scope:

WRC Bulletin 442 summarizes an extensive program on Polytetrafluoroethylene (PTFE) gaskets. From 1993 to 1995, tests were sponsored by eleven gasket producers and users in an effort to develop a protocol for qualifying the tightness and hot performance of PTFE gaskets based on a measure of their margin of safety against gross leakage and on their mechanical and tightness resistance to extremely high loading. Over two hundred sophisticated tests were performed on twenty-seven PTFE based products including hot blow-out tests at various pressures in various test fixtures and room temperature tightness tests (ROTT tests) including a crush load sequence. These tests define and refine the necessary safety margins on relaxation, gross leak (blow-out) and tightness for these materials. The resulting protocol contains requirements for tests involving hot relaxation, gross leakage (blow-out) resistance, gasket constants and high stress performance (crush). The protocol is intended to accommodate all foreseeable types of PTFE based gasket products and makes use of a special NPS 3 Class 150fisture developed and proven for the hot gross leak aspect of the qualification scheme