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An SwRI-developed smart pig supports testing of NDE technologies that can be applied to in-line pipeline inspection. Using an onboard power supply and data-acquisition system, the pig records up to 50 hours of data while moving with the product flow through an operating pipeline. |
Magnetic flux leakage (MFL) is a commonly used method for in-line detection and characterization of pipeline corrosion. Assessment of the strength of corroded pipes is often based on estimates of corrosion depth from MFL data. Traditional assessment methods consider pipeline hoop stress from internal pressure but do not account for local pipe wall stress components due to bending or axial loading. Early work by SwRI showed that MFL defect signals are influenced by pipe wall stress. SwRI is now using MFL data to extract information on the pipe's biaxial loading and has developed assessment algorithms that take into account biaxial stresses in the pipe wall. The methodology is being demonstrated using test specimens containing simulated corrosion defects outfitted with a magnetizing coil and an internal computer-controlled scanner with magnetic field detectors.
Using up-to-date instrumentation and extensive test facilities, experienced SwRI corrosion engineers and scientists provide a responsive resource to resolve corrosion-related problems for the pipeline industry. In particular, the Institute offers a variety of corrosion assessment and mitigation services, including:
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Corrosion may occur beneath disbonded coatings even with application of cathodic protection. Institute engineers assist with identifying and monitoring problem areas, recommending the most cost-effective mitigation or repair methods. |
In this multidisciplinary program, SwRI is developing a comprehensive numerical model for predicting the evolution of environmental chemistry and potential/current distribution under disbonded coatings on buried steel pipelines. In the SwRI model, the first of its kind, an extensive thermodynamic engine is coupled with a transport model to predict spatial and temporal distribution of chemical species. The user may choose from a wide range of input parameters, including soil chemistry, disbondment geometry, and applied cathodic protection. SwRI conducted laboratory studies to simulate disbonded coating under tape. Such a model enables pipeline companies to determine if specific soil conditions, coatings, and operational parameters can lead to localized corrosion or stress corrosion cracking.
A s the nation's pipeline infrastructure ages, performance degradation and structural safety are of increasing concern. SwRI provides independent, third-party, pipeline integrity assessment services that can be tailored to specific needs, operating conditions, defects, and possible accident scenarios. These assessments employ the latest technological advancements, many of which were developed at the Institute, and have included:
Results of these assessments have benefited the pipeline industry by providing:
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Nonlinear finite element analyses are used to predict wrinkling of pipelines under complex service-based loadings. The experimentally validated analyses accurately predict strains, stresses, and the wrinkling failure mode observed during the experiments. |
SwRI engineers developed analytical techniques to accurately assess the burst and bending capacity of corroded oil transmission pipes subjected to combined loading conditions of internal pressure, bending caused by settlement, and axial compression due to constrained thermal expansion. SwRI performed full-scale burst tests on pipes with simulated corrosion-induced metal loss under these combined loads. Engineers used elastic-plastic, large-deformation finite element analyses to simulate the burst behavior observed in the tests. This work was then expanded to include axially compressive loads using test results and parametric finite element computations. Staff members then developed theoretically based engineering models and software to facilitate practical applications of the test and analysis results. Finally, SwRI developed a nonlinear finite element procedure and validated the predictions using full-scale tests to predict wrinkling in corroded pipelines subjected to combined loads.
Today's pipeline operators recognize the increasing need to maintain the integrity, responsiveness, and efficiency of their system while demonstrating "as low as reasonably achievable" financial and operational risk levels. Using a multidisciplinary approach to pipeline risk management, SwRI engineers employ Institute-developed probabilistic and financial risk assessment tools to evaluate the performance of pipelines, reciprocating machinery, turbomachinery, inspection methods, and damage prevention/mitigation schemes. SwRI's risk-assessment tools use information and models developed from:
SwRI's cost-optimization studies use sophisticated engineering models to predict the likelihood of failure and to assess consequential costs with and without maintenance events and scheduled inspections. Maintenance expenses and inspection costs are balanced with the consequential costs of leaks and loss asset value. These data are then used to calculate the optimal use of available resources.
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SwRI-developed maintenance optimization software, MANTOP™, uses probability of failures and consequential cost to determine if and when a maintenance action should be taken. Maintenance funds should be spent if the net present value is positive. |
SwRI engineers have developed software programs to perform integrity and risk analyses, including:
NESSUS™ -- Probabilistic structural mechanics and reliability/risk analysis (www.nessus.swri.org)
MANTOP™ -- Maintenance optimization based on net present value
PE LIFESPAN FORECASTING -- Evaluation of plastic pipe structural integrity
GRIWRAP™ -- Analysis of long-term performance of composite overwrap repairs
SAFE -- Strain-based failure prediction of corroded pipelines under combined loadings
DARWIN™ -- Design Assessment of Reliability With INspection (www.darwin.swri.org)
Risk Assessment and Analysis
Mechanical Testing
Corrosion Studies
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Using this four-point bending and axial loading test facility for large diameter pipe, SwRI engineers perform pressurized tests to develop guidelines for the analysis of rupture and wrinkling behavior (see Technology Today®, Fall 1996, Where the Pipeline Meets the Permafrost). |
NDE Development and Application
Nonmetallic Piping
Technology Assessment and Guidelines
Pipeline operation depends on reliable and efficient compression. With extensive experience in serving the pipeline industry, the Institute offers solutions to a broad spectrum of operational problems associated with reciprocating and rotating compressor systems. Through optimizing system performance and providing design and analysis capabilities, SwRI helps pipeline and storage companies achieve reliability, integrity, safety, optimum performance, and minimum costs through the life cycle of their compression equipment.
Reciprocating compressors have traditionally been the workhorse of the U.S. natural gas industry. SwRI maintains a substantial base of equipment and an experienced staff, ready to document, diagnose, and solve performance, reliability, maintenance, and safety problems in the field. SwRI's experience includes large, older, slow-speed units and the more recently installed high-speed units, driven by gas engines or electric motors. Typical field analyses and measurements include:
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An SwRI engineer installs a transducer to determine the dynamic cylinder pressure and to document the power and flow of a motor-driven compressor during an investigation to compare capacity control options. |
Throughout the industry, the thermal efficiency of reciprocating compressors ranges from less than 50 to more than 90 percent. Reducing valve and piping losses while preserving mechanical integrity represents an opportunity to lower fuel consumption and increase compression capacity without capital investment. Gas transmission normally requires a low compression ratio, in which losses in valves and pulsation control orifices are most significant. SwRI developed diagnostic and simulation tools to address these issues. Using heated pressure transducers for consistency, engineers measure cylinder pressure variation, correct it for measurement distortions, and fit a physical model. Exercising the model identifies how valve and orifice resistance and valve dynamic response contribute to performance and integrity under different operational scenarios and quantifies the benefits of possible modifications. Under EPRI funding, this capability is being applied to assess, technically and economically, alternative capacity control techniques for electric motor-driven compressors.
Many pipeline operating companies regard a gas turbine-driven centrifugal compressor as their first choice for new capacity and for replacement of older reciprocating compressors. Although noted for reliability and operational efficiency, these compressors and their piping can experience surge, stall, flow-induced vibrations, torsional and lateral critical speeds, and blade or impeller failures. SwRI offers numerous services to help operating companies achieve cost-effective solutions to problems from compressor start-up through the life cycle, including:
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Using comprehensive metallurgical evaluations, an Institute scientist determines in-service degradation modes for a gas turbine component. |
Gas turbine overhaul represents a major expense, and pipeline operators need to optimize their overhaul timing decisions. One project developed guidance for blade maintenance on the RB211-24C aero-derivative turbine for pipeline service. It defined factors influencing repair and replacement decisions for the high-pressure turbine blades, including metallurgical evaluation of serviced blades to determine in-service degradation modes and determination of expected blade life as a function of engine operation. Institute engineers evaluated the potential for blade repair and for extending blade life and durability with protective coatings. SwRI engineers identified several opportunities to extend the life of the high-pressure turbine blades, including recognition of part-load operation, improved shroud repair, and multiple refurbishments. These improvements result in significant cost savings to the turbine operator.
The Institute has one of the world's largest natural gas engine technology programs. Working with major engine manufacturers, SwRI has developed technology to enhance reliability, performance, and controllability of natural gas engines and to reduce engine operating costs. Using Institute-developed emissions control technology, engineers document and enhance engine emissions performance. SwRI capabilities include:
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Institute engineers use a 1,400-horsepower natural gas engine to test experimental ceramic valve inserts designed to reduce valve recession. |
SwRI has led the formation and development of the advanced reciprocating engine system (ARES) program. Funded jointly by the Department of Energy and industry, this program has set ambitious goals for ARES cost, thermal efficiency, reliability, maintainability, and emissions. The program involves collaboration by government agencies, universities, manufacturers, users, and research organizations. SwRI has performed feasibility analyses to define the goals and is testing engines to confirm the assumptions. Efforts address a number of advanced technologies including alternative engine cycles, variable valve timing, engine modeling, design for knock mitigation, exhaust gas recirculation, reformer technology for fuel gas, turbocharger enhancement, and exhaust aftertreatment. The program currently emphasizes power generation, but the technology will directly apply to engines for mechanical drive of compressors and, in many cases, can be retrofitted.
More than 45 years ago, SwRI developed an innovative, industry-sponsored analog design facility for compressors and piping systems. In addition to providing design services, today's Gas Machinery Research Council design facility generates funds for research to enhance compression technology and associated pipeline operations. Most recently, these enhancements have responded to changing emphasis resulting from deregulation, increased competition, and new compression technologies. Having completed more than 7,000 plant design and problem-solving projects, SwRI addresses a variety of design analysis needs, including:
Pulsation and Vibration Control
Centrifugal Surge and Pulsation Control
Piping Dynamics
System Mechanical Dynamics
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SwRI engineers apply a combination of digital and analog design tools to optimize reliability, capacity, and efficiency of compressor and piping systems. |
In a series of projects, SwRI significantly advanced the understanding of crankshaft failures and developed methods for failure control. In the early 1980s, SwRI assessed criteria for determining the severity of crankshaft misalignment with the use of laboratory experiments, finite element modeling, and field monitoring. Although these projects resulted in guidelines that greatly reduced crankshaft failures, industry continued to suffer excessive failures, some caused by foundation deterioration and sag. To assess crankshaft and foundation conditions, the Institute developed a software package (WEBMAP®) that displays the shaft misalignment shape in the vertical and horizontal planes. SwRI also devised and updated modeling methods using personal computer-based finite element packages, designed an on-line crankshaft strain measurement device, and published a series of databases, guidelines, prediction methods, reports and papers, and training materials on foundation design, maintenance, and repair. With this knowledge, SwRI engineers help pipeline companies ensure crankshaft integrity through improved foundation installation and repair.
Aero-Derivative (A-D) Gas Turbines
Industrial Gas Turbines
Centrifugal Compressors
Reciprocating Compressors
Engines
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Institute staff members use systematic failure analysis and predictive tools to isolate and mitigate the causes of costly failure, such as this torsional vibration fracture of a crankshaft. |
Emissions
Piping
Foundation
General
Operational and condition monitoring and flow measurement of pipelines, compressors, and prime movers provide key data that result in improved pipeline efficiency and responsiveness to customer demands. SwRI offers research, testing, and engineering consultation for issues related to operational and condition monitoring. Specifically, expertise is available for:
Since 1991, the Institute has operated the GRI Metering Research Facility (MRF), located at SwRI's headquarters in San Antonio. Recognized as the premier natural gas measurement laboratory in the world, the MRF provides a high level of test accuracy, controllability, and rangeability. As the MRF operator, SwRI provides the following natural gas measurement services:
SwRI also has extensive experience with unusual flow problems, such as wet gas (multiphase) flow measurement; hydrate and paraffin detection, prevention, and remediation; and liquid or solid-particle detection and monitoring.
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SwRI engineers routinely conduct tests at field meter stations to determine if flow pulsation or other operational problems are adversely affecting mea surement accuracy. Critical components, such as the primary flow element, secondary instrumentation, and flow computer, are examined as part of the on-site evaluation. |
A verification testing project, conducted at the GRI MRF, confirmed that two test meters performed according to accepted industry standards. The baseline performances of two 12-inch-diameter multipath ultrasonic gas flow meters were established experimentally and then tested with different upstream piping configurations. These tests, which determined the effects of piping installation on meter accuracy, showed that the upstream piping configuration could produce flow distortions that result in a bias error in flow measurement. Each meter was also tested with a flow conditioner installed upstream to determine if the conditioner could eliminate or minimize the meter bias associated with various upstream piping configurations. Four commercially available flow conditioners were evaluated. After optimizing flow conditioner location relative to the meter, it was determined that the best flow conditioner reduced measurement bias due to the piping installation to less than 0.2 percent of reading, which was the resolution of the test facility's reference standard.
The United States spends nearly $1 billion each year on fuel to pump natural gas through the nation's pipelines. An additional $300 million is spent to maintain compressor station equipment. The Institute helps control energy and maintenance costs for compressor users. SwRI field engineers characterize pipeline problems through diagnostic testing and nondestructive examination; determine the root cause through pulsation, vibration, and failure analyses; predict the consequences; assess alternative design options using appropriate simulation tools; and help clients decide on an economical and technically viable solution. Institute engineers address a variety of problems, including:
In association with industry leaders, the Institute develops and evaluates methods and criteria to detect and diagnose operational problems in compressor stations. These problems include leakage from valves, rings, and packing; excessive valve resistance and dynamic strain; capacity shortfall; cylinder and compressor frame misalignment; high thermal loads; and torsional resonance. Using these technologies, engineers can assess the condition of operating equipment at a compressor station and determine the need and value of corrective action.
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To monitor excessive vibration caused by flow instabilities and blade passing, an SwRI technician installs a strain gauge on the discharge piping of a centrifugal compressor. |
With support from industry, SwRI engineers developed compressor diagnostics software to assist compressor operators in detecting performance changes, quantifying valve leak severity, improving throughput measurement accuracy, and characterizing phenomena such as valve flutter. For typical gas transmission compressors, this project demonstrated how deviations from predictions of an accurate thermodynamic model could be used to identify operating faults. Tests on natural gas compressors demonstrated that this approach could quantify the leak severity in terms of wasted power or lost flow, either of which could be used for economic assessment of severity. The software distinguished and corrected for pressure modulations associated with the measurement channel and identified the point at which the valve flutter became significant.
Leak or line-break detection and control are significant safety and environmental issues for pipeline operators. Rapid response in identifying and controlling pipeline leaks or line breaks may be a life or death matter. Pipeline operators strive to ensure that their systems are run in a safe and environmentally friendly manner. Institute engineers provide assistance with leak detection and line-break identification and control through:
In addition to being concerned about leaks and line breaks, pipeline operators focus on limiting harmful exhaust emissions from compressor engines. Emission standards have been established by the federal government. Institute engineers assist operators in meeting their exhaust gas monitoring needs by providing the latest measurement techniques.
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Institute engineers simulate a pipeline break on a gas transmission pipeline in which several line-break detection systems were being compared. SwRI used these test results to advise the pipeline-operating company on the preferred detection system for this pipeline. |
In response to an industry need for effective leak and corrosion control, SwRI surveyed potential technology capable of remotely sensing pipeline leaks and other potential safety problems from a vehicular or aerial platform. This work led to the development of remote-sensing equipment for detecting and tracking an electrical signal injected into the pipeline's cathodic protection system. Because current leakage along a pipeline is a strong indicator of corrosion, SwRI engineers are designing an incipient leak-detection system. The system operates on a moving vehicle and has a built-in global positioning system that can locate leaks accurately and provide real-time mapping information.
Right-of-way monitoring is a critical activity for all pipeline operators. Right-of-way intrusions may cause problems in urban areas, particularly those areas involving new housing developments. Third-party damage is the leading cause of pipeline breaks. Federal, state, and local legislation is being implemented to help control third-party intrusions into pipeline rights-of-way. Because most states have a "one call" system to locate buried pipelines quickly, it is essential that pipeline operators know precisely where their pipelines are buried and are able to locate these buried pipelines promptly when requested.
SwRI is a leader in developing new technology for addressing these important issues. The Institute offers technical support for a variety of right-of-way issues, including:
SwRI is studying the use of long wavelength, infrared video cameras to detect large vehicles and construction equipment intruding onto the pipeline right-of-way. Also, Institute transportation engineers are evaluating long-wave, infrared video technology in highway auto-mated traffic management systems to see vehicle traffic at night and in heavy fog. This method is a promising one in that traffic monitoring technology is improving and infrared video costs are decreasing. SwRI is continuing to fund internal research and development efforts in the infrared detection area.
Flow Measurement
Multiphase Flow
Pipeline Condition Monitoring
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This weigh tank at the SwRI-operated GRI Metering Research Facility measures, with high precision, the mass of gas collected during a high-pressure, high-volume test. |
SwRI's multidisciplinary, integrated approach to problem-solving provides innovative solutions to complex technical problems. With more than 3,100 staff members and approximately 650,000 square feet of computer and laboratory facilities, the Institute provides technical support in a number of disciplines. In addition to the Institute's pipeline-specific capabilities, SwRI has extensive supporting technologies and facilities in the following areas:
As part of a long-held tradition, all project results arising from client-sponsored research, including patents rights when applicable, belong exclusively to the client. SwRI generally retains the rights to Institute-funded advancements.
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SwRI maintains fire-testing facilities to qualify pipeline and well-head components in accordance with American Petroleum Institute standards. |
The Institute periodically conducts training workshops in pipeline technology to satisfy client needs in areas in which SwRI has extensive knowledge and expertise. Some of the workshops are discussed below. More details are provided on the Institute's website at www.swri.org.
Annual SwRI/GMRC Gas Compressor Engine Workshop
Sponsored by Southwest Research Institute and the Gas Machinery Research Council (GMRC), the SwRI/GMRC Gas Compressor Engine Workshop details the effects of turbo-charging, engine design, combustion parameters, friction, heat transfer, and other parameters on engine power, fuel consumption, and exhaust emissions.
GMRC at (972) 620-4024 or click on website www.gmrc.org
Fundamentals of Engines and Compressors
This one-week workshop is designed to provide students with a basic understanding of the workings of natural gas engines and compressors.
GMRC at (972) 620-4024 or click on website www.gmrc.org
Controlling Pulsations in Compressor and Piping Systems
This short course, sponsored by SwRI and the Southern Gas Association (SGA), covers the significant improvements made during recent years in analytical capabilities used by the GMRC. Course material includes the latest results from GMRC research efforts.
SGA at (972) 620-8505 or click on website www.southerngas.org
Applied Compressor Mounting and Foundation Design Workshop
This workshop gives those engineers responsible for reciprocating compressor installation the knowledge, tools, and experience for applying the latest compressor mounting and foundation design techniques to maintain their machines at optimum reliability.
GMRC at (972) 620-4024 or click on website www.gmrc.org
Ultrasonic Gas Flow Meter Workshop
This workshop provides comprehensive information on ultrasonic gas flow meter technology, including fundamental principles of meter operation, meter selection and sizing, new meter research and development, installation guidelines, meter problem identification and resolution, meter calibration and verification, and the status of industry standards.
SGA at (972) 620-8505 or select website www.southerngas.org
Factors in Gas Meter Station Design and Operations Short Course
This short course provides information for designing and operating natural gas flow metering facilities, including meter station design practices, new meter research and development, meter problem identification and resolution, metering equipment calibration and verification, and gas composition determination.
SGA at (972) 620-8505 or click on website www.southerngas.org
Probabilistic Analysis and Design Course
This one-week course provides information for engineers, scientists, and technical managers for managing uncertainty and risk of structural, mechanical, and other engineering systems using advanced probabilistic methods.
SwRI at (210) 522-6566 or click on website www.swri.org/psamsc
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