Experimental Study On Fatigue Characteristic Of UHP Tubular Reactor

With the development of China's petrochemical industry,the role of UHP vessels in the production of petrochemical products is even more important.The conditions of the UHP vessels are very harsh,and are affected by factors such as temperature,pressure,and corrosion,which may easily lead to fatigue failure.Autofrettage of the UHP vessels may generate favorable residual stress on the inner wall of the vessels,and then greatly improve the bearing capacity and the fatigue life of the vessels.But the UHP vessels in service of China were all imported from abroad in the 1970 s and 1980 s.At present,they have entered the final stage of designed life,and their fatigue life has been severely reduced.Therefore,it is of great significance to carry out experimental research on the fatigue characteristic of the UHP tubular reactor in service.Based on previous researches,the UHP tubular reactor,which has been in service for 21 years,was taken as the research object.Through the theoretical formula reasoning,finite element numerical simulation,experimental verification and other methods,the fatigue characteristics were undertaken.The main work of this paper is as follows:(1)The three-dimensional stress formulas with four different conditions including thermal Stress,only in working conditions,autofrettage and working conditions after autofrettage were considered.The stress distribution law was analyzed,and the fatigue life before and after autofretage was compared and analyzed.(2)The fatigue test was performed on the UHP tubular reactor.The rule of the external wall hoop strain was obtained,and concluded the relationship between the external wall strain and the cycles.The remaining life of UHP tubular reactor after test was calculated by the nominal stress method.(3)The re-autofretage test of the UHP tubular reactor was performed.The relationship between the internal pressure of the loaded internal wall and the circumferential strain of the external wall was obtained.The fatigue life loss during service and the fatigue life after reautofretage were calculated.At the same time,the relationship between the pressure of reautofretage and the residual stress of the inner wall was established.(4)Based on the physical and chemical performance test data,finite element stress analysis and fatigue life calculation were performed on the above four working conditions,which achieved the finite element simulation method for the life assessment of the in-service reactor,and enriched the theory and the method for analysis of fatigue characteristics of tubular reactors in service.In this paper,through the quantitative evaluation of the fatigue characteristic of the tubular reactor,it provides support for the safe operation of the UHP tubular reactors,which is of a certain engineering application and academic reference value.