How do you select valve packing for different applications?

Packing selection factors: process fluid (compatibility), temperature (limits vary by material), pressure (affects sealing requirements), stem size and motion (linear, rotary), and emission requirements. Common types: PTFE (general purpose, -200 to 230 degrees C, good chemical resistance), graphite (high temperature to 650 degrees C, nuclear, steam), and low-emission designs (EPA compliance, multiple rings with bellows backup). Arrangement: multiple rings with anti-extrusion rings, spring loading for consistent seal. Proper installation: correct ring orientation, proper loading (not over-tightened), and break-in procedure. Monitor and adjust during operation.