Detonation and Transition to Detonation in Partially Water-Filled Pipes

Detonations and deflagration-to-detonation transition (DDT) are experimentally studied in horizontal pipes which are partially filled with water. The gas layer above the water is stoichiometric hydrogen-oxygen at 1 bar. For detonation cases, ignition and transition occur outside of the water-filled section. For DDT cases, ignition and transition occur over the surface of the water. Pressure and hoop strain are measured incrementally along the pipe, with pressure transducers located both above and below the water. The detonation wave produces an oblique shock train in the water, and the curvature of the pipe is seen to focus the shocks at the bottom, resulting in peak pressures that are 4–6 times higher than the peak detonation pressure. Such pressure amplification is observed for water depths of 0.25, 0.5, 0.75, 0.87, and 0.92 pipe diameters. For a water depth of 0.5 diameters, pressure is also recorded at several circumferential locations in order to measure the shock focusing phenomenon. Peak hoop strains are found to decrease with increasing water depth, and transition to detonation is seen to occur for water depths as high as 0.92 pipe diameters.

Intense X-Ray Measurement of Transient Hydraulic Phenomena in Molten Pool During Laser Welding Process

Spatial temperature distribution during the laser welding process has a huge effect on any residual stress distribution. Therefore, understanding of the transient hydraulic phenomena which affect the temperature distribution in the molten pool is very important. In this work, intense X-ray measurement at the Super Photon ring-8 GeV (SPring-8) facility well carried out to document the transient hydraulic phenomena in the molten pool during the laser welding process. Based on in-situ observation of inside material, the experimental results confirmed that the molten pool shapes, hydraulic condition such as flow velocity, etc.. In the case of laser power is 330W and spot diameter is 1mm, we observed the steady flow which consisted of downward flow and upward flow. The flow velocities were about 19.5 mm/s and 9.0 mm/s, respectively. Moreover, the rate of phase change was obtained from molten pool shape during laser welding. The rate of phase change was not constant during laser welding. Thus the interface shape might change at all time. Therefore, to evaluate the temperature distribution, it is necessary to consider not only convection but also the interface shape. These results indicate that the intense X-ray measurement during laser welding is very effective for the understanding the molten pool phenomena.

Submerged Pressure Vessel Testing Hazards

It is common practice to proof test high pressure vessels prior to their use in the field. One technique for leak testing these vessels is submersion in water. A test failure at high pneumatic pressure and can pose several hazards to nearby personnel, such as projectile launch and blast loads. Submerged underwater testing can provide some level of protection from these hazards. However, it is largely unknown how much water cover is needed to prevent a projectile from escaping. The purpose of this test program was to record the mitigating effects of water on hazards caused by a sudden pressure vessel failure. The test program entails submerging a pressure vessel underwater inside a tank. The vessel is then pressurized to failure, releasing a blast wave and launching a projectile. The event is recorded using high speed photography which is used to observe the effects of the gas release and the projectile motion. A discussion of the test events and associated physics is provided.

Kendall Analysis of Cannon Pressure Vessels

Engineering mechanics analysis of cannon pressure vessels is described with special emphasis on the work of the late US Army Benet Laboratories engineer David P. Kendall. His work encompassed a broad range of design and analysis of high pressure vessels for use as cannons, including analysis of the limiting yield pressure for vessels, the autofrettage process applied to thick vessels, and the fatigue life of autofrettaged cannon vessels. Mr. Kendall’s work has become the standard approach used to analyze the structural integrity of cannon pressure vessels at the US Army Benet Laboratories. The methods used by Kendall in analysis of pressure vessels were simple and direct. He used classic results from research in engineering mechanics to develop descriptive expressions for limiting pressure, autofrettage residual stresses and fatigue life of cannon pressure vessels. Then he checked the expressions against the results of full-scale cannon pressure vessel tests in the proving grounds and the laboratory. Three types of analysis are described: [i] Yield pressure tests of cannon sections compared with a yield pressure expression, including in the comparison post-test yield strength measurements from appropriate locations of the cannon sections; [ii] Autofrettage hoop residual stress measurements by neutron diffraction in cannon sections compared with expressions, including Bauschinger corrections in the expressions to account for the reduction in compressive yield strength near the bore of an autofrettaged vessel; [iii] Fatigue life tests of cannons following proving ground firing and subsequent laboratory simulated firing compared with Paris-based fatigue life expressions that include post-test metallographic determination of the initial crack size due to firing. Procedures are proposed for Paris life calculations for bore-initiated fatigue affected by crack-face pressure and notch-initiated cracking in which notch tip stresses are significantly above the material yield strength. The expressions developed by Kendall and compared with full-scale cannon pressure vessel tests provide useful first-order design and safety checks for pressure vessels, to be followed by further engineering analysis and service simulation testing as appropriate for the application. Expressions are summarized that are intended for initial design calculations of yield pressure, autofrettage stresses and fatigue life for pressure vessels. Example calculations with these expressions are described for a hypothetical pressure vessel.

Remote Field Eddy Current Testing Technology for Ferromagnetic Heat Exchanger Tubes

As a conventional NDT method, eddy Current testing (ET) has been greatly developed both in instrumentation and technique in recent years. Remote Field Eddy Current Testing (RFET) is a representation of this advancement. The principle of RFET and the composition of the testing system are detailedly discussed in this paper. And then, its application in the ferromagnetic heat exchanger tubes is described simply.

Effectiveness of AE On-Line Testing Results of Atmospheric Vertical Storage Tank Floors

By comparing acoustic emission (AE) online inspection results of vertical tank floors with validation testing results by other methods including magnetic flux leakage (MFL), visual examination (VT), Magnetic Particle Testing (MT) or Penetrant Testing (PT), vacuum leak detection or destructive cutting, the dependability and precision of AE inspection results are analyzed, and the successful experience of AE online testing of atmospheric tank floors is summarized.

Experimental Study on a Multiple-Use Spherical Containment Vessel

In this paper, we present experimental results of three explosion tests performed on a multiple-use spherical containment vessel, which has been employed to withstand internal blast loading from 25 kg TNT high explosive in the past ten years. The experimental observations of the blast loading and the vessel response histories are compared, and it can be found that the remarkable strain increase occurs in the second response cycle of the strain-time history may be caused by the effect of the reflected shock wave. The occurrence of strain growth at different locations of the vessel are specially concerned, and details on the vibration modes and frequency spectra of the spherical vessel are investigated. Based on the present experimental results and the previous theories, three possible mechanisms of strain growth are discussed, which leads to a conclusion that the effect of reflected shock waves, modal superposition and nonlinear modal coupling may all contribute to strain growth.

Quantitative Risk Analysis of Hydrogen Events at WTP: Part 2 of 2 — Development of Event Frequency-Severity Model

In late 2008, a Hydrogen in Piping and Ancillary Vessels (HPAV) Assessment Team was chartered by the U.S. Department of Energy’s (DOE) Office of River Protection (DOE-ORP) to investigate the extent of operational complexity in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) due to conservatisms in hydrogen event analysis methodology and related design constraints. The HPAV Assessment Team recommended that a Quantitative Risk Analysis (QRA) be performed to analyze normal plant operating and upset conditions that can lead to accumulation of hydrogen in piping, and determine the frequency and severity of ensuing postulated hydrogen events such that WTP can make risk-informed decisions regarding hydrogen event mitigation strategies and improve operational flexibility. The QRA application is based on an in-depth review of hydrogen event-affected systems conducted by an interdisciplinary team of system engineers, process engineers, plant operations modelers, operators, and safety personnel to ensure facility ownership of the overall process. The QRA evaluates hydrogen event-affected systems for both normal system operations and possible upset conditions as a result of internal and external events (including human error). The Operational Frequency Analysis (OFA) and Event Progression Logic (EPL) analysis provide an integrated framework for the analysis of initiating events from which hydrogen accumulation can occur and the quantitative analysis of the physical progression of ensuing hydrogen ignition events. The purpose of this paper is to describe the QRA methodology, models, and testing used to quantify the system demand resulting from postulated hydrogen event types, frequencies, and severities, with emphasis on the latter stages of the QRA, overall execution and application.

Basic Characteristics of Eddy Current Testing Using Resonant Coupling

It has been demonstrated that magnetic resonant coupling is effective for improving the characteristics of ECT sensor, especially the lift-off-dependent reduced sensitivity and noise. The lift-off-dependent reduced sensitivity and noise are caused by the decrease of voltage gain from the exciter coil to detector coil. Magnetic resonant coupling is generally usable to increase the voltage gain from the transmitter coil to the receiver coil. Magnetic resonant coupling was applied to ECT in these experiments to investigate the phenomena of magnetic resonant coupling in the ECT. In the ECT setup, the voltage gain G increased more than 6 times by magnetic resonant coupling at a frequency of 105 kHz. The voltage gain ratio (GR/GNR) was rising 1.12 times when the lift-off length increased from 1mm to 2 mm. This result verified that magnetic resonant coupling has the potential for improving the characteristics of ECT. The EDM slit signal and the lift-off noise were calculated from the experimental results, respectively. Using magnetic resonant coupling, the EDM slit signal increased 1.5 times and the lift-off noise was reduced by 34 % at a lift-off length of 2mm. these results confirmed that magnetic resonant coupling is effective for improving the characteristics of ECT. Additional experiments were performed in order to verify the effect of magnetic resonant coupling for the wobbling (lift-off) noise in the tube inspection. In the vibration test of the ECT sensor inside the tube, the lift-off noise decreased by 28 % on average by magnetic resonant coupling. In the scanning test of the ECT sensor inside the tube, the wobbling and other noises were obviously reduced by magnetic resonance coupling.