may result in failure of the well. A procedure was needed for predicting the maximum stresses in producing oil and gas wells, specifically the well casing, induced by nearby, buried, explosive detonations.

An extensive experimental and analytical program were funded and performed over a six (6) year period 1975-1981. The program was divided into two (2) parts: In the first part, similitude theory, empirical analyses and test data were used to derive equations for estimating maximum ground displacement and particle velocity. The ground motions provided the forcing function imparted to a buried pipeline. In the second part, similitude theory, conservation of mass and momentum, and approximate energy methods were used to derive functional relationships for the maximum pipe strains and stresses. Experimental data from more than sixty (60) field tests ere used to develop equations for estimating maximum pipe stresses induced by point and parallel line explosive sources buried in homogeneous soil media. The pipe stress and ground motion data from these experiments were used to develop an equation for computing an effective standoff distance so that the point source soil equations could be used to approximate the casing response. The large amount of data used and the wide range of these data make the solutions applicable to most blasting situations near producing oil and gas wells.

This report provides comprehensive and detailed information for pipeline as well as oil and gas operators to predict the effect of buried explosives and thus the safety of a well(s) while in-service through proper assessment of stresses and guidelines for the appropriate selection of explosive charges, techniques and methods. This will avoid unexpected damages, operational costs, provide guidance for \operator qualification\" for blasting near in-service wells and minimize liabilities to the operator.
L51544 Criteria to Stop Active Pit Growth
Authors: Thompson  , Beavers  , Han
Published: August 2023

The purpose of this research program was to determine the requirement to stop active pitting and compare that to the requirement to stop general corrosion and prevent pit initiation.

This report examines the cathodic protection requirement to stop active pitting in buried natural gas transmission lines and compare it to the cathodic protection requirement to stop general corrosion and further prevent pit initiation. During the two-year period of this research program, two different pit geometries were examined: (1) a small diameter pit of 10 mils in diameter and approximately 10 mils deep which had less than five mils of active pit growth prior to cathodic polarization, and (2) large diameter pits of 1/2-inch in diameter which had approximately 50 mils of pit growth prior to cathodic polarization. Statistical analyses were used to determine whether pit growth continued during the cathodic polarization portion of the experiment or whether the active pit growth was stopped.
L51579 Field Weldability of High Strength Pipeline Steels
Authors: Pargeter
Published: August 2023

There are a number of economic advantages that arise through using high strength pipeline steels. The reduced wall thickness leads to lower steel tonnage requirements and provides scope for reducing welding time. Until relatively recently, the API specification 5L�" Specification for Linepipe" only covered steels up to 70 ksi minimum yield strength.

This document reports on small scale weldability tests on two X80 grade steels and presents mechanical property data on full-size circumferential girth welds. Small scale SMA weldability was assessed using the WIC test with cellulosic consumables of matching strength. Weld metal, rather than HAZ, hydrogen cracking was found to occur at preheat temperatures below approximately 110 C (230 F). Heat affected zone cracking was not observed in any of the WIC tests.
L51607 Pipeline Coating Impedance Effect on Powerline Fault Current Coupling
Authors: Kiefner  , Maxey  , Eiber
Published: August 2023

Prior research leading to the development of predictive electromagnetic coupling computer codes has shown that the coating conductance is the principal factor in determining the response of a pipeline to magnetic induction transmission line. Under power line fault conditions, a high voltage may stress the coating causing a significant change in its conductance, and hence, the coupling response. Based upon laboratory experimentation and analysis, a model has been developed which allows prediction of the modified coating characteristics when subjected to high voltages during fault situations.

The program objective was the investigation of a method to determine the high voltage behavior of an existing coating from low voltage in-situ field measurements. Such a method appeared conceptually feasible for non-porous coatings whose conductance is primarily a result of current leakage through existing holidays. However, limited testing has shown that difficulties in determining the steel-electrolyte capacitance limit the application of the method.

Methods for field measurement of the pipeline coating conductance were studied for both DC and AC signal excitation. AC techniques offer the advantage that cathodic protection current interruption is not required, thus eliminating depolarization effects. However, ac field measurement techniques need additional refinement before these methods can be generally applied.
L51450 Origins of High-Fracture-Initiation Energy in High-Strength Pipe
Authors: Hale
Published: August 2023

For the study, duplicate pairs of pressed-notch DWTT specimens were selected that had exhibited large differences in fracture resistance in the tear tests. Metallurgical evaluations were conducted in an effort to identify correlations between metallurgical characteristics of the specimens and the large differences in fracture resistance observed for a given pipe. The chemical composition, microstructure, inclusion content, extent of midwall segregation, hardness profiles through the pipe-wall thickness, and the appearance of the fracture surfaces were documented, and comparisons were made between the duplicate specimens. The various pairs of DWTT specimens that were evaluated exhibited widely varying metallurgical characteristics among the pipes, particularly the content of secondary (or minor) microstructural constituents. However, significant differences between duplicate DWTT specimens were not observed consistently among the various pairs. Thus, metallurgical factors apparently were not responsible for the differences in fracture resistance measured during testing of the specimens.
L51516 Preventing Pipeline Failure in Areas of Soil Movement - Part 1
Authors: Kiefner J.F. , Tuten J. M. , Wall T. A.
Published: August 2023

Ordinarily, buried pipelines undergo little or no movement in service. In a stable soil environment the longitudinal stress in a pipeline seldom approaches the limiting design value set by applicable codes and regulations. Pipeline serviceability under such conditions is seldom, if ever, threatened by the degree of longitudinal stress. In contrast, localized areas may exist along a pipeline where soils and/or slopes are unstable or where subsidence or differential settlement can occur. In these areas, longitudinal stresses may become severe enough to cause a failure. Over the years various techniques have been developed to monitor the status of pipelines in unstable areas, and various remedial techniques have been attempted. In more recent times, with the advent of Arctic and offshore pipelining, such potential movements of pipelines are being taken into account in the initial designs. In any case, there is a continuing need to develop better monitoring and remedial techniques to prevent pipeline failures in unstable soil areas. The objectives of this project are to develop a versatile and reliable prototype strain monitoring system, to demonstrate its applicability on an actual pipeline, and to establish allowable limits on strains due to soil movement or subsidence. The scope of the project includes:(1) Review of previous or on-going monitoring efforts by others.(2) Analysis of strains and development of models to predict strain behavior(3) Calculations to establish limits on strains(4) The design and construction of a microprocessor-controlled automatic monitoring system(5) The implementation of the system on an actual pipeline(6) The collection, analysis and interpretation of strain data from the system.
L51575 Mechanics-Based Analysis of SCC in a Carbonate-Bicarbonate Environment
Authors: Leis  , Walsh
Published: August 2023

Stress-corrosion cracking (SCC) occurs occasionally in line-pipe steels. Reviews of this cracking indicate that the environment is carbonate-bicarbonate and that the cracking is primarily intergranular. Research sponsored by the PRCI Line Pipe Research Supervisory Committee (LPRSC) has over the years identified metallurgical and electrochemical parameters as playing a role in the process. This work has also argued the significance of strain rate and its relationship to the service loading, given that dissolution is indicated as the controlling mechanism. While much has been learned about the mechanism of cracking, very little has been learned about how to directly relate the nucleation and growth of cracks to the loading, the metallurgy, and the environmental parameters.

The continual development of new line-pipe steels, the probable development of reliable in-line inspection (ILI) tools to detect SCC, and the occasional discovery of cracking colonies during field surveys have recently centered attention on methods to rank line-pipe resistance to SCC and characterize crack-growth rates. Ranking line-pipe resistance to SCC may be done in terms of a threshold stress for nucleation of SCC or the rate of crack growth at some crack depth beyond nucleation. Estimating remaining life of cracks located by an ILI tool or confirmed in a field survey involves only crack growth rate data or data that define a threshold stress for continued growth. Recent attention of the SCC subgroup of the LPRSC, therefore, has focussed on experimental protocols to assess susceptibility, determine thresholds, and establish growth rate behavior. The tapered-tension test (TTT) has been developed to determine stress thresholds for crack nucleation, whereas several different prenotched or precracked geometries have been or are now being used to assess crack growth. Attention has also focussed on modelling SCC thresholds and crack growth behavior so that data developed under laboratory conditions can be adapted to assess field cracking situations. Models are being explored for both threshold and crack-growth conditions. This report presents the development and validation for a model that is being adapted to line-pipe problems for the SCC subgroup. This model deals with the threshold for and the growth of SCC cracks up to about 0.020-inch deep.
L51769 Limit States and Reliability-Based Pipeline Design
Authors: Zimmerman  , Chen
Published: August 2023

The objective is to develop fully calibrated limit states design (LSD) procedures for pipelines. Limit states design, also known as load and resistance factor design (LRFD), provides a unified approach to dealing with all relevant failure modes and load combinations of concern. It explicitly accounts for the uncertainties that naturally occur in the determination of the loads which act on a pipeline and in the resistance of the pipe to failure. The load and resistance factors used are based on reliability considerations; however, the designer is not faced with carrying out probabilistic calculations. LSD suggests that if pipelines are designed directly for those scenarios which are known to be the major causes of pipeline failure, the result will be better design in terms of both safety and economy. This study shows that LSD is a rational and logical design process that can provide consistent levels of safety and give the designer a clear picture of the structural response of the pipe for all credible failure modes.
L51714 Development of Fitness-for-Purpose Assessment Procedures for Branch Welds
Authors: Kirk
Published: August 2023

One major difficulty in developing fitness-for-purpose based flaw acceptance criteria for pipeline branch connections is the calculation of the stress distributions in the vicinity of the welds. Even with the latest computer aided modeling technologies, direct finite element modeling of branch connections using 3-D solid elements can be time consuming and cost prohibitive. Therefore, it is necessary to investigate the possibility of using more computationally-efficient finite element approaches to determine the stress distributions local to branch connections.

This report describes work to develop flaw acceptance criteria based on fitness-for-purpose principles for branch connections in pipelines. The effort concentrated on investigating finite element modeling methodologies to predict accurately the stress distributions local to branch connections. These stress distributions can be used to develop fitness-for-purpose based flaw acceptance criteria that are consistent with those already developed for girth welds.
L51780 Interaction of Multiple Through-Thickness Defects Under Plastic Collapse Conditions Part 1
Authors: Denys  , Lefevre
Published: August 2023

The objective of this research project is to generate experimental information with the aim to quantify the conservatism of current interaction rules and to develop more accurate (less conservative) rules for "thin-walled" structures under plastic collapse. The conservatism in current defect interaction rules for ductile materials has been assessed by examining the failure behaviour of 8 mm and 10 mm thick, narrow (width: 100 mm and 120 mm) and wide (width: 427 mm) plate, specimens containing two coplanar or non-coplanar through thickness notches. The test results were compared to the failure characteristics of single notched plates and analysed in terms of Gross Section Yielding (GSY). The tests were conducted on three different materials in order to determine the effect of the Y/T ratio on defect interaction behavior.
L51801 Impact of Short-Term Depolarization of Pipelines
Authors: Thompson  , Lawson
Published: August 2023

The objectives of this project were to identify the negative impacts of extended depolarization of a pipeline with respect to measuring a 100 mV depolarization criteria and secondly to establish procedures for estimating the appropriate time over which depolarization is measured. The effort included laboratory testing for examining macro-cell couples and coating performance and field testing to examine depolarization phenomena associated with operating pipelines.
L52249 Failure Initiation Modes of Pipe with High Charpy Transition Temperature
Authors: Wilkowski Gery
Published: August 2023

This project was developed to establish a general methodology to; (a) determine a simple way to assess what is the lowest temperature where ductile crack initiation will occur for a sharp crack or a blunt flaw (i.e., corrosion), (b) to developed several optional approaches to predict the transition temperature shifts that depend on what type of lab specimen data are available, and (c) show validation from past tests as well as by conducting tests on older vintage linepipe steels. This report presents a methodology that determines the lowest temperature where ductile fracture would occur for either a sharp cracks or blunt corrosion flaws in older low-toughness linepipe base metals. It is applicable to either axial or circumferential flaws in pipes under quasi-static loading, i.e., normal operating conditions with no sudden transient loads. The results showed that ductile initiation of a surface crack can occur at a significantly lower temperature than the Charpy transition temperature. A master curve of transition temperatures for different pipe thickness and crack geometries was developed and validated on 1927 and 1948 vintage pipes. The master-curve of transition temperatures comes from accounting for thickness effects, loading-rate effects, and constraint effects (for a surface crack) on the transition temperatures of the flawed pipe relative to the Charpy transition temperature. These transition temperature shifts were empirically determined from hundreds of past full-scale tests and literally thousands of laboratory tests, and then checked against data developed on much older vintage linepipe steels, i.e., the 1927 and 1948 pipes in this project.
L52281 Evaluating the Need for Loading Specifications for Highway Transportation of Line Pipe
Authors: Francini
Published: August 2023

Standards have been in place for many years providing procedures for the proper loading of line pipe for shipment by railroad and by vessel, namely, API Recommended Practice 5L1 and API Recommended Practice 5LW, respectively. These practices were developed in response to a recognized need to avoid excessive stresses in the transported pipe caused by unfavorable positioning of the pipe on cradles or supports combined with inertial loadings on the stacked pipe from railcar or vessel motion. The need for this effort became apparent as a result of hydrostatic test failures that occurred in newly constructed pipelines where the failure origins exhibited fatigue even though the pipe had not yet entered service, as well as in-service failures originating at shipping-damage defects that survived the commissioning hydrostatic test but enlarged while the line was in service.

The scope of this study consisted of three phases. The first phase was to document the industry position with respect to line pipe transport. The second phase was to perform a detailed technical analysis of the susceptibility of line pipe to damage from inertial loadings during highway transportation. The third phase was to develop a prototype standard giving minimum specifications designed to avoid damage. The resulting work product can be used as a starting point by an appropriate standards-writing body for development of a specification in accordance with its standards development process.
L51838 Cyclic Stress Strain Behavior and SCC Susceptibility of Line Pipe Steels
Authors: Leis
Published: August 2023

This report presents results of a preliminary evaluation of a mechanical property that has the potential to correlate with susceptibility to Stress-corrosion cracking (SCC). This mechanical property measures the evolution of the microplastic response of line pipe steels, which underlies high pH SCC, and is believed by many to be essential for near-neutral SCC. If such a property can be proven to reflect susceptibility to SCC, operators could better contain maintenance costs and specify steels for new pipelines that are inherently resistant to SCC. Limited experimentation using X60 line-pipe steel indicated that the onset, duration, and intensity of microplasticity correlated with electrochemical indicators of SCC for the high-pH cracking environment. These results show sensitivity sufficient to detect the incidence and magnitude of plastic strain that evolves in load-controlled cycling under conditions typical of pipeline service, as well as in histories where such behavior has been exhausted by prior strain hardening. Thus, these data indicate that the protocol evaluated herein is potentially capable of identifying susceptible steels, and has sensitivity of the order needed to discriminate susceptibility between steels.

Benefit: While the concept and related experimental techniques hold promise as a screening tool for susceptibility, some experimental issues must be resolved before its use can be conclusively established. These and other related aspects are outlined in the discussion section, and the recommendations section of the report.