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Ohno T.,Aoyama Gakuin University | Kobayashi N.,Aoyama Gakuin University | Oyamada K.,High Pressure Gas Safety Institute of Japan
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

A significant fire and explosion accident on spherical storage tanks for Liquefied Petroleum Gas (LPG) at Chiba prefecture in Japan were occurred due to the strong ground motion of the 2011 Great East Japan Earthquake. The braces made of steel pipe for supporting columns of a spherical tank, which was filled with water for purging air at that time, were broken by the strong seismic inertia force. Then, buckling of columns was occurred by the aftershock. To clarify the failure mechanism of the pipe braces of its supporting frame of a spherical tank, the elastic and elastic-plastic finite element analysis (FEA) was performed. From FEA results, the failure mechanism of the pipe brace was revealed as follows; (1) high stress was generated in the intersection of long and short braces due to the structural discontinuities, (2) the generated high stress was a trigger of the failure initiation of the damage of the supporting frame, (3) the breakage of the intersection of the long and short braces of the supporting frame was caused overturn of the spherical tank at the aftershock of predominant earthquake. In this paper, the fracture mechanism of the spherical storage tank was clarified for prevention of the same type accidents, and the effective reinforcement method of pipe braces of spherical tanks was proposed for securing safety. Copyright © 2015 by ASME. Source


Oka Y.,Yokohama National University | Yoshida T.,Yokohama National University | Kondo T.,High Pressure Gas Safety Institute of Japan | Ito S.,Japan National Institute of Advanced Industrial Science and Technology | Katoh K.,Fukuoka University
Journal of Thermal Analysis and Calorimetry | Year: 2010

In Japan, tert-butyl mercaptan (TBM) is mainly employed as an odorant of LPG. However, the sulfur component in TBM gives the adverse effect for environment and human body and/or has a negative impact on reforming catalyst of fuel cell and other types of cogeneration systems. In this way, the development of sulfur-free odorant is expected. This study focuses on the thermal stability and combustibility of 2-hexyne, 1-pentyne, n-butyl isocyanide (BIC), and ethyl isocyanide (EIC) that is expected as the candidate odorants. As the result of DSC measurement, the comparison of TDSC indicated that 2-hexyne and 1-pentyne are more thermally stable than BIC and EIC. However, in 2-hexyne and 1-pentyne, the slight exothermic peaks were observed at lower temperature region before those main exothermic peaks. In 2-hexyne, copper or aluminum increased the heat amount of that slight exothermic peak observed before main peak. In 1-pentyne with zinc, TDSC was approximately decreased to 279 °C from 337 °C of 1-pentyne alone. As the results of ARC measurement, in the presence of oxygen, the exothermic heat of 2-hexyne and 1-pentyne was observed at approximately 50-100 °C. This heat release may be corresponding to the slight heat release observed by DSC, and it thought to be results from the reaction with atmospheric oxygen. In this way, for the practical application of 2-hexyne and 1-pentyne as odorants, it is important to suppress the invasion of oxygen in the cylinder to low as much as possible in respect of the storage of the candidate odorant. As a result of thermal equilibrium calculation, even if either candidate odorant is added at about 100 ppm, there is little influence on propane combustibility from the adiabatic flame temperature, species of combustion gas and their yields. © Akadémiai Kiadó, Budapest, Hungary 2009. Source


Konosu S.,Ibaraki University | Ogasawara K.,Mitsui Engineering and Shipbuilding Co. | Oyamada K.,High Pressure Gas Safety Institute of Japan
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

This paper develops a procedure for plastic collapse assessment of vessel (run pipe) - nozzle (branch pipe) intersections with an arbitrarily positioned local thin area (LTA) under different loading conditions, namely internal pressure, external moment on a nozzle applied along various directions with respect to the vessel main axis, and pure bending moment on a vessel. Although simplified procedures for plastic collapse assessment based on the p-M (internal pressure ratio and external bending moment ratio) diagram method have been previously proposed for straight cylindrical vessels and pipe bends with an LTA, very few studies have dealt with the determination of plastic collapse load for an LTA in the critical region of intersecting vessels subjected to internal pressure and external moment loading. This is likely due to the complexity of the stresses caused by the applied loads in the critical region, which arises from geometric discontinuities. In this paper, simple and empirical formulae for predicting conservative plastic collapse loads for an LTA in the critical region of the intersecting vessels are proposed based on the analytical results of stresses at defect-free vesselnozzle intersections by using linear finite element analysis (FEA). Localized elastic stress retardation factors are taken into account in the evaluation by the results of a non-linear FEA. Consequently, a p-M diagram method is developed for application to vessel-nozzle intersections with an LTA. © Copyright 2015 by ASME. Source


Oyamada K.,High Pressure Gas Safety Institute of Japan | Konosu S.,Ibaraki University | Ohno T.,High Pressure Gas Safety Institute of Japan
Nuclear Engineering and Design | Year: 2012

Pipe bends are common elements in piping systems such as power or process piping, and local thinning typically occurs on pipe bends due to erosion and/or corrosion. Therefore, it is important to establish the plastic collapse condition for pipe bends having a local thin area (LTA) under combined internal pressure and external bending moment. In this paper, a simplified plastic collapse assessment procedure in the p-M (internal pressure ratio and external bending moment ratio) diagram method for pipe bends with a local thin area simultaneously subjected to internal pressure, p, and external in-plane bending moment, M, due to earthquake, etc.; is proposed, which is based on the reference stresses derived from the Tresca theory under a three axes condition. The plastic collapse loads derived from the proposed p-M diagram method are ascertained by comparing with the results of experimental testing with full-scale pipe bends and those of FEA for the same sized pipe bends with an LTA having various dimensions as well. © 2012 Elsevier B.V. All rights reserved. Source


Oyamada K.,High Pressure Gas Safety Institute of Japan | Konosu S.,Ibaraki University | Ohno T.,High Pressure Gas Safety Institute of Japan
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2012

Pipe bends are common elements in piping system such as power or process piping, and local thinning are typically occurred on pipe bends due to erosion or corrosion. Therefore, it is important to establish the plastic collapse condition for pipe bends having a local thin area (LTA) under combined internal pressure and external bending moment. In this paper, a simplified plastic collapse assessment procedure in p-M (internal pressure ratio and external bending moment ratio) diagram method for pipe bends with a local thin area simultaneously subjected to internal pressure, p, and external out-of-plane bending moment, M, due to earthquake, etc., is proposed, which is derived from the reference stress. In this paper, only cases of that an LTA is located in the crown of pipe bends are considered. The plastic collapse loads derived from the p-M diagram method are compared with the results of both experiments and FEA for pipe bends of the same size with various configurations of an LTA. Copyright © 2012 by ASME. Source

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