Research On Dynamic Behavior Of Secondary Seal Of Mechanical Seal

Non-contacting mechanical seals are being widely used in many different kinds of fluid machines, and they are key elements due to their impacts on the safety, working-performance and liability of the main machines. Mounted in the floating ring of mechanical seal, secondary seal makes a crucial role in the floating ring’s tracking ability, which links to sealing characteristic of mechanical seal directly. Consequently, a comprehensive research on secondary dynamic behavior is of theoretical and practical value in the aspect of improving sealing performance and liability of mechanical seal. In this paper, spring-energized seal ring, with its coat made of PTFE, is chose to be the research subject and its dynamic behaviors are well studied with the help of analytical and experimental method.A test rig is invented for the experimental study on the dynamic behavior. It can measure the secondary seal’s breakaway distance and the maximum friction when secondary seal is subject to one-way rectilinear motion under variable medium pressures. And secondary seal’s stiffness and damping parameter, when it is forced to conduct the reciprocating motion in terms of different amplitudes and frequencies, also can be measured utilizing this equipment.Based on the result of mechanical property of the initial 3-D bended coil-spring utilizing the numerical experiment, a 2-D equivalent spring is established. Further, this paper attains the axial symmetry model of the whole sealing system. Using this model, an adequate research has been devoted to the contact characteristic and structural strength of secondary seal system. Meanwhile, the validity of this model is validated by comparing with the existing data.Combined the Coulomb-Friction model, a theoretical model is developed to aim at the research on the secondary seal’s breakaway distance and the maximum friction, called BDMF model for short. This model can research the fretting frictional characteristic of the whole process from seal’s pre-slide to the total-slide as well as can predict its breakaway distance and the maximum friction under different medium pressures. And the simulation results give a well-matched coherence with the experimental ones, which demonstrates the correctness of the BDMF model. Afterwards, applying the BDMF model, this paper analyses the force-displacement relation of the secondary seal on the occasion that mechanic seal opens and closes.As the other part of research, this paper studies the secondary seal’s stiffness and damping by means of experiments and provides the test results under comprehensive conditions, such as the various frequencies and amplitudes of reciprocating motion. All the data offers a reliable reference for mechanical seal’s dynamical model. Based on the research, this paper makes a study on the influence rule on breakaway distance and the maximum static friction as well as sealing performance of secondary seal from three aspects: material, geometry and assembly parameter.