To avoid leakage to the outside and to achieve a correct static seal in flanged joints, the gasket must be correctly selected. The variables to choose this element should be: pressure, temperature and process fluid.
When selecting a soft gasket, special care must be taken with the service temperature. Common elastomers work well up to 121°C, aramid fibers with nitrile binder up to 204°C, carbon fiber sheets up to 343°C, graphite sheets up to 454°C and PTFE sheets up to 232°C. It is important not to exceed the design conditions for soft gaskets; high temperatures cause deterioration of the fibers, crystallization and degradation of the static sealing materials.
In standard spiral wound gaskets, there are 2 models, WR and WRI, the difference between these two models is the internal ring of the WRI model. It is recommended to use WRI gaskets in high pressures and/or large diameters, it is also necessary to use the internal ring when the winding filler (spiral wound sealing area) is PTFE. One of the main functions of the inner ring in a spiral wound gasket is to provide additional support to the radial force to prevent the buckling effect caused by large torques from the installation; the inner ring distributes the loads better, preventing the winding from unwinding and being transported through the pipeline and affecting sensitive equipment inside the line.