Development of a method for optimal design of metal-polymer valving seal
Students Name: Marets Andrii Tarasovych
Qualification Level: magister
Speciality: Electronic Industry Equipment
Institute: Institute of Mechanical Engineering and Transport
Mode of Study: full
Academic Year: 2020-2021 н.р.
Language of Defence: ukrainian
Abstract: Marets A.T., Sheremeta R.M. (head). Development of a method for optimal design of metal-polymer valving seal. Master’s qualification work. - Lviv Polytechnic National University, Lviv, 2020. Extended annotation. Sealing technology is a branch of technology that develops scientific bases and practical methods of sealing objects, design and operation of sealing devices. At the present stage of development of mechanical engineering, in such fields as energy, petrochemistry, electronic production, space research and others, there is an urgent need to raise the technical level of sealing devices. Reliability of the car or the device as a whole largely depends on qualitative indicators of sealing devices. The performance of sealing devices determines the resource and reliability of most technical facilities. This forces us to constantly increase the requirements for sealing devices and stimulates work to improve them. One of the main elements of sealing technology is a valve device. The main elements of the valve device are a fixed locking element (saddle), usually rigidly fixed in the actuator housing, and a movable locking element (shut-off device - the valve). During the operation of the valve device by landing the shut-off device on the saddle, the flow of the working medium is blocked and sealing is carried out on a seal made of elastic material (metal or polymer). The resource and tightness of the valve device depend on the choice of the type of valve seal and the sealing force. Under the action of sealing force, the elastic seal is deformed, while some work is carried out. In the vast majority of existing, valve seal designs, this work significantly exceeds the work required for sealing. In this regard, it is important to analyze the basic principles of calculating the force required to seal the elastic element. When developing a universal method for determining the tightness of the sealing joint, it is necessary to take into account both the factors that ensure the tightness of the contact area, and structural, technological and operational. There is no clear boundary between these groups of factors, but the presence of such a classification somewhat simplifies their overall analysis. The first group includes the following characteristics: 1. Power: sealing force in the contact zone created by the load setter (spring or actuator), the coefficient of dynamism of the device, determined by the speed of the valve on the saddle (the speed of application of the sealing load), the stiffness of the sealed joint. 2. Structural: geometrical parameters of the contact zone, which include the conditional passage diameter of the valve-seat path, the contact scheme (plane, cone, shell, etc.), the width of the sealing zone and the material of the sealing surfaces. 3. Technological - parameters of technological processing of elements of sealing connection: roughness, wavyness, deviation of forms. 4. Physico-mechanical properties of the material of the surface layer of the elements of the sealing joint: yield strength, modulus of elasticity, hardness, microhardness. 5. Parameters of the working environment in the compaction zone: pressure, temperature, viscosity, density, desorption energy, etc. The design and technological characteristics include: manufacturing errors, installation and assembly of sealing elements and their fasteners, technological variation of tolerances on the dimensions of the valve seal in the accepted process of manufacturing structural elements. Performance includes characteristics that take into account the effects of fluctuations in ambient pressure and temperature, as well as the action of external power loads. In the general case, determining the tightness of the sealing connection of valve devices requires solving a number of problems related to determining the plot of contact pressures, convergence of rough surfaces, geometric parameters of microchannels in the contact zone of sealing elements, the mechanism of mass transfer through the contact zone. Having created a model that qualitatively and quantitatively explains the behavior of the mechanical system of the valve sealing process, we can proceed to the task of synthesis, ie to calculate the design parameters of the sealing connection, the behavior of which is predicted in operation. For technological reasons, the shape of the synthesized elements should be formed by figures of the correct geometric shape. The term "optimal design of metal-polymer valve seal" should be understood as the use of certain calculation and design techniques for the design of the sealing joint, which has a given performance. The object of research is a metal-polymer valve seal. The subject of research - calculation and design of metal-polymer valve seal. The purpose of research: development of a technique of optimum designing of metal-polymeric valve consolidation with the set operational parameters. The results of the study allow: to determine the optimal geometric dimensions of the valve seat profile, which provide the minimum sealing force of the metal-polymer valve pair at a given resource and tightness. Key words: hermetology; valve seal, mathematical model; optimization; calculation; designing.