各種の常温・高温密封試験におけるガスケットひずみを用いた密封特性評価方法の提案

概要

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The relationship between the gasket stress and the tightness parameter has been used in the sealing performance evaluation of gaskets using the ROom Temperature Tightness / Hot Operational Tightness Test (ROTT/HOTT) proposed by the Pressure Vessel Research Council (PVRC). A new evaluation method using the gasket strain rather than the gasket stress is proposed in this paper. In the present study, a new test sequence, namely, the Preheated Hot Operational Tightness Test (PHOTT) is proposed in order to cancel the thermal strain of the experimental setup. A testing machine for ROTT, HOTT and PHOTT that continuously controls the gasket temperature up to 450 °C is constructed. The proposed test can be conducted under either stress controlled or strain controlled conditions, whereas conventional tests are conducted under mixed stress and strain conditions with fluctuating temperature. Test results obtained at room and elevated temperature show that the relationship between the gasket strain and the tightness parameter become a unique relationship on the log-log chart. Therefore, calculation of the bolt load for the assembly process and the operational process is expected to be simplified by evaluating the leakage based on the gasket strain. In addition, the proposed evaluation method is applicable to both asbestos and non-asbestos gaskets (compressed sheet gaskets and spiral wound gaskets).