Stress Analysis of Packed Stuffing-Boxes

Packed stuffing-boxes are mechanical sealing systems that are extensively used in pressurized equipment such as valves and pumps. Yet there is no standard design procedure in use to verify their mechanical integrity and leak tightness. It is only recently that standard test procedures to qualify packing materials have been suggested for adoption in both North America and Europe. Nonetheless the assessment of the structural integrity of the housing requires a well-documented design procedure to insure safe use of packed stuffing-boxes. While the packing contact stress with the side walls is predictable using existing models there is no analytical methodology to verify the stresses and strains in the stuffing-box housing. This paper presents an analytical model that analyzes the stresses and strains of the stuffing-box components including the packing rings. The developed model is validated both numerically using FEM (finite element method) and experimentally on an instrumented packed stuffing-box rig that is specially designed to measure the structural integrity and leakage tightness of different packing materials.