bluuebunny/crossref_metadata_2025 huggingface dataset:
PR-373-124509-R01 Guideline for Onshore Pipeline Route Evaluation and Selection
Authors: Powers
Published: August 2023

Route selection for onshore pipelines has become progressively more complex over the past several decades due to ongoing land development and expansion of public and private infrastructure, coupled with increased population. During the same period, protection of the environment and avoidance of negative impact to sensitive cultural features have become paramount objectives for all cross-country pipeline projects. With these issues, regulatory and permitting requirements have become more challenging, and compliance has become more arduous. Recognizing these challenges, the Pipeline Research Council International (PRCI) initiated a project to evaluate current route selection methodologies and identify aspects in need of improvement. The final product of this effort is this guidance document, Guideline for Onshore Pipeline Route Evaluation and Selection. The route selection guideline was developed to provide pipeline owners, engineering organizations, and pipeline specialists with comprehensive guidance for onshore pipeline route evaluation and selection. The guideline is expected to benefit pipeline owners and contractors alike by eliminating or reducing costs resulting from failure to anticipate conditions that could impact construction. More specifically, pipeline construction contractors should benefit from more confident route definition that will allow the reduction of contingency items in their cost estimates.
PR-336-06206-R01 Engine Control for Legacy Engines - Cylinder and Cycle Level Control
Authors: Brunner  , Huschenbett  , Beshouri
Published: August 2023

The reduction or even elimination of cylinder to cylinder combustion variation and cycle-to-cycle combustion instability may result in further nitrous oxides (NOx) reductions at the same engine average air/fuel ratio (and hence turbocharger operating point) or allow operation at a leaner air/fuel ratio before the onset of instability. Reductions in imbalance and instability can also reduce carbon pollutant emissions, reduce break specific fuel consumption (BSFC) and improve engine operability. Achieving these goals requires a better understanding of the sources and impacts of that imbalance and instability and then the development techniques to reduce if not eliminate both.

This effort focuses on combustion instability of legacy large bore pipeline reciprocating engines operating at very high air/fuel ratios to meet higher emission standards. The report provides a detailed cycle-to-cycle analysis of acquired pressure and ion current data of four test engines in-cluding Clark T-series family and Cooper Bessemer GMV/W engines. The possibility of upcom-ing misfire or poor combustion prediction is investigated and discussed. The document further investigates advanced cylinder balancing strategies as well as the benefits of improved pre-combustion chamber performance.
PR-312-08206-R03 Methods to Reduce the Greenhouse Gas Footprint from Pipeline Compressor and Pump Stations
Authors: Panak  , McCarthy
Published: August 2023

This report is intended to serve as an engineering reference document that reviews, considers, and evaluates the technical and economic viability of existing and developmental greenhouse gas (GHG) emission reduction technologies and work practices for application to natural gas pipeline compressor stations and hydrocarbon liquid pipeline pump stations.

The report is arranged so readers can track information organized in tables in sequential sections. Following sections that provide an introduction and background, Section 3 lists GHG emission sources in three categories: combustion, vented, and fugitive sources (or equipment leaks). Section 4 lists GHG emission reduction technologies and work practices for each of the emission sources. Section 5 presents technical feasibility and emission reduction information for each technology and work practice. Section 6 presents costs and economic analysis for each technology and work practice. The mitigation approaches include developmental technologies and less information is provided for these examples. Appendices B through D provide detailed information for the technologies and work practices that are considered the highest potential.
PR-275-09207-R01 Method and Procedure for Remaining Life Assessment of the Combustion Turbine Disks
Authors: Bernstein
Published: August 2023

A study of the remaining rotor life of gas turbines (or combustion turbines) used in the oil and gas industry was performed by Gas Turbine Materials Associates (GTMA). The study focused upon analytical methods of determining the remaining rotor life using a reduced data set, where not all of the operating data is known. As part of this study, a survey of oil and gas users was performed on their rotor life. An analytical model and methodology for determining the remaining rotor life was developed. This model and methodology was applied to the GE MS5002 gas turbine. By using this model for a PRCI member, the life of a rotor was safely extended for 100,000 hours beyond its design life. GTMA estimated that this PRCI member saved approximately $1,000,000 from this one application, and that repeated applications of the model for this, and other, PRCI members would save well over $10,000,000. The results of this work should also be applicable to other gas turbines, including those used by electric utilities, IPP�s, and other industrial operators.
L51432 Cathodic Protection for Offshore Pipelines
Authors: Kiefner  , Maxey  , Duffy
Published: August 2023

A design methodology has been developed for cathodic protection systems on off-shore pipelines using galvanic anode bracelets. The methodology developed allows optimum spacing and sizing of anodes necessary for pipeline protection to be determined so as to satisfy minimum energy and weight criteria. It incorporates an electrical model of the pipeline that takes into account the effects of the non-linear polarization characteristics of the pipe steel and the galvanic anodes. The model allows design calculations to be made for a pipeline either completely in water or mud, and in addition, at the water-mud interface where current flow to the pipeline is governed by the characteristics of two different Media. Theoretical potential profiles can also be predicted for pipeline holidays and galvanic bracelet anodes. Profiles in the water surrounding the pipeline can be computed for both situations of the pipeline in water or under mud cover.

The objective of this program was to develop mathematical equations which describe the potential and current profiles of offshore pipelines cathodically protected with galvanic bracelet anodes. Equations developed have been implemented into a computer program. The purpose of this work is to provide a technically sound basis for cathodic protection system design, and to resolve concerns regarding the interpretation and implementation of available pipe potential measurement techniques.
L11777 Addition of Inhibitors to the Soil Above Pipelines to Minimize Stress-Corrosion Cracking
Authors: Davies  , Fessler
Published: August 2023

A research investigation was undertaken to determine the rate of movement of selected inhibitors in various soils. Most of the research dealt with soluble phosphates. The use of chromates as soil additives was not considered feasible because of the toxicity of chromates, and silicates were not as effective as phosphate in inhibiting stress-corrosion cracking. The investigation consisted of the following four parts:

A brief literature survey on the movement of phosphates in soils
A laboratory investigation of the horizontal movement of phosphates and silicates in selected soils
A limited field study of the downward movement of phosphates in a clay soil
A laboratory investigation of the downward movement of phosphates in various soils.
L20170 Threshold Pressure in Gas Storage
Authors: Ibrahim  , Tek  , Katz
Published: August 2023

In the early 1950's, attention was turned to the use of underground water sands for storing natural gas in those areas where depleted gas reservoirs were not available. Underground gas storage means that gas is transferred from producing fields to other reservoirs, usually closer to market areas, where it is stored until needed to supplement other natural gas supplies in meeting market requirements. Its primary functions are to meet peak demands of the winter season especially for residential heating and to provide off-peak depositories for pipeline gas. Because underground storage permits fuller utilization of pipeline facilities and more effective gas deliveries to market, it is an important factor in conservation, elimination of flare gas and the development of new markets.

Gas storage in aquifers requires that the reservoir pressure be raised above the original discovery value to inject the gas. Early experiences with aquifer storage operations raised the question of the mechanism by which caprock held natural gas beneath it. At about the same time that aquifers were being developed, it was found advantageous to store gas at pressures above discovery in depleted gas or oil fields. The practice of operating at pressures above discovery gradually developed inquiries into the quality of caprocks and the insitu behavior of gas below the caprock.
PR-343-12607-R01 Sensitivity of Clamp-On Ultrasonic Meters to Installation Effects and Pipe Condition
Authors: Zanker
Published: August 2023

From experimental data, published papers and manufacturers� information, a Best Practices Guide to the Installation and Use of Clamp-On Ultrasonic Meters in Natural Gas Service has been produced. The guide provides information on the fundamental principals of Clamp-on meters in natural gas service as well as best practices for installation.
L51488 Effects of Stress Relief Due to Hydrostatic Testing on Girth Weld Failure
Authors: Glover
Published: August 2023

Fitness-for-purpose analyses are being increasingly used in the engineering assessment of the safety of gas pipelines. The potential need for this arises because of the likelihood of a defect being present in the girth weld. Many of these analyses make an allowance for the residual stress caused by the weld, whilst others do not. It has been argued that if a defect survives the field hydrostatic test that the residual stress distribution will be altered and this could subsequently affect the tolerable defect size analysis. Four full-scale tests were carried out, two at each wall thickness; one of which was as-welded and one hydrostatically tested. In order to simulate the field hydrostatic test a novel laboratory technique was developed that minimized the end load during pressurization. The results of the full-scale tests, that failed by ductile tearing, show that for similar defect sizes the strain to failure is the same whether in the as-welded or hydrostatically tested condition. The strain to initiate tearing, however, is quite different. In the case of the 24" (610 mm) thin wall tests the strain to initiate tearing increases from 0.09% (as welded) to 0.17% (hydra test). For the 36" (914 mm) thick wall tests the equivalent figures are 0.11% and 0.12%. These results are consistent with the radial deflection measurements which predicted a much higher axial residual strain for the thinner wall pipe material. The results, do point out the effect of the residual stress oncleavage failure. The overall results are consistent with the various Engineering Critical Assessment techniques, however, the approach of CSA Z184 may prove to be more appropriate. This approach makes no allowance for residual strain for either brittle or ductile failure.
PR-381-12604-R01 Better Defining the Uncertainties for the AGA-8 Equation
Authors: Lemon
Published: August 2023

In order to revise the AGA-8 documentation for publication in 2014, better knowledge of the 0.1% uncertainty level in the equation of state is needed. The 0.1% uncertainty level has been identified by an AGA-8 task group as the acceptable limit of error for density and compressibility factor calculations. With the availability of a new high-accuracy wide-range equation of state described in the introduction, it is now possible to locate regions within AGA-8 that are most likely outside the 0.1% uncertainty limit, which was not possible in 1992 due to limited experimental data.
L00033 A Theoretical Model for Crack Propagation and Arrest in Pressurized Pipelines
Authors: McGuire
Published: August 2023

A theoretical basis for predicting the speed of axial crack propagation and conditions for crack arrest in pipelines was developed and based on a formulation that would be independent of full-scale pipe experiments. This capability would aid in designing pipe experiments and assist in specifying pipeline crack arrest requirements. While exhibiting some degree of success, the model has not been completely adequate for these purposes. The present work was undertaken to fortify some known deficient aspects of the model in order to complete the work.

The development of a mathematical model for steady-state crack propagation in a pressurized pipe is described. Recent work was focused on a key parameter in the model--the location of the plastic yield hinge relative to the moving crack tip. This quantity was determined by forcing agreement with crack speeds observed in the full-scale line pipe tests. The maximum crack driving force predicted by the model is taken as a measure of the minimum fracture toughness value required for crack arrest. Comparisons with existing empirical formulations for the minimum required Charpy energy given in this report demonstrates that this approach is quite reasonable. Simple predictive formulas for backfill and non-backfill conditions approximating the exact prediction of the model are supplied for use in line pipe design.
L51382 A Study of Cathodic Protection of Buried Steel Pipeline Within a Steel Casing
Authors: Hennon  , Kimmel
Published: August 2023

Cased carrier pipes at railroad and highway crossings exist under a multitude of physical and environmental operating conditions, which individually or collectively influence the ability to achieve cathodic protection on the carrier pipe. For a given cased carrier system, operating parameters are subject to change both by design and from naturally occurring circumstances. A change in one parameter can and many times does change other parameters due to interactions among the significant factors. Throughout the history of the pipeline industry, pipeline owners have designed new cased carrier systems and altered, or opted not to alter, existing systems based primarily on their own experiences. Thus, for a given set of conditions, different owners have used different designs. This situation is most easily illustrated by the lack of consensus as to whether or not the casing should be electrically shorted to the carrier under any or all sets of conditions. These considerations prompted PRCI to initiate a study to determine the effectiveness of cathodic protection on simulated buried cased steel pipelines by systematic laboratory procedures and to incorporate the results into a form readily usable in the field.

The objective of the program as originally conceived was: (a) Phase I, Determination of the effectiveness of cathodic protection on simulated buried cased steel pipelines by systematic laboratory experiments; (b) Phase II, Correlation of the laboratory data by computer modeling. Phase I was conducted as originally planned and amended to incorporate computerized analysis of the data. Because of the results of that analysis, the scope of Phase II was changed to the characterization and/or detection of carrier-to-casing electrical resistances.
L51585 Effects of Seasonal Variations on Requirements to Prevent Corrosion in Soils
Authors: Han
Published: August 2023

It has been widely recognized that the pipe-to-soil potential of pipelines under cathodic protection varies seasonally, depending primarily on the soil moisture content. In dry seasons, for instance, the pipe-to-soil potential becomes less negative so that meeting the -0.85 V (Cu/CuS04) criterion can be difficult if not impossible. The American Gas Association (AGA) through the Pipeline Research Council International, Inc. (PRCI), accordingly, initiated a research program at Battelle Columbus Division to study the effects of soil moisture content on corrosion and cathodic protection of underground pipelines. Cathodic protection is widely used for preventing corrosion in underground, buried structures. The overall objective of this research was to examine the effects of seasonal variations in soil moisture on the cathodic protection requirements to prevent corrosion of pipe steel in soils.

The research consisted of four major tasks: Task 1: Characterization of the Effects of Moisture Content; consisted of a series of laboratory experiments in which the electrochemical behavior of pipe steel in soils of different moisture contents were examined. Task 2: Characterization of the Effects of Cyclic Moisture Fluctuations; was concerned with evaluating, through another series of laboratory tests, the effects of seasonal moisture fluctuations on the electrochemical behavior of cathodically-protected pipe steel. Task 3: Cathodic Protection Requirements as a Function of Moisture Content; consisted of analyzing the results of Tasks 1 and 2 and thereby assessing the cathodic protection potential and current requirements as a function of soil moisture content. Task 4: Field Tests; was concerned with verifying the laboratory results, obtained in Tasks 1, 2, and 3, in the field. This verification was done by (1) comparing and correlating the laboratory results with available field data from other PRCI funded projects and (2) performing a limited field test.
L51597 Feasibility Study of New Technology for Intake Air Filtration
Authors: Lawson
Published: August 2023

Inlet air filters are widely used to remove solids and liquid droplets from the ambient air before it enters the compressor of a gas turbine. Clean inlet air provides many advantages: Less corrosion of the compressor and of gas-path hot parts, such as the turbine, decreased compressor fouling, less erosion of the compressor bladeThese in turn prevent deterioration of output and heat rate, and reduce maintenance costs. Compressor fouling is caused by the ingestion of substances that deposit and adhere to blade surfaces, resulting in reduced aerodynamic efficiency and decreased available output. Air contamination could be significantly reduced by the use of more efficient air filtration systems, especially through the reduction of the quantity of smaller particles ingested. The consequent lower loss of output power and decreased cleaning efforts provide lower costs of operation and increased shaft power.

This work was composed of three major efforts: 1) A literature search was performed to establish the state of the art for particle removal from gases, particularly by electrostatic precipitation, and to identify the leading vendors of the equipment-considering both experience and technical expertise. 2) Two chosen companies were visited to determine their technical capabilities as they apply to gas turbine inlet air filtration. 3) A representative gas turbine was specified by PRCI as being the equivalent of a GE Model 3002J turbine, with airflow of 91,200 acfm. A specification based upon that airflow was prepared and submitted to the two vendors. Each vendor prepared a proposal for a filter system compliant with the specification. The proposed air filtration equipment is sufficiently different from existing products that it was judged not beneficial to visit manufacturing facilities. Both vendors are reputable suppliers of air filtration equipment.

This study is intended to provide definitive information relative to the use of new technology for air inlet filtration on gas turbines in gas pipeline pumping applications.
PR-201-094507-R01 Wrinklebend Evaluation Study and Tool Development
Authors: Dotson  , Alexander
Published: August 2023

The content of this report represents a multi-year assessment focused on evaluating wrinklebends and their impact on the integrity of pipeline systems across the United States. Although the exact number of wrinklebends existing in the United States is not known, a reasonable estimate is on the order of hundreds of thousands. At the present time, the youngest of these wrinklebends would be approximately 65 years old, considering that by the mid-1950s wrinklebends were generally considered an unacceptable construction practice.
L52270 Basics of Metal Fatigue in Natural Gas Pipeline Systems - A Primer for Gas Pipeline Operators
Authors: Rosenfeld  , Kiefner
Published: August 2023

The natural gas pipeline industry is rapidly implementing comprehensive integrity management practices to meet the demands of new regulatory imperatives and public interests. These new demands require formal integrity management planning programs be developed and applied where pipeline failures could affect High Consequence Areas�. A formal integrity management plan (IMP) incorporates some process for identifying threats to a pipeline's integrity. Such threats come in many forms and are uniquely dependent on a wide range of attributes associated with an individual pipeline segment. Interest (or concern) has arisen regarding metal fatigue as one such possible integrity threat. We know from some pipeline failures that occasionally and under certain circumstances, fatigue may constitute a potential threat.

The cumulative body of knowledge derived by theory, test, and experience on the subject of fatigue and its effects on piping, pressurized equipment, and welded structures is vast in scope and detail, and it is not the intention of this document to summarize that. Rather, it is intended that this document provide natural gas pipeline operators and others interested in natural gas pipeline safety with a useful understanding of the extent to which fatigue could pose a legitimate and actionable safety threat, as well as to demonstrate the author's opinion that in most respects, fatigue remains a comparatively minor risk component of the overall spectrum of threats to natural gas pipeline safety.
L51839 Methods for Evaluating the Toughness of Weld Heat-Affected Zones in Line Pipe Steels
Authors: Leis  , Groeneveld  , Francini
Published: August 2023

This report discusses how fracture toughness and weldability are achieved in modern higher-strength line pipe and outlines why a coarse-grain (CG) heat-affected zone (HAZ) develops when welding these steels. The possible effects of this CG-HAZ on the toughness of weld seams in Grade X80 line pipe are reviewed in reference to: 1. criteria in use by pipe producers to achieve and control the toughness of the HAZ and weld metal, 2. test methods to characterize the toughness of the weld metal and HAZ, and 3. the applicability of such test methods to Grade X80 line pipe.
L30005 Possible Means for Prevention of External Damage to Pipelines
Authors: Connell  , Smith
Published: August 2023

Pipeline companies in the United States have, over the years, demonstrated an outstanding record of public and employee safety, even though the industry has gone through a period of unprecedented growth since the mid- 1940's. This record is the result of a responsible and continuing program to improve the design, construction, and operation of the over 220,000 miles of pipeline. Failures in pipelines caused by humans operating mechanical equipment such as graders, bulldozers, ditchers, etc., appear to be increasing slightly, whereas failures from all other causes have decreased. This program was carried out to determine the causes and to develop recommendations to reduce the incidence of externally caused� failures.

An analysis was made of a number of externally caused incidents and company policies pertinent to this type of incident. This analysis was based on detailed information obtained from a selected group of cooperating pipeline companies and it resulted in a number of conclusions and recommendations.
L51897 Cathodic Protection Conditions Conducive to SCC
Authors: Beavers
Published: August 2023

The objective of this research project was to define pipeline conditions where use of the 100 mV polarization criterion may be conducive to possible SCC problems. Each of the controlling conditions for the two recognized forms of SCC (high pH SCC and near neutral pH SCC) was examined, using a combination of analysis of previous research results, analysis of unpublished field data, and laboratory testing. In the original proposal, it was not planned to analyze field data but the data became available and the analysis has yielded some significant findings. The results of the literature survey, the analysis of the soil and electrolyte data from the SCC field digs, and the testing performed in this project all indicate that cathodic protection is generally beneficial in mitigating near-neutral pH SCC. Furthermore, the only testing reported in the literature, which suggests that cathodic protection is detrimental to this form of cracking, was performed under unrealistic conditions where cathodic polarization was applied to pipe steel samples containing growing cracks, but the beneficial environmental polarization that accompanies cathodic protection was not allowed to occur. One conclusion from this current research is that it is not necessary to consider the near neutral pH form of cracking in the selection of the CP criterion.
L52282 State-of-the-Art Assessment of Alternative Casing Repair Methods
Authors: Bruce
Published: August 2023

Many natural gas storage wells suffer damage during normal storage operations. Storage operators spend upwards of $100 million per year recovering lost deliverability. Damage to casings in gas storage wells is largely the result of localized loss of metal from corrosion; however, other types of damage do occur. Individual corrosion pits can be found either on the inside or outside of the casing wall. Repair methods that are currently used for natural gas storage well casings include patches, plugs, liners, etc. While currently-used repair methods can be a cost-effective means of repairing damaged casings as compared to the cost of running an entirely new casing, there is a need to identify and develop alternative casing repair methods that are more economical and/or do not have inherent operational disadvantages. Many of the current repair methods are proprietary, and as a result, are relatively costly to perform. In addition, many of these repair methods (e.g., tube and packer system repairs) result in a decreased cross-sectional area, which creates operational limitations due to flow restrictions and reduces the ability to perform well logging operations.

The objective of this project was to review current state-of-the-art casing repair technologies to identify more cost effective alternatives. The most prominent form of underground U.S. gas storage is depleted reservoirs. American Petroleum Institute specification 5CT contains the industry standard design guidance for new casings; however, there are no industry standard repair procedures and each state has their own. The most common state required repair integrity test is pressure testing. Casings must withstand tensile, burst, and collapse loads. Most state repair procedures do not specify a target mechanical property that defines repair success. It is therefore easy to assume that a repair should return a casing back to its original integrity level; however, it may not be necessary. The major types of damage mechanisms are corrosion, threaded connection separation, sealant leaks, split casings, and drill bit damage. While a literature search indicated that the most commonly used types of cost effective repair processes are squeezes, liners, and plating, industry feedback indicated that liner repair is the most commonly used repair process. Adhesively bonded, helically-wound, steel strip repair and magnetic pulse welding are the most promising alternative repair technologies identified, mainly because both are applicable for a broad range of damage types and as an alternative to both traditional casing liner and expandable tubular repair technologies.
L30500 Analysis of the Effects of High-Voltage Direct-Current Transmission Systems on Buried Pipelines
Authors: Hopper
Published: August 2023

The economics of high voltage direct current for long-distance transmission of electrical energy have been reported as very attractive, to the extent that several projects are in the making. Several reasons other than the savings in transmission costs, for example the exchange of peak power between time zones and seasonal zones, would permit utilities to save on plant investment for generating capacity while maintaining a high level of service.

This report summarizes work on the initial phase of a study to determine the effects of high-voltage direct-current (H.V.D.C.) electric transmission lines on buried pipeline systems. Pipeline Research Council International, Inc. initiated this work in response to an anticipated threat posed by the Pacific Northwest-Southwest Intertie H.V.D.C. system now being designed (and other possible H.V.D.C. lines in the future) because of the announced plans to pass direct current through the earth. The objectives of the overall program are:(1) To determine the nature and magnitude of problems that will be created by the earth current from H.V.D.C. systems, and(2) To devise means of protecting pipelines from the effects of such currents.

A computer program was written based on a mathematical model of a buried pipeline in the environment created by an H.V.D.C. system. Excellent agreement was obtained between computed soil potential gradients and measurements obtained during a field test of H.V.D.C. in Oregon. Reasonably good agreement was also obtained between measured pipe-to-soil potentials on the Pacific Lighting Gas Supply Company pipeline near Camino, California, and computed values during a field test of H.V.D.C. power transmission.
L51936 Factors Influencing Girth Weld Reliability in Older Pipelines
Authors: Koppenhoefer
Published: August 2023

Many older pipelines were constructed without either the benefit of detailed weld inspection or the understanding of the requirements for girth weld performance that currently exists. Consequently, they often contain discontinuities that exceed today's workmanship standards. Operators of pipeline facilities are now being required, by recent legislation and regulation, to provide a higher level of assurance of the integrity of their pipeline systems. Older pipelines present some unique challenges in meeting these requirements.

The objective of this project was to develop a technical basis for demonstrating the integrity of older pipelines at reasonable cost. This work addresses the characteristics of girth welds in older pipelines that prevent assessment of their fitness for service using standard available procedures. The present work focuses on developing a closed-form stress-intensity solution that includes the effects of weld cap size. In addition, this work improves test methodologies for measurement of appropriate material properties in low-strength girth welds.
L51605 The Use of Flattened Specimens to Measure the Charpy V-Notch Impact Properties of Thin-Wall Pipe
Authors: Williams D. N.
Published: August 2023

API Specification 5L, Supplemental Requirement SR5, 37th Edition, requires that Charpy V-notch (CVN) impact properties of pipe from which full size (0.394 x 0.394 inch) transverse specimens cannot be obtained, because of wall-thickness/pipe-diameter limitations, be measured with unflattened 2/3 size (0.263 x 0.394 inch) or l/2-size (0.195 x 0.394) transverse specimens. Since the use of subsize specimens is known to introduce significant problems in measuring transition temperature interest has been expressed in the possibility of measuring CVN impact properties with flattened specimens to maximize specimen thickness, i.e., use full wall thickness, when subsize specimens are necessary. The present study was undertaken to examine the merit of this approach.

This work was done under the NG-18 workgroup, report 182.
L51762 Investigation of Fatigue Properties of Girth Welds with Root Imperfections Allowed
Authors: Orth
Published: August 2023

Fatigue analysis of welded components and structures according to established codes is based upon either S-N design curves or fracture mechanics principles. Fatigue damage in nominally sound joints is commonly estimated using an appropriate S-N curve in conjunction with a linear cumulative damage rule (i.e., Miner"s rule). By comparison, fracture mechanics is used to assess the growth of an imperfection during a period of cyclic loading, or to assess whether an imperfection will remain dormant under the applied cyclic loading condition. Thus, the S-N approach is used mostly during initial design, while the fracture mechanics approach is used mostly to justify the continued operation of existing structures. As the aim of this investigation is the rationalization of certain features of API-1104, an initial design code, the S-N approach was used here.

The work described in this report was aimed at determining the effect of root imperfections allowed by API 1104 on the fatigue properties of girth welds, and to recommend a S-N curve appropriate for girth welds in pipelines. S-N curves were developed for single-sided girth welds without a backing strip using pipe strip specimens containing various sizes of incomplete root penetration and lack-of-root sidewall fusion.
L41002 Toughness of Submerged Arc Welds in Pipeline Steels
Authors: Glover A.G.
Published: August 2023

A series of seven line pipe and weld metals have been studied varying in strength level from X60 to X70, in diameter from 26" to 48", and in thickness from 0.375" to 0.720". The weld metals were all made using a two-pass, high-heat-input, submerged-arc weld by either a U and O or spiral technique. The pipes and weld metals were assessed for their microstructural content and tensile strength, and Charpy impact energies and crack tip opening displacements were measured in the pipe, heat-affected zone and weld metal at room temperature and at -45 �C.
L00035 Examination of the Properties of Quench and Tempered Fitting
Authors: Williams
Published: August 2023

The properties of a pipe fitting reported by the manufacturer normally are measured using test specimens prepared from trim material that is removed from the fitting after forming and that, subsequently, is welded to the fitting for heat treatment with the fitting.

The goals of this investigation were to determine the uniformity of properties in a representative fitting and to determine how well properties measured on test specimens cut from the fitting match the manufacturer's test report. A quenched and tempered 30 x 30 x 30 inch straight tee fitting was used in this study. The yield strength and ultimate tensile strength only varied a few ksi at the various locations examined. Total elongation was slightly lower in specimens with the major axis transverse to the plate rolling direction. Energy-absorption values from longitudinal Charpy V-notch tests at 20 F showed significant variation, ranging from 37 to 86 ft-lbs. The measured tensile yield strength was about 15 ksi lower than that reported by the manufacturer. Finally, limited studies to determine the effects of stress-relief treatments showed that stress relieving for 1 hour at 1100 F reduced energy adsorption values by about 25 ft-lbs. A similar treatment for 5 hours at 950 F had little effect on the tensile or impact properties.
L01974 Characterization and Treatment Evaluation of Hydrostatic Test Water Effluent
Authors: Barkley Dr. William A.
Published: August 2023

This investigation of the pollution aspects of the hydrostatic test effluent concerned three separate phases: (1) the study of the existing and new 1972 water pollution laws pertinent to this type of water pollution, (2) the characterization of the hydrostatic test water effluent as a possible pollutant, and (3) evaluation of treatment methods of the hydrostatic test water prior to its return to receiving waters. It was determined that the polluting parameters of the hydrostatic test water that were significant were iron and chemical oxygen demand (COD). In new pipelines concentrations of iron and COD are low in old pipelines the iron concentration is high for the entire dewatering period and will usually, therefore, require treatment before being returned to the receiving state waters.
L51732 Fitness for Purpose Assessment Procedures for Sleeve Welds in Pipelines-Summary Report
Authors: Svedeman
Published: August 2023

Weld flaw acceptance criteria in the main body of the API 1104 pipeline code-Welding of Pipelines and Related Facilities is based on 'good workmanship' criteria. In allowing relaxed flaw acceptance criteria, the achievement of a critical CTOD value ensures that the flaws will remain stable during installation and service. This document presents alternative flaw acceptance criteria for pipeline girth welds which are based on the philosophy of fitness-for-purpose. The alternative flaw acceptance criteria can be applied in situations where specified minimum fracture toughness values are achieved in crack tip opening displacement (CTOD) tests performed on specimens notched into both the weld metal and heat-affected zone (HAZ). The alternative flaw acceptance criteria presented in Appendix A of API 1104 are restricted specifically to pipeline girth welds. In comparison, the flaw acceptance criteria in API RP1107-Recommended Pipeline Maintenance Welding Practices-which deals with pipeline sleeve welds are based entirely on 'good workmanship' standards.
L51736 Chemical and Electrochemical Conditions on Steel at Disbonded Coatings
Authors: Perdomo  , Payer
Published: August 2023

The objective of this research was to study the effects of cathodic protection at coating holidays and associated areas of disbondment through simultaneous determination of the electro-chemical reactions and chemical changes taking place in the environment adjacent to the steel substrate. Primary parameters of interest were applied potential, solution conductivity, pH oxygen in solution. The experimental plan was comprised of six interrelated studies involving both laboratory simulations and modeling. It was found that an effective CP system provides sufficient current flow at the exposed steel surface to modify the ground water in the immediate environment by lowering soluble oxygen levels and increasing its alkalinity. Further, corrosion protection is achieved in the shielded areas under the disbonded coating where current flow is minimal, through this chemical modification of the aqueous environment, and it is not necessary that current flow into all of the disbonded region. Three conditions of import to pipeline corrosion protection were also simulated in this investigation. Chemical environment and electric potential distribution within disbond regions were measured for the affects of interruption and reapplication of current; the occurrence of wet/dry cycles at the holiday and the presence of prior corrosion products.
L51798 Effects of Phosphoric Acid Treatment on the Performance of Fusion-Bonded Epoxy Coatings
Authors: Partridge Paul E.
Published: August 2023

The objective of this research was to develop data from comparative testing to evaluate the test performance (up to 28 day duration) of FBE pipe coatings when applied over contaminated as well as uncontaminated surfaces with and without phosphoric acid treatment. This project was based on a package drafted by Mr. E.G. Pierson, a former PRCI member employed by Exxon Pipeline Company. The scope of this work was adapted from the research guide lines in the original request for proposal (RFP). Some of these introductory comments were extracted from the RFP as well.
L51908 AC Grounding Effects on Cathodic Protection Performance in Pipeline Stations.pdf
Authors: Gummow
Published: August 2023

Most AC powered equipment at pipeline stations and at motorized valve sites isrequired, by code, to be electrically grounded to one or more ground electrodes. These grounding systems are normally electrically bonded to the AC power distribution grid, which can be quite extensive. Piping, either intentionally or inadvertently, is often connected to the AC electrical grounding grid in pipeline stations. Grounding grid conductors are usually bare and composed of copper or tinned copper, and ground rod materials can consist of a wide variety of metals such as copper-clad steel, carbon steel, stainless steel, galvanized steel, and galvanic anode alloys of zinc and magnesium. The interconnection of these grounding materials to the piping can increase the current requirements of the cathodic protection system, distort the current distribution pattern and complicate the accurate measurement of the pipe potentials.

Benefit: The primary objective of this research project was to assess the impact of various types of grounding materials on the performance and testing of cathodic protection systems. The two major issues in this regard were the effects on current requirements and the accuracy of pipe-to-soil potential measurements. In addition, some related issues investigated as follows:the electrical resistance of each groundrod-to-earth was to be measured to determine whether or not there were any changes in the resistance-to-earth as a result cathodic polarization;the potential of galvanized steel was to be measured with increasing zinc consumption to determine if there is a well defined relationship between potential and zinc consumption; the National Electrical Code (NEC) was to be reviewed with respect to the insertion of AC coupling/DC isolating devices in series between the piping and the electrical grounding network.

The results of this investigation were intended toprovide information to design more effective cathodic protection facilities for piping in pipeline stations having electrical grounding systems, anddetermine whether or not the resistance of the electrical grounding system increases as a result of receiving cathodic protection, andrecommend pipe-to-soil potential survey techniques to maximize measurement accuracy in the presence of an AC grounding grid, andevaluate the use of DC isolators/AC couplers to interconnect the piping to either the secondary or primary AC grounding system.
L51522 Hydrodynamic Forces on Pipelines
Authors: Sorenson T. , Bryndum M.B. , Jacobsen V.
Published: August 2023

The aim of this study was to provide hydro-dynamic force coefficients applicable for the determination of forces on pipelines resting on the sea bed when exposed to wave and current flows. This has been achieved through an extensive model test program in which the parameters important for the phenomena have been investigated within wide ranges for a number of flow conditions including irregular waves. The results of the more than 1,000 individual tests have been presented in the form of non-dimensional coefficients determined from three distinctly different types of analysis. These coefficients have been presented as functions of the governing parameters in a series of easily accessible diagrams. The report contains three parts. Part I presents the results of the model test study and the comparison of these results with other data. Part II deals with force calculations in irregular waves, including a statistically based comparison of predictions using traditional and improved force expressions. Part III presents the results of the model tests with a partially buried pipe.
L51444 Effects of Hydrostatic Retesting on Stress Corrosion Cracking
Authors: Barlo
Published: August 2023

The problem of stress-corrosion cracking in gas transmission pipelines has been the subject of research sponsored by Pipeline Research Council International, Inc. and supervised by the NG-18 Line Pipe Research Committee. This research effort is directed towards practical solutions that can be applied to new and existing pipelines. However, it is recognized that stress-corrosion cracking is a time dependent process and, in general, it is not yet possible to locate where, or identify when, stress corrosion cracking is occurring. In lieu of this information, the industry has developed procedures to locate and eliminate stress-corrosion cracks or other defects in the pipe, should they occur. Hydrostatic retesting is a destructive pressure test of breaking out those stress-corrosion cracks that could result in a leak or rupture in service and straining other cracks or flaws that survive the retest.

Stress-corrosion cracking experiments were carried out in the laboratory to determine the effect of hydrostatic retest pressure on the subsequent growth of cracks that survive the retest. For these experiments, 8-inch diameter pressurized pipe specimens were used with various size notches machined into the pipe to simulate preexisting stress-corrosion cracks. Experiments were conducted with the notches covered by a 4.8 percent sodium carbonate + 7.6 percent sodium bicarbonate environment at 175 F and held at -720 mV (Cu/CuS04) as the pipes were subjected to various cyclic operating pressures from about 50 percent to 85 percent SMYS and to hydrostatic retest pressures of either 90, 100, or 110 percent SMYS held for 24 hours. The effect of hydrostatic retest pressure was assessed from post-test crack-growth rate measurements on the notches in companion experiments, one pipe held at the operating pressure for about 1 month and the other held similarly but with the intervening hydrostatic retest.
L51818 Microtunneling Design Guidelines for the Gas Transmission Industry
Authors: Clyde Greiner Woodward
Published: August 2023

Microtunneling is an underground method of constructing pipelines using a sophisticated, remotely controlled, laser guided, steerable boring machine to install a pipe or casing using pipe jacking techniques. The line can either be installed directly by microtunneling or it can be installed inside a casing that is installed using microtunneling methods. This report discusses the following key topics relative to the design of a pipeline to be installed using microtunneling methods: Microtunneling methods and equipment. Case histories of similar pipelines installed using microtunneling methods. Project planning considerations. Geotechnical investigation and laboratory testing recommendations. Microtunneling design considerations. Design criteria for casings and jacking pipes. Shaft design considerations for jacking and receiving pits. Contract documents and contracting approaches. Guidelines for developing preliminary construction cost estimates. Recommendations for construction monitoring. This report contains comprehensive design guidelines in sufficient detail to address the design considerations typically involved with a routine microtunneling project. Use of these guidelines will result in the most cost effective microtunneling design and minimize costs and risks to your microtunneling project. The numerous references cited should be consulted for additional information when needed.
L51650 The Significance of Local Hard Zones on the Outside of Pipeline Girth Welds-Further Studies
Authors: Ginn B. J.
Published: August 2023

In an earlier project it was demonstrated that it may be permissible to relax the NACE MR-01-75 (2) hardness restriction of 22HRC maximum for regions of a pipeline girth weld that are not in direct contact with H2S-containing environments. The objective of this report is to provide quantitative data on which permissible relaxations in hardness limits for external local hard zones in pipelines designed for sour service can be made. This report presents additional data to supplement that obtained in a previous PRCI project conducted at TWI. Further pipe materials with differing pipe wall thickness have been welded, exposed to an internal H2S containing environment and examined for sulphide stress corrosion cracking (SSCC).