Study On The Fracture Failure Analysis Of Single-seat Regulating Valve Stem

The main function of the regulating valve is to regulate the pressure,flow,temperature of the medium,and so on.It is the final control element in the production operation.As the most common control valve,single-seat control valve is widely used in petrochemical,electric power,textile,metallurgy and other industries.It is often exposed to harsh environments such as high temperature,high pressure,inflammable and explosive,vibration,humidity and dust,so the frequency of failures will increase dramatically.The fracture of the stem of a single-seat regulating valve is one of the common faults.The fracture of the stem makes the regulating valve lose its ability in an instant,which directly threatens the safe and stable operation of the device system.Therefore,it is of high economic and social value to study the problem of single seat regulating valve stem fracture.In this paper,the problem of metal fatigue fracture failure at the valve stem diameter changing position in the regeneration tower of a petrochemical enterprise of Sinopec is studied.The main contents of this paper are as follows:(1)Based on the structural characteristics of the single seat regulating valve stem,the mechanism of metal fatigue failure,the fracture characteristics of metal fatigue failure,etc.It is found that the stress concentration of the single-seat regulating valve stem at the step of variable diameter angle of the stem leads to the fatigue fracture failure of the stem.(2)Based on the case of single-seat regulating valve stem failure in a petrochemical enterprise of Sinopec,the failure valve stem was studied.It is found that the fracture of the valve stem belongs to the fatigue failure of stress concentration by the analysis of macro-morphology,micro-morphology,chemical composition,hardness,metallographic structure and energy spectrum.(3)Using the fluid simulation module of ANSYS software,the three-dimensional numerical simulation of the flow field inside the control valve is carried out to study the changing law of its pressure field and velocity field.At the same time,the fluid-solid coupling vibration of the valve stem and valve core is analyzed by using the fluid-solid couplingmodule.It is concluded that the valve stem vibrates violently and even resonates due to the cavitation at the throttle of the valve core when the valve position is small.(4)Based on the analysis and research,the measures to prevent the fatigue failure of the control single-seat regulating valve stem are given.The occurrence of valve stem fatigue fracture can be controlled by regulating valve operation,exerting management supervision,doing well the selection of valve type and optimizing the structure of valve stem.In particular,through optimizing the stem diameter transition,can effectively control stem fatigue failure.Some constructive suggestions are put forward to solve the problem of fatigue fracture at variable diameter of single seat regulating valve stem,and some references are provided for production and application.