An Overview of GMAW Including Applications, Common Problems and Solutions

Gas Metal Arc Welding (GMAW) is said to be one of the easiest welding processes to learn and use. Because of its high deposition rates and little post-weld cleaning required, GMAW is a popular choice for a variety of applications including almost all commercially important metals. Another factor contributing to the widespread use of GMAW is the various modes of metal transfer including short circuit, spray, surface tension transfer (STT), etc. These different modes of transfer enable GMAW to be tailored to different situations. For instance, some applications may require deep penetration or other applications may be for welding very thin sections. However, these factors along with others may result in inferior welds if not monitored closely. Problems such as weld porosity, lack of fusion, and lack of shielding gas coverage can all lead to inadequate welds which can lead to larger problems if not corrected. Many common drawbacks to the GMAW process can be remedied quite easily with proper time and attention. Taking the time and effort to produce a sound weld may, however, negate the superior deposition rates of GMAW thereby limiting its use to fewer applications. This welding process can be extremely effective when used properly. However, the key is to not sacrifice weld quality for the sake of production. GMAW applications, modes of transfer, along with common problems and solutions associated with the process will all be discussed and detailed.

Qualification of Portable Phased Arrays to ASME Section V

This paper describes the processes required to approve new and advanced inspection techniques for ASME Section V, specifically for Olympus NDT’s OmniScan portable phased array unit. The rationale and processes required for Section V, both Article 4 and the new Article 14 for advanced techniques, is described. The various processes are applied to encoded electronic scanning (i.e. fixed angle raster scanning, or E-scans); the same processes can be applied to encoded Sectorial scans (S-scans) where the beam is swept through a range of angles, and manual S- and E-scans. A variety of techniques, procedures, methodology and reporting documents have been developed for phased arrays. In addition, an update is given on other code developments.

Experimental Research and Application of UT Inspection Method for Detection of Defects on Pressure Vessels and Pipelines Under High-Temperature Environment

High temperature UT inspection techniques can be used to conduct random inspection on line on the key locations of pressure vessels and pipelines in operation so as to find out fresh defects in time and determine inspection time. It can also be used for real-time monitoring and control of defect-containing pressure vessels and pipelines and provide a basis for safety assessment of equipment so as to ensure safe operation of pressure vessels and pipelines. The propagation velocity of ultrasonic wave in metallic pressure-bearing equipment and its amplitude vary with temperature, therefore, the factors that influence UT inspection ability and measuring accuracy will be increased. In this paper the variation in sound velocity and attenuation law of ultrasonic shear wave in common pressure vessels and pipelines in the range of room temperature ∼ 450 °C is studied, the sound velocity decreases linearly as temperature rises and the attenuation coefficient α decreases as temperature rises, from 0.006 dB/mm at room temperature to 0.08dB/mm at 450 °C. The factors that influence inspection accuracy of ultrasonic shear wave are discussed, including variation in sound velocity, loss in interface sound pressure, thermal expansion, and so forth. The method for detection of weld defects within above temperature range using the ultrasonic shear wave is established, including scanning manner, measurement of defect height and length and their position correction, and so forth. The present situation of online high-temperature UT inspection technology for pressure vessels and pipelines in China is summarized through online UT inspection examples of petrochemical equipment under local high-temperature environment.

Risk-Based Inspection Analysis for High Pressure Hydrogenation Cracking Unit

High pressure hydrogenation cracking unit is the core equipment system in the aromatic plant, which is subjected simultaneously to the action of hydrogen and high pressure and high temperature. In this paper, quantitative analysis method of RBI was carried out by Orbit-Onshore software, which was developed by DNV corporation. In API 581, the risk situation for a certain equipment unit were classified into four grades, such as low risk grade and medium risk grade and medium-high risk grade and high grade, which is expressed as risk matrix. The whole risk distribution of 553 equipment and piping items was obtained, and in which the hydrocracking reactors and the reactor effluent air coolers are belong to ‘medium-high risk’ grade. Based on the RBI results, an optimum inspection plan was developed by the author to reduce the risk level for the hydrogenation cracking unit. It is concluded that the optimum inspection plan was completely satisfied with the engineering specification of the aromatic plant, after the validation of the inspection activity in 2004.

Special Phased Array Applications for Pipeline Girth Weld Inspections

Ultrasonic phased arrays present major improvements over conventional multiprobe ultrasonics for inspecting pipeline girth welds, both for onshore and for offshore use. Probe pans are lighter and smaller, permitting less cutback; scans are quicker due to the smaller probe pan; phased arrays are considerably more flexible for changes in pipe dimensions or weld profiles, and for different scan patterns. More important, some of the potential advantages of phased arrays are now becoming commercially available. These include: • Compensating for variations in seamless pipe wall thickness. • Wedge temperature compensation. • Improved focusing for thick and thin wall inspections. • Premium inspections for risers, tendons and other components. • Small diameter pipes. • Multiple displays. • Clad pipe. The paper describes the latest phased array UT results for special applications.

2D Natural Convection and Radiation Heat Transfer Simulations of a PWR Fuel Assembly Within a Constant Temperature Support Structure

Two-dimensional simulations of steady natural convection and radiation heat transfer for a 14×14 pressurized water reactor (PWR) spent nuclear fuel assembly within a square basket tube of a typical transport package were conducted using a commercial computational fluid dynamics package. The assembly is composed of 176 heat generating fuel rods and 5 larger guide tubes. The maximum cladding temperature was determined for a range of assembly heat generation rates and uniform basket wall temperatures, with both helium and nitrogen backfill gases. The results are compared with those from earlier simulations of a 7×7 boiling water reactor (BWR). Natural convection/radiation simulations exhibited measurably lower cladding temperatures only when nitrogen is the backfill gas and the wall temperature is below 100°C. The reduction in temperature is larger for the PWR assembly than it was for the BWR. For nitrogen backfill, a ten percent increase in the cladding emissivity (whose value is not well characterized) causes a 4.7% reduction in the maximum cladding to wall temperature difference in the PWR, compared to 4.3% in the BWR at a basket wall temperature of 400°C. Helium backfill exhibits reductions of 2.8% and 3.1% for PWR and BWR respectively. Simulations were performed in which each guide tube was replaced with four heat generating fuel rods, to give a homogeneous array. They show that the maximum cladding to wall temperature difference versus total heat generation within the assembly is not sensitive to this geometric variation.

Detonation Chamber of Chemical Munitions: Its Design Philosophy and Operation Record at Kanda, Japan

Destruction of chemical weapons is a technical area that involves extensive international cooperation, with open discussion among a wide variety of participants aimed at elimination of these weapons of mass destruction. The most common methods for destruction of chemical weapons are: (1) chemical neutralization and (2) incineration after separation of the chemical agent from the weapon’s explosive charge. When the munitions are stockpiled, the agent and the explosive charge are easily separated by means of reverse assembly or water jet cutting. However, for munitions that are not stockpiled, complete separation of agent and explosive charge is nearly impossible.

Hydrodynamic Modeling of Detonations for Structural Design of Containment Vessels

Los Alamos National Laboratory (LANL), under the auspices of the U.S. Department of Energy (DOE) and the National Nuclear Security Administration (NNSA), has been conducting confined high explosion experiments utilizing large, spherical, steel pressure vessels to contain the reaction products and hazardous materials from high-explosive (HE) events. Structural design of these spherical vessels was originally accomplished by maintaining that the vessel’s kinetic energy, developed from the detonation impulse loading, be equilibrated by the elastic strain energy inherent in the vessel. In some cases, the vessel is designed for one-time use only, efficiently utilizing the significant plastic energy absorption capability of ductile vessel materials [1]. Alternatively, the vessel can be designed for multiple use, in which case the material response is restricted to the elastic range [2]. Within the last decade, designs have been accomplished utilizing sophisticated and advanced 3D computer codes that address both the detonation hydrodynamics and the vessel’s highly nonlinear structural dynamic response. This paper describes the hydrodynamic modeling of HE reaction products phase, which produces transient pressures resulting in an impulsive load on the vessel shell. Modeling is accomplished through either (a) empirical/analytical methods utilizing a vast experimental database developed primarily for the Department of Defense (DoD) or (b) through application of numerical hydrodynamics codes, such as the Sandia National Laboratories (SNL) shock-wave physics code, CTH [3], which accurately model the thermochemistry and thermophysics of a detonation. It should be noted that this paper only addresses blast load prediction using the methods stated and does not include an assessment of structural response methods.

Phased Array UT Application for Boiling Water Reactor In-Vessel Inspection

This paper describes development and application of Phased Array Ultrasonic Testing (UT) and Remotely Operated Vehicles (ROV) for In-Vessel Internals Inspection. Stress Corrosion Crack (SCC) on reactor internals is one of the most important issues since 1990s, and demand to inspect the reactor internals is increasing. Instrument manufactures and inspection venders have developed and applied 1) Phased Array UT technologies and technique as one of our Non-Destructive Examination (NDE) technologies, 2) several kinds of ROVs and special tools for probe delivery and positioning. They are available and effective in In-Vessel Inspection (IVI) and maintenance, which shall be conducted in the narrow room under water. Furthermore, the UT technique for Alloy 182 weld that used to be difficult to detect and size flaws was developed and deployed in the BWR IVI. UT experiences in reactor vessels are increasing in recent years. An immersion technique by Phased Array UT is a key to perform the In-vessel UT on a complex geometric surface to be inspected, and to achieve very wide accessible range by ROVs or simple special tools efficiently. Advantages of the water immersion method and a ROV development result are shown in this paper. Particularly, TOSHIBA developed a flat type ROV for Shroud (Shroud ROV), which can be held against the surface of the shroud by thrusting propellers and scan mechanically through narrow gap within 2 inches {50mm}. The ROV’s positioning accuracy and applications for Shroud UT are shown. As the field experience, this introduces the UT results for CRD Stub tube Alloy 182 weld that is located on the vessel bottom head in Hamaoka UNIT 1 of Chubu Electric Power Company in Japan. An axial SCC flaw was detected by underwater visual testing, after the CRD stub tube leakage was detected. Then UT examination for the flaw was accomplished on the Alloy 182 weld in the vessel. We evaluated that the flaw penetrated into the weld metal of the CRD stub tube-pat weld and didn’t propagate into the low alloy of Reactor Pressure Vessel base metal. After UT sizing, the CRD stub tube was removed and replaced. The examination result was proven to have a good agreement with the actual crack depth. As a result, the efficiency of our Phased Array Technique was confirmed. As the other immersion method application, UT coverage example and accessible range for Shroud inspection are shown.

Research and Development of Earthquake Isolation System Using Vertically Utilized Coiled Spring

This paper describes the research and development of new type of the isolation systems suitable for various structures. Basic concept of the new isolation system is to realize cost effective design without any reduction in the isolation performance. This paper presents results obtained from experimental and analytical studies to evaluate isolation performances of newly developed the isolation system. In the experiment, static tests were first carried out using a 0.20 scale model (55 kg mass, and 0.50 m × 0.50 m × 0.27 m size) for isolated-light-weight-structures model which was supported by two linear ball bearings and, restoring force was provided to superstructure by transversal stiffness of a coiled spring, so as to examine restoring force characteristic of the coiled spring. Second, dynamic tests were implemented in order to investigate the isolation performance of the isolation system against several actual seismic inputs. In analysis, seismic response analyses for the scale model, regarding the vibration tests using the actual seismic wave, were carried out to evaluate the response analytical method for the isolation system using the coiled spring. From these results, the followings are clarified. (1) Analytical results for the isolated light-weight-structures model agree well with experiment results. (2) The newly developed seismic isolation system using the coiled spring reduced response accelerations of the light-weight-structures sufficiently.