0

Operations and Maintenance

2002;():1-5. doi:10.1115/IPC2002-27033.

Under the auspices of the American Society of Mechanical Engineers (ASME), a new standard supplement has been produced to aid operators in the development and implementation of an integrity management program. This new standard supplement will outline the technical requirements for implementation of an operator’s integrity management plan as well as the programmatic elements overall. Historically, integrity management has been an integral part of pipeline operations. Contained throughout ASME B31.8, integrity management requirements are specified. One purpose of this new supplement is to formalize a more deliberate process for the management of integrity and to push adoption of an industry consensus standard by the Office of Pipeline Safety. An ad-hoc task team was assembled earlier this year to develop the standard supplement. The task team consists of members from the Office of Pipeline Safety (OPS), from the National Association of Pipeline Safety Regulators, and from the gas transmission and distribution industry. With an opportunity to create a new standard, the task team was able to fundamentally and deliberately rethink the process and the protections provided. The standard supplement is the repository for twenty technical studies and reports completed by a variety of scientific and technical organizations. These studies and reports provide the technical platform for the standard supplement. It is anticipated that the standard will serve as a “hub” for many other standards, eight of which are presently under development. The B31.8 code was the predecessor to the pipeline safety regulations, which were first promulgated in 1970. The code is an international code and is approved by the American National Standards Institute (ANSI). It was felt that an ASME consensus standard would be the best home as the companion to the proposed regulations due to the strict policies of both ASME and ANSI for public comment, due process, and technical justification. The standard supplement provides guidance for two methods of compliance, a prescriptive track and a performance track. The prescriptive track will be very conservative but easier to implement. The performance track will be more flexible but will require significantly more data to implement. Within the standard supplement, the operator would have the option of following either track. This new standard supplement represents a new way for regulations, research and standards to be coordinated. It provides for performance based regulations referencing technically based standards that are developed from focused research.

Topics: ASME
Commentary by Dr. Valentin Fuster
2002;():7-10. doi:10.1115/IPC2002-27040.

Double Block and Bleed (DBB) is the term commonly used to describe the systems or valving arrangements that provide double barrier pressure isolation of those performing work on a pipeline system downstream of the barrier. The consequences of releasing pipeline pressure downstream to an unsuspecting maintenance crew go without stating. If the risks are so high as to demand not single, but double barrier isolation between the fury of pipeline pressure and the safety of personnel and equipment, why then has it been so difficult to develop a consensus for the definition or description of DBB systems? This paper will explore in detail the internationally published definitions for DBB and analyze their merits with respect to pipeline safety. Definitions from organizations such as the American Petroleum Institute (API), Occupational Health and Safety (OHSA), the International Standards Organization (ISO) will be reviewed to determine what they contribute or fail to contribute to the intent of worker protection. Some Provincial Governments have written specific requirements for pipeline isolation into law, while others do not address the matter. These issues will also be explored and compared to the practices of companies operating oil and gas pipelines. Some insight on the division of definitions is offered through an understanding of the purposes or needs of the definer. For example, a valve manufacturer with a need to demonstrate that his valve will indeed block flow from both directions and thereby permit maintenance of the valve without removal from the pipeline may not fully appreciate the pipeline maintenance employee’s need to isolate himself from pipeline pressure by two independent barriers. It will be shown that standards and specifications are available to support both perspectives and that there are compelling reasons for deriving commonality between these perspectives. With the development of International Standards for oil and gas pipelines and increasing emphasis on the harmonization of various national standards, matters such as operator safety must not be compromised. Interesting opportunities exist to revisit topics such as definitions for DBB and perhaps derive a set of words that allows consensus and encompasses the true intent of the concept.

Topics: Safety , Pipelines
Commentary by Dr. Valentin Fuster
2002;():11-20. doi:10.1115/IPC2002-27113.

The primary objective of the work described in this paper is to examine the fate of H2 S contaminated natural gas slugs as they travel through a gas pipeline network. The important phenomenon that affects the spread of the H2 S slug as it travels downstream of a pipe is the diffusion with the sweet gas at the front and back interface of the slug. It was determined that the diffusivity constant (D) used in the calculation of the interface spread varies along the pipeline, which prohibits the use of a closed form solution of the Fick’s law equation. An effective time parameter has been introduced to account for the variation in the diffusivity in a “marching in time” scheme of solution. The model has been utilized to demonstrate the effects of pipe diameter, mean flow velocity and pipe internal roughness on the contamination spread. A test loop has also been constructed to validate the diffusion coefficient in gaseous flows. Excellent agreement was obtained between the measured vs. predicted results. The mean error in predicting the interface spread was approximately 6.2%.

Commentary by Dr. Valentin Fuster
2002;():21-37. doi:10.1115/IPC2002-27119.

A recent ‘fingerprint’ smart pigging inspection recorded over 40,000 metal loss (corrosion) features in a 57km 42” diameter, dry gas pipeline supplying a major LNG facility in Indonesia. The pipeline had been in operation for less than 6 months. Assessment of these results by the inspection company identified 10 sections of pipe that required repair according to ASME B31.G, indicating that the pipeline was not ‘fit for purpose’. The pipeline operator immediately cut out these 10 sections to ensure the continued safe operation of the new pipeline. A detailed pipeline corrosion study subsequently identified the features as corrosion that had occurred during transport and storage of the line pipe. In addition, the corrosion was found to be less severe than initially thought and the same work assessed the remaining defects and, calculations using DNV Guideline RP F101, showed that the features were all acceptable. It was concluded that the high sensitivity of the smart pigging tool, combined with the failure to identify the cause of the features and the simple initial feature assessment overestimated the significance of the corrosion defects. This demonstrates the need for good care and inspection of line pipe during transport storage and construction. It also highlights the need to conduct engineering assessments to determine the inspection philosophy and to quantify the ‘workmanship’ level of metal loss features acceptable on a fingerprint run, before the run takes place. Otherwise new pipelines containing ‘custom and practice’ defects could be the subject of lengthy and costly disputes between operator and constructor. This paper proposes a method for assessing baseline survey data that provides an acceptance level for pre-existing defects. This methodology will assist operators in assessing smart pigging data from new pipelines.

Commentary by Dr. Valentin Fuster
2002;():39-53. doi:10.1115/IPC2002-27131.

When welding onto an in-service pipeline, to facilitate a repair or to install a branch connection using the “hot tapping” technique, two risks need to be considered. The first is the risk of burnthrough, where the welding arc causes the pipe wall to be penetrated allowing the contents to escape. The second is the risk of hydrogen cracking that arises from the fast cooling rates that tend to be produced by the ability of the flowing contents to remove heat from the pipe wall. To prevent hydrogen cracking, at least one of the three conditions necessary for its occurrence must be eliminated. Beyond the use of low-hydrogen electrodes to minimize hydrogen levels, it is prudent to develop and use procedures that minimize the formation of crack susceptible microstructures. This paper reviews existing methods for selecting parameters and qualifying procedures for welding onto in-service pipelines. HAZ hardness is an indicator of the susceptibility of a microstructure to cracking. A widely-used value below which it is generally agreed that hydrogen cracking is not expected is 350 HV. Unfortunately, there is no one hardness level above which the risk of hydrogen cracking becomes unacceptable. This paper also describes the development of a hardness evaluation criterion that can be used to quantify the trade-offs that can be made between HAZ hardness, hydrogen level, and chemical composition. Finally, the results of a recently-completed group-sponsored project, where procedures for welding onto in-service pipelines were developed over a wide range of conditions, are also reviewed. The results can be used to select an appropriate procedure that is resistant to hydrogen cracking for a particular application. The use of these results allows in-service welding to be carried out in a safe, cost-effective manner, allowing both economic and environmental benefits to be realized by avoiding pipeline shutdown and interruption of service.

Topics: Welding , Pipelines
Commentary by Dr. Valentin Fuster
2002;():55-60. doi:10.1115/IPC2002-27194.

The Araucária to Paranaguá Pipeline (OLAPA) owned by PETROBRAS, was built in 1976 in Paraná State, Brazil, connecting an oil refinery nearby the city of Curitiba to a marine terminal near Paranaguá Seaport. The pipeline had been operating normally for 25 years, moving liquefied petroleum gas (LPG) and diesel fuel to the refinery as well as petrochemical Naphtha and light cycle oil (LCO) in the opposite direction. The second week of February 2001 came along with heavy and continuous summer rain on Paraná State most of which on a hilly terrain portion crossed by the pipeline, currently regarded as an environment preservation area of the Atlantic Rain Forest. On 16th day, that same month, while the line was on shut in condition, a hardly noticeable landslide across the right-of-way led the pipeline to the complete rupture, succeeded by product spill. Further analysis on the rupture section pointed to circumferential cracks caused by axial stress induced by a slow and steady slide on the adjacent soil. Surveys on other regions possibly affected by similar soil movement on the right-of-way warned operations staff that there could be more weakened sections along the pipeline, therefore pipe failures and product spill might still happen due to the continuation of the rainy season. Product removal became required to avoid environmental threats. The purging procedure should meet two main constrains, i.e., minimize pressure and volume flow through the identified risky locations. This paper describes the planning and execution of such purging process, tailored for a weakened pipeline on an environmental sensitive area, adopting unconventional methods to move liquid products upward high steeps, considering restrains to operational pressures around one third of normal values.

Commentary by Dr. Valentin Fuster
2002;():61-68. doi:10.1115/IPC2002-27212.

This paper describes the damage caused by a tropical storm to a 48” gas pipeline considered to be the main natural gas supplier within Mexico’s distribution network. Included is a detailed description of the temporary and permanent repairs and rehabilitation carried out. The pipeline section damaged during this natural event is located in a wide water crossing of the river “Tecolutla” in Veracruz, southern Mexico. The construction process to make a new crossing included horizontal drilling using state of the art technology, extensively applied and improved within the industry during the past 10 years. To accomplish the operation, a novel technique was applied, since the pipeline dimensions (48” diameter and 853 m length), required special tools and equipment. Only twice before in the world have projects similar to this one been attempted. This was the first ever application in Mexico. Therein lies the uniqueness and importance of its successful completion, despite the logistical problems and unforeseen difficulties that the contractor was presented with, such that at times it appeared that the work would not be successfully completed. The need to keep the pipeline operating during the project caused delays in most of the scheduled activities. A key factor to ensuring a successful end to this project was the contractor selection. Supervision and quality control were also important issues during the project’s development. The horizontal drilling approach allowed different arrangements for the pipeline crossing to be assessed. The arrangement chosen avoids the use of a gate valve and a bypass on the right side of the crossing, with the advantage of keeping this pipeline section 7 metres below the riverbed.

Commentary by Dr. Valentin Fuster
2002;():69-77. doi:10.1115/IPC2002-27307.

Enbridge Pipelines Inc. operates the world’s longest and most complex liquids pipeline network. As part of Enbridge’s Integrity Management Program In-Line Inspections have been and will continue to be conducted on more than 15,000 km of pipeline. This extensive program is comprised of a mature metal loss and geometry inspection component as well as a crack inspection program utilizing the most sophisticated In-Line Inspection (ILI) tools available. Enbridge conducted its first ultrasonic crack inspection with the British Gas Elastic Wave Vehicle (Now GE Power Systems – Oil & Gas – PII Pipeline Solutions) in September 1993 on a Canadian portion of it’s 864–mm (34”) diameter line. The Elastic Wave Vehicle was also used for crack detection on additional segments of this same 864–mm (34”) diameter line during the following years, 1994, 1995 and 1996. Enbridge then conducted its first crack inspection with the Pipetronix UltraScan CD tool (Now also GE Power Systems – Oil & Gas – PII Pipeline Solutions) in November 1997 on a segment of this 864–mm (34”) diameter line that was previously inspected with the Elastic Wave Vehicle. The UltraScan CD tool was then utilized again in 1999, 2000 and 2001 completing crack inspection of the Canadian portion of this 864–mm (34”) diameter line. Enbridge conducted its first magnetic crack inspection with the PII TranScan (TFI) Circumferential Magnetic inspection tool in December 1998 on a United States portion of another 864–mm (34”) diameter line. This same section of line was subsequently inspected with the PII UltraScan CD tool in July 2001. This paper discusses the comparison of results from overlapping crack inspection data analysis from these three PII crack detection tools. Specifically, the overlap of the UltraScan CD and Elastic Wave Vehicle along with the overlap of the UltraScan CD and TranScan (TFI) tool. The relative performance of each crack detection tool will be explored and conclusions drawn.

Commentary by Dr. Valentin Fuster
2002;():79-86. doi:10.1115/IPC2002-27344.

For any pipeline company to be successful and be seen as a respected global citizen, the impact of its operation on health, safety and the environment must be minimal and its productivity must be optimized at the lowest possible costs. In order to accomplish this an integrated maintenance management process must align to the business needs without impact on safety and the environment. This process must create an environment where by maintenance events are measured to determine their impact on the safety, environmental, and business goals. As a result the maintenance strategy is adapted to maximize the safety, environmental and business performance. An integrated maintenance management process will enhance the revenue earning capability of the business and not be a burden on it. To make the difference, a step change in thinking is required. For example: • Reducing maintenance activity whilst improving performance. • Establishing a benchmark performance model for the pipeline asset. • Maintenance must be seen as a dynamic process continually striving to improve performance. • Maintenance as a tool to identify and reduce health, safety, environmental and business risks to a level as low as reasonably practicable (ALARP). • Maintenance as a contributing factor to an increase in revenue earning capability through an increase in efficiency, as opposed to maintenance seen purely as a cost burden. • Maintenance management as a structured tool to reduce inventory and lifecycle costs, instead of subjective judgement. • Maintenance management as a tool to capture and protect corporate maintenance and operational knowledge, versus the costly process of reinventing the wheel over and over again by repetitive unwanted events. This way of thinking requires vision and commitment of the upper (corporate) management level as the maintenance and operational departments can never reach this goal individually. Subsequently, it requires total commitment of all departments and a proactive approach towards integrated asset management. Maintaining multi-million dollar pipeline assets is not an easy task and the costs involved are enormous. This paper describes an adaptive approach for an Integrated Maintenance Management System where the maintenance strategies are directed to where they will most benefit the safety, environmental and business goals of the asset.

Commentary by Dr. Valentin Fuster
2002;():87-92. doi:10.1115/IPC2002-27394.

Pipeline companies face a difficult task in cost-effectively managing pipeline maintenance activities. Complexity is introduced due to geographical expanse, remote locations, access to qualified contractors and the desire to hire locally, and contract management of available suppliers. Pipeline companies have traditionally provided maintenance activities through in-house resourcing, or management of a multitude of available contractors. With increasing efforts to focus in-house resources on core pipeline operations, there has been a corresponding shift in moving noncore maintenance activities to outside providers. This has introduced an increase in administration costs associated with supplier qualification activities, document management and payment processing. TransCanada PipeLines Limited has developed a model where core skills have been retained to perform critical activities in-house and less essential services have been contracted out, along with the management of the subcontracts. This model relies on a central dispatch service along with a large base of subcontractors strategically located along our pipeline system to provide these services. The process involves two basic steps — managing subcontractors and performing work. Managing subcontractors is the key to the process. This part of the process proactively provides TransCanada with qualified subcontractors at the right place, the right time and for the best price. This paper will discuss the alliance model we’ve implemented in conjunction with Ledcor Industrial Maintenance Ltd. for contracted services and how this arrangement is crucial to our success in managing maintenance activities cost effectively. We will describe the model, how it was developed and implemented, how it works and some of the benefits that make it a successful contribution to regional operations. We will also discuss some of the key lessons learned. Further details on the process will be presented, along with the bottom-line benefits associated with this type of relationship.

Commentary by Dr. Valentin Fuster

Innovative Projects and Emerging Issues

2002;():93-96. doi:10.1115/IPC2002-27019.

The consumption of petroleum products in India has been growing at a high rate. In order to meet the growing demand for petroleum, additional refining capacity is planned to be created involving augmentation of some of the existing refineries and construction of new refineries. While the refineries will be in a position to meet the demand of petroleum products, the critical and vital issue will be to supply crude oil to the refineries and to reach the products to various consumption centers in an efficient, reliable and cost effective manner. In addition to the liquid petroleum, Natural Gas is emerging as the major source of energy/feedstock. Infrastructure for storage and transportation of Natural Gas are also required to be set up in a big way to meet the projected demand. This can best be done by constructing new pipelines which are recognized worldwide as the most reliable and cost effective mode of transportation of oil and gas. In addition to the requirement for new pipelines, there is a need for upgradation of technology in the existing cross-country pipelines, many of which are more than 20 years old. Moreover, Indian Government has, as part of the process of liberalisation of the economy through a series of measures focused on the infrastructural developments, technology upgradation, trade policies and financial reforms, has opened the core sector of Petroleum to private investment. Thus, considerable scope exists not only for consultants, equipment and material manufacturers/suppliers and contractors for providing their services but also for making investments in the Indian pipeline industry. This paper describes the prospects/opportunities in the Indian pipeline industry.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
2002;():97-106. doi:10.1115/IPC2002-27042.

The Northstar project is the first crude oil production facility constructed offshore in the Beaufort Sea. Produced crude oil is transferred via a buried subsea pipeline to shore and overland to the Trans Alaska Pipeline Pump Station PS1 facility. During the permitting process, concern was expressed that a very small chronic leak in the subsea oil line would remain undetected during the winter months of continuous ice cover. Therefore, the US Army Corps of Engineers stipulated that a prototype leak detection system be installed that would capable of detecting a threshold leak less than 32 BOPD. This paper addresses the efforts to develop and install the LEOS leak detection system for arctic operations. The system is based on the well-established LEOS leak detection technology (manufactured by Framatome ANP, formerly by Siemens AG). The system comprises a perforated plastic tube with a thin water impermeable acetate outer sheath that allows hydrocarbon molecules to diffuse into the air filled tube. The air inside the tube is replaced periodically (every 24 hours) and is passed through a hydrocarbon-sensing module. The module contains resistors sensitive to the presence of very small concentrations of hydrocarbon molecules. The presence and location of a leak is determined by measuring the time taken for the localized concentration of hydrocarbon molecules associated with a leak to reach the end of the tube. LEOS components and materials were engineered to survive installation during arctic winter conditions. It was also necessary to protect the plastic LEOS sensor tube as it was lowered through the ice, attached to the pipeline, into a pre-excavated trench and then backfilled. The 10km long LEOS tube was delivered to site in 31-coiled 300m (1000-ft) bundles that were transported from Germany to Alaska. The LEOS sensing tube was preinstalled in a protective outer polyethylene tube which was unreeled through a reverse bending jig. Crude oil production started at the Northstar production facility in October 2001 and the LEOS system has been operational since then and is providing the highest degree of assurance that no oil is escaping from the pipeline.

Topics: Design , Leakage
Commentary by Dr. Valentin Fuster
2002;():107-118. doi:10.1115/IPC2002-27064.

Due to increasing costs and inconveniences in replacing deteriorated sewer pipelines by conventional excavation methods, the trenchless or ‘no-dig’ technology is being extensively used. In trenchless technology, a polymer or reinforced polymer is applied to the inside of the deteriorated host pipe to prevent ground water from seeping into the sewer pipelines. In this research, a testing method was developed to determine the long-term creep behavior of encased polymer liners used in sewer rehabilitation. Short-term tests, following the ASTM D790 procedure, were conducted on pipe liner samples to determine the initial elastic modulus and compare it to the elastic modulus obtained from long-term testing of the encased liner. Long-term tests were conducted on 6 ft. lengths, 12 in diameter polymer liner samples encased in steel pipes. Fabrication service was provided by the industries participating in the research. The thicknesses of the polymer liners were selected according to the typical use of each product in the field. Three samples each of five liner materials were tested under constant external hydrostatic pressure to find their long-term structural properties and to present creep-buckling models. A pressure regulator, pressure transducer, and several pressure gages at different points in the water line were used to maintain constant hydraulic pressure in the gap between the steel host and the polymer liner. A novel method was developed for sealing the ends of the encased liner samples for testing. The long-term creep data was collected with strain gages bonded along the inner circumference of the liner and connected to a Data Acquisition System (DAS). The temperature of the liners was monitored continuously with the use of a thermocouple. The strain data collected from the DAS was compensated for differences in temperature throughout the period of testing, initial deformation, and coefficient of thermal expansion. Several viscoelastic models were investigated in order to fit the data. The data is used to predict the long-term modulus used in design.

Topics: Pipes , Testing
Commentary by Dr. Valentin Fuster
2002;():119-124. doi:10.1115/IPC2002-27068.

The KEIHIN KANSEN pipeline of Tokyo Gas Co. Ltd., the construction of which was decided in 1986, has finally been completed after a long design and construction period of 13 years. KEIHIN KANSEN is a typical urban pipeline connecting Tokyo and Yokohama, the most crowded cities in Japan. This paper outlines the plan and concept of safety, and quality of the pipeline. Here are in particular described the piping works within the Keihin/ Asahi tunnel by shield method, focusing on its design scheme, study results, and experiments on pipeline supports for large reaction force.

Topics: Pipelines , Cities
Commentary by Dr. Valentin Fuster
2002;():125-135. doi:10.1115/IPC2002-27078.

The North American energy pipeline system represents a security challenge. Taking a holistic view of the problem allows the operator to construct and implement a strategy systematically. The solution involves a multi-disciplinary approach using a combination of business tools and technology to provide enhanced protection, and rapid restoration and recovery in the event of an attack. • Mapping of “high consequence” areas, including pipeline segments near population centers, water resources, or environmentally sensitive regions, will allow energy companies to more logically allocate security resources, but there may remain vast stretches of pipeline where physical barriers are impractical. • Formal decision analysis techniques can be effectively used to assess potential threats, analyze vulnerabilities, prepare contingency plans and set priorities. • Hardware elements of the solution will draw heavily upon technological innovations, including the use of active earth observation imagery and sophisticated sensing equipment for surveillance and early detection. • Strategic planning exercises will allow operators to think through the problem before a threat occurs and to put in place resources to react to a threat and to respond, restore, and recover from an attack. This is particularly true in coordination across a region. The expanding effort to safeguard the continent’s energy infrastructure will rely upon a greater level of (1) government-industry cooperation, particularly in the areas of data and information collection/analysis/dissemination, (2) technological adaptation/innovation, including greater use of sensing and surveillance technologies, (3) the development of financial and insurance products that fit the specific needs of energy asset owners and operators, (4) communication with key constituencies: customers, suppliers, regulators, law enforcement agencies, and financial markets, (5) customized training for employees, (6) government supervisory and enforcement authority to inspect and penalize companies that do not implement the appropriate level of security, while providing a due diligence safe harbor for those that are proactive; and (7) an unwavering commitment to protect vital assets, human, physical, and otherwise. It is critical that pipeline security programs focus on long-term, sustainable solutions that are customized to fit the specific needs of particular energy asset networks. The paper contains a specific example of pipeline infrastructure management system and display screen examples.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
2002;():137-145. doi:10.1115/IPC2002-27114.

Natural gas pipelines have an excellent safety record but on rare occasions they rupture and decompress. When this happens their contents cool rapidly and form two phases. The decompression behaviors of multiphase fluid released from pipeline are not well understood. Pipeline decompression modeling is useful in characterizing the rapid transient flow that occurs when a pipeline ruptures. Numerical simulation can provide detailed data for analyzing the consequences of pipeline bursts and the mechanical performance of pipelines as they decompress. Decompression behavior of fluids is complicated by the formation of two-phase flow due to gas cooling or liquid flashing effects. Based on the time-space-ensemble composite averaging procedure, a two-fluid flow model is derived for simulating high-pressure natural gas pipeline decompression. The composite averaging operator is supported and demonstrated by simple experimental data. A set of constitutive equations is formulated for the closure of the system of equations. The conservation equations along with closure equations are examined for compliance with the second law of thermodynamics. Characteristics analysis is performed to ensure that the set of equations is well-posed mathematically.

Commentary by Dr. Valentin Fuster
2002;():147-155. doi:10.1115/IPC2002-27121.

EnCana Resources is enjoying economic success at their Steam Assisted Gravity Drainage (SAGD) research facility at Senlac, Saskatchewan. This has been achieved largely due to the successful application of new and innovative ideas and technologies. During the summer of 2001, PanCanadian Energy (now EnCana Resources) made use of a novel buried piping technology at the Senlac Thermal Project to solve the problem of connecting distant well pairs to the processing plant. The four-kilometer pipeline system accommodated a thermal growth of approximately 12 meters over its entire length using buried expansion loops and “Z” bends. The pipeline was installed at an estimated 30% cost savings over conventional above ground methods. This paper summarizes the successful installation of this unique piping technology at Senlac and its applicability to future commercial SAGD projects in the context of the heavy oil reserves in Alberta.

Commentary by Dr. Valentin Fuster
2002;():157-164. doi:10.1115/IPC2002-27197.

In this work we discuss the importance of visualization, simulation and monitoring pipelines constructed in areas geologically unstable. In particular it is of great concern pipelines crossing Serra do Mar, in Brazil, where there are colluvium deposits subject to slow movements not traceable by a simple visual inspection most of the times. In order to guarantee the structural integrity of the pipeline it is necessary to measure the tensions transmitted by the ground to the pipeline. Knowing that the soil-pipeline interaction is extremely complex the implementation of an extensive program involving visualization, simulation and monitoring that includes not only the slope but also the pipeline becomes mandatory. This program seeks the collection of information that allows the establishment of a reliable interaction model. This model must be capable of providing operational control parameters and subsidize the decision of an intervention in the pipeline. Therefore the safety of pipeline operations can be maximized through instruction of operators and establishment of monitoring and inspection routines. Right now, in a joint effort of CENPES and TRANSPETRO, a complete set of visualization and numerical simulation software platform is available and it is being used to build a 3D model of all the geotechnical risky areas in Serra do Mar. Also the installation and operation of a pilot monitoring system, including piezometers and inclinometers on the slope and strain gauges on the pipeline, at three different pipelines crossing Serra do Mar, with data acquisition in real time is being undertaken.

Commentary by Dr. Valentin Fuster
2002;():165-173. doi:10.1115/IPC2002-27198.

The present intervention systems, for solving pipeline blockage or leak problems, are reaching their limits. New realities demand new technology for unusual interventions. In looking for better solutions, it was necessary to bypass the traditional methods used by the oil industry in order to investigate the inner surface of the pipeline. This work describes the development of a remote controlled apparatus, which is flow rate independent. This device could move freely inside the pipelines. A robot and its remote control operation system are the important factors, which would response to these new demands. The robot could be designed with special features such as the introduction of a specific solvent to dissolve or break the blockage; it could also be used as a tool-carrier. The system is able to drive accurately to the problem point, and use the adequate device to inspect and even to repair the inner surface structure of the pipeline.

Topics: Robots , Pipelines
Commentary by Dr. Valentin Fuster
2002;():175-182. doi:10.1115/IPC2002-27302.

Differential movement in permafrost terrain due to ground freezing or thawing challenges the reliability of buried pipelines proposed for transporting natural gas from Prudhoe Bay and the Mackenzie Delta. Arctic pipelines designed to operate at conventional pressures (that is, below 10 MPa) are susceptible to wrinkling, bulging, and ovalling due to the differential movements they cause at interfaces between frozen and unfrozen ground and between different types of soil. Arctic pipelines designed to operate at superhigh pressures—defined here as pressures above 25 MPa—can accommodate the differential movements. A fair comparison between large diameter artic pipelines with operating pressures in the range from 10 to 42 MPa was made by accurately simulating flow performance with Greenpipe’s PipeCraft™ software. For any given design flow, superhigh pressure dense phase pipelines have smaller diameters and thicker walls, making them more flexible and better able to handle differential movements. And at superhigh pressures, Joule-Thomson cooling is negligible so that flowing gas stays close to ground temperature, reducing potential for frost heave or thaw settlement in the first place. Although weight per meter of superhigh pressure pipelines is similar to conventional pressure pipelines of similar flow capacity, increased flexibility means they are easier to lift and handle during construction. They also conform more easily to the terrain, resulting in less excavation and less pipe bending to make them fit the contours of the trench. The net result is reduced construction costs. When construction, maintenance and reliability are factored into the selection process, superhigh pressure dense phase pipelines provide a cost effective option for handling the challenges of arctic environments.

Commentary by Dr. Valentin Fuster
2002;():183-188. doi:10.1115/IPC2002-27306.

The Chinese West-East Gas Pipeline project is the greatest gas pipeline in Chinese history. Its construction indicates that the Chinese gas pipeline technology reaches a new level. In this paper, the design, material selection, compression stations, control system, schedule of construction, financing and international cooperation of this project were described.

Topics: Pipelines , China
Commentary by Dr. Valentin Fuster
2002;():189-193. doi:10.1115/IPC2002-27322.

The energy shortage in Brazil prompted for the need of alternative and reliable energy sources that could be put into operation in a short period of time while being environmentally friendly and with flexibility to be installed around the country, taking advantage of the existing electric grid and therefore minimizing overall investments. Gas fired power plants proved to be the best selection, which covered all the requirements. The Ministry of Mines and Energy of Brazil set a program addressing initially 55 thermo power plants totaling about 20,402 MW. From this total 18,263 MW of installed power was from 49 gas fired power plants demanding gas volumes in the range of 88 MMm3/d most of this power to be available from 2001 to 2003. With this challenge, Petrobras has started to design a gas pipeline network expansion plan with investments of more than 1 billion US$ for its system alone, including new gas pipelines, new compressor and custody transfer stations and loop lines. In line with this expansion project more investments are required for the Bolivia-Brazil Gas Pipeline in Bolivia (0.2 billion US$) and Brazil (0.35 billion US$), and the new gas pipeline from Argentina to Brazil (0.25 billion US$) totaling 1.8 billion US$ of additional investments in gas pipeline expansion. All of this expansion design was based on technical and economic analysis that took into consideration the availability of gas supply from Brazil, Bolivia and Argentina. This paper presents the scope of the expansion, the technical and economical assumptions and the hydraulic simulation that was used to allow an investment decision.

Topics: Pipelines , Networks
Commentary by Dr. Valentin Fuster
2002;():195-197. doi:10.1115/IPC2002-27367.

Oil Transporting Company Transneft is a world leader in the field of oil transportation, basic tasks of which are timely and qualitative oil delivery to consumers both in Russia and outside Russia under conditions of equal access to the system of oil-trunk pipelines.

Commentary by Dr. Valentin Fuster
2002;():199-204. doi:10.1115/IPC2002-27383.

A pair of autonomous microcontroller-based robots were designed, built, and tested to inspect the inside of an 8 in pipe. The pair consists of a “scout” which travels along the inside of the pipe and scans the surface for holes using an array of touch sensors. Once a hole is found, the “scout” communicates the position of the hole to a second “mule” robot that has an on-board sealant dispensing system. After the scout moves out of the way, the mule moves to the hole location and dispenses sealant to seal the hole. Both robots are controlled by a BASIC Stamp microcontroller and propelled by servomotor driven wheels in response to sensor input. Communication is accomplished using wireless RF transceiver boards. This paper discusses the design, build, and test of these cooperative robots; the problems encountered, and how these problems were solved in order to successfully meet the project requirements of creating a two robot system that could find and simulate the sealing of holes in pipes.

Topics: Robots , Pipes
Commentary by Dr. Valentin Fuster

Design and Construction

2002;():205-210. doi:10.1115/IPC2002-27011.

PETRONET undertook to evaluate the conversion of two liquid pipelines designed and constructed under ASME B31.4 to gas service under ASME B31.8. In a liquid pipeline, a rupture will result in small length of pipe (3 m–10 ft.) opening to release product and pressure. The same failure mechanism in a pipeline with gas service can be far more damaging. Under certain combinations of product, pressure, temperature and material, a rupture can result in a running fracture that can travel for miles. The releasing energy from the compressed gas can sustain the fracture mechanism until some barrier or material change can absorb the energy and allow the fracture to arrest. This can be the critical decision point in any planned service conversion. If the pipe material and operating conditions indicate that a running fracture may develop, then either the pipe has to be replaced or an arrest mechanism installed. The economics usually preclude pipe replacement so it becomes critical to develop a method of retrofitting suitable arrest units economically and safely. Clock Spring® Crack Arrestors have proven to be an economical solution to this challenge. This paper presents a case study of the conversion of a 457 mm (18-inch) pipeline, designed and constructed in accordance with ASME B31.4 for liquid service, to gas operation under ASME B31.8. The pipeline is located in South Africa and is operated by PETRONET. The use of Clock Spring® Crack Arrestors saved million dollars over pipe replacement and was a key issue in the economic justification of the conversion.

Commentary by Dr. Valentin Fuster
2002;():211-216. doi:10.1115/IPC2002-27012.

Geosynthetic Clay Liner’s (GCLs) are an established sealing product in the geoenvironmental industry. They are used in landfill applications as caps and base liners, secondary containment for fuel storage facilities, as well as within various other containment structures such as dams, canals, rivers, and lakes. Rolled out like a carpet to provide a durable impermeable liner, Geosynthetic Clay Liners consist of a layer of high swelling sodium bentonite sandwiched between two geotextiles. Manufactured around the world in different techniques, the Canadian manufactured GCL, is mechanically bonded by needlepunching from one nonwoven geotextile through the bentonite to the other nonwoven or woven geotextile. The low hydraulic conductivity of the GCLs are used mainly as a replacement to thick, difficult to build compacted clay liners to provide a barrier to liquids and gases, offering both a technical and economical advantage. GCLs, with an average thickness of 7mm, offer a volume advantage over Compacted Clay Liners. They are more capable of withstanding freeze-thaw and wet-dry cycles; offer substantial construction cost savings in reduced on-site QC/QA and a quicker installation. Furthermore, GCLs offer equivalent or lower rates of release of fluids and chemicals than Compacted Clay Liners (CCLs). Bentonite is a clay mineral with expansive characteristics and low permeability, where montmorillonite is the chief mineral. Montmorillonite, swells when contacted with water approximately 900% by volume or 700% by weight. When hydrated under confinement, the bentonite swells to form a low permeability clay liner, the equivalent hydraulic protection of several feet of compacted clay. A relatively new engineering material for some, geosynthetic clay liners have been used extensively over the past two decades, and are finding increasing use in every sector of the environmental industry. This paper will review the technical properties of these materials, their documentation at the research level, their integrity as a sealing barrier and recent field applications in the pipeline industry. Further, because these materials are factory produced, their properties are predictable, assisting the engineer to design with a high confidence level. Technical properties and economical benefits are sure to further increase GCL installations around the world to protect our environment and more importantly our groundwater.

Commentary by Dr. Valentin Fuster
2002;():217-228. doi:10.1115/IPC2002-27015.

This paper discusses the evolution of line-pipe steel against the background of the failure incidence and the design basis for transmission pipelines, with a focus on those transporting natural gas. Working-stress design (WSD) is introduced as background for analysis of incident experience. It is shown that failure incidence does not correlate with the WSD factor of safety on pressure-induced stress, leading to the underlying causes of failure and discussion of alternative design philosophies, and consideration of safety factors other than those based on stress, or the effect of pressure. Full-scale test data are discussed to rationalize why failure frequency does not correlate with factor of safety. These results point to a very large factor of safety on pressure, with failure pressure found much in excess of the specified minimum yield stress (SMYS), the reference stress for WSD-based pipeline design. Full-scale failure at pressures much in excess of that for in-service incidents motivates discussion of causes of such failures and brings into question the utility of alternative design philosophies. The role of toughness is introduced as key to the success of WSD and alternative design philosophies. The historical evolution of both strength and toughness is then introduced along with apparent differences in toughness depending on how it is characterized. Historical trends are contrasted to those for modern steels, with diametrically opposing trends evident. The implications for design are discussed with reference to fracture control plans and methods to characterize required arrest toughness.

Topics: Steel , Pipes , Piping design
Commentary by Dr. Valentin Fuster
2002;():229-238. doi:10.1115/IPC2002-27030.

BP America Inc., Enbridge Pipelines Inc., and TransCanada PipeLines Limited recently sponsored a comprehensive technical review of the use of wheel and chain trenchers for excavating pipeline ditches for large diameter, long distance oil and gas pipelines in permafrost. The purpose of the review was to identify techniques that could be implemented to improve the productivity of trenchers in permafrost and reduce pipeline construction costs. This paper summarizes the key findings of the study. The study included an analysis of data obtained from previous field trials and construction case histories in permafrost, including the results from proprietary trials that have never been published. The study found that the primary subsurface conditions affecting the productivity of both wheel and chain trenchers in permafrost soil are: 1) the concentration and lithology of cobbles and boulders; 2) the presence and strength of bedrock within the depth of trenching; and 3) the tensile strength of the permafrost soil. With current technology, neither wheel nor chain trenchers can achieve satisfactory rates of production if more than 5 to 10 percent cobbles or boulders are present, or if hard bedrock exists within the depth of trenching. The study evaluated a number of techniques for improving the productivity of both wheel and chain trenchers in permafrost soil which may or may not contain hard inclusions. These methods included pre-blasting along the ditchline using either conventional blasting techniques or shaped charges. In addition, a wide variety of multi-pass trenching techniques were evaluated as part of the study.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
2002;():239-245. doi:10.1115/IPC2002-27043.

This paper assesses two aspects of liquid flow in pipes. The first aspect is the relation between pipe critical flow depth and flow discharge. The critical flow depth in a pipe is generally expressed as an implicit function. The paper proposes two simple expressions that can be used to explicitly express pipe critical flow depth as a function of pipe diameter and discharge. The approximation errors associated with these proposed expressions were found to be within 1.0%. The second aspect is the flow transition from open pipe flow to full pipe flow in a long pipe. Theoretically, when a pipe is close to flowing full, a given discharge may correspond to multiple head differences. This paper presents a practical solution approach that yields a unique solution for the pipe flow depth for a given discharge in the transition zone.

Topics: Pipe flow
Commentary by Dr. Valentin Fuster
2002;():247-253. doi:10.1115/IPC2002-27051.

There currently exist documented project implementation risk analysis and management processes that can be applied to pipeline projects [1]. The more macro type methodology of Reference [1] can be combined with the more detailed analysis presented in this paper to achieve better management of project cost and schedule, and presents an opportunity for the pipeline industry to reduce overall project cost and schedule overruns. Given the significant number of very large, prospective pipeline projects in the world today, many with challenging economic viabilities, effective risk analysis and management may very well make the marginal difference if a particular project proceeds or not.

Commentary by Dr. Valentin Fuster
2002;():255-261. doi:10.1115/IPC2002-27058.

Value Improving Practices (VIPs) are formal structured processes applied to capital projects and operating facilities to improve profitability or value above that attained through good engineering and project management practices (Reference [1]). VIPs are most commonly applied to projects resulting in chemical processing facilities, but not so frequently applied to cross-country pipeline projects. Based upon the authors’ experiences, this paper will describe the practical application of VIPs on pipeline projects and the significant benefits that may be expected. More specifically, the following fourteen (14) Kellogg Brown & Root (KBR) project VIPs will be discussed as to their exact purpose, and how and when they should be applied during the pipeline project life cycle: 1. Setting Business Priorities and Classes of Facility Quality; 2. Technology Selection; 3. Process Simplification; 4. Customization of Standards & Specifications; 5. Constructability; 6. Design to Capacity; 7. Waste Minimization; 8. Predictive Maintenance; 9. Process Reliability Simulation; 10. Energy Optimization; 11. Value Engineering; 12. Commissioning & Startup Planning; 13. Shared Learning; 14. 3D-CAD. This paper will continue with a more in depth discussion of two VIPs that have major applicability on pipeline projects: Technology Selection and Constructability. The relationship of the VIPs with BP’s Pipeline Cost Reduction Project will also be discussed.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
2002;():263-270. doi:10.1115/IPC2002-27061.

Pipeline systems incorporate numerous welded small bore attachments such as instrument connections or stabbings, vent and drain points and bypasses around full bore valves. These are susceptible to fatigue failure due to high frequency vibration excited both through the structure and by pressure fluctuations in the gas. Three examples of such fatigue failures are presented, showing that there may be several vulnerable welds in a connection. Detailed modelling of the potential consequences of the releases from such failures suggest that there may be situations in which unacceptable hazards may arise. Hence methods are described for rapid measurement of stresses in attachments, one based on accelerometers and the second on a frictional strain gauge system. Results from field measurements show how a simple screening criterion has been developed using established fatigue design methods to assess the results and identify cases requiring urgent action.

Commentary by Dr. Valentin Fuster
2002;():271-278. doi:10.1115/IPC2002-27062.

Recent developments in the control of propagating ductile fractures in gas pipelines have proposed using the Crack Tip Opening Angle (CTOA) as a measure of fracture resistance. This is attractive as it can be related directly to the geometry of the fracturing pipe and also can be implemented easily in finite element models of the propagating fracture process. Current methods of determining CTOA in linepipe have been based on the standard DWTT specimen. This geometry often does not allow a fully slant fracture to develop, and is loaded in bending rather than tension. A novel specimen design has been developed to measure CTOA under quasi-static conditions and applied to a X80 (Grade 555) pipeline steel. The experimental work involved development of the design to ensure crack path stability. CTOA was obtained directly by measurement from video images. The CTOA values dropped from an initially high value to a steady state value of about 8 degrees when fully slant crack growth was achieved. This required crack growth over a distance of about 5 to 12 times the test section thickness. The crack growth was modeled numerically using the Gurson ductile void growth material model. The finite element modeling was able to qualitatively reproduce the crack path instability observed in practice, and the fall of CTOA from the initial high value to a steady state condition. Although further work is required to improve the modeling, the work carried out to date has demonstrated that there is the potential to apply damage mechanics methods to predict the laboratory specimen response and then to model the structural response.

Commentary by Dr. Valentin Fuster
2002;():279-285. doi:10.1115/IPC2002-27075.

During the life cycle design and implementation of a pipeline system, there exist a number of opportunities for system optimization analysis. Such analysis has traditionally involved the use of linear programming and simulation techniques. However, these approaches have limitations as more complex problems are considered with more involved and complex criteria. The Ostrofsky Design-Planning Optimization Morphology (OD-POM) is especially powerful because it can handle non-linear objective functions including probabilistic variables. This approach allows the assessment of the interaction among the criteria so that consideration can be given to each criteria as independent. Because of its rigor and sophistication, the methodology compares alternatives in a much more accurate manner for the given data than less comprehensive approaches (for example, linear programming). This example includes the subjective criteria, explicitly in a quantifiable manner and allows the evaluation of the relative importance of the criteria.

Commentary by Dr. Valentin Fuster
2002;():287-298. doi:10.1115/IPC2002-27089.

The increasing needs of natural gas, foreseen for the next years, makes more and more important the type of transportation chosen, both from strategic and economic point of view. The most important gas markets will be Northern America, Europe, Asia and Russia but the demand shall be fulfilled also by emerging producers as Kazakhstan, Turkmenistan and Eastern Siberia that at the moment are developing their resources in order to be competitive on Gas market. In this way producers and customers will be placed at greater and greater distances implying realization of complex gas transportation pipeline network, when use of LNG tankers is impossible or uneconomic. On the base of these considerations in 1997 began a feasibility study on X100 steel, given that, comparing different design approaches, it has been observed that consistent savings could be obtained by means of using high grade steel and high pressure linepipes. In this multi-sponsored project (Eni group, European Community of steel and Carbon, CSM, Corus and Europipe) CSM and Corus group were involved in the laboratory and full-scale pipes testing, Europipe was the pipes producer and Snam Rete Gas was involved in field weldability and technical coordination. No technical breakthrough, but only improvements in the existing expertise were involved in the X100 production; consequently, the production window is very narrow. However optimized steelmaking practices and processes enabled the material to reach the desired properties: strength, toughness and weldability. This paper is intended to present the general results arising from this project, in terms of steel properties (chemical composition, mechanical properties), ductile and brittle fracture resistance (results of full scale burst tests, West Jefferson tests) and field weldability, but above all the know-how stored till now on high grade steel and its possible use from a Gas company and a Pipe maker point of view.

Commentary by Dr. Valentin Fuster
2002;():299-306. doi:10.1115/IPC2002-27093.

In the summer of 2000, TransCanada PipeLines Ltd. (TransCanada) upgraded portions of the Western Alberta System (WAS) NPS 36 gas pipeline through the town of Cochrane Alberta. The pipeline upgrade required the installation of new sections of pipe to meet the higher Class Location designation due to population density increase. Environmental concerns, expressed by federal and provincial regulators and the Cochrane community for the in-stream disturbance associated with a conventional “open cutting” installation, prompted TransCanada to design a directionally drilled crossing. A unique challenge to this project was the Bow River crossing within a congested and restricted right of way. The project team developed and implemented a series of innovative solutions which led to the successful conclusion of the project in September 2000. This paper summarizes the unique design and construction implemented in this project.

Topics: Drilling , Pipelines , Rivers
Commentary by Dr. Valentin Fuster
2002;():307-313. doi:10.1115/IPC2002-27095.

This paper presents and compares two case studies in which gravel foundations for steel oil tanks were built in early winter. The subzero weather presented challenges in the preparation of the site and the compaction of the gravel due to water freezing in the gravel and frozen subgrades. This conference paper will be useful to the pipeline industry in planning future tank foundations constructed in subzero temperatures. The first case studies a project — Tank 46 at Hardisty — that used aluminum coils running hot water to keep the overlying sand and gravel warm prior to placement and compaction. The second case studies a dual project — Tanks 301 and 302 at Kirby Lake — that used a heated tent to cover the tank foundation work as well as “tiger torch”-heated culverts to warm the overlying gravel stockpiles. The goal was to maintain water content in the gravel unfrozen until the design compaction levels were achieved. The two cases are compared on the effectiveness of compaction, ease of workflow and costs.

Commentary by Dr. Valentin Fuster
2002;():315-325. doi:10.1115/IPC2002-27108.

Early consideration of geotechnical conditions in coating selection and backfill design could prove technically, economically and environmentally beneficial. In addition, bedding, padding and backfilling requirements are not specified on a project specific basis and the current methodology for design, engineering and construction does not allow optimisation of the coating and backfill system. This paper is intended to review the financial and technical issues that need to be considered when selecting external coating systems for the corrosion protection of high-pressure transmission pipelines.

Commentary by Dr. Valentin Fuster
2002;():327-331. doi:10.1115/IPC2002-27112.

The overwhelming bulk of oil and gas in pipeline construction is done by welding the individual joints of pipe together. In a broad sense, welding is a metal-joining process wherein coalescence is produced by heating to a suitable temperature. In pipeline construction, this temperature has to be sufficient to render fusion of the joint. The mechanical and metallurgical properties and distortions usually present in weld structures are strongly influenced by preheating and interpass temperatures that are applied during the welding process. Basically, interpass temperatures depend on two factors: composition of the material and cooling rate. It is very important to choose the correct interpass temperatures, however, this is not a completely dominating matter. The objective of this paper is to present a study on the effect of different interpass temperatures on morphology, microstructure and consequently on microhardness of welded API 5L X65 steel. The welds were deposited by a Flux Cored Arc Welding Process and the heat input was held constant during all welding production. The interpass temperatures were calculated by different methods. Such temperatures were later verified experimentally. Temperature data were collected via a data acquisition system. The geometry and microstructure characterizations were performed via light optical microscopy and image analysis. These data were related to the different thermal cycles obtained. The results showed that the morphology, the microstructure and the microhardness of welded API 5L X65 steel were strongly influenced by the interpass temperature, revealing how important it is to choose the appropriate value.

Commentary by Dr. Valentin Fuster
2002;():333-339. doi:10.1115/IPC2002-27120.

Ductile Fracture propagation phenomena have been widely investigated by researchers in the last years, with particular regard to large metallic structures such as pressurized vessels or gas pipelines. A large number of burst tests have been carried out by Centro Sviluppo Materiali S.p.A. (C.S.M.) in the last decades to identify a set of significant parameters characterizing fracture propagation conditions; the aim is to foresee the behavior (speed and its derivatives) of longitudinal running cracks. The optimal choice of these parameters is strongly helped by appropriate use of Finite Element analysis. To this goal a Finite Element software has been developed, it allows the correct computing of some particular aspects of fracture propagation and the behavior of pressured real gases during decompression. In the present paper a pipeline burst test, carried out on a X100 grade pipeline, and all laboratory tests and data manipulations necessary to build up the whole procedure have been discussed. One of the main objectives is the setting of a procedure able to identify the fracture parameters, when a ductile propagation occurs, avoiding any scatter due to transient effects.

Commentary by Dr. Valentin Fuster
2002;():341-348. doi:10.1115/IPC2002-27123.

Service failures in the welded connections of heavy-walled fittings attached to thin-walled line pipe were found to have been caused in part by inadequate attention to the critical need for dimensional balance in the attachment details associated with such components. The basis for present ASME Code specifications for end bevel and fillet weld dimensions of attached reinforcements was reviewed and evaluated. Nominal stresses in hot tap and stopple tee end fillet weld details were evaluated. Revisions to the ASME Code specifications for hot taps, stopples, and saddle-type branch reinforcements are proposed that are intended to prevent similar service failures.

Topics: Fittings
Commentary by Dr. Valentin Fuster
2002;():349-361. doi:10.1115/IPC2002-27125.

The traditional approach to pipelines design is to select a wall thickness that maintains the hoop stress below the yield strength multiplied by a safety factor. The main design condition implied by this approach is yielding (and by extension burst) of the defect-free pipe. Failure statistics show that this failure mode is virtually impossible as the majority of failures occur due to equipment impact and various types of defects such as corrosion and cracks. Recent investigations show that these failure causes are much more sensitive to wall thickness than to steel grade. As a consequence, current design methods produce variable levels of safety for different pipelines — small-diameter, low-pressure pipelines for example have been shown to have higher failure risks due to mechanical damage than large-diameter, high-pressure pipelines. In addition, the current design approach has been shown to have limited ability to deal with new design parameters, such high steel grades, and unique loading conditions such as frost heave and thaw settlement. The paper shows how these limitations can be addressed by adopting a reliability-based limit states design approach. In this approach, a pipeline is designed to maintain a specified reliability level with respect to its actual expected failure mechanisms (known as limit states). Implementation involves identifying all relevant limit states, selecting target reliability levels that take into account the severity of the failure consequences, and developing a set of design conditions that meet the target reliability levels. The advantages of this approach include lower overall cost for the same safety level, more consistent safety across the range of design parameters, and a built-in ability to address new design situations. Obstacles to its application for onshore pipelines include lack of familiarity with reliability-based approaches and their benefits and lack of consensus on how to define reliability targets. The paper gives an overview of the reliability-based design approach and demonstrates its application using an example involving design for mechanical damage.

Commentary by Dr. Valentin Fuster
2002;():363-370. doi:10.1115/IPC2002-27129.

The large deformation behavior of cold bend was experimentally and analytically investigated. Full-scale large deformation experiments were conducted on two API X80 grade cold bends with a bending angle of approximately 9 degrees for both closing and opening modes. Finite element (FE) analyses were also conducted to simulate the large deformation behavior by considering the distribution of tensile properties after the cold bending process. The results of the simulation were in good agreement with the large deformation experiments. The deformability of cold bend in the opening mode was greater than that in the closing mode. Changes in the tensile properties due to the cold bending process had a large influence on the deformability of cold bend. In particular, distribution of the part with work hardening after the cold bending process had large effect on the deformability in the closing mode.

Topics: Deformation , Pipes
Commentary by Dr. Valentin Fuster
2002;():371-379. doi:10.1115/IPC2002-27130.

The general situation of West-East Gas Transmission Pipeline Project has been introduced. The selection of operating pressure, material grade, steel pipe type, microstructure and the fracture control of the pipeline have been discussed according to international gas pipeline developing trends and related research achievements. The research and production of X70 grade acicular ferrite pipeline steels and spiral submerged arc welded pipes have been introduced finally.

Topics: Steel , Pipelines , Pipes
Commentary by Dr. Valentin Fuster
2002;():381-388. doi:10.1115/IPC2002-27140.

Welding residual stresses are an important consideration in the fracture mechanics based fitness-for-purpose (FFP) assessment of steel structures. Reliable predictions of structural integrity can only be made provided that welding residual stresses are adequately accounted for. In the majority of cases, their magnitude is not known and can vary widely. In the absence of detailed information, it is common practice to assume that the welding residual stress is tensile, uniform through the thickness and of yield strength magnitude. However, this assumption will often lead to conservative fracture assessments which may lead to the conclusion that a weld repair is necessary when in practice the structure is safe to continue operation. In this paper, an integrated thermal-metallurgical-mechanical finite element (FE) model is described which simulates the formation of residual stresses at pipeline girth welds. The simulation takes into account detailed variations of the microstructure in the weld and heat affected zone (HAZ) in order to predict residual stress levels. Results of the FE analysis were validated with measurements of the microhardness and surface residual stresses using the air abrasive center hole drilling method. Sensitivity of residual stress levels to steel strength level, pipe wall thickness and pipe misalignment is discussed. The effects of hydrotesting and the alleviation of welding residual stresses are also described.

Commentary by Dr. Valentin Fuster
2002;():389-394. doi:10.1115/IPC2002-27141.

An essential prerequisite for a longitudinally welded large-diameter pipe to meet the most stringent quality requirements are efficient production units and the latest technologies for online quality control. To capture all data obtained during the various steps of production and testing and to control these data within close tolerances, an integrated IT-system covering all production stages — from the steel mill to the pipe coating — is indispensable to ensure a precise traceability of data and products. By an extensive automation of data acquisition and control, the factor of human errors can be excluded. In the following we would like to give you an overview of measures and investments which have already been realized by Europipe over the last years or which are going to be introduced with the aim to meet customer’s ever increasing demands on quality.

Commentary by Dr. Valentin Fuster
2002;():395-401. doi:10.1115/IPC2002-27152.

This paper describes the efforts involved in successfully designing a large scale offshore liquid fuel unloading system. The hydraulic transient analyses conducted during various design stages produced acceptable transient pressures under various transient events including pump trip, normal and emergency shutdowns (ESDs), confirmed that the maximum marine tanker design rail pressures were within limits, and determined that the transient pulse loading on various above-ground pipe segments can be substantially reduced by providing effective surge relief devices. The paper also describes experience gained in designing and maintaining the air vessels to ensure their availability in protecting the system piping.

Topics: Fuels
Commentary by Dr. Valentin Fuster
2002;():403-407. doi:10.1115/IPC2002-27155.

X70 large diameter linepipe with helical seam SAW were developed, with 1016mm OD and 14.6mm WT. Acicular ferrite type linepipe steel is adopted for the base material, which was found having high toughness and low yield strength loss after pipe forming. The very stringent requirements for toughness, i.e. 190J/140J for average/minimum for pipe body and 120J/90J for average/minimum for weld and HAZ were meet successfully. The yield strength loss due to Bauschinger effect was found lower than 20 MPa, which benefited.

Commentary by Dr. Valentin Fuster
2002;():409-413. doi:10.1115/IPC2002-27161.

The performance of a pipeline is related to both the stress levels to which the pipe is exposed and the characteristics of the pipe material itself. For steel pipe in particular, the grade of skelp used and its deformation history during fabrication can influence both the effective yield strength and subsequent (if any) plastic deformation of the final pipe product. To understand and quantify this relationship between pipe forming and pipe properties, three concurrent areas of study were undertaken: instrumented plant trials to understand and quantify strain history during pipe forming, characterization of the constitutive behaviour of pipe steel deformation under complex loading and the development of a finite element analysis (FEA) stress model to couple the effects of forming history and constitutive material behaviour on the mechanical performance of a steel pipe under an internal pressure. Strain gauge technology and digital imaging were used to measure dynamic strain histories and geometry of the pipe imparted by the forming process. These plant measurements provided unique insight into the dynamics of the forming operation and detailed data for the FEA model verification. A series of tension/compression tests were conducted on X-52 and X-70 steel to quantify the kinematic hardening behaviour of these materials under complex loading conditions. This data was used to formulate the constitutive equations of the steel in the FEA model. The numerical stress model was developed using the commercial finite element package ABAQUS. Loading simulations of the pipe using the FEA model were conducted to illustrate the effect of both steel characteristics and forming history on pipe performance.

Topics: Steel , Pipes
Commentary by Dr. Valentin Fuster
2002;():415-427. doi:10.1115/IPC2002-27169.

The strain capacity of girth welds containing surface-breaking welding defects is examined through numerical analysis and experimental verification under a PRCI (Pipeline Research Council International) funded project. Some important insights on the various factors affecting the girth weld strain capacity are generated. The defect size is identified as one of the most important factors in determining strain capacity of a girth weld. Other factors, such as the strain hardening rate of the pipe and weld metals, weld strength mismatch, fracture toughness, and weld cap height, can play a significant role if the defect size is within certain limits. It is discovered that the girth weld response to the remotely applied strain may be characterized by a three-region diagram. For a given set of defect size and weld strength mismatch conditions, the crack driving force may be bounded, unbounded, or gradually changing, with respect to the remotely applied strain. A set of parametric equations is developed that allow the computation of allowable strains with the input of defect depth, defect length, CTOD toughness, and weld strength mismatch. The comparison of the developed strain criteria with full-scale bend tests and tensile-loaded CWPs (curved wide plates) shows the criteria are almost always conservative if lower bound CTOD toughness for a given set of welds is used. However, the criteria can significantly underpredict strain capacity of girth welds with short defects. Although defect length correction factors were added to the strain criteria based on the comparison of axisymmetric finite element (FE) results and full-scale bend test results, a more thorough investigation of the effects of defect length on strain capacity is needed. Future investigation that incorporates the finite length defects is expected to greatly reduce the underprediction. The influence of other factors, such as strain hardening rate, should be further quantified.

Commentary by Dr. Valentin Fuster
2002;():429-435. doi:10.1115/IPC2002-27180.

Substantial differences amongst metallurgical and mechanical properties of base metal (BM), weld metal (WM) and heat-affected zone (HAZ) occur in general in welded steel structures It is common practice in various engineering structures to evaluate the fracture performance of welded structures by mechanical testing. Especially, the HAZ of steel welded joints shows a gradient of microstructure and mechanical properties from the fusion line to the unaffected base metal. This study is concerned with the effects of metallurgical and mechanical factors on the fracture performance of API 5L X65 pipeline steel weldments, as they are generally used for main natural gas transmission pipelines in Korea. First of all, we investigated the microscopic and macroscopic fracture behavior of the various micro-zones within the HAZ from the viewpoint of metallurgical factors. The effects of mechanical factors such as welding residual stress in steel weldment and strength mismatch between BM and WM, particularly in high strength steel weldments, are also analyzed. Therefore, the fracture performance of API 5L X65 pipeline steel weldment was mainly dependent on the change of macrostructure and its distribution in the welded joints.

Commentary by Dr. Valentin Fuster
2002;():437-444. doi:10.1115/IPC2002-27182.

Permanent ground movement is expected in seismic areas and in permafrost regions, and pipelines buried in those areas need to be designed to have sufficient deformability. Especially, bends need to have superior deformability, because it was pointed out in the recent earthquake event that deformation tends to concentrate in the connection region of pipelines. Severe deformation can lead to a fracture of the pipe wall and this may cause explosion of the pipeline or leakage of the gas, which need to be prevented in the areas with high population density. In spite of the importance of deformability for pipe bends, there are only a few reports on this issue. Furthermore, those investigations are limited for up to X65 grade induction pipe bends. In this study, two types of API X80 grade induction pipe bends, 610mmOD × 11.0mmWT and 610mmOD × 16.6mmWT, bending radius of three times the pipe diameter and bending angle of 90 degree for both, were manufactured using longitudinally submerged arc welded pipes as mother pipes. And large scale bending test using X80 grade pipe bend was conducted by applying closing displacement on the tangents under the internal pressure of 12MPa by water. Bending load was continuously applied up to the maximum load point, and then prescribed displacement was applied until twice the maximum load point. Local deformation was shown in the middle of the bend portion, however, no cracking was observed. Furthermore, EF analysis of bending test was performed for precise estimation of stress/strain response of pipe bend, and analytical results were compared with experimental data. These bending tests proved that large deformability could be expected on the X80 grade pipe bends even under the high internal pressure. In order to investigate ductile cracking behavior of the X80 grade induction pipe bend, notched round bar tensile tests were also conducted, and the criterion for ductile cracking was compared with X65 grade bend material. Relation between equivalent plastic strain and stress triaxiality at a ductile crack initiation point was determined by FE analysis, and this analysis proved that X80 grade bend material has enough resistance to ductile cracking compared to X65 grade bend. This result also corresponds to the results of the bend test, which is showing enough deformability of the X80 grade induction bends.

Commentary by Dr. Valentin Fuster
2002;():445-449. doi:10.1115/IPC2002-27185.

The world production capacity on large-diameter welded pipe amounts to more than 12 million tons per year 20–25% are produced as spiral sub-arc welded (SAW) pipes, with the balance of 75–80% being longitudinal SAW pipes (from plates). For most spiral-weld producers, a sizeable portion of line pipe is for water transportation, rather than hydrocarbon. In the past, the relative structural weakness of spiral-welded pipe, due to larger welded area, limited the growth of its use in the oil industry. With the development of more advanced production technology, the acceptance of spiral-welded pipes in the oil and gas industry has increased significantly. In this paper, the principals of the spiral manufacturing technology from coil by the two-step-method are introduced and the innovations of Corinth Pipework’s production facility are outlined in detail, including the sophisticated NDT techniques and the Quality Management System.

Commentary by Dr. Valentin Fuster
2002;():451-455. doi:10.1115/IPC2002-27188.

The West-East Pipeline is the first of high-pressure, high-grade steel (X70) and large diameter (Φ1016mm) gas transmission pipeline in China. Evidently, Safety of the Pipeline is the most important case that the gas company have to take care of. Previous study showed that strength mismatch of girth weld had great effect on the integrity of the pipeline. Overmatch is preferred for low-grade pipeline (steel grade is usually X60 or lower). As to the high-grade pipeline, in order to reduce the sensitivity of cold crack, hydrogen induced crack (HIC) and stress induced corrosion crack (SCC), etc., under-matched girth weld is recommended somewhere. In this paper, based on a lot of mechanical test results, the effect of different mismatched girth weld on property of the West-East Pipeline is analyzed. The study indicated that mismatch of girth weld has effect on property of the Pipeline, such as limit load, fracture toughness and threshold defect sizes, etc. According to the research results, some advices are presented for design, maintenance and repair of the Pipeline.

Topics: Safety , Pipelines
Commentary by Dr. Valentin Fuster
2002;():457-466. doi:10.1115/IPC2002-27193.

Heated pipelines buried in soft clay can develop a very challenging behavior. The thermal expansion of the pipelines normally induces buckles, which will be supported by the passive soil reaction. The buckles of the pipelines in soft clay can generate a non-linear inelastic behavior that is an unstable situation named “snap through”. In such situation the pipeline can jump from a configuration of a few centimeters displacement to another of meters displacement. Once the snap through situation has developed, there is the possibility of a local pipeline buckling, causing the pipeline rupture and as a consequence an oil spill. This paper presents the results obtained during the analysis of the rupture of a buried heated pipeline in the Guanabara Bay of Rio de Janeiro, Brazil. A very sophisticated procedure including a simulation of the thermal mechanical interactions between the soil and the pipeline structure was developed for back analysis of the thermal inelastic pipeline buckling. Computer modeling was carried out using the finite element method considering of the non-linear material behavior of the soil and pipeline, and nonlinear geometrical behavior of the pipeline. A cyclic thermal-mechanical soil-pipeline structure interaction model was the challenging aspect of the simulation, that explains the trigger mechanism of the snap through behavior of heated pipelines, which was responsible for the rupture of the pipeline in Guanabara Bay.

Topics: Pipelines , Soil
Commentary by Dr. Valentin Fuster
2002;():467-473. doi:10.1115/IPC2002-27215.

There has been a general trend in the natural gas pipeline transmission industry towards high-pressure pipelines using higher strength steels. However, as the strength has been increased, so have issues of weldability and fracture control. TransCanada PipeLines has been developing and testing a hybrid product since 1996 called Composite Reinforced Line Pipe (CRLP® ) to address these issues. This is a patented technology developed by NCF Industries and licensed on a worldwide basis to TransCanada PipeLines. CRLP® is composed of high performance, composite material reinforcing a proven high-strength, low alloy steel pipe. The composite reinforces the steel pipe in the hoop direction, thereby increasing its pressure carrying capacity, while providing a tough, corrosion-resistant coating. This paper discusses recent research work concerning the use of CRLP® for large-diameter gas pipeline systems. Aspects discussed include analysis and design methodologies, full-scale testing, and field trials.

Commentary by Dr. Valentin Fuster
2002;():475-484. doi:10.1115/IPC2002-27225.

Investigations in the development of a predictive critical buckling strain equation have shown that the grade of the material is one of five fundamental non-dimensional parameters in determining the critical local buckling strain for line pipe under combined loads. Further to this, the shape of the material curve also plays a significant role in the resulting critical buckling strain. Over 50 full-scale test specimens have been tested at the University of Alberta and effective numerical finite element analytical models have been developed. A parametric study consisting of 170 analyses was performed using the numerical models and critical buckling strain equations were derived. One of the essential variables in the new equations is a function of the specimen’s material properties. The results indicate that the higher the grade of the material the lower the value of the critical buckling strain. Furthermore, the level of agreement between the new equations and the experimental data was found to be dependent on the shape of the material curve for the specimen. Experimentally, two basic material curve shapes were observed, namely: specimens with a “rounded” material curve through the yield strength and specimens with a material property that exhibited a distinct “yield plateau” or yield point. Comparison of the experimental and numeric data showed that the specimens that were fabricated from material with a distinct yield plateau had different critical buckling strains when compared to specimens tested with rounded material curves. A subsequent parametric study was undertaken to examine the effect that the different shaped material curves had on the local and global behaviour. The results of this subsidiary parametric study showed that the global moment capacity was essentially independent of the shape of the material curve (the ratio of the peak moment from the yield plateau material to the peak moment for the rounded material was 1.018). However, the local critical buckling strain was significantly lower for the specimens analyzed with the material that had the yield plateau (the ratio of the critical strains for the two different material curves was 0.710).

Commentary by Dr. Valentin Fuster
2002;():485-493. doi:10.1115/IPC2002-27227.

Different flow pattern maps and theoretical models were employed to determine the flow velocity needed to provide the dispersed-bubble flow in a hydrotransport pipeline. Comparison and analysis of the results has been carried out. The maximum and minimum bubble sizes were determined by semi-experimental methods. A log-normal function was employed to describe the bubble size distribution. A model for the bubble size change in the turbulent pipe flow was applied to study the evolution of the overall bubble size distribution. This model takes into account the competing factors influencing the bubble size: 1) dissolution (turbulent diffusion) of air in the liquid, causing bubble shrinkage; 2) pressure drop along the pipeline, causing bubble growth. Numerical analysis shows that the bubble dissolution rate strongly depends on the initial air hold-up and initial bubble size. An increase of air hold-up leads to a fast decrease of the dissolution rate. At sufficient high air hold-ups, the dissolution effect becomes negligible and air bubble sizes are dominantly controlled by the pressure drop. Smaller bubbles have higher dissolution rates than larger ones. Compared with a pure liquid flow under the same flow conditions, the effect of air hold-up is stronger in the slurry flow because of the smaller volume occupied by the liquid.

Commentary by Dr. Valentin Fuster