bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Relevance of ILI and Field Trending
Authors: Abdolrazaghi Mona , Hubert Yvan , Hassanien Sherif
Published: November 2016

In pipeline integrity threat management, the comparison of In-Line Inspection (ILI) and field results (trending) is typically used as an effective approach to determine the performance of ILI tool. ILI and field trending typically influences the integrity threat management of unmitigated features. Hence, pipeline operators should ensure collecting an adequate number of excavated ILI features from the field which are statistically relevant and represent the entire population of ILI data. The number of the trended data points is considered a sample from the entire population of ILI reported features. Nevertheless, it is considered a biased sample since it is drawn from the ILI population based on selective threat mitigation criteria. This paper describes several sampling methodologies with a focus on advantages and disadvantages of each approach. A Bayesian approach is introduced as an appropriate approach to the integrity sampling problem.
Double Block Isolation: What Are the Options?
Authors: Whiteis Kyle , Dum Frank
Published: November 2016

Conventional pipeline maintenance and modification work requires removal of fluids from inside the pipeline section where work will be performed. In order to complete this task, the pipeline must either be depressurized (blown down) or temporarily isolated.

Depressurization can be costly because the pipeline cannot stay in service during the time of decommissioning, intervention and re-commissioning, and depend significantly on factors like pipeline size, length and pressure. As a result, valuable production is lost and downstream customers may be affected. Also, the significant environmental issues associated with the removal of pipeline inventory further escalate the overall costs and complexities of the maintenance/repair process. Depressurization might not even be an option for repair/maintenance work on long pipeline sections.

An alternative to depressurization of the entire pipeline is isolation of the pipeline section requiring maintenance or repair. This method allows the pipeline to stay in service, production downtime and loss of pipeline product are kept to a minimum, with associated environmental and economic benefits.

A wide range of methodologies, both intrusive (such as hot tapping and plugging) and non-intrusive (inline isolation plugs), can be used to isolate in-service pipeline sections. Both approaches are well accepted in the industry, with the choice of one over the other being largely governed by factors such as location and accessibility of the pipeline, operating pressures, pipeline inventory, and costs.

Some maintenance/ repair operations using isolation methods require a facility shutdown. These cases often require double barriers to safeguard personnel and facility equipment during pipeline maintenance. Although the philosophy, definition, and requirements of double barriers have been described in various international codes and standards, certain misconceptions persist surrounding double barrier terminology and its application to pipeline pressure isolation tools. The objective of this paper is to clarify the concepts of double barrier isolation, and to examine how both intrusive and non-intrusive methods can be used to provide double barrier isolation that meets the accepted requirements. The paper also addresses methods that can be used when standard isolation is not practical.
Fundamental Research on Method of Characteristics Based on Cubic Interpolated Profile Scheme in Water Hammer Analysis
Authors: Tanaka Yoshikazu , Mukai Akie , Taruya Hiroyuki , Tsuda Kazuhiko
Published: November 2016

This paper introduces basic research conducted to develop a numerical analysis technique for water hammer analysis. The CIP (Cubic Interpolated Profile) scheme was applied to obtain more accurate results without greatly causing a spatial interpolation error depending on the Courant number in the method of characteristics. Regarding this technique, the authors derived a well-formed error formula by applying a linear stability analysis. Characteristics of the interpolation error were clarified by comparing existing interpolation schemes with the method of characteristics. The interpolation error of CIP scheme was superior to the Spatial Linear Interpolation Scheme, was approximately equal to the Time Linear Interpolation Scheme and the cubic spline interpolation scheme with sufficient number of computational grids. The calculation efficiency of the CIP scheme was superior to the other schemes excepting the Spatial Linear Interpolation Scheme.
Experimental Validation of a Finite-Element Model to Simulate an Impact on Pipeline due to Vehicles or Heavy Object Fall
Authors: Fernandez Charles , Bertin Maxime , Cardin Philippe
Published: November 2016

This paper deals in a first part with an experimental program aimed at studying mechanical impacts on pipelines. Tests have been performed at CRIGEN-ENGIE-LAB, the Center of Research and Innovation for Gas and New Energies of ENGIE (previously GDF SUEZ) on pipes under pressure and pipes without internal pressure with an impact tool whom length is greater than the external diameter of the pipes and a tool similar to an excavator tooth.

In a first part, the paper presents the tests which show a very good behavior of the pipelines. None have failed for the large impact-tool, which is equivalent in terms of impact energy to a 1000 kg-vehicle impacting a pipeline at ∼32 km.h−1 (∼20 miles.h−1).

In a second part, the paper deals with existing analytical solutions: the Det Norske Veritas model for dent assessment and the EPRG model for mechanical damage assessment due to an excavator tooth. Comparisons with the CRIGEN tests show that the DNV equation is not always conservative in terms of predicted rupture energy and that the third-party damage EPRG model predicts correctly the rupture for the tooth-like tool but does not seem adapted for the longer tool.

In a third part, an explicit finite-element model (performed with the commercial software Abaqus) has then been used to simulate numerically the tests. Different material behavior laws have been tested: a classical elastic-plastic law and a law with a time-dependence (Cowper-Symonds). The comparison between the final geometry of the impacted pipeline and the computational solution is quite satisfactory. A numerical strain criterion is extrapolated and then applied to some real configurations.

This paper presents the tests, the analytical comparisons, the computational models and some applications to the fall of heavy long objects as well as vehicle impact on pipelines.
Methodology for Comparing Field Applied Liquid Epoxy and Hot Bituminous Tape Coating Repairs Using Inline Inspection Data
Authors: Tsaprailis Haralampos , Abdolrazaghi Mona , Liang Jeff
Published: November 2016

In this paper, pipelines with similar parameters (e.g., diameter, environment, temperature of the product, etc.) are used to compare the effectiveness of field repair coatings (i.e., liquid epoxy and tape coating systems) against external corrosion. Liquid epoxy and tape coating systems are compared based on number of corrosion features, severity, morphology and distribution of features over depth and length. Once corrosion defects are assessed in the field and a repair coating is applied, In-Line Inspection (ILI) tools can detect and size the corrosion features under these coatings. If the corrosion feature is growing, the growth can be detected and measured using ILI data assessment. In this paper, data from both field nondestructive examination (NDE) and ILI measurements collected from 1996 to 2013 are used to assess the corrosion growth rate (CGR) under both types of repair coatings. The CGR with respect to depth is compared for both liquid epoxy and tape coatings and then normalized by the number of corrosion features over the segment. In addition, the effectiveness of cathodic protection was evaluated at the locations of the assessed repair coating. Ultimately, this paper provides useful information to pipeline operators for decision making regarding the choice of repair coatings based on operational data collected over 14 years.
Pipeline Diagnostics With Ultrasonic Meters
Authors: Gailey Nicole , Rasool Noman
Published: November 2016

Canada and the United States have vast energy resources, supported by thousands of kilometers (miles) of pipeline infrastructure built and maintained each year. Whether the pipeline runs through remote territory or passing through local city centers, keeping commodities flowing safely is a critical part of day-to-day operation for any pipeline. Real-time leak detection systems have become a critical system that companies require in order to provide safe operations, protection of the environment and compliance with regulations. The function of a leak detection system is the ability to identify and confirm a leak event in a timely and precise manner. Flow measurement devices are a critical input into many leak detection systems and in order to ensure flow measurement accuracy, custody transfer grade liquid ultrasonic meters (as defined in API MPMS chapter 5.8) can be utilized to provide superior accuracy, performance and diagnostics.

This paper presents a sample of real-time data collected from a field install base of over 245 custody transfer grade liquid ultrasonic meters currently being utilized in pipeline leak detection applications. The data helps to identify upstream instrumentation anomalies and illustrate the abilities of the utilization of diagnostics within the liquid ultrasonic meters to further improve current leak detection real time transient models (RTTM) and pipeline operational procedures. The paper discusses considerations addressed while evaluating data and understanding the importance of accuracy within the metering equipment utilized. It also elaborates on significant benefits associated with the utilization of the ultrasonic meter’s capabilities and the importance of diagnosing other pipeline issues and uncertainties outside of measurement errors.
Past Bank Erosion as a Guide for Bank Erosion Prediction at Pipeline Crossings
Authors: Roberge Laurent , Ferris Gerald , Weatherly Hamish
Published: November 2016

This paper presents a methodology which uses past bank erosion behaviour as a predictor of future performance. The methodology employed in the bank erosion study consists of the following main steps: identifying a reach to examine, classifying the watercourse, estimating key hydrotechnical properties, obtaining historical air photographs of the reach, georeferencing or orthorectifying the airphotos, mapping the position of the channel edge, obtaining the historical records of nearby gauges to estimate the return period of floods that have occurred between successive pairs of historical air photographs, and finally combining the results to provide correlations between the rates of bank erosion and the rarity of the floods that have occurred.

More than 70 bank erosion studies have been completed in the past two years at a variety of watercourses. This paper provides three case histories that illustrate the methodology and then proceeds to provide some tentative relationships that could be used to focus future bank erosion studies on those sites most active, and used to provide a preliminary estimate of the amount of bank erosion that could be expected in both design settings and existing pipeline integrity evaluations.

In this study wandering rivers are more laterally active than other channel pattern types. Although the smallest floods do not cause large-scale changes to the banks, significant bank erosion can be caused by either moderate (20-year) or extreme (100-year) events with a rough trend to larger bank erosion in larger floods. No significant correlation between the time elapsed between successive air photos and the magnitude of erosion was found, suggesting that bank erosion is an event-driven process rather than time dependent.
Full-Scale Elevated Temperature Testing of Composite Repairs in Bending and Compression
Authors: Sheets Colton , Rettew Robert , Alexander Chris , Axenova Tanya
Published: November 2016

The increasing use of composite repair systems in critical and complex applications has brought greater scrutiny to their design and performance. This has been especially true in high-temperature, immersed environment applications where ambient temperature test results with industry standard de-rating factors are all that is available for design. Since this approach does not always adequately capture environmental effects or the performance of composite systems at elevated temperatures, it is beneficial to perform full-scale testing which accurately replicates the in-situ application. In order to accomplish this, a full-scale testing program was developed that subjected multiple composite repair systems to internal and external loads at temperatures up to 120 °C with and without water immersion.

This program involved the reinforcement of 12.75-inch × 0.375-inch pipe samples that had simulated corrosion defects. Full-scale load and pressure testing was conducted to simulate the long-term performance of the composite repair systems in the environmental conditions of the application. A strain based performance threshold of 0.4% strain at 120 °C and 100% SMYS was used to develop a competitive program that ranked the participating systems and reduced the number of acceptable repairs from six down to three. This approach increased the efficiency of the full-scale testing and allowed for more in-depth analysis of the top-performing systems.

The results of the full-scale testing of six composite repair systems at elevated temperature allowed for a quantitative measure of their effectiveness under in-situ conditions. Several of the systems were shown to provide inadequate reinforcement under these conditions; however, it was also observed that appropriately designed and installed systems are capable of meeting the intense demands of elevated temperature, harsh-service conditions.
The Development and Use of an Absolute Depth Size Specification in ILI-Based Crack Integrity Management of Pipelines
Authors: Foreman Geoff , Bott Steven , Sutherland Jeffrey , Tappert Stephan
Published: November 2016

To provide a more insightful and accurate feature description from Crack In-line Inspection (ILI) reporting as per the Fitness For Service analysis in API 1176, individual crack dimensions must be established to a given accuracy. PII Pipeline Solutions established an absolute depth sizing specification conforming to the dig verification processes of API 1163. This change represented a significant shift from a traditional reporting format for depth sizing in “bands” of 1–2 mm, 2–3 mm and > 3 mm depths within crack ILI inspection reporting.

When assessing features with characteristics stated in a sizing band, the pipeline integrity assessment approach required a conservative assumptions that all of the features in that band must be treated as if they are in the deepest band value. The implication then meant that the specification created only 3 sizes of crack depths 1–2 mm, 2–3 mm, > 3 mm (± 0.5mm tolerance at 90% certainty). In practical terms a large quantity of features in the significant band of 2–3 mm must be treated as potential dig candidates with a depth of at least 3 mm, making length characteristics as the only severity ranking basis for any priority dig selection.

Previous attempts at establishing absolute depth sizing for crack inspection required a series of calibration digs. The large sample size over multiple inspection runs and pipeline sections allowed for a statistical specification algorithm is developed as part of the analysis process, therefore no additional reporting time, or excavation cost was involved. The new absolute sizing algorithm has provided operators with a means of prioritizing digs, based upon individual feature length and depths. Replacing the traditional depth bands with individual feature specific peak depths and thereby providing a major step forward in achieving a cost effective process of prioritizing crack mitigation in pipelines.

Following the dig verification process in API 1163, significant populations of infield NDE results were utilized on a variety of pipeline sections of different diameters. Predicted absolute depth estimation accuracy was determined for specific feature types and thereby created a depth tolerance, with statistical certainty levels established that match those available and recognized with metal loss ILI. This paper describes the process and the means by which an absolute depth crack ILI specification was established using characteristics from a significant set of real features. It also describes benefits realized within pipeline integrity engineering of moving to such a new reporting protocol.
Experimental Study on Inverse Fracture in Drop-Weight Tear Test and Other Laboratory Test: Current Activities in HLP Committee, Japan, Report 2
Authors: Tagawa Tetsuya , Fujishiro Taishi , Amano Toshihiko , Aihara Shuji , Igi Satoshi
Published: November 2016

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against long brittle fracture propagation. However, there is an ambiguity in its evaluation if the inverse fracture appears (100% shear area prior to cleavage fracture from the notch) on the DWTT fracture surfaces. Although cause of the inverse fracture is not fully understood, compressive pre-straining near the impact hammer has been discussed as a possible cause.

In the present work, DWTTs for X65, X70 and X80 were performed. In addition to conventional DWTT specimen with a pressed notch (PN), PN specimen with a back slot and specimens with a chevron notch (CN) or a static pre-cracked (SPC) were examined. The fracture appearances were compared in the different strength and in the different initial notch type. The frequency of the inverse fracture appeared in these DWTTs were different in each material and each specimen type, but there were no cases free from the inverse fracture.

The inverse fracture was investigated by fractography and the hardness profiles along the under layer of the fracture surfaces. Also, the strain histories during impact in DWTTs were measured by the digital image correlation technique based on the high-speed camera images.

The DWTT specimen purpose is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. The DWTT results should be examined with a manner of a running brittle crack in a pressurized linepipe. A large scale brittle crack arrest test, so called temperature gradient ESSO test was also performed for X65 mother plate. The shear area fraction measured in DWTT fracture appearance was compared with the local shear lip thickness fraction in ESSO test. The count of the inverse fracture was discussed in comparison with the long brittle crack arrest behavior in ESSO test.
Fracture Behavior in West Jefferson Test Under Low-Temperature Condition for X65 Steel Pipe With High Charpy Energy: Current Activities in HLP Committee, Japan, Report 1
Authors: Amano Toshihiko , Igi Satoshi , Sakimoto Takahiro , Inoue Takehiro , Aihara Shuji
Published: November 2016

This paper describes the results of pressure vessel fracture test which called West Jefferson and/or partial gas burst testing using Grade API X65 linepipe steel with high Charpy energy that exhibits inverse facture in the Drop Weight Tear Test (DWTT).

A series of pressure vessel fracture tests which is as part of an ongoing effort by the High-strength Line Pipe committee (HLP) of the Iron and Steel Institute of Japan (ISIJ) was carried out at low temperature in order to investigate brittle-to-ductile transition behavior and to compare to DWTT fracture behavior. Two different materials on Fracture Appearance Transition Temperature (FATT) property were used in these tests. One is −60 degree C and the other is −25 to −30 degree C which is defined as 85 % shear area fraction (SA) in the standard pressed notch DWTT (PN-DWTT). The dimensions of the test pipes were 24inches (609.6 mm) in outside diameter (OD), 19.1 mm in wall thickness (WT). In each test, the test pipe is cooled by using liquid nitrogen in the cooling baths. Two cooling baths are set up separately on the two sides of the test vessel, making it possible to obtain fracture behaviors under two different test temperatures in one burst test. The test vessel was also instrumented with pressure transducers, thermocouples and timing wires to obtain the pressure at the fracture onset, temperature and crack propagation velocity, respectively.

Some informative observations to discuss appropriate evaluation method for material resistance to brittle facture propagation for high toughness linepipe materials are obtained in the test. When the pipe burst test temperatures are higher than the PN-DWTT transition temperature, ductile cracks were initiated from the initial notch and propagated with short distance in ductile manner. When the pipe burst test temperatures were lower than the PN-DWTT transition temperature, brittle cracks were initiated from the initial notch and propagated through cooling bath. However, the initiated ductile crack at lower than the transition temperature was not changed to brittle manner. This means inverse facture occurred in the PN-DWTT is a particular problem caused by the API DWTT testing method. Furthermore, results for the pipes tested indicated that inverse facture occurred in PN-DWTT at the temperature above the 85 % FATT may not affect the arrestability against the brittle fracture propagation and it is closely related with the location of brittle fracture initiation origin in the fracture appearance of PN-DWTT.
Reinforcing Large Diameter Elbows Using Composite Materials Subjected to Extreme Bending and Internal Pressure Loading
Authors: Alexander Chris , Kania Richard , Zhou Joe , Vyvial Brent , Iyer Ashwin
Published: November 2016

A study was conducted to evaluate the use of E-glass/epoxy composite materials for reinforcement of large-diameter elbows. Using a combination of sub-scale and full-scale testing, the study demonstrated that when properly designed and installed, composite materials can be used to reduce strain in reinforced elbows considering bending loads of up to 3.6 million ft-lbs (4.88 million N-m), cyclic pressures between 720 psi (4.96 MPa) and 1,440 psi (9.93 MPa), and burst testing. The stresses measured in the composite material were well below designated ASME PCC-2 design stresses for the composite materials. During testing, there was no evidence that previously applied bending loads reduced the overall burst pressure capacity of the composite-reinforced elbows. Finite element modeling was used to optimize the geometry of the composite reinforcement. The resulting design guidance from this study was used to provide direction for possible reinforcement of large-diameter elbows for in-service pipelines.
Development Towards a Novel Approach for Assessment of Corroded Pipe
Authors: Wilkowski Gery M. , Krishnaswamy Prabhat , Uddin Mohammed , Punch Ed , Hioe Yunior
Published: November 2016

This paper describes an initial feasibility effort completed in a Small Business Innovative Research (SBIR) Phase I project for DOT-PHMSA to develop a novel approach for the assessment of the remaining strength of corroded pipe. The goal was to assess what failure criterion might be for modern line-pipe steels (e.g., X80) compared to pre-1970 pipes that were used to validate the B31G and RSTRENG methodologies[1]. In the process, the methodology will be able to handle many situations that B31G cannot handle, i.e., high longitudinal stress, corrosion that is more circumferentially oriented than axially oriented, interactions of longitudinal and hoop stresses, and multiple adjacent corrosion patches without empirical criteria.

For the assessment of improved failure criteria, two series of SENT specimens were tested with a systematic variation in the bluntness of the notch from sharp crack to large radii. This was done for a 1960 vintage X52 steel, and a modern X80 steel. The sensitivity to notch acuity was much lower in the modern X80 steel, but both steels had ductile fracture start before maximum load even with the bluntest flaw.

To better assess the driving force, an automated meshing system was pursued, where field laser scans of corroded pipe surfaces were used to created detailed 3D FE meshes of the corrosion profile. One example case was used to assess all the nuances of creating the FE mesh in an automated system, which is quite complicated. The results were used to compare predictions for this case to B31G, Modified B31G, and RSTRENG predictions using the X80 steel pipe properties. In the process of these initial FE analyses, it was found that the assumption used in the B31G type analyses (including RSTRENG) used an equivalent flaw depth with the flaw actual length, whereas the more accurate procedure would be to use the maximum flaw depth with an equivalent length.

The system if developed is intended to be Cloud-based on the Ohio State Supercomputer Center, so that anyone world-wide could conduct such FE analyses without having to have a license for the FE solver software or a supercomputer. Such a validated FE analysis would also a B31G Level 3 analysis.
Basic Performance of Normal Incidence Method for Inspection of Middle Zone of Wall Thickness of LSAW Steel Pipes
Authors: Matsui Yutaka , Iizuka Yukinori
Published: November 2016

This paper describes the performance of the ultrasonic normal incidence method as a technique for inspection of the middle zone of wall thickness of LSAW (Longitude Submerged Arc Welding) steel pipes. Generally, the tandem method is applied to LSAW seam inspection of the middle zone of wall thickness. However, it is difficult to adjust the locations and angles of each probe.

Therefore, the normal incidence method using one probe for inspection of the middle zone of wall thickness was studied. Because the probe arrangement is simple, it is possible to reduce the time and effort required to adjust the probe location and angle. In the normal incidence method, it is possible to transmit and receive a mirror reflection because the ultrasonic wave is transmitted perpendicularly to a planar flaw under a high refraction angle. As a result of comparison experiments of the normal incidence method and tandem method, the amplitude of the echo from flat bottom drilled hole (F.B.H.) is 12dB higher in the normal incidence method than in the tandem method. The normal incidence method also has wide area sensitivity in the circumferential direction, however, the amplitude of the reflection echo changes ±25% when the incidence angle of the pipe changes ±0.3°. Thus, in practical applications, strict control of the deviation of the pipe incidence angle is necessary. This suggests that the reliability of this technique can be improved by compensating for sensitivity variations, for example, fluctuations associated with tracking backlash.
Effects of High Strain Rates on Ductile Slant Fracture Behaviour of Pipeline Steel: Experiments and Modelling
Authors: Hojjati Reza , Steinhoff Matthias , Cooreman Steven , Van den Abeele Filip , Verleysen Patricia
Published: November 2016

Good material properties are required to ensure the safe and reliable design of oil and gas transmission pipelines. The main objective of the study, presented in this paper, is to examine the influence of high strain rates on the hardening and ductile fracture behaviour of an API 5L X70 pipeline steel by means of a combined experimental/numerical approach. For this purpose, the impact toughness of the material is assessed using instrumented Charpy V-notch (CVN) impact tests at a wide range of temperatures. To characterize the mechanical response of an X70 pipeline steel subjected to high strain rates, split Hopkinson tensile bar (SHTB) experiments are performed. These experiments allow deriving the true effective stress versus plastic strain, strain rate and temperature. Both the CVN and SHTB tests results are used for fundamental material research and constitutive material modelling. For the numerical simulations, the modified Bai-Wierzbicki (MBW) model is applied. The MBW model represents the influence of the stress state on the plastic behaviour and the onset of damage, and quantifies the microstructure degradation using a dissipation-energy based damage evolution law. The model hence allows for an accurate prediction of the ductile fracture mechanisms. The combined experimental/numerical approach is then used to simulate the upper shelf ductile fracture behaviour of an API X70 pipeline steel for high strain rate and Charpy tests. Based on the available experimental data, a new parameter set has been determined. Using these new material parameters, good correlations between numerical simulations and experimental observations have been obtained for both the split Hopkinson tensile bar tests and the Charpy impact tests.
Thermal Response of Gas Pipeline Metal to Gas Decompression
Authors: Godbole Ajit , Michal Guillaume , Lu Cheng , Venton Philip , Colvin Philip
Published: November 2016

During natural gas pipeline processes that involve severe depressurization (e.g. blowdown), the gas experiences very significant cooling. The general impression in the industry has been that the adjacent pipeline metal also experiences cooling to a comparable extent. Should this actually be the case, the metal would be rendered susceptible to embrittlement. This would increase the possibility of fracture, thus compromising the integrity of the pipeline. To avoid the perceived possibility of fracture, pipeline design specifications tend to recommend special materials that can withstand low temperature. Such materials are often very expensive.

However, recent experimental and analytical investigations into the heat transfer effects during pipeline decompression have shown that although the gas does undergo considerable cooling during events such as blowdowns, the metal is not cooled to nearly the same extent. These investigations resulted in a model of the blowdown. The model was based on the finding that the thermal response of the pipeline metal at a particular location is largely determined by the formation of a sharp negative spike in the gas temperature as the decompression wave passes that location.

The present paper offers a more detailed version of the blowdown model, taking into account the transient temperature variations through the thickness of the pipe wall. The additional investigations offer insight into the phenomenon of ‘thermal shock’ in the pipeline metal. It is found that the metal response to a thermal ‘spike’ differs markedly from that to a thermal ‘shock’ imposed on the surface of the metal. It is shown that the possibility of damage due to unequal expansion/contraction in the material across the pipe wall thickness is minimal during a blowdown.
Probabilistic Assessment of Crack Detection ILI Effectiveness for Managing Stress Corrosion Cracking on Buried Pipelines
Authors: Tehsin Nauman , Al-Saif Abdulaziz , Qurashi Mosa M. , Polasik Steven J. , Bubenik Thomas A.
Published: November 2016

Continuous management of Stress Corrosion Cracking (SCC) on buried pipelines is an important element of an Integrity Management Program. Crack detection inspection tools have been widely used in the pipeline industry for locating SCC. There are some potential limitations with these tools; therefore estimating the probability of detection (POD), probability of identification (POI) and sizing accuracy is essential to validate the inspection results. The relationship between field-identified and ILI-reported features is a key component.

This paper probabilistically assesses detection, identification, and sizing accuracy of a crack detection ILI tool. The paper also describes a procedure for estimating the true defect population from the number and severity of SCC features reported by an ILI using statistical analyses. As part of the analyses, transition matrices were developed.

The ILI data set was generated from 26 pipelines with a known history of SCC defects. Excavation data was collected from field reports where over 300 crack-like features were identified by Nondestructive Examination (NDE). The results obtained from the field were compared against the ILI reported features and ILI detection limits.

Statistical models using three-parameter (shape, scale, and threshold) Weibull distributions were found to best model the depth and length distributions. The statistical analyses were based on results from True Positive features (i.e., reported by ILI tool and found in the field), False Negative features (i.e. not reported by the ILI tool and found in the field to be above the detection threshold of the ILI tool), and Unreported features (not reported by the ILI tool and found in the field to be below the detection threshold of ILI tool).

To determine the impact of an excavation program after an ILI run, an approach was developed to analytically grow the defects over time. Probabilistic models were then used to predict ILI feature lists and simulate prior and future ILI results from the defect population. This task was performed by creating an inverse transition probability matrix. The methodology is the basis for the development of line-specific SCC Management Programs.
De Facto Hydrostatic Test Pressures: A Study in Double Stroking
Authors: Warman David J. , Gruzdowich Nicholas J. , Kleeman Harold E. , Boardman Sean C. , Duruike Ugochukwu N.
Published: November 2016

The pipeline industry has traditionally utilized the double stroke method to limit pipe yielding during pressure testing. Yet few case studies are available which indicate the actual state of stress in a pipeline segment where the pressure — volume plot indicates that the double stroke point has been reached. Examination of a typical stress-strain curve of pipeline steel indicates that the double stroke point typically occurs midway between the elastic limit and the defined yield strength and that the elastic limit can occur at 80% of the defined yield stress.

The purpose of this paper is to develop a model to better understand the actual stresses a pipeline experiences during a hydrostatic test. For analysis, the double stroke point is used as the test case, which results in insights about the actual stresses seen on the pipeline and an understanding about what double stroking actually means. The double stroke point was chosen for analysis since it is commonly used as a ceiling on hydrostatic test pressure and, although literature provides clarity on its definition, few experiments and tests have been performed to gain a practical understanding of its affect on a pipeline.

Analysis was done on a real world example and the results were compared to a Monte Carlo simulation to model the sensitivity of the various parameters. The results of the real world test case of known pipe attributes indicated that the strains in all pipe joints would stay below 0.5% at the double stroke point. When a Monte Carlo simulation was applied to the pipe variables of the same test section, 0.5% strain was exceeded on several outlying joints, but in those cases the hoop stress utilizing Barlow’s equation was in-excess of 125% SMYS. The analysis in this paper provides a tool for predicting the range of actual stresses the pipeline is experiencing when hydrostatically tested, and in doing so, also provides a firmer grasp on what double stroking actually means for a pipeline.
Pipeline Strain and Vibration Monitoring by Smart Materials
Authors: Pargen Sascha , Magerstaedt Michael , Larink Dirk , Mönster Tilman , Rentmeister Nils
Published: November 2016

Dielectric elastomer sensors (DESs) are a new class of mechanical strain and vibration sensors and can be used to fabricate unique intelligent elastomeric products with tailor made properties. Here, a new sensing method was developed to measure strain and vibration of pipelines using a combination of highly flexible DESs and novel polyurea coatings (intelligent coating). The structural health monitoring system described here is suitable to improve safety and maintainability of critical pipeline sections. Such system can be applied to both steel and to polymeric or composite pipes. Basically, the investigated DESs are compliant capacitors consisting of an elastomeric polyurethane film, highly flexible electrodes and surrounding polyurethane insulation. Due to the building block chemistry of polyurethane elastomers, the mechanical, electrical, thermal and chemical properties of DESs can be adapted to specific application scenarios. The versatility of the sensor concept allows the design of DESs with variable hardness (Shore A: 30 to 95), active surface (1–1500 cm2), thickness (200 μm – 1 cm) and sensitivity. Applied electrodes consist of conductive particles which are integrated in an elastomeric matrix. The capacitance of a DES is proportional to the area of overlapping electrodes (active sensor area) and it is inversely proportional to the elastomeric film thickness. In case of deformation due to tensile or pressure loading, the active sensor area expands while the thickness of the elastomeric film decreases. Both effects result in a measurable, linear increase in capacitance. When installed along the axial direction on the exterior of a pipe, the DES is sensitive to strain changes parallel to the pipe axis and allows to detect displacement or deformation that may cause the pipeline to fail. The strain sensitivity of the system depends upon the precision of the capacitance measurement. A typical setup allows a measuring accuracy of at least 0.1 % strain.
Effect of Rolling Parameters on the Low-Temperature Toughness and Microstructure of High-Strength Linepipe Steel
Authors: Stallybrass C. , Völling A. , Meuser H. , Grimpe F.
Published: November 2016

In recent years, large-diameter pipe producers around the world have witnessed a growing interest to develop gas fields in arctic environments in order to fulfill the energy demand. High-strength linepipe grades are attractive for economic reasons, because they offer the benefit of a reduced wall thickness at a given operating pressure. Excellent low-temperature toughness of the material is essential under these conditions. Modern high-strength heavy plates used in the production of UOE pipes are produced by thermomechanical rolling followed by accelerated cooling (TMCP). The combination of high strength and high toughness of these steels is a result of the bainitic microstructure and is strongly influenced by the processing parameters. For this reason, the relationship between rolling and cooling parameters of heavy plate production, the low-temperature toughness and the microstructure is at the center of attention of the development efforts at Salzgitter Mannesmann Forschung (SZMF) in collaboration Salzgitter Mannesmann Grobblech (SMGB).

It has been shown previously that a variation of the processing parameters has a direct influence on the microstructure and correlates with mechanical properties that are accessible via small-scale tests. Modern characterization methods such as scanning electron microscopy in combination with electron backscatter diffraction have broadened our understanding of the underlying mechanisms and have helped to define processing conditions for the production of heavy plates with optimized low-temperature toughness in small scale tests. Within the present paper, the results of a recent laboratory investigation of the effect of a systematic variation of rolling parameters on the microstructure and low-temperature toughness of as-rolled and pre-strained Charpy specimens are discussed. In these trials, final rolling temperatures above the onset of the ferrite-austenite transformation and cooling stop temperatures above the martensite start temperature were selected. The microstructure of the plates was investigated by scanning electron microscopy and electron backscatter diffraction. In a series of Charpy tests in a specific temperature range, it was found that plate material in the as-rolled condition is not strongly sensitive to variations of the selected processing parameters, whereas pre-straining the Charpy specimens made it possible to assess the potential of individual processing concepts particularly with regard to low-temperature toughness.

In addition to Charpy testing, the toughness was also quantified via instrumented drop-weight tear (DWT) testing. By comparing total energy values from regular pressed-notch DWT-test specimens to J-integral values determined in drop-weight testing of pre-fatigued DWT-test specimens, the impact of variations of specimen type on material tearing resistance is shown.
A Life-Cycle Approach to the Assessment of Pipeline Dents
Authors: Turnquist Michael , Smith Ian
Published: November 2016

The application of in-line inspection (ILI) to assess pipelines for various anomalies is standard practice in the pipeline industry. When ILI data identifies the presence of anomalies such as denting or ovalization, current convention is to perform either a depth-based or strain-based assessment to assess the severity. Although a strain-based methodology is generally accepted in the pipeline industry, this approach does not address all of the primary damage mechanisms associated with pipeline dents. Assessment based upon either depth or strain alone may not only provide non-conservative results but also fail to properly rank dents in order of their true severity. A life-cycle assessment approach that considers the damage caused by the dent formation, the stress intensification effect of the dent profile, and the severity of future pressure cycling provides an improved understanding of the probability of failure, allowing for more informed integrity management decision making.

Strain-based assessment of dents in pipelines is typically performed by calculating the local curvatures in the dent geometry as measured by ILI. Local strains are then calculated based on these local curvatures. However, this approach does not address that once a dent has been formed, continued pressure cycling at that location is what will ultimately cause a failure. The current strain-based methodology does not account for the severity of the pressure cycling at the dent.

A new and innovative methodology has been developed which takes a life-cycle approach to the assessment of pipeline dents. This approach estimates the remaining life of a dent based on fatigue damage accumulation. Finite element analysis (FEA) is used to calculate various stress concentration factors (SCFs) based on the geometry of the dent. These SCFs are used to calculate an equivalent alternating stress for a unit pressure cycle event. Past representative pressure cycling data is gathered using a rainflow counting approach. The amount of damage accumulated during each pressure cycle is calculated using stress or strain based (S-N) fatigue curves; this allows for a damage rate to be calculated based on past operational history. A remaining life can be estimated based on this damage rate and an estimation of the initial fatigue damage accumulated during formation of the dent. This estimation is made based on previous elastic-plastic FEA of various scenarios which simulate the formation and shakedown of a pipeline dent.

Case studies which explore the use of different assessment methods to analyze dents will be presented. A comparison of different assessment methodologies will illustrate the improved understanding of the probability of failure of dents based upon the life-cycle assessment.
Integrity Management and Life Extension for a CALM Buoy Oil Export Terminal
Authors: Gordon Robert B. , Ruiz-Rico Juan Carlos , Brongers Michiel Peter Hein , Gomez Julian
Published: November 2016

This paper applies state-of-the-art integrity management and life extension methodologies to address degradation and failure modes specific to CALM buoy export terminals. The main objectives are to (1) classify the components of the export terminal according to their criticality, (2) establish risk-based inspection and maintenance plans to reduce or mitigate risk to acceptable levels and (3) assess remaining life.

The method is applied to a CALM buoy operating off the coast of Colombia. This buoy serves as the oil export terminal for all crude oil transmitted by the Ocensa pipeline, which has a capacity of 560 kBPD or around 60% of total Colombia oil production. The buoy is nearing the end of its design life, and options for life extension have been investigated based on an integrity assessment of the current condition of the equipment. As part of the assessment, detailed plans for future Risk Based Inspections (RBI) and Mitigation, Intervention, and Repair (MIR) have been developed.
Integrity Management of Ground Movement Hazards
Authors: Wang Yong-Yi , West Don , Dewar Douglas , McKenzie-Johnson Alex , Sen Millan
Published: November 2016

Ground movements, such as landslides and subsidence/settlement, can pose serious threats to pipeline integrity. The consequence of these incidents can be severe. In the absence of systematic integrity management, preventing and predicting incidents related to ground movements can be difficult. A ground movement management program can reduce the potential of those incidents.

Some basic concepts and terms relevant to the management of ground movement hazards are introduced first. A ground movement management program may involve a long segment of a pipeline that may have a threat of failure in unknown locations. Identifying such locations and understanding the potential magnitude of the ground movement is often the starting point of a management program. In other cases, management activities may start after an event is known to have occurred. A sample response process is shown to illustrate key considerations and decision points after the evidence of an event is discovered. Such a process can involve fitness-for-service (FFS) assessment when appropriate information is available. The framework and key elements of FFS assessment are explained, including safety factors on strain capacity. The use of FFS assessment is illustrated through the assessment of tensile failure mode. Assessment models are introduced, including key factors affecting the outcome of an assessment. The unique features of girth welds in vintage pipelines are highlighted because the management of such pipelines is a high priority in North America and perhaps in other parts of the worlds. Common practice and appropriate considerations in a pipeline replacement program in areas of potential ground movement are highlighted. It is advisable to replace pipes with pipes of similar strength and stiffness so the strains can be distributed as broadly as possible. The chemical composition of pipe steels and the mechanical properties of the pipes should be such that the possibility of HAZ softening and weld strength undermatching is minimized. In addition, the benefits and cost of using the workmanship flaw acceptance criteria of API 1104 or equivalent standards in making repair and cutout decisions of vintage pipelines should be evaluated against the possible use of FFS assessment procedures. FFS assessment provides a quantifiable performance target which is not available through the workmanship criteria. However, necessary inputs to perform FFS assessment may not be readily available. Ongoing work intended to address some of the gaps is briefly described.