Research On Axial Press-in Type Pipe Fittings

In the field of metal pipe connection, welding is traditionally used, while thereare some obvious shortcomings, for instance, pipeline will be polluted with weld fluxslag, internal coating must be damaged, its efficiency is low, its labor intensity is high,its cost is high, the environment will be polluted with welding fume, and the weldingdefects and residual stress bring about serious influence on the connecting quality ofpipes. Therefore, it is significant to explore the method of connecting pipes differentfrom welding for engineering practical value. Under these circumstances, a newtechnology of weldless pipe connection——axial press-in type pipe fittings isresearched in this paper. During the connection, the coupling will have radialelasto-plastic deformation under the compression loading exerted by the axial thrust tothe sleeve, so the pipes are connected and sealed. The mechanics principle of pipefittings is analyzed, a mechanic model is established, and based on this conclusion,calculation formula of precompact force P, shrink range△between the couple andsleeve and internal pressure q is solved. And some examples of pipe fittings of2inches in diameter are calculated. On the basis of the established mechanic model, allkinds of factors on quality of the connection are analyed, the sealing performance ofthe connection is put up, and its interference fit process, anti-tensile process andinternal pressure performance is simulated with the use of MARC finite elementmethods, and the stress and strain and the connecting force of the interference fitprocess are calculated and analyzed during the simulation, the simulative results arenearly identical with those of the mechanic model. Based on the theoretical analysis,test specimen of axial press-in type pipe fittings of2inches in diameter is prepared.The results of the interference fit and anti-tensile experiments proved that theestablished mechanic model and the results of the simulation are right, and indicatedthe designed pipe fittings reasonable, which has the important engineering practicalvalue.The research results provided theory basis for structure design of axial press-in type pipe fittings, and laid the groundwork for its application and development.