Finite Element Optimal Design Of High-pressure Long-distance Pipeline Fixed Ball Valve

With the application of new material and tehcnology in valves, andthe population of Numerical Contorl equipmcnt, especially theapplication of ANSYS FEA sotfware in the desing of valves, the desingand mnauacfturing level of valves made good imporvement.However,thereisstilladistanceintherequiredparameters withwest-eastgas pipeline project. a large diameter pipeline construction can be moreeconomicaland improve thedeliveryof media pressure ina certain rangethan a few small diameter pipeline construction, also can increase theeffectiveness. Therefore, the requirements of long-distance pipelinevalves are much higher than the general valves. In order to ensure thesafety of long-distance pipeline reliable operation, requirements oflong-distance pipeline valves are more reliable, higher sealing, higherstrength.This paper analyzes the development process of domestic andinternationallong-distancepipelinevalvesandabsorbedtheiradvantages.On this basis, we adopted advanced design techniques and developed thelargest pipeline valves with nominal diameter 1500mm and nominalpressure15MPa.Alloftheworkinthisthesisarelistedasfollows: (1) By utilizing finite element analysis software ANSYS, a finiteelement model for rubber O -boundry was set up. Through analying theshape changes and the size and distribution of contact pressure of thesame groove, different cross section and compression rates, drawing slotwidth has no effect on the contact pressure. Larger the notch fillet radius,the greater the maximum contact pressure and shear stress, but slow tochange, with little iMPact, describing the possible location of cracks ofO-ring and providing a theoretical basis for the installation andreasonableuse.(2)Inordertofacilitatereplacementwhentheringdamagedorfailed,activities sleeve valve seat combined together by two ring parts andadopted O-ring seal, whose material is nitrile rubber, hardness is90.Under the pressure of 15MPa, its maximum seal gap is 0.3mm. Thecontact part of cylinder type tube of activities sleeve and O-ring aresimplified as plane strain problem, and use ANSYS to calculate themaximum material deformation of less than 0.3mm along radiusdirection and meet the allowable stress of activities sleeve's wallthickness.(3) We developed a two-way seal structure pipe valve, whose valveseat cross section is rectangular shape, and calculated the average sealingpressure of sealed valve seat and ball. Based on calculated results, wesimulate valve seat with bilinear kinematic hardening material model and valve core with rigid-body model, using area-area contact finite elementanalysis, taking the average sealing pressure as the foundation, which getfromtheoreticformulaandcalculatetheactualregularitiesofdistribution.The results indicate rectangular seal has a small compressibility, a moreuniformcontactstress,abiggersealingface,abettersealingeffec.(5) Establishmenting of valve body after valve body wall thicknessis determined according to equal thickness presssure. With necessarysimplification, appling thermal-structural coupled analysis and structuraloptimization computation, getting the best valve body wall thicknessfromtheoptimizationofthicknesscomputedbyformula.(6) When the ball core groove worn, the stem and the ball rotation isnot synchronized, easily leading to rotation errors. Using four keys toconnect the stem and the ball, which can help ensure the synchronousrotationandmaintenance.