Full definition
Pre-formed braided or molded rings of sealing material that are stacked in a stuffing box (packing gland) around a rotating or reciprocating shaft to prevent leakage of the process fluid. The rings are compressed by a packing gland follower, which forces the packing material against the shaft and stuffing box bore to create a seal. Materials: graphite-impregnated (for high temperature -200 to +650°C in non-oxidizing media, excellent sealing and low friction), PTFE/Teflon (universal chemical resistance, -200 to +260°C, low friction), aramid/Kevlar (high pressure, abrasive fluids, pumps, valves), carbon fiber (high speed and temperature), PTFE/graphite combination (versatile, moderate temperature/pressure), and flax/cotton (economical, water service only). Cross-section sizes: 3×3 mm to 50×50 mm (square). Per API 622 (valve packing), ASME and EN standards. Packing requires controlled leakage (2-60 drops/min for pumps) to lubricate the shaft — zero-leakage overtightening causes shaft scoring and premature packing failure. Replacement: remove old packing, inspect shaft sleeve for wear, install rings with staggered joints, and adjust gland to achieve target leakage rate. Brands: John Crane, Chesterton, Garlock, Palmetto.