Low Friction Packing for Control Valves. Constructed from a high-quality carbon fiber core and a PTFE shell to reduce friction where air operated valves are used for steam, water, air, and process control applications. When to use graphite or teflon packing; Author: sponge (NC) When should graphite string-type packing be used and when should teflon string-type packing be used? What application is graphite better for and what application is teflon string-type packing better for? Fire safe ball valve can have virgin Teflon seats and still pass a fire test. The graphite used in the body seal and usally on top of the lower stem bearing are actually "insulators" to try and prolong the vaporizing of the Teflon. Anything left in these areas of the valve will help reduce the leakage to atmosphere when pressurized during the test. KITZ Graphite and Metal Seated Ball Valves 1. Choice of trim for heated abrasive service Metal seated ball valves are guaranteed for a maximum service temperature of 572˚F (Trim symbol 5H) and 932˚F (Trim symbol 6H). For hard graphite seated ball valves, a maximum service temperature of 932˚F is also guaranteed (Trim symbol 3H).