Xu's Designs and Parameters for Sealing Elements

摘要

Any leak-free achievement needs a sealing surface that has microcosmic irregularities fully complementary to a surface to be sealed and that can be qualified only by compressive working or installing in position. ASME Code mistakes the working stress needed to result in a qualified gasket in installation for the stress needed to enable a qualified gasket to function well or maintain its leak-free connection, and only considers the influence of the sealing material's strength but never its elasticity on sealing. Undoubtedly, ASME Code's leak-free Maintenance Factor im/i and Minimum Necessary Sealing Stress iy/i of gaskets are both wrong in values. Similarly, neither is the gasket parameters system substituted for the gasket factors im/i and iy/i by PVRC and EN 13555. Actually, the stronger the strength and the elasticity of a sealing contact layer, the more difficult for its sealing element to create or maintain a fully deformed contact; whereas the stronger the strength and the elasticity of a contact layer substrate, the easier for its sealing element to create or maintain a fully deformed contact; i.e. the index used to measure the difficulty for a sealing element to create or maintain a leak-free connection is its sealing difficulty factor m1 = its contact's elastic modulus iEsubc/sub/i/its substrate's elastic modulus iEsubs/sub/i; so it is the most difficult for a rubber element to create or maintain a leak-free connection because its imsub1/sub/i ≡ 1, the easiest for a grease coating because its imsub1/sub/i = 0, and easier for the other sealing elements than for a rubber element because their imsub1/sub/i can be made smaller than 1 (or imsub1/sub/i 1) by designing and coating.