A common question is why does a seat material, such as PCTFE, have different ratings depending upon the device?

The temperature and pressure ratings of a material utilized for a soft seat or seal, such as PCTFE, PFA, FKM, etc., are a function of material properties and the design application. How a seat or seal is captured and supported can make a difference in the ultimate temperature and pressure ratings of the device. The same seal material can have different ratings in different devices. Seemingly equivalent products from different manufacturers often have different ratings for the same materials of construction. A good example are FKM O-rings as their published application guides have different ratings for fully captured static seal applications compared to dynamic (moving) seal applications.

Product ratings are validated by testing during product development. Pressure and temperature ratings can also be limited by other product design elements or features. Seat material ratings can also vary by manufacturer due to design or other factors such as testing parameters.