EFFECT OF MATERIAL PROPERTIES OF GASKET ON THE SEALING PERFORMANCE OF PIPE FLANGE CONNECTIONS AT ELEVATED TEMPERATURE

The sealing performance of the pipe flange connection depends on the compressive gasket stress. Therefore, the unexpected leakage can be avoided by estimating the change in compressive gasket stress during operation. In order to make such estimation, the material properties of the gasket are required as well as those of bolt and flange material. When the pipe flange connection is used under heated condition, the thermal expansion coefficient shows an important role. For example, if the thermal expansion coefficient of gasket is larger than that of pipe flange material, the gasket stress is expected to be increased by increasing the temperature and the sealing performance of pipe flange connection is improved. However, a gasket tends to be softening at high temperature. Beside, the creep phenomenon of gasket induces the decrease of gasket stress. Thus, the behavior of the gasket is complicated and it should be investigated to make a reliable design. In this paper, the high temperature properties, including thermal expansion and stress relaxation property of spiral wound gasket with expanded graphite are examined by compression tests at elevated temperature. The stress analysis with high temperature material properties obtained from the compression tests also conducted to estimate the sealing performance of pipe flange connection. As a result, the pipe flange connection with spiral wound gasket is expected to keep the superior sealing performance at 300 C for long time.