The most common packing materials available today are: Graphite, TFE, Glass Fiber used for the control valves.
Control Valve Packing Materials
Graphite: This is a pure form of ordinary carbon. In yarn or foil form, this material can meet most industrial plant criteria.
TFE: TFE is highly resistant to chemicals and has low friction. The useful temperature limit is about 500° F. TFE is not abrasive to shafts and has a low extrusion tendency.
Glass Fiber: Generally mixed with other materials, glass fiber has high strength and chemical resistance. It resists wear and abrasion but can damage shafts. Dimensionally stable, it does not cold flow when under compression.
Metals: To meet the requirements of sealing and accommodating the walls of the packing box, most metals in this use are in the form of foil or ribbon. It is twisted or rolled, often in combination with other materials, to make a shape that will conform with the square cross section of braided or die-formed packing. Babbit, aluminum and copper are examples.
Other packing material variations are:
- Graphite yarn interbraided
- Graphite foil die-molded
- Asbestos braid was a common material, but is not generally supplied presently.
- PTFE V-ring