Jam Style Graphite Packing Arrangements – Graphite packing arrangements are commonly specified in applications where high temperatures (temperatures above 450 degrees F) disallow the use of PTFE materials, or in applications where it is necessary to limit leakage through the packing bore in the event of a fire.
A typical graphite packing arrangement (refer to Figure 27) includes die formed ribbon rings and braided filament rings. Although graphite is well suited to high temperature applications, graphite has several negative characteristics, including the following:
• Graphite is a high-friction material, and high friction can cause jerky valve
stem movement. If overtightened, graphite packing may totally seize the valve stem.
• Graphite tends to consolidate (compress) over time; therefore, frequent packing adjustments are required.
• Graphite tends to corrode. To prevent valve and packing damage, sacrificial zinc washers are often included in the packing arrangement.