A trapezoid-sectional annular sealing arrangement, including a trapezoid-sectional annular cavity and gasket or packing used to realize the sealing connection of two fluid-containing members connected by fastening threads or bolts, wherein the said annular gasket or packing is enclosed in the said annular cavity formed by the said two fluid-containing members as joined together by fastening threads or bolts, the said trapezoid is disposed to converge radially and inward, the annular gasket or packing has a sectional area slightly bigger than the sectional area of the annular cavity, and the annular cavity is preferably designed to completely sink into one face of the two end faces to be joined. The sectional area and gyro-radius of the annular gasket with a material thermal expansion coefficient different from the annular cavity will either increase or decrease in response to temperature changes at the same time relative to the annular cavity to enhance or retain the original sealing connection.
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