The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all of its components can be made much smaller than the diameter of the pipe to be inspected. For this reason, RFEC was chosen as a technology for unpiggable pipeline inspections by DOE-NETL with the support of OTD and PRCI, to be integrated with platforms selected by DOENETL. As part of the project, the RFEC laboratory facilities were upgraded and data collection was made nearly autonomous. The resulting improved data collection speeds allowed GTI to test more variables to improve the performance of the combined RFEC and platform technologies. Tests were conducted on 6-, 8-, and 12-inch seamless and seam-welded pipes. Testing on the 6-inch pipes included using seven exciter coils, each of different geometry with an initial focus on preparing the technology for use on an autonomous robotic platform with limited battery capacity. Reductions in power consumption proved successful. Tests with metal components similar to the Explorer II modules were performed to check for interference with the electromagnetic fields. The results of these tests indicated RFEC would be able to produce quality inspections while on the robot. Mechanical constraints imposed by the platform, power requirements,more » control and communication protocols, and potential busses and connectors were addressed. Much work went into sensor module design including the mechanics and electronic diagrams and schematics. GTI participated in two Technology Demonstrations for inspection technologies held at Battelle Laboratories. GTI showed excellent detection and sizing abilities for natural corrosion. Following the demonstration, module building commenced but was stopped when funding reductions did not permit continued development for the selected robotic platform. Conference calls were held between GTI and its sponsors to resolve the issue of how to proceed with reduced funding. The project was rescoped for 10-16-inch pipes with the intent of looking at lower cost, easier to implement, tethered platform applications. OTD ended its sponsorship.« less

The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all of its components can be made smaller than the diameter of the pipe to be inspected. For these reasons, RFEC was selected as a technology to be integrated with the Explorer II robotic platform for unpiggable pipeline inspections. The research work is a continuation of a prior DOE-NETL project but is now directed towards a seamless integration with the robot. The laboratory set-up has been improved and data collection is nearly autonomous. With the improved collections speeds, GTI has been able to test more variables. Tests have been run on 6-inch and 12-inch seamless and seam-welded pipes. Testing on the 6-inch pipes have included using five exciter coils, each of a different geometry. Two types of sensor coils have been tested. With a focus on preparing the technology for use on the Explorer II, improvements in power consumption have proved successful. Tests with metal components have been performed to check for interference with the electromagnetic field. The results of these tests indicate RFEC will produce quality inspections while on the robot. GTI has also been testing manufactured detection boards currently used for boiler tube inspections. These boards are appropriately compact for use on the Explorer II robot and are able to detect defects at the speed of robot travel. In addition to advanced sensor development, GTI has participated in sensor/platform definition and module design activities. Mechanical constraints, power requirements, limited control and communication protocols, and potential busses and connectors have been addressed. GTI has conducted a proper design process to produce a sound design for the RFEC components to fit into two modules. The remaining work to be performed in the design of the sensor module is packaging and strengthening.

In-line inspection tools cannot inspect most of the natural gas transmission pipelines and distribution mains due to restrictions in the pipelines that will not allow a tool equipped with current inspection technologies to pass. Remote field eddy current (RFEC) inspection is an excellent candidate for inspecting a pipeline with multiple diameters, valve and bore restrictions and tight or miter bends. The results of this paper show that the RFEC technique can inspect pipeline materials, and that all of the components needed for RFEC inspection can be made much smaller that the pipe diameter RFEC inspection is commercially available for inspecting small diameter piping without restrictions, several hundred feet at a time. The prototype design described in this paper shows this technology will work in a free-swimming tool that can inspect miles of pipeline at time and bypass restrictions.

Magnetic Flux Leakage (MFL) is currently the standard method of gas pipeline inspection in spite of the fact that the accuracy of MFL is only about 10%. Ultrasonic inspection has much better accuracy and is not sensitive to permeability changes but normally requires a liquid couplant to get sufficient energy into the pipe wall. Reported here are the laboratory results of Gas Technology Institute’s (GTI) effort to investigate newly developed transducers that use gas as the coupling media. The combination of transducers specifically designed for this application and high gain amplifiers produced signals strong enough to measure wall thickness in steel at pressures from 200 to 1000 PSIG. Investigations showed that both the sensitivity of the transducers and the gas-metal coupling are functions of pressure and, therefore, limit the useful pressure range. Tests were run in pulse-echo mode and pitch-catch mode to determine the advantages and limitations of each. The average ultrasonic wall thickness will be used to calibrate the MFL improving the accuracy of its measurements.

A summary assessment of the start-of-the-art for pipeline assessment technologies. It is a good primer for those new to pipeline inspection technologies. This is a final report from a PHMSA research project.

Stress corrosion cracking (SCC) is a complex phenomenon that involves various interacting physical and chemical processes. There is a combination of determinism and stochasticity that results in SCC colony evolution. A statistical model that generates a random field of corrosion pits and crack initiation at randomly selected pits is proposed in this work. A thermodynamic model of individual SC crack growth has been recently developed within the framework of the Crack Layer theory. Mathematical realization of the SC crack growth model is presented in the form of relations between the crack growth, hydrogen diffusion and corrosion rates on one hand and corresponding thermodynamic forces on the other. Experimental program for determination of the kinetic coefficients employed in crack growth equations is briefly reported. Finally, application of the individual crack growth law to random configuration of multiple cracks results in a simulation of SCC colony evolution, including a stage of the large-scale crack interaction. The solution of the crack interaction problem via FRANC2D Finite Element Methods results in a computer simulation of multi-crack cluster formation within the colony.

Stress corrosion cracking (SCC) is a complex phenomenon that involves various interacting physical and chemical processes. It has been most commonly found in the form of "colonies" of cracks where determinism and chance result in SCC colony development. A statistical model of a random field of corrosion pits formation and multiple crack initiation is proposed. A thermodynamic model of crack growth is also proposed within a framework of the Crack Layer theory. A SCC growth model is presented in the form of relations between crack growth rates, hydrogen diffusion and corrosion, together with corresponding thermodynamic forces kinetic coefficients employed in crack growth equations. Finally, application of the individual crack growth law to the multiple random crack configurations results in a simulation of SCC colony evolution..

The conditions under which a pit defect is formed in a pipe can influence local stress concentrations which, in turn, affect the Magnetic Flux Leakage (MFL) signal. In this study MFL, Magnetic Barkhausen Noise (MBN) and neutron diffraction (ND) techniques are used to monitor and compare the local stress distributions surrounding simulated pits in plate and pipeline samples. Our study shows two important findings. Firstly, mechanically machining of simulated corrosion pits creates considerable machining stresses around the defect Conversely, electrochemical machining (ECM) produces no measurable residual stresses. Secondly, all three techniques indicate that, provided stresses are high enough hr produce local yielding, there are significant differences in local stress concentrations depending on whether the pit was electrochemically machined prior to stress application or while the sample was under stress. The latter case is more relevant to pipelines which corrode whilst in service since operating line pressures normally produce pipe wall hoop stresses of up to 70% yield strength.

To advance the capability of nondestructive internal pipeline inspection devices, commonly called inspection pigs, two test bed vehicles have been built as test platforms for use in the GRI Pipeline Simulation Facility. This report describes the magnetic flux leakage test bed vehicle. Magnetic flux leakage was selected for a specific test bed vehicle implementation because it is the most commonly used in-line inspection technology for the detection of metal loss defects in gas-transmission pipelines. The other test bed vehicle is called the advanced sensor test bed vehicle, which can be used for experiments involving ultrasonics, eddy currents, electromagnetic acoustic transducers, or hybrid techniques. The magnetic flux leakage test bed vehicle was designed to simulate magnetic flux leakage technology, as well as advance the state of the art of the technology.

Magnetometer surveys above gas pipelines show stress induced magnetic anomalies at pipe bends. This suggests a potential technique for the noninvasive monitoring of stress in buried pipelines, etc. Laboratory measurements of the magnetic field changes due to the elastic bending of 110 mm diameter pipe are presented. The effects of orientation with respect to the earths field and of internal pressu...

Pipelines constructed on unstable terrain (e.g., permafrost), submarine lines, etc. may shift, producing stresses which can lead ultimately to rupture. We have used magnetometer surveys to detect bending stresses in buried pipelines and to monitor new construction. The perturbations to the earth’s field are large and complex; typically fluctuations of 5–10 kilogamma are found 2 m above 1 m diameter buried line. These signals record initial magnetisations, joints, construction history, etc. and include the results of stress induced magnetisation changes. The magnetostrictive effect in steel depends on field, stress, and cyclic history. There is little basic data on the inverse effect, stress induced changes in magnetization. In a pipeline the bending stress distribution is complex so that fringing field changes due to stress magnetisation changes are not calculable. However, experience now enables us to interpret some of the features of our magnetometer surveys. Since stress effects are large we are optimistic that we can eventually develop the technique for surveying pipelines for unusual stress concentrations.

Polycrystalline hydronium ββ″-alumina with f(β) of 0.16 to 0.25 has been fabricated with an electrical conductivity of ∼ 10−2 Ω−1cm−1 at 22°C and an activation energy of 0.24 eV (T < 100°C) and 0.09 eV (T > 100°C). This is comparable with single crystal behaviour. Proton magnetic resonance is correlated with conductivity and the effects of disorder on the conduction plane of the β″-alumina structure are shown to be important.

Neutrons scattered by the air between a sample and a detector array effectively increase the incoherent scattering cross section. A simple formula is derived which gives the required correction.

The Van Hove scattering function, S(Q,ω), has been measured for xenon gas at five state conditions along the 30 C isotherm using the time-of-flight correlation spectrometer at Oak Ridge National Laboratory (ORNL). The data are normalized by division of S(Q,ω) by the static structure factor so that at each Q value the normalized function has unit area: these curves are bell-shaped and are compared to two kinetic calculations by Dufty and Lindenfeld (unpublished). At the lowest density (0.185×1022 atom/cm3) the experimental data are consistent with the perfect gas and the two models. But at the highest density (0.458×1022 atom/cm3) the data probably differ significantly from these models.