bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Factor Modelling in the Pipeline Industry
Authors: Urra Susan , Green Jessica
Published: July 2013

Most pipeline leaks and ruptures can be attributed to some degree to human factors. Therefore, identifying, measuring and improving areas of potential human factor issues can greatly decrease the risk of pipeline failure.

‘Human factors’ refers to the study of various aspects of human characteristics and job experience, job and task design, tools and equipment design, and work environment which can affect pipeline operations and overall system performance.

Enbridge Pipelines has developed a risk assessment model that assesses the risk of human factors along the company’s nationwide liquid pipeline system. The Human Factors Risk Assessment Model generates a risk score for each aspect of the pipeline as well as an overall risk score which highlights the business areas of highest concern.

The implementation of the model included the execution of a pilot study to calibrate the model. To perform the pilot, data was collected from the control center, field and office locations through different methodologies such as survey, interview and databases available.

The results from the control room operation surveys indicate that the main areas of human error potential in the control room can be mitigated by decreasing the number of manual calculations the operators have to complete and ensuring operators aren’t taking on extra work that should be completed by other areas. These workload improvements would decrease the chance of an operator having to complete two or more control operations at the same time. Lastly, controlling the amount of phone activities that interfere with monitoring and control operations also gives an opportunity to reduce the potential for human error in the control room.

Improvements that can be made in the office to reduce human error potential include the development of a human factors standard and improving the critical procedure observation and management of change systems.

Measuring, acknowledging and mitigating human factor risks at Enbridge will yield a decrease in the risk of pipeline failure across the entire liquid pipeline system.
Development of a Novel Electromagnetic Quantitative Residual Stress Sensor for Characterization of Steel Pipeline Mechanical Damage
Authors: Lasseigne Angelique N. , Koenig Kamalu M. , Jackson Joshua E.
Published: July 2013

Nondestructive residual stress mapping of damage in pipeline steel has been demonstrated as a new approach for pipeline integrity management. The handheld system for rapid characterization pipelines has been used on dents and wrinkles, two of the most common forms of mechanical deformation. The ability to compare residual stresses with design stresses will allow for a much more accurate criteria for use in fitness-for-service and improved modeling of pipeline stresses. As the capabilities of in-line inspection technologies continue to improve, operators are often faced with thousands of indications that require examination. Accurate assessment of residual stresses will provide a more effective method of combatting the most common form of pipeline failures, mechanical damage.

The residual stresses associated with the mechanical damage forms the basis for the nucleation and growth of cracks at areas with the highest residual stresses. Quantitative, real-time knowledge of the through-thickness residual stress levels associated with the mechanical damage will enable enhanced Risk-Based Inspection and drastically improve pipeline integrity. The development of a non-destructive, quantified residual stress measurement system to evaluate the damage severity on pipeline steels through the structural coatings (without any removal) will enable improved integrity assessment and reduce the number of unnecessary removal and replacement activities. The development of a real-time, through-thickness residual stress sensor to assess steel pipeline mechanical damage is presented in this paper.
Implications of Reduced Heating of Heavy Crude Pipeline on Pump Lubrication Systems
Authors: Lopez Byron G.
Published: July 2013

OCP Ecuador S.A. was designed for transporting heavy crude oil from the Ecuadorian Amazonian forest to the Pacific Ocean, crossing the Andes (highest point @ 4060 masl). OCP have four pumping stations PS1, PS2, PS3, PS4 located across the first 182km.

Main pumps were designed with an inherent product circulation from pressure connection via orifice to mechanical seal (API Plan 11) for lubricating and cooling. In order to achieve required viscosity, crude oil from the main line must be heated. Low sulfur crude oil (LSCO) is burned for this purpose.

In order to optimize fuel consumption, some efforts were conducted since 2006. The first aim was to increase feed rate of lubricating oil, in order to extend the viscosity within seals up to 700cP. This modification resulted in considerable heat exchange depletion, representing about 50% of costs reduction related to reduce heating of crude oil in the main line.

Since 2009, there were some adverse scenarios, which forced the company to seek more and better ways to optimize the fuel oil consumption. These scenarios were:

• The continued decline in the quality of crude oil delivered by the shippers quality from shippers. Reduced quality was seen as a threat to the integrity of mechanical seals.

• Unavailability of LSCO in the country,

• The under-utilization of transport capacity due to low volumes of oil (30% of its capacity).

Facing this situation, OCP decided to analyze the technical and economic feasibility of operating without heating oil, in an intermediate pump station (PS3: KP 148 @ 1800 masl). This pump station, at the time of the study, was operated heating crude oil.

The greatest difficulty in achieving the goal of reducing heating oil was the maximum viscosity that mechanical seals could withstand, without affecting its integrity. To mitigate this threat, an API plan 32 was designed and implemented in PS3.

Simultaneously, the organization was evaluating the possibility of installing a similar system in PS4, where climatic conditions are more adverse than PS3. Based on thermal models and after risk evaluation and cost benefit analysis, OCP decided to run operations accepting the risk of potential damage to the seals in PS4.

At the moment, OCP Ecuador S.A. is operated without heating crude oil and API plan 32 was placed on standby, reducing considerably the operating costs.

This paper is intended to share the learned lessons, some actions taken; obstacles faced up as well as achieved results in this cost reduction effort.
Geohazard Mapping and Identification Along Pipeline Right-of-Ways Using Space-Borne Synthetic Aperture Radar
Authors: Henschel Michael D. , Robert Gillian , Deschamps Benjamin , Gailing Richard W.
Published: July 2013

Many energy pipelines traverse hilly and mountainous terrains that are prone to landslides and other geohazards. The mapping, identification, and monitoring of geohazards along pipeline right-of-ways are essential in effectively managing the risks they may pose to pipeline integrity and human safety. One approach to monitoring potential geohazards is to use space-borne synthetic aperture radar (SAR). SAR is an effective and proven technology used to monitor ground surface change over vast areas and can be used in a cost-efficient manner, especially in areas that are remote or challenging.

This paper focuses on aspects of a novel three-fold approach for monitoring geohazards using satellite radar imagery. This is accomplished by combining interferometric SAR (InSAR), automated amplitude change detection, and polarimetric change detection. The resulting analyses are to be merged into a new geohazard index map that will provide a simplified overview of the change influence for given pipeline segments over an extensive area. It is anticipated that the geohazard index map would be used to support operator decision-making in proactively mitigating the potential adverse effects identified.

A brief introduction to the methodologies employed and a discussion of the validation that is currently underway as a joint project between MDA Geospatial Services and Southern California Gas Company is provided by this paper.
Research and Development of Heavy Wall X80 Transmission Pipeline Steel With High Deformation Characteristics for Polar Environments at Shougang Steel
Authors: Zha Chunhe , Jiang Zhonghang , Wang Wenjun , Li Jiading , Li Shaopo , Ding Wenhua , Stalheim Douglas , Bai Xuejun
Published: July 2013

Oil and gas transmission pipeline steels with high deformation capability are required for environments (earthquake zones, permafrost zones, forest heave, deep sea applications, etc.) where large strata movement may occur. When large strata movement occurs the pipeline is exposed to large plastic deformations that can result in failure. Transmission pipelines that must operate in these environmental conditions utilize a strain based design strategy to protect the pipeline from failure. This strain based design strategy for these transmission pipeline environments requires that the steel design used for pipe production must not only have the capability to withstand the high internal operating pressure but must also have good deformation resistance characteristics.

Shougang Steel has conducted research into the metallurgical design required for heavy wall X80 transmission pipeline steel with high deformation and good low temperature mechanical property characteristics. This research coupled with the production capability of the Shougang Steel’s Qinhuangdao China (Shouqin) 4.3 m heavy wide plate mill has resulted in the successful production of a cost effective low C-Nb X80 alloy design with good deformation and low temperature toughness capabilities suitable for applications such as the natural gas TCPL/ExxonMobil proposed Alaskan Pipeline Project. This paper will discuss Shougang Steel’s research and development of heavy wall X80 pipeline steel. Key process parameter and equipment capabilities of the Shouqin 4.3 m wide heavy plate mill along with heavy wall X80 production results will be discussed.
Circumferential Compression Material Characterization for Pipe Collapse Load Prediction
Authors: Meijer Garret , Kaiser Trent
Published: July 2013

Pipe collapse limits are controlled by circumferential compressive material response. In addition to yield strength and elastic modulus, elastic-plastic transition and plastic collapse performance of thick-wall pipes also depends on the character of yielding and post-yield hardening. Accurate characterization of all these properties is necessary to obtain a reliable estimate of collapse load. Common standardized material test methods provide convenient means to acquire basic mechanical properties (i.e., yield strength, elastic modulus and elongation) under laboratory conditions (i.e., room temperature and relatively rapid loading). However, these test methods include specimen preparation, such as pipe-wall straightening, and rapid strain rates that are known to impact material response, particularly in the yield transition and post-yield regimes that are important to elastic-plastic collapse. Therefore, these common laboratory techniques are useful for providing an index of material properties, but their simplified methodologies can have a significant impact on the accuracy of collapse performance estimates.

This paper describes a circumferential compressive material testing technique, developed to complement strain-based design in the energy industry, used to demonstrate differences in pipe material response measured from circumferential compressive tests and standard axial tensile tests. This technique avoids straightening the pipe wall by plastic deformation that leads to artificial rounding of the measured stress-strain yield behavior. Strain controlled loading is used to reveal yield behaviors that may be impacted by changing strain rates under stroke and load control testing.

Accurate circumferential compressive material characterization improves the identification of yield and anisotropic behaviors (tension-compression and axial-circumferential) that arise from material processing, pipe manufacturing and subsequent loading. The impact of the material response is illustrated in a numerical pipe collapse simulation that directly incorporates the measured stress-strain behavior. The impact of yield strength, stress-strain yield shape and post-yield hardening are explored. Using the measured stress-strain behavior and collapse simulation results, the sensitivity of collapse load predictions to material behavior is discussed and the requirement for accurate circumferential compressive and in-situ material characterization is demonstrated.
Variable Frequency Drive Applications and Their Electrical Protection Scheme for Liquids Pipelines
Authors: Ramirez Oscar , Yu Ting
Published: July 2013

Motor and pump units can start either directly across the line (utility) or through a VFD. If the power system is weak (high impedance and relatively low available MVA), the result will be limitations on the maximum size of motor that may be started directly across the line. Currently some available power systems are not capable of starting large motors across the line and therefore VFD systems are required.

A VFD can be used for starting purposes or to operate a motor/pump unit (unit) continuously. Liquids pipelines have been using VFDs for unit starting purposes and for pressure control while either one of the units connected to the VFD or while there is a dedicated VFD per unit.

One VFD can be used to operate all the units. The VFD starts the motor, ramps it up, and synchronizes it with the utility to switch the motor from VFD operation to utility operation. The VFD follows the same sequence with the next unit. The VFD also switches the motor from utility operation to VFD operation. With pumps in series, one unit can remain connected to the VFD for pressure control in liquids pipelines.

Each unit can also be controlled by a dedicated VFD, allowing independent control of each unit for start-up and speed control. Both single VFD or dedicated VFD per unit offer advantages. Benefits of using a single VFD for all units are cost savings for some applications, a backup start across the line when allowed by the power system, and station pressure control. The benefits of a dedicated VFD per unit application include more flexibility in flow and pressure control, ease of expansion without interrupting existing operations for an extended period, energy efficiency, and redundancy.

Motor protection schemes for the above two VFD applications are discussed and compared in this paper. In order to maintain a safe and reliable pipeline system, comprehensive motor protection functions are provided to the pump unit. Although the principles are the same, there are some differences between the two motor protection applications.

For a dedicated VFD per unit application, the VFD protection/control circuitry normally provides motor protection because the motor is always connected to the VFD. RTDs over-temperature protection is not typically a standard feature of VFDs, however, it can be provided by proper PLC programming or the VFD incoming feeder protection relay.
Development of Pipeline Integrity Performance Indicators for Canadian Energy Pipelines
Authors: Reed Mike , Lee Rachel , Coote Bob
Published: July 2013

In 2004, in response to a number of internal and external drivers, the Pipeline Integrity Working Group (PIWG) of the Canadian Energy Pipeline Association (CEPA) undertook to develop pipeline integrity performance indicators. The PIWG wished to create indicators that would assist in reporting performance to regulatory stakeholders and provide its member companies with a means of comparing their respective integrity performance with the performance of their peers in the industry.

The development of meaningful performance indicators is not as straightforward as it might appear. The performance indicator analysis and reporting has evolved since the initial report prepared in 2004, and now trends in the indicators are emerging that can be used to improve understanding of the issues and successes related to pipeline integrity management.

This paper describes development of the CEPA pipeline integrity performance indicators including:

• Stakeholder expectations;

• Characteristics of the CEPA performance indicators;

• The steps in development the performance indicators;

• Key elements;

• Data collection;

• Data analyses;

• Reporting;

• Significant modifications;

• Issues; and

• Next steps.
Compressive and Tensile Strain Capacities of 48” X80 Line Pipes
Authors: Tajika Hisakazu , Igi Satoshi , Sakimoto Takahiro , Endo Shigeru , Tsuyama Seishi , Muraoka Ryuji , Arakawa Takekazu , Suzuki Nobuhisa
Published: July 2013

This paper presents the results of experimental studies focused on the strain capacity of X80 linepipe. A full-scale bending tests of X80 grade, 48″ high-strain linepipes pressurized to 60% SMYS were conducted to investigate the compressive strain limit and tensile strain limit. The tensile properties Y/T ratios and uniform elongation of the pipes had variety. Three of four pipes are high strain pipes and these Y/T ratios are intentionally low with manufacturing method. One of these high-strain pipe was girth welded in its longitudinal center to investigate the effect of girth weld to strain capacity. The other was set as a conventional pipe that have higher Y/T ratio to make comparative study.

The compressive strain limit focused on the critical strain at the formation of local buckling on the compression side of bending. After pipe reaches its endurable maximum moment, one large developed wrinkle and some small wrinkles on the pipe surface during bending deformation were captured relatively well from observation and strain distribution measurement. The tensile strain limit is discussed from the viewpoint of competition of two fracture phenomena: ductile crack initiation/propagation from an artificial notch at the HAZ of the girth weld, and strain concentration and rupture in the base material at the tension (opposite) side of the local buckling position.
Simulation of the Response of Buried Pipelines to Slope Movement Using 3D Continuum Modeling
Authors: Fredj Abdelfettah , Dinovitzer Aaron
Published: July 2013

Pipeline integrity is affected by the action of external soil loads in addition to internal fluid pressure. External soil loads can be generated by landslides or at sites subject to ground subsidence, heave or seismic effects. Under these varied conditions of ground movement potential pipeline safety involves constraints on design and operations. The design processes includes developing an understanding of strains that could be imposed on the pipe (strain demand) and strain limits that the pipe can withstand without failure. The ability to predict the pipeline load, stress or strains state in the presence of soil restraint and/or soil displacement induced loading is not well described in design standards or codes of practice.

This paper describes the ongoing work involved in a study investigating the mechanical behavior of buried pipelines interacting with active landslides. Detailed pipe-soil interaction analyses were completed with a 3D continuum SPH method. This paper describes the LS-DYNA numerical modeling process, previously developed by the authors, which was refined and applied to site-specific conditions. To illustrate the performance of the modeling process to consider a translational slide, additional numerical model validation was completed and is described in this paper. These comparisons illustrate that good agreement was observed between the modeling results and experimental full scale trial results.

Sample results of the application of the validated 3D continuum modeling process are presented. These results are being used to develop generalized trends in pipeline response to slope movements. The paper describes both the progress achieved to date and the future potential for simplified engineering design tools to assess the load or deformation capacity requirements of buried pipelines exposed to different types of slope movement.
Formation of Martensite/Austenite (M/A) in X80 Linepipe Steel
Authors: Reichert Jennifer M. , Garcin Thomas , Militzer Matthias , Poole Warren J.
Published: July 2013

Linepipe steels are usually microalloyed with Nb to promote the formation of complex microstructures that lead to the required mechanical properties. In particular, Nb in solution affects significantly the austenite decomposition kinetics and the resulting microstructure. A systematic study has been carried out to quantify the influence of Nb on the austenite decomposition kinetics in X80 linepipe steel. Continuous cooling transformation tests were conducted with a Gleeble 3500. The transformation products include ferrite, granular and upper bainite and M/A (martensite/ retained austenite) constituents. For this study optical microscopy was used to investigate the formation of M/A constituents that critically determine the fracture toughness. A relation between M/A and the surrounding microstructure is observed. In combination with an existent model for the prediction of the microstructure evolution during weld thermal cycles, the area fraction, size and morphology of M/A can be predicted for the simulated HAZ, based on the prior austenite grain size, cooling rate and amount of Nb in solution.
Continued Advancements Regarding Capacity Prediction of Strain-Based Pipelines
Authors: Fairchild Doug P. , Kibey Sandeep A. , Tang Huang , Krishnan Venkat R. , Wang Xiangyu , Macia Mario L. , Cheng Wentao
Published: July 2013

In areas of large ground movements, pipelines may be subjected to large longitudinal strains. It is imperative that strain-based design methods are developed for such pipelines. As reported previously, a comprehensive experimental and numerical program to characterize the tensile strain capacity of welded pipelines was undertaken. Models were developed that are capable of predicting strain capacity based on input parameters such as pipe geometry and properties, internal pressure, weld flaw geometry, weld properties, and high-low misalignment. These models (equations) have been validated against a data base of about 50 full-scale pipe strain tests that included a broad range of geometries and pipe grades (8–42″, 13–25mm, X60–X80). In the current paper, further developments are described. A pressure factor has been incorporated into the models. Whereas the previous models assumed that the circumferential stress from internal pressure was 80% of the specified minimum yield strength (SMYS) of the pipe, the pressure factor allows the calculation of strain capacity as a function of pressure that results in hoop stresses from zero to 80% of SMYS. Additionally, ranges for pipe yield-to-tensile ratio and weld tearing resistance curves (R-curves) have been expanded. New equations and associated flaw assessment diagrams for example cases are provided.
A GIS-Based System to Assess the Environmental Consequence of a Liquid Pipeline Rupture at Watercourse Crossings
Authors: Ripley Neil , Scordo Elisa , Baumgard Alex
Published: July 2013

BGC Engineering Inc. (BGC) was retained by a large pipeline operator to develop a GIS-based system to assess and rank the environmental consequence of a pipeline rupture on watercourse crossings within their pipeline system. Several physical, biological and socio-economic factors contribute to the environmental consequence of a pipeline rupture on a watercourse. This study examined select spatial and vulnerability factors, and did not consider biologic or economic impacts. Three factors were selected as part of the initial study to prioritize the pipeline watercourse crossings according to: (1) size of the watercourse at the pipeline crossing, (2) proximity of each individual crossing to larger downstream watercourses, and (3) pipeline liquid flow rate volume. A spatial analysis was conducted to determine the first two factors, while input for the third factor was provided by the pipeline operator. Watercourse size was determined using Strahler’s stream order classification (Strahler 1952), while proximity to larger downstream watercourses was assessed using a Geographic Information System (GIS). This paper presents an overview of the data sources and methods used to develop an initial screening tool for identifying high consequence crossings within a pipeline system, and highlights the challenges encountered with acquiring and processing data to include in a consequence rating system. As with other pipeline risk assessments, the main challenges of this work include data availability, data integrity and resource limitations. This system is intended to fit within the pipeline operator’s current geohazard integrity management program and direct resources for a multi-year baseline field inspection program.
The Effect of Low Sulfur Content on the Weldability of Linepipe Steel
Authors: Cameron Kimberly K. , Pettinger Alfred M.
Published: July 2013

Over time, the demand for high-strength linepipe has increased significantly. One of the challenges for developing higher strength linepipe has been maintaining an appropriate level of fracture toughness, yield to tensile strength ratio, and weldability. Fortunately, significant progress has been made in the production of high strength line pipe steel. A major improvement in steel making has been the utilization of secondary steel treatments to refine the steel and accurately control alloy additions to achieve a higher level of steel cleanliness. In particular, these refining treatments have enabled the achievement of extremely low sulfur levels.

For most purposes, restricting sulfur content is desirable to help prevent a reduction in mechanical properties such as fracture toughness of the steel. Fortunately, steelmaking and desulfurization technologies have advanced to the point where pipeline steel with sulfur contents less than the requirements by API 5L are available on a large scale.

Extremely low sulfur contents, however, can lead to other problems when welding steels. These weldability problems are related to the fact that sulfur is a known surface active agent for steels. Low sulfur concentrations lead to a reversal of the Marangoni convection in the weld pool, which is responsible for the large differences in weld penetration on otherwise identical steels. Additionally, when welding heats of unmatched sulfur concentrations, the arc will tend to deviate towards the low sulfur heat and axially shift the root of the weld if one of the heats was below a critical value for the sulfur content and the other was above this value.

Although this phenomenon has been primarily observed in stainless steels, the increasing ability to produce linepipe steel with extremely low sulfur contents has led to the possibility that this phenomenon could also occur in low carbon pipeline steels. One pipeline system utilizing cellulosic consumables for shielded metal arc welding (SMAW) of X70 steel with sulfur contents an order of magnitude below that permitted by API 5L and with widely varying sulfur contents shows evidence of this effect. The profiles of the welds in this system exhibited a tendency for lack of penetration, asymmetric weld roots, and concave welds.

One approach to ameliorate this would be the specification of a lower permissible amount of sulfur.
Evaluation of Anisotropic Pipe Steel Stress-Strain Relationships Influence on Strain Demand
Authors: Hart James D. , Zulfiqar Nasir , Zhou Joe
Published: July 2013

Buried pipelines can be exposed to displacement-controlled environmental loadings (such as landslides, earthquake fault movements, etc.) which impose deformation demands on the pipeline. When analyzing pipelines for these load scenarios, the deformation demands are typically characterized based on the curvature and/or the longitudinal tension and compression strain response of the pipe. The term “strain demand” is used herein to characterize the calculated longitudinal strain response of a pipeline subject to environmentally-induced deformation demands. The shape of the pipe steel stress-strain relationship can have a significant effect on the pipe strain demands computed using pipeline deformation analyses for displacement-controlled loading conditions. In general, with sufficient levels of imposed deformation demand, a pipe steel stress-strain curve with a relatively abrupt or “sharp” elastic-to-plastic transition will tend to lead to larger strain demands than a stress-strain curve with a relatively rounded elastic-to-plastic transition. Similarly, a stress-strain curve with relatively low strain hardening modulus characteristics will tend to lead to larger strain demands than a stress-strain curve with relatively high strain hardening modulus characteristics. High strength UOE pipe can exhibit significant levels of anisotropy (i.e., the shapes of the stress-strain relationships in the longitudinal tension/compression and hoop tension/compression directions can be significantly different). To the extent that the stress-strain curves in the different directions can have unfavorable shape characteristics, it follows that anisotropy can also play an important role in pipeline strain demand evaluations.

This paper summarizes a pipeline industry research project aimed at evaluation of the effects of anisotropy and the shape of pipe steel stress-strain relationships on pipeline strain demand for X80 and X100 UOE pipe. The research included: a review of pipeline industry literature on the subject matter; a discussion of pipe steel plasticity concepts for UOE pipe; characterization of the anisotropy and stress-strain curve shapes for both conventional and high strain pipe steels; development of representative analytical X80 and X100 stress-strain relationships; and evaluation of a large matrix of ground-movement induced pipeline deformation scenarios to evaluate key pipe stress-strain relationship shape and anisotropy parameters. The main conclusion from this work is that pipe steel specifications for high strength UOE pipe for strain-based design applications should be supplemented to consider shape-characterizing parameters such as the plastic complementary energy.
Routing Analysis in a Heavily Dissected Jungle Environment
Authors: Morrison Ian F. , O’Leary Dennis , Piraux Olivier , Harris Rob , Dauphin Raphaël
Published: July 2013

The selection of a pipeline route is of great importance in minimizing the levels of construction and maintenance cost and in determining the outcomes of reliability, environmental impact, social impact and development timeframe. The decision of choosing one route over another must be informed by the correct balance between significant variables using a structured and transparent process, arriving at repeatable results.

Predictable outcomes depend on knowing what information is important in a particular context and utilizing information with a known level of accuracy. Each step in the process of refining a design and cost estimate is a function of the effort put into engineering design as well as the accuracy of the inputs. Knowing what information is required and how to get that information quickly and economically is key to meeting cost and time goals in the pipeline development process.

Finding “the best” route varies from being a simple process in agricultural table lands, to a very complex process in rugged, remote, ecologically sensitive lands on the development frontier. In this paper the authors describe the process that was used in a heavily dissected jungle environment in a remote area of Northern Peru. Constraints included a very limited footprint for construction and operations, steep unstable slopes, continually varying grades and terrain types and a large number of water crossings.

Issues that are discussed in this paper include: decision making for data acquisition and applicable remote sensing technology, terrain analysis tools, routing methodology, integration of construction methodology with terrain elements and route optimization and decision making processes.
Hierarchical Bayesian Corrosion Growth Model Based on In-Line Inspection Data
Authors: Al-Amin M. , Zhou W. , Zhang S. , Kariyawasam S. , Wang H.
Published: July 2013

A hierarchical Bayesian growth model is presented in this paper to characterize and predict the growth of individual metal-loss corrosion defects on pipelines. The depth of the corrosion defects is assumed to be a power-law function of time characterized by two power-law coefficients and the corrosion initiation time, and the probabilistic characteristics of the parameters involved in the growth model are evaluated using Markov Chain Monte Carlo (MCMC) simulation technique based on ILI data collected at different times for a given pipeline. The model accounts for the constant and non-constant biases and random scattering errors of the ILI data, as well as the potential correlation between the random scattering errors associated with different ILI tools. The model is validated by comparing the predicted depths with the field-measured depths of two sets of external corrosion defects identified on two real natural gas pipelines. The results suggest that the growth model is able to predict the growth of active corrosion defects with a reasonable degree of accuracy. The developed model can facilitate the pipeline corrosion management program.
Factors Affecting the Generation of High-pH Environments Required for Stress Corrosion Cracking (SCC)
Authors: Yan Li , Worthingham Robert , King Fraser , Been Jenny
Published: July 2013

A series of seven experiments have been performed to investigate the effects of various environmental and operational parameters on the generation of high-pH SCC environments under disbonded permeable coating. The parameters investigated include:

• the rate of CO2 generation;

• direct CO2 production in the disbonded region under the coating;

• preferential gas-phase transport of CO2;

• the magnitude of the cathodic current density; and

• simulated trapped water composition.

In general, the total carbonate/bicarbonate concentrations of the simulated trapped water increased with:

• increased CO2 flow rate;

• direct production of CO2 under the disbonded coating;

• increased cathodic current density; and

• rapid gas-phase transport of CO2 through holidays above the level of the solution.

Ca2+ and Mg2+ cations in groundwaters could buffer the solution in the disbondment at a range of pH 8 to 9 lower than the pH required for the occurrence of high pH SCC. Formation of insoluble carbonate minerals was detected in the simulated disbondment and in the coating with solutions rich in Ca2+ and Mg2+. However, the presence of poorly soluble Ca2+ and Mg2+ cations did not affect the total carbonate/bicarbonate concentration in the inner cell.

These observations suggest that environments conducive to high-pH SCC are more likely to occur under the following circumstances:

• in regions where the CO2 generation rate is higher, typically wetter and warmer locations;

• for coating systems or in regions where there can be microbial activity under the disbonded coating;

• in areas where the pipe is not permanently below the water table and where the coating has defects or holidays; and

• in areas with a history of higher cathodic current density (which generally results in higher carbonate/bicarbonate concentration) and periodic loss of cathodic polarization.
How New Vintage Line-Pipe Steel Fracture Properties Differ From Old Vintage Line-Pipe Steels
Authors: Wilkowski G. , Shim D.-J. , Hioe Y. , Kalyanam S. , Brust F.
Published: July 2013

Newer vintage line-pipe steels, even for lower grades (i.e., X60 to X70) have much different fracture behavior than older line-pipe steels. These differences significantly affect the fracture control aspects for both brittle fracture and ductile fracture of new pipelines.

Perhaps one of the most significant effects is with brittle fracture control for new line-pipe steels. From past work brittle fracture control was achieved through the specification of the drop-weight-tear test (DWTT) in API 5L3. With the very high Charpy energy materials that are being made today, brittle fracture will not easily initiate from the pressed notch of the standard DWTT specimen, whereas for older line-pipe steels that was the normal behavior. This behavior is now referred to as “Abnormal Fracture Appearance” (AFA). More recent work shows a more disturbing trend that one can get 100-percent shear area in the standard pressed-notch DWTT specimen, but the material is really susceptible to brittle fracture. This is a related phenomenon due to the high fracture initiation energy in the standard DWTT specimen that we call “Abnormal Fracture Behavior” (AFB). This paper discusses modified DWTT procedures and some full-scale results. The differences in the actual behavior versus the standard DWTT can be significant. Modifications to the API 5L3 test procedure are needed.

The second aspect deals with empirical fracture control for unstable ductile fractures based on older line-pipe steel tests initially from tests 30-years ago. As higher-grade line-pipe steels have been developed, a few additional full-scale burst tests have shown that correction factors on the Charpy energy values are needed as the grade increases. Those correction factors from the newer burst tests were subsequently found to be related to relationship of the Charpy energy values to the DWTT energy values, where the DWTT has better similitude than the Charpy test for fracture behavior (other than the transition temperature issue noted above). Once on the upper-shelf, recent data suggest that what was once thought to be a grade correction factor may really be due to steel manufacturing process changes with time that affect even new low-grade steels. Correction factors comparable to that for X100 steels have been indicated to be needed for even X65 grade steels. Hence the past empirical equations in Codes and Standards like B31.8 will significantly under-predict the actual values needed for most new line-pipe steels.
New Regulatory Requirements in 2012: Challenges of Pipeline Regulatory Compliance and the Tools to Meet Them
Authors: Flo Daniel S. , Walker Rachel E. , Fasking Todd M.
Published: July 2013

From smart phones to Facebook, instant connectivity has become a way of life. But for organizations charged with pipeline permitting and compliance—highly complex processes with multiple, sometimes conflicting rules and regulations—instant connectivity is not yet the norm. In many ways, companies dealing with these issues are still living in the age of acetate and plat books. And regulatory compliance is not likely to get easier anytime soon. In the wake of high-profile leaks and explosions, Congress recently signed into law tougher requirements for pipeline safety, Public Law 112-90. Fortunately, the technology now exists to electronically monitor and track nearly every aspect of regulatory compliance—from pre-construction to post-construction—in a way that allows for instant access and rapid analysis of natural resources, cultural resources, constructability constraints, and compliance risks. This paper discusses challenges pipeline companies face in complying with new and existing legislation and outlines innovative approaches for meeting regulatory requirements. It offers examples of web-server-based tools for data management that determine regulatory needs, actions, and post-maintenance follow-up. It also provides examples of how these tools and effective communication with regulators can streamline the regulatory process to save time and money.
Overcoming Technical Limitations in Identifying and Characterizing Critical Complex Corrosion
Authors: Kariyawasam Shahani , Yeung Patrick , Clouston Stuart , Hurd Geoffrey
Published: July 2013

In 2009 a pipeline within the TransCanada pipeline system experienced a rupture. As this pipeline was already under a rigorous In Line Inspection (ILI) based corrosion management program this failure led to an extensive root cause analysis. Even though the hazard causing the failure was microbiologically induced corrosion (MIC) under tape coating, the more troubling question was “Why had the severity of this anomaly not been determined by the ILI based corrosion management program?” This led to an investigation of what key characteristics of the ILI signals resulting from areas of “complex corrosion” are more difficult to correctly interpret and size and furthermore where the line condition is such that manual verification is needed. By better understanding the limitations of the technology, processes used, and the critical defect signal characteristics, criteria were developed to ensure that “areas of concern” are consistently identified, manually verified and therefore the sizing is validated at these potentially higher risk locations.

These new criteria were applied on ILI data and then validated against in-the-ditch measurements and a hydrotest. This process in conjunction with optimization of ILI sizing algorithms enabled the operator to overcome some of the known challenges in sizing areas of complex corrosion and update its corrosion management process to improve the detection and remediation of critical defects. This paper describes this investigation of the failure location, development of the complex corrosion criteria, and the validation of effectiveness of the criteria.

The criteria are focused on external corrosion and have been currently validated on pipelines of concern. Application to other lines should be similarly validated.
Large-Scale Hydrogen Jet Flame Radiant Fraction Measurements and Modeling
Authors: Ekoto Isaac W. , Houf William G. , Ruggles Adam J. , Creitz Leonard W. , Li Jimmy X.
Published: July 2013

Analytic methods used to establish thermal radiation hazard safety boundaries from ignited hydrogen plumes are based on models previously developed for hydrocarbon jet fires. Radiative heat flux measurements of small- and medium-scale hydrogen jet flames (i.e., visible flame lengths < 10 m) compare favorably to theoretical calculations provided corrections are applied to correct for the product species thermal emittance and the optical flame thickness. Recently, Air Products and Chemicals Inc. commissioned flame radiation measurements from two larger-scale hydrogen jet flames to determine the applicability of current modeling approaches to these larger flames. The horizontally orientated releases were from 20.9 and 50.8 mm ID pipes with a nominal 60 barg source pressure and respective mass flow rates of 1.0 and 7.4 kg/s. Care was taken to ensure no particles were entrained into the flame, either from the internal piping or from the ground below. Radiometers were used to measure radiative heat fluxes at discrete points along the jet flame radial axis.

The estimated radiant fraction, defined as the radiative energy escaping relative to chemical energy released, exceeded correlation predictions for both flames. To determine why the deviation existed, an analysis of the data and experimental conditions was performed by Sandia National Laboratories’ Hydrogen Safety, Codes and Standards program. Since the releases were choked at the exit, a pseudo source nozzle model was needed to compute flame lengths and residence times, and the results were found to be sensitive to the formulation used. Furthermore, it was thought that ground surface reflection from the concrete pad and steel plates may have contributed to the increased recorded heat flux values. To quantify this impact, a weighted multi source flame radiation model was modified to include the influence of planar surface radiation. Model results were compared to lab-scale flames with a steel plate located close to and parallel with the release path. Relative to the flame without a plate, recorded heat flux values were found to increase by up to 50% for certain configurations, and the modified radiation model predicted these heat fluxes to within 10% provided a realistic steel reflectance value (0.8) was used. When the plate was heavily and uniformly oxidized, however, the reflectance was sharply attenuated. Model results that used the surface reflectance correction for the larger-scale flames produced good agreement with the heat flux data from the smaller of the two flames if an estimated reflectance of 0.5 was used, but was unable to fully explain the under predicted heat flux values for the larger flame.
Useful Trends for Predicting Corrosion Growth
Authors: Kariyawasam Shahani , Wang Hong
Published: July 2013

The objective of an effective corrosion management program is to identify and mitigate corrosion anomalies before they reach critical limit states. Often as there are many anomalies on pipelines an optimized program will mitigate the few corrosion anomalies that may grow to a critical size within the next inspection interval, without excavating many of the anomalies that will not grow to a critical size. This optimization of the inspection interval and the selection of anomalies to mitigate depend on understanding of corrosion growth. Prediction of corrosion growth is challenging because growth with time is non linear and highly location specific. These characteristics make simplistic approaches such as using maximum growth rates for all defects impractical. Therefore it is important to understand the salient aspects of corrosion growth so that appropriate decisions on excavation and re-inspection can be made without compromising safety or undertaking undue amounts of mitigative activities.

In the pipeline industry corrosion growth between two in line inspections (ILIs) has been measured by comparing one ILI run to the next. However many types of ILI comparison methodologies have been used in the past. Within the last decade or two comparison techniques have evolved from box matching of defect samples to signal matching of the total defect populations. Multiple comparison analyses have been performed on the TransCanada system to establish corrosion growth rates. Comparison of the results from these various analyses gives insight into the accuracy and uncertainty of each type of estimate.

In an effective integrity management process the best available corrosion growth data should be used. To do so it is important to understand the conservatism and the uncertainty involved in each type of estimate. When using a run-comparison to predict future growth it is assumed that the growth within the last ILI interval will continue (with associated uncertainty) during the next inspection interval. The validity of these assumptions is examined in this study.

In the context of this paper these assumptions are validated for external corrosion on onshore pipelines. Characteristics of internal and offshore corrosion are very different in space and time variation.

Correlations of external corrosion growth in onshore pipelines with defect size and location are also examined. Learning from multiple corrosion growth studies gives insight into the actual corrosion rate variation along a pipeline as well as general growth characteristics. Different types of corrosion growth modeling for use in probabilistic or deterministic integrity management programs are also discussed.