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GUEST EDITORIAL

Rose Joseph L. Special Issue on the Nondestructive Evaluation of Pipeline and Vessel Structures J. Pressure Vessel Technol. 127, 213 (2005) (1 page);   doi:10.1115/1.1992499
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RESEARCH PAPERS

Miyasaka Chiaki, Tittmann Bernhard R. Acoustic Microscopy Applied to Ceramic Pressure Vessels and Associated Components J. Pressure Vessel Technol. 127, 214-219 (2005) (6 pages);   doi:10.1115/1.1990212

Alumina ceramic is being used extensively for external pressure vessels in naval applications. The material is also used in valves and other components, where reliability, immunity from corrosion, and high temperatures are required. This report presents a technique for the nondestructive evaluation of alumina ceramic components. The cracks were produced by CO2 laser radiation. Since there is a need for the detection of very fine cracks, scanning acoustic microscopy was found to be superior to optical methods for imaging surface and subsurface cracks. We address the issue of crack initiation with the use of postirradiation analysis. This article reports our results on the evaluation of the surface and interior cracks with optical, scanning laser, scanning electron, and scanning acoustic microscopy. We present images of surface and subsurface microcracks generated at different power levels of a high power CO2 laser system. The spatial variation of the Rayleigh wave velocity is measured by the V(z) curve technique. These preliminary data suggest that, with some improvement, the V(z) technique may detect residual stress with high spatial resolution.

Bray Don E., Vela John, Al-Zubi Raed S. Stress and Temperature Effects on Ultrasonic Properties in Cross-Linked and High Density Polyethylene J. Pressure Vessel Technol. 127, 220-225 (2005) (6 pages);   doi:10.1115/1.1990214

Cross-linked polyethylene is widely used in the manufacturing of rotationally molded tanks for the agriculture, petroleum, and chemical industries. These tanks are exposed to a number of environmental effects, which can lead to material degradation. Measuring ultrasonic wave speed change in the outer wall of the tank is a method that shows promise for evaluating the ultraviolet (UV) degradation effects. In order to evaluate the UV effects in the field, however, the effect of stress and temperature on the wave speed first must be established. A series of tests was performed to establish the ultrasonic properties in cross-linked as well as linear polyethylene at a range of temperatures from 6°Cto44°C (22°Fto112°F). The change is linear, as expected. For the stress tests, the velocity decreased with tension, also as expected. Tests were performed from approximately 689kPato9.6MPa(100to1400psi). Results from these tests were incorporated into the overall algorithm used for evaluating tank degradation.

Tittmann B. R. Sonic Pressure Vessel Sensor J. Pressure Vessel Technol. 127, 226-229 (2005) (4 pages);   doi:10.1115/1.1990208

A sensor method and apparatus are described for measuring the pressure of a gas within a sealed commercial pressure vessel mounted into an assembly. A sonic transducer is used to apply an oscillating force to the surface of a vessel. The frequency of the sonic wave is swept through a range which caused resonant vibrations of the gas in the vessel. A receiving transducer measures the amplitude of the resultant vibration at the vessel surface and reveals the resonant frequency of the gas at peaks in the amplitude of the sweep. The resonant frequency obtained depends upon the composition of the gas, its pressure and temperature and the shape of the confining vessels. These relationships can be predetermined empirically so that the pressure inside the vessel can be calculated when the composition of the gas, its temperature and shape of the confining vessel are known. The output of the receiver is fed into a computer which is programmed to calculate the pressure based upon these predetermined relationships which are stored in the computer.

Lee Min-Rae, Lee Joon-Hyun, Kim Jung-Teak. Condition Monitoring of a Nuclear Power Plant Check Valve Based on Acoustic Emission and a Neural Network J. Pressure Vessel Technol. 127, 230-236 (2005) (7 pages);   doi:10.1115/1.1991880

The analysis of acoustic emission (AE) signals produced during object leakage is promising for condition monitoring of the components. In this study, an advanced condition monitoring technique based on acoustic emission detection and artificial neural networks was applied to a check valve, one of the components being used extensively in a safety system of a nuclear power plant. AE testing for a check valve under controlled flow loop conditions was performed to detect and evaluate disk movement for valve degradation such as wear and leakage due to foreign object interference in a check valve. It is clearly demonstrated that the evaluation of different types of failure modes such as disk wear and check valve leakage were successful by systematically analyzing the characteristics of various AE parameters. It is also shown that the leak size can be determined with an artificial neural network.

Lozev M. G., Spencer R. L., Hodgkinson D. Optimized Inspection of Thin-Walled Pipe Welds Using Advanced Ultrasonic Techniques J. Pressure Vessel Technol. 127, 237-243 (2005) (7 pages);   doi:10.1115/1.1991876

In this paper an effective way to optimize the inspection of welds in thin-walled pipe less than 6 mm (0.24 in.) thick using automated ultrasonic testing (AUT) is described. AUT offers a better solution than radiography for detecting and sizing of planar defects. However, cap width, weld shrinkage and defect sizing put constraints on the actual ultrasonic approach for inspection of pipes with wall thickness less than 6 mm (0.24 in.). The applications of high-frequency single/multiprobe techniques and phased-array technology for inspection of thin-walled pipe welds have been investigated in this paper. It has been demonstrated that combining an advanced ultrasonic phased-array technique with a novel approach for modeling and simulation of ultrasonic inspection have potentially significant advantages for enhanced detectability, better sizing and improved flaw characterization of randomly oriented planar fabrication imperfections in thin-walled pipe welds.

Lozev M. G., Smith R. W., Grimmett B. B. Evaluation of Methods for Detecting and Monitoring of Corrosion Damage in Risers J. Pressure Vessel Technol. 127, 244-254 (2005) (11 pages);   doi:10.1115/1.1991877

Offshore pipeline failure statistics have been collected for more than 30 years now and illustrate that the riser predominantly fails as a result of corrosion. The consistent wetting and drying in the splash zone combined with defects in the coatings are the usual contributors to the problem. Risers are inspected at some determined frequency and can be done by internal and external methods. Inspecting by either means brings into account caveats and limitations from the technology used as well as human factors. For example, external inspections can be inefficient and inaccurate with some tools missing defects in areas of coating disbondment. In addition, internal inspections sometimes create false positives and can miss defects. These inaccuracies in the technologies or the techniques used may miss defects that eventually lead to failure. On the other hand, using corrosion mapping and fitness-for-service (FFS) assessment from the data collected, along with the inherent conservatism of this data from limited measurement accuracy, may result in the premature replacement of risers. A literature search is being conducted to review existing riser inspection methods and identify candidate nondestructive methods for riser inspection. These methods should be capable of detecting and monitoring general corrosion, localized corrosion pitting, and stress-corrosion cracking (sulfide or hydrogen induced) as external or internal corrosion damage. Thus far, this search has found that assessing the remaining service life of aging risers is largely dependent on the accuracy of analyzing corrosion damage to the riser surface in the atmospheric, splash (tidal), submerged, and buried environmental zones. The accuracy of each technology was analyzed. The capabilities and limitations of each method/technique used for riser inspection are summarized. The investigation is focused on long- and short-range ultrasonic techniques used for initial screening and corrosion mapping. These techniques can be deployed to detect a significant reduction in wall thickness using guided and torsional waves or to map accurately a corrosion damage using single/multiple transducers and phased-array probes in manual or automated mode. A pulsed eddy-current technique that uses a stepped or pulsed input signal for the detection of corrosion areas under insulation (CUI) is also being evaluated. This allows the detection of wall-thinning areas in the riser without removing the outside coatings. In addition, it is found that filmless, real-time, and digital radiography can be used to find internal and external corrosion defects in an insulated splash zone while the riser remains in service. A survey of nondestructive evaluation (NDE) manufacturing companies, NDE inspection companies, and operating companies was completed to collect information about current instrumentation and inspection/operators’ experience for riser inspection. Examples of advanced riser inspection instrumentation and field results are included. The ability of the candidate technologies to be adapted to riser variations, the stage of standardization, and costs are also discussed.

Reis Henrique, Ervin Benjamin L., Kuchma Daniel A., et al. Estimation of Corrosion Damage in Steel Reinforced Mortar Using Guided Waves J. Pressure Vessel Technol. 127, 255-261 (2005) (7 pages);   doi:10.1115/1.1989352

Corrosion of reinforced concrete is a chronic infrastructure problem, particularly in areas with deicing salt and marine exposure. To maintain structural integrity, a testing method is needed to identify areas of corroding reinforcement. For purposes of rehabilitation, the method must also be able to evaluate the degree, rate, and location of damage. Toward the development of a wireless embedded sensor system to monitor and assess corrosion damage in reinforced concrete, reinforced mortar specimens were manufactured with seeded defects to simulate corrosion damage. Taking advantage of waveguide effects of the reinforcing bars, these specimens were then tested using an ultrasonic approach. Using the same ultrasonic approach, specimens without seeded defects were also monitored during accelerated corrosion tests. Both the ultrasonic sending and the receiving transducers were mounted on the steel rebar. Advantage was taken of the lower frequency (<250kHz) fundamental flexural propagation mode because of its relatively large displacements at the interface between the reinforcing steel and the surrounding mortar. Waveform energy (indicative of attenuation) is presented and discussed in terms of corrosion damage. Current results indicate that the loss of bond strength between the reinforcing steel and the surrounding concrete can be detected and evaluated.

Baskaran G., Balasubramaniam K., Krishnamurthy C. V., et al. Ray Based Model for the Ultrasonic Time-of-Flight Diffraction Simulation of Thin Walled Structure Inspection J. Pressure Vessel Technol. 127, 262-268 (2005) (7 pages);   doi:10.1115/1.1989353

It is necessary to size the cracklike defects accurately in order to extend the life of thin-walled (<10mm) components (such as pressure vessels) particularly for aerospace applications. This paper discusses the successful application of ray techniques to simulate the ultrasonic time-of-flight diffraction experiments for platelike structures. For the simulation, the diffraction coefficients are computed using the geometric diffraction theory. The A and B scans are simulated in near real time and the different experimental parameters can be interactively controlled due to the computational efficiency of the ray technique. The simulated results are applied to (1) defect signal identification for vertical defects, (2) inspection of inclined defects, and (3) study the effect of pulse width or probe frequency on experimental results. The simulated results are compared with laboratory scale experimental results.

Teitsma Albert, Takach Stephen, Maupin Julie, et al. Small Diameter Remote Field Eddy Current Inspection for Unpiggable Pipelines J. Pressure Vessel Technol. 127, 269-273 (2005) (5 pages);   doi:10.1115/1.1991878

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.

Nestleroth J. Bruce, Davis Richard J. The Design of a Mechanical Damage Inspection Tool Using Dual Field Magnetic Flux Leakage Technology J. Pressure Vessel Technol. 127, 274-283 (2005) (10 pages);   doi:10.1115/1.1989349

This paper describes the design of a new magnetic flux leakage (MFL) inspection tool that performs an inline inspection to detect and characterize both metal loss and mechanical damage defects. An inspection tool that couples mechanical damage assessment as part of a routine corrosion inspection is expected to have considerably better prospects for application in the pipeline industry than a tool that complicates existing procedures. The design is based on study results that show it is feasible to detect and assess mechanical damage by applying a low magnetic field level in addition to the high magnetic field employed by most inspection tools. Nearly all commercially available MFL tools use high magnetic fields to detect and size metal loss such as corrosion. A lower field than is commonly applied for detecting metal loss is appropriate for detecting mechanical damage, such as the metallurgical changes caused by impacts from excavation equipment. The lower field is needed to counter the saturation effect of the high magnetic field, which masks and diminishes important components of the signal associated with mechanical damage. Finite element modeling was used in the design effort and the results have shown that a single magnetizer with three poles is the most effective design. Furthermore, it was found that for the three-pole system the high magnetization pole must be in the center, which was an unexpected result. The three-pole design has mechanical advantages, including a magnetic null in the backing bar, which enables installation of a pivot point for articulation of the tool through bends and restrictions. This design was prototyped and tested at Battelle’s Pipeline Simulation Facility (West Jefferson, OH). The signals were nearly identical to results acquired with a single magnetizer reconfigured between tests to attain the appropriate high and low field levels.

Kwun Hegeon, Kim Sang Young. Magnetostrictive Sensor for Generating and Detecting Plate Guided Waves J. Pressure Vessel Technol. 127, 284-289 (2005) (6 pages);   doi:10.1115/1.1991874

The development of a magnetostrictive sensor for generating and detecting guided waves in ferromagnetic plate is described. The sensor consists of a channel-shaped core and coils wound around the core along its length. It is shown that the sensor is capable of generating and detecting both the symmetric and antisymmetric Lamb wave modes and the shear horizontal wave modes in plates. It is also found that the beam pattern produced by the sensor follows the pattern expected for a line source in a two-dimensional medium.

Topics: Sensors , Waves , Probes , Signals
Shuttleworth Paul, Maupin Julie, Teitsma Albert. Gas Coupled Ultrasonic Measurement of Pipeline Wall Thickness J. Pressure Vessel Technol. 127, 290-293 (2005) (4 pages);   doi:10.1115/1.1991875

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.

Rizzo Piervincenzo, Bartoli Ivan, Marzani Alessandro, et al. Defect Classification in Pipes by Neural Networks Using Multiple Guided Ultrasonic Wave Features Extracted After Wavelet Processing J. Pressure Vessel Technol. 127, 294-303 (2005) (10 pages);   doi:10.1115/1.1990213

This paper casts pipe inspection by ultrasonic guided waves in a feature extraction and automatic classification framework. The specific defect under investigation is a small notch cut in an ASTM-A53-F steel pipe at depths ranging from 1% to 17% of the pipe cross-sectional area. A semi-analytical finite element method is first used to model wave propagation in the pipe. In the experiment, reflection measurements are taken and six features are extracted from the discrete wavelet decomposition of the raw signals and from the Hilbert and Fourier transforms of the reconstructed signals. A six-dimensional damage index is then constructed, and it is fed to an artificial neural network that classifies the size and the location of the notch. Overall, the wavelet-based multifeature analysis demonstrates good classification performance and robustness against noise and changes in some of the operating parameters.

Zhao Xiaoliang, Varma Venugopal K., Mei Gang, et al. In-Line Nondestructive Inspection of Mechanical Dents on Pipelines With Guided Shear Horizontal Wave Electromagnetic Acoustic Transducers J. Pressure Vessel Technol. 127, 304-309 (2005) (6 pages);   doi:10.1115/1.1991879

Circumferential guided ultrasonic Shear Horizontal (SH) wave Electromagnetic Acoustic Transducer (EMAT) pairs mounted on a mobile fixture in a through-transmission mode were used for detection and characterization of mechanical dents on the outer surface of a pipe wall from inside the pipe. The dents were created on a 12 in. diameter standard seamless steel pipe by hydraulically pressing steel balls of various sizes into the pipe wall. n1 mode SH wave was directed through and along the wall of the pipe. Multiple measurements were obtained both from the dents and from the no-flaw region of the pipe using the EMAT pair. Dent features were extracted with a Principal Component Analysis (PCA) technique and classified into “cup” and “saucer” types using Discriminant Analysis (DA). The overall approach is able to detect and classify dents of depth 25% through wall or deeper, which should meet the needs of the pipeline safety inspection community (U.S. Department of Transportation, Research and Special Program Administration). Preliminary dent depth estimation potential is also shown via an amplitude correlation approach.

Rose Joseph L., Zhang Li, Avioli Michael J., et al. A Natural Focusing Low Frequency Guided Wave Experiment for the Detection of Defects Beyond Elbows J. Pressure Vessel Technol. 127, 310-316 (2005) (7 pages);   doi:10.1115/1.1989350

Long range ultrasonic guided wave inspection is advancing rapidly and is quite commonplace today. Benefits of using longitudinal or torsional modes are being established in special circumstances of improved sensitivity, resolution, or penetration power. The possibility of inspection under insulation, coatings, or with water filled pipes or around elbows is possible. Detection of defects beyond a pipe elbow is difficult for axisymmetric wave impingement onto the elbow. For nonaxisymmetric input to the elbow region, however, via partial loading around the circumference, natural focusing occurs because of angular profile variation around the circumference of the pipe. Sample computations of possible angular profiles are illustrated. An experiment is also reported here to demonstrate this inspection process.

Hayashi Takahiro, Kawashima Koichiro, Sun Zongqi, et al. Guided Wave Focusing Mechanics in Pipe J. Pressure Vessel Technol. 127, 317-321 (2005) (5 pages);   doi:10.1115/1.1990209

Guided waves can be used in pipe inspection over long distances. Presented in this paper is a beam focusing technique to improve the SN ratio of the reflection from a tiny defect. Focusing is accomplished by using nonaxisymmetric waveforms and subsequent time delayed superposition at a specific point in a pipe. A semianalytical finite element method is used to present wave structure in the pipe. Focusing potential is also studied with various modes and frequencies.

Topics: Waves , Pipes
Hayashi Takahiro, Kawashima Koichiro, Sun Zongqi, et al. Guided Wave Propagation Mechanics Across a Pipe Elbow J. Pressure Vessel Technol. 127, 322-327 (2005) (6 pages);   doi:10.1115/1.1990210

Wave propagation across a pipe elbow region is complex. Subsequent reflected and transmitted waves are largely deformed due to mode conversions at the elbow. This prevents us to date from applying guided waves to the nondestructive evaluation of meandering pipeworks. Since theoretical development of guided wave propagation in a pipe is difficult, numerical modeling techniques are useful. We have introduced a semianalytical finite element method, a special modeling technique for guided wave propagation, because ordinary finite element methods require extremely long computational times and memory for such a long-range guided wave calculation. In this study, the semianalytical finite element method for curved pipes is developed. A curved cylindrical coordinate system is used for the curved pipe region, where a curved center axis of the pipe elbow region is an axis (z axis) of the coordinate system, instead of the straight axis (z axis) of the cylindrical coordinate system. Guided waves in the z direction are described as a superposition of orthogonal functions. The calculation region is divided only in the thickness and circumferential directions. Using this calculation technique, echoes from the back wall beyond up to four elbows are discussed.

Demma A., Cawley P., Lowe M., et al. The Effect of Bends on the Propagation of Guided Waves in Pipes J. Pressure Vessel Technol. 127, 328-335 (2005) (8 pages);   doi:10.1115/1.1990211

The practical testing of pipes in a pipe network has shown that there are issues concerning the propagation of ultrasonic guided waves through bends. It is therefore desirable to improve the understanding of the reflection and transmission characteristics of the bend. First, the dispersion curves for toroidal structures have been calculated using a finite element method, as there is no available analytical solution. Then the factors affecting the transmission and reflection behavior have been identified by studying a straight-curved-straight structure both numerically and experimentally. The frequency dependent transmission behavior obtained is explained in terms of the modes propagating in the straight and curved sections of the pipe.

Topics: Waves , Pipes
Mondal Shyamal C., Wilcox Paul D., Drinkwater Bruce W. Design of Two-Dimensional Ultrasonic Phased Array Transducers J. Pressure Vessel Technol. 127, 336-344 (2005) (9 pages);   doi:10.1115/1.1991873

Two-dimensional (2D) phased arrays have the potential to significantly change the way in which engineering components in safety critical industries are inspected. In addition to enabling a three-dimensional (3D) volume of a component to be inspected from a single location, they could also be used in a C-scan configuration. The latter would enable any point in a component to be interrogated over a range of solid angles, allowing more accurate defect characterization and sizing. This paper describes the simulation and evaluation of grid, cross and circular 2D phased array element configurations. The aim of the cross and circle configurations is to increase the effective aperture for a given number of elements. Due to the multitude of possible array element configurations a model, based on Huygens’ principle, has been developed to allow analysis and comparison of candidate array designs. In addition to the element configuration, key issues such as element size, spacing, and frequency are discussed and quantitatively compared using the volume of the 3D point spread function (PSF) as a measurand. The results of this modeling indicate that, for a given number of elements, a circular array performs best and that the element spacing should be less than half a wavelength to avoid grating lobes. A prototype circular array has been built and initial results are presented. These show that a flat bottomed hole, half a wavelength in diameter, can be imaged. Furthermore, it is shown that the volume of the 3D reflection obtained experimentally from the end of the hole compares well with the volume of the 3D PSF predicted for the array at that point.

Luo Wei, Zhao Xiaoliang, Rose Joseph L. A Guided Wave Plate Experiment for a Pipe J. Pressure Vessel Technol. 127, 345-350 (2005) (6 pages);   doi:10.1115/1.1989351

The plate approximation of a pipe is a topic discussed for decades. Rules have been established to make the comparisons. Presented here is a related topic, but one to answer the question of whether an easy-to-conduct plate experiment can be used to predict what happens in a pipe for ultrasonic guided wave. For longitudinal guided waves in a pipe, the approximation is valid clearly only over a very short distance or inordinate closeness to a defect for wave scattering analysis; but for circumferential guided waves, the validity is unclear and therefore it is worthwhile to study criteria on the approximation and simplification of a pipe experiment as a plate experiment by means of wave mechanics analysis and modeling computation. Circumferential shear horizontal (SH) waves in pipes and SH waves in plates were studied in this paper toward this goal and it was found that the wave frequency and wall thickness to radius ratio were the two key parameters with respect to the similarity. Dispersion curves and wave structures of the SH waves in plates and in pipes were compared to find the origin of the similarity. Experimental simulations and modeling with boundary element methods were also carried out for the reflection and transmission coefficients of the SH waves impinging into a defect, from which some criteria have been established for the plate model approximation. Although a pipe model is more accurate for pipe experiments, a plate model often gives a quick and reasonable solution especially when it is difficult to establish a pipe model.

TECHNOLOGY REVIEW

Moles Michael, Dubé Noël, Labbé Simon, et al. Review of Ultrasonic Phased Arrays for Pressure Vessel and Pipeline Weld Inspections J. Pressure Vessel Technol. 127, 351-356 (2005) (6 pages);   doi:10.1115/1.1991881

Major improvements in weld inspection are obtained using Phased Array technology with capability for beam steering, electronic scanning, focusing, and sweeping the ultrasonic beams. Electronic scanning is much faster than raster scanning, and can optimize angles and focusing to maximize defect detection. Pressure vessel (PV) inspections typically use “top, side, end” or “top, side, TOFD” views, though other imaging is possible. Special inspections can be performed, e.g., for specific defects, or increased coverage. Defects can be sized by pulse-echo as per code, by time-of-flight Diffraction or by back diffraction. New PV inspection codes, particularly ASME Code Case 2235, permit the use of advanced ultrasonic inspection techniques. Pipeline girth weld inspections use a unique inspection approach called “zone discrimination,” and have their own series of codes. While similar equipment is used in pipeline as in PV inspections, the pipeline philosophy is to tailor the inspection to the weld profile and predicted lack of fusion defects. Pipeline displays are specifically designed for near real-time data analysis. Both ASME CC 2235 and the pipeline codes permit the use of Fitness-For-Purpose, which reduces construction costs. Overall, phased array systems meet or exceed all PV and pipeline codes.

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