Effect of Tapered Housing on the Axial Stress Distribution in a Stuffing Box Packing

Abstract

The sealing performance of a packed stuffing-box used in pumps and valves is strongly dependent on the distributions of the axial stress and the contact pressure between the packing rings and the side walls. In particular the stress state of the bottom packing ring that is in contact with the internal fluid which is at its minimum is the leak controlling parameter. This minimum axial stress and its resultant radial stress control the pore size and therefore dictate the quantity of leak that passes through the packing rings. This paper presents a new design feature that improves the stress distributions. The introduction of a variable gap between the packing and the side walls helps producing a more uniform distribution of the stresses in the packing rings while increasing the minimum stress. An analytical model that takes into account the effect a tapered housing on the distribution of the axial stress in a stuffed packing box is also developed. The analytical model is validated by comparison with numerical finite element simulations.