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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.

Typical results of Aged Tensile Relaxation tests (named ATRS) and FIRe Simulation (FIRS) tests are discussed in terms of gasket quality, suggested performance criteria and a correspondence between thermal aging and damage to elastomer bound sheet gaskets that holds to 1200°F. ATRS fixture development, and recent extensions of ATRS applications to higher temperatures and to composite gaskets are noted. The relationship of ATRS test results to hot tightness tests (HOTT and AHOT) is also examined in the context of a suggested scheme for estimating long term sheet gasket performance.