Valve Stem Packing Leakage Causes | Standard Packing Replacement Process Guide

Valve stem packing leakage ranks the first among common external leakage faults of industrial valves, occurring frequently on ball valves, globe valves, gate valves and butterfly valves in various industrial pipelines. The packing assembly is the core external sealing component of valves, responsible for blocking the gap between the movable valve stem and valve body to prevent medium penetration. Once the packing fails, process medium will seep outward along the valve stem continuously, leading to medium loss, on-site environmental pollution and potential operational safety hazards. On-site statistics show that packing leakage is mainly caused by five practical factors: material aging and elastic fatigue, high-temperature carbonization failure, long-term friction shear wear, uneven compression and non-standard installation. Under high-temperature steam and heat conduction oil working conditions, ordinary graphite packing will gradually harden and lose original elasticity, completely losing sealing performance. The repeated rotation and lifting of the valve stem will generate continuous shear force on the packing layer, wearing the packing and expanding sealing gaps over time. In addition, asymmetric tightening of gland bolts will cause unilateral gaps between the packing and stem, resulting in local seepage. The packing replacement operation must strictly comply with on-site safety specifications to avoid safety accidents. First, completely isolate the faulty valve from the pipeline system and fully release the internal medium pressure. It is strictly prohibited to replace packing with pipeline pressure retained, so as to prevent medium spraying and scalding accidents. After disassembling the gland flange, thoroughly clean all residual old packing fragments and dirt in the packing cavity. Any residual debris will affect the fitting tightness of new packing and lead to secondary leakage. New packing rings need to be installed layer by layer, with all joints staggered alternately to avoid straight-through leakage channels inside the sealing layer. For valves operating in high-temperature working conditions, coating professional high-temperature graphite lubricant during installation can effectively improve the flexibility of the packing and enhance the overall sealing effect. The gland bolts shall be tightened diagonally and evenly to ensure the valve stem moves smoothly without jamming, while eliminating external leakage gaps. As a key preventive maintenance item, regular packing replacement every 6 to 12 months can effectively avoid sudden stem leakage faults and ensure long-term stable operation of industrial valves.