In the present paper, the characteristics of the metal flat gasket and the flange connection with metal gasket were examined experimentally at room temperature. In addition, the sealing mechanism of the metal-metal contact gaskets was studied. The gaskets used were fabricated by aluminum, copper and Cr-Mo steel flat gaskets. Firstly, according to JIS B 2490, the effects of the gasket materials, surface roughness and gasket width on the sealing characteristics of the above metal flat gaskets were measured. That is, the gaskets were compressed using a material testing machine while the leakage was measured. The relationship between the compression stress and the amount of leakage was obtained. In the metal-metal gasket contact region, it was found newly that the amount of leakage depended on the gasket yield stress because the contact surfaces increase due to the surface roughness. The amount of leakage was found to decrease rapidly when the plastic deformation occurs at the contact gasket surfaces. In addition, the amount of leakage was measured for bolted flanged connections (flange nominal diameter: 2”) with metal gaskets. Furthermore, the contact gasket stress distributions in the connection were analyzed using 3-D FEM analysis. Using the obtained results from the FEM stress analysis, the characteristic of bolted flanged connections with metal flat gasket was elucidated. The estimated result were fairly good agreement with the measured results. It is found that when the plastic deformation occurs at the contact gasket surface, the sealing performance increases substantially.

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For the basis of understanding the hydrogen embrittlement of quenched and tempered high strength steels, behavior of lattice defects during fatigue straining has been explored through thermal desorption analysis (TDA) that utilizes hydrogen as a tracer. The TDA curves are successfully analyzed using Gaussian distribution; it can be separated into several peaks originated by dislocation, grain boundary, vacancy, and vacancy cluster and it enables quantitative argument of them. When hydrogen is not pre-charged, the specimen failed with striation fracture surface. TDA clarified vacancy formation by straining only 10 cycles. It increases with further straining until vacancy cluster is formed at 1000 cycles. Soaking in FIP solution (20mass% NSCN aqueous solution) before fatigue test made the life decreased to about one half of that without hydrogen pre-charging, accompanying quasi-cleavage facet. TDA revealed enhanced formation of vacancy and vacancy cluster;vacancy after 1cycle and vacancy cluster after 100 cycles. Vacancy cluster definitely degrade the fatigue life through quasi-cleavage facet connecting vacancy cluster. The enhanced hydrogen charging by cathodic polarization forced the life more decreased to about one seventh, where grain boundary facet becomes mixed with quasi-cleavage facet. By TDA measurement, enhanced hydrogen charging is shown to yield more hydrogen partition to grain boundary. This may be the cause of inter-granular facet.

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High-temperature high-cycle fatigue properties until 10⁷ or 10⁹ cycles of nickel based superalloy Alloy713C were investigated at 600, 700 and 800°C. For Alloy713C as casting, fatigue fracture originated from casting defects in high-cycle region. While for Alloy713C treated by hot isostatic pressing (HIP) , fatigue fracture originated from the specimen surface. In high-cycle region, fatigue life of Alloy713C treated by HIP was longer than that of Alloy713C as casting.

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On August 6, 2012, the Chevron USA Refinery in Richmond, California, USA experienced a catastrophic pipe failure in the ＃4 Crude Unit. The pipe ruptured, releasing flammable, hydrocarbon process fluid which partially vaporized into a large vapor cloud. The flammable portion of the vapor cloud ignited just over two minutes after the pipe ruptured. The ignition and subsequent continued burning of the hydrocarbon process fluid resulted in a large plume of unknown and unquantified particulates and vapor traveling across the Richmond area. Approximately 15, 000 residents from the surrounding area sought medical treatment due to the release. The U. S. Chemical Safety and Hazard Investigation Board released the interim investigation report on April 19, 2013. The report concluded that the carbon steel pipe failed due to thinning caused by sulfidation corrosion, which was accelerated by the low-silicon content of the failed component.

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