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To better understand the performance of flexible graphite sheet gaskets, a Pressure Vessel Research Council (PVRC) sponsored program has been launched in 1991, and extended in 1992-93 by the participation of a private gasket manufacturer company. The elevated temperature behaviour of these materials with and without different types of metallic reinforcement and/or passivating corrosion and oxidation inhibitor has been evaluated according to specific room and elevated test procedures and gasket quantification tools developed for the Material Testing Institute (MTI) and the PVRC. The program consisted in combinations of short to long term (up to 6 months) mechanical screening tests at temperatures from 650°F to 1100°F. The test results are used to compute creep/relaxation resistance, thickness change, weight loss, density change and post aging tensile strength of gasket specimens subjected to the various aging conditions.

Paper describes the special test equipment developed for evaluating the elevated temperature leakage performance of gaskets. Early results indicate that an elevated temperature test must be run over a period of days or weeks in order for the time/temperature effects to be meaningful. The objective was therefore to develop test methods which would permit the aging of a test gasket in a Kiln for as long as desired before being evaluated for tightness. Results of leakage tests on asbestos and non-asbestos rubber-bound sheet gasket materials are presented. They indicate that the aged hot tightness tests (named AHOT) are effective and offer many possibilities including long term aging at temperatures beyond the limits of the tightness test machine. These tests are therefore suitable as means to confirm elevated temperature gasket performance estimates from screening tests.