Properties Analysis And Structural Optimization For The Welded Metal Bellows In Mechanical Seals

The welded metal bellows mechanical seal is largely used for the axial seal of hot oil pump in refinery. Using metal bellows instead of the spring and support ring to account for the high temperature auxiliary sealing problem. Welded metal bellows not only plays a buffer or a compensation for the axial displacement result from the fretting and axial vibration, but also by their own elastic and sealing medium pressure to impose certain pressure with the seal face to play seal role. The membrane of bellows in the failure of high temperature under normal circumstances are elastic-loss and fatigue damage, which many scholars at home and abroad to analysis and calculate the strain, stress and life of the membrane, Using traditional methods and modern design methods (the finite element method and design optimization).First, based on the actual production of bellows membrane as a research object, the mechanical model has been established by analyze the stress of membrane. Using ANSYS software to calculate the static stress ,were obtained the combination stress which is composed of three static combined stresses, such as axial deformation stress, membrane stress, centrifugal stress, structure deformation and the node stress distribution chart, numerical and position of the maximum stress point. The result shows that axial movement brings on the stress of bellows. So, it is necessary to control strictly the compress quantity of the bellows, moreover, the maximum stress could be decreased ,endurance life of membrane could be enhanced also by increase the curvature radius of the circular arc which consist in the maximum stress and other effective measures.Secondly, Practice has proved that as bellows membrane in the conditions of high temperature and a high-speed axial vibration, the membrane failure under normal circumstances are elastic-loss and fatigue damage. Using transient dynamics (FULL) analytical method of ANSYS to calculate the value and location of the maximum dynamic stress, analyze the relationship between the maximum dynamics stress and the quantity of vibration. The result shows that the fatigue life of membrane could be enhanced and the dynamical stress also could be decreased by reduce the vibration movement.Based on the analytic result of the combination static stress and transient dynamic stress in this paper, and on the ground of fatigue life computation method, named local stress-strain, the fatigue life of membrane is calculated. The solution is comfortable compared with actual production of breakage, and to meet the requirements of overhaul.To further enhance the life of membrane, the membrane that the structure has been partly optimized design parameters, namely by changing the diaphragm style, diaphragm depth, diaphragm width and the maximum stress point where the radius of curvature arc structure , took hold of the optimal parameters of increase the membrane's stiffness at the same time reducing the stress, so as to achieve extension of the life of the membrane, which will provide reference data for the actual production.