Sealed and Delivered

Abstract

Engineers at A.W Chesterton Co., Stoneham, MA, applied computational fluid dynamics (CFD) to a new model of their heavy-duty cartridge dual seal Chesterton's dual seal consists of two pairs of seal rings. Mechanical seals are widely used to prevent leakage from fluid-handling equipment such as centrifugal pumps and mixers. Outer pair rotates with the shaft; inner pairs are fixed and contain a channel for the barrier fluid. The seal confines process fluids to the areas on the left. Taper is visible along the lower edge of the inner seal rings and on the corresponding surface of the shaft covering. CFD images described in the article depict the axial circulation of the seal's barrier fluid for a typical untapered seal design and the improved circulation resulting from the tapered surface design. The change in flow patterns results in an improvement in heat removal, from 0.7 to 1.1 kW. In order to validate the accuracy of the CFD results, physical experiments were conducted in Chesterton's seal test laboratory, using a variety of flow rates, rotation speeds, and fluids. The seals that do incorporate the innovative design have performed well in the field, operating at cooler temperatures that should result in seal life at least 30 percent longer,