WRC - BULLETIN 507
LONG TERM PRESSURIZED GRAPHITE GASKETED JOINT TESTS
Report 1: Long Term Pressurized Graphite Gasketed Joint Tests Luc Marchand, Michel Derenne, Olivier Sakr, Hakim A. Bouzid
Report 2: Long Term Performance Of Flexible Graphite Based Gaskets Under Nitrogen Exposure; Luc Marchand, Michel Derenne
Report 3: Additional Long Term Pressurized Joint Tests On Corrugated Flexible Graphite Gaskets; Luc Marchand, Michel Derenne
The long term performance and elevated temperature capabilities of flexible graphite based gaskets have been the focus of several PVRC research projects. This WRC Bulletin combines a series of recent, inter-related research projects which have been commissioned to further quantify the long term performance of flexible graphite gaskets in different atmospheres, and to validate earlier service life and performance predictions which are based on shorter duration exposure.
Initiated in 1996, PVRC project 96-09G was the first of a series of pressurized media tests launched to investigate the effect of long term pressurized hot air exposure on the performance of two different types of reinforced flexible graphite based gaskets that are commonly used in industry today. One a foil reinforced sheet type flexible graphite gasket material and the second a corrugated insert flexible graphite gasket. The project was designed to supplement and confirm the long term graphite gasket life predictions that are based upon the results of previous PVRC projects 91-8, 93-3 and 94-25. While the long duration stress relaxation and leak rate results correlated well with the quantification methods identified in the earlier research for the reinforced sheet type material, the resultant performance of the corrugated insert type gasket was not as expected and, at the time, could not be explained.
PVRC project 00-BFC-12G was commissioned to investigate the possible causes for the fast rate of degradation that occurred with the corrugated insert flexible graphite gaskets in the earlier PVRC 96-09G investigation. This experimental work studied the effect of long term pressurized hot air exposure on the performance of two different brands of corrugated insert flexible graphite gaskets, and in particular identified the effect of three important parameters on the degradation rate of these gaskets.
All previous performance qualifications and the resultant service life prediction tools were performed under hot air exposure. In an effort to qualify the accuracy of the qualification and service life prediction tools in non-oxidizing atmospheres, PVRC project 99-04G was commissioned. This project investigates the effect of long term pressurized hot nitrogen exposure on the performance of foil reinforced flexible graphite type gaskets and corrugated insert flexible graphite gaskets. Comparisons were made with the long term pressurized hot air test results of earlier PVRC projects and a method was established that can adjust the PVRC qualification tools for the calculation of long term gasket temperature and service life for these materials when employed in non-oxidizing environments. The method is based on the establishment of a recommended Ag (Equivalent Aging Parameter for Flexible Graphite) value that is specific for an internal fluid exposure condition