Failure Analysis And Numerical Simulation Of The Crankshaft Of The Oxygen Compressor

Oxygen compressor(oxygen press)is widely used in petrochemical,steel and metallurgical industries,while the accidents of the fatigue fracture in the key parts of the crankshaft sometimes happen.Compressor crankshaft fracture failure is a kind of brittle fracture,which will often cause the entire production plant unplanned parking without any sign,resulting in huge economic losses.Especially for oxygen compressors,due to the high working pressure,oxygen medium has a strong combustion.So if there is the occurrence of a sudden fracture of the crankshaft,it will cause serious explosion accidents and casualties.Therefore,this paper makes the failure analysis and numerical simulation of the crankshaft fracture accident of the oxygen press,which is of great practical value and theoretical significance for optimizing the crankshaft structure as well as ensuring the safe operation of the compressor.In this,I chose a large-scale refining enterprise’s double-row fifth level oxygen press fracture failure crankshaft as the research object.I have analyzed the chemical composition,hardness and fracture morphology of the crankshaft,carrying out the kinematics and dynamics analysis of the compressor crank link mechanism as well.Also,I have used the finite element simulation method to calculate the stress and deformation of the crankshaft under normal and abnormal conditions,eventually putting forward a improved scheme of the crankshaft structure optimization.The main research work and conclusions are as follows:(1)I have confirmed the failure mode of crankshaft fracture by chemical composition analysis,hardness detection and fracture macroscopic and microscopic topography analysis of crankshaft material.The results show that the crankshaft is broken at the shaft end keyway where the pulley hub is mounted.The crack occurs at the corner of the bottom of the keyway,and the fracture is clearly stripe,which belongs to fatigue fracture;(2)I established the displacement,velocity and acceleration equations of the two rows of piston movements,analyzing the compressor crank link mechanism of reciprocating inertia force,eccentric mass centrifugal force,piston force and the transmission torque and other loads,eventually defining the dangerous conditions of the crank during the rotation as well as the load values and the position of the action;(3)By established a three-dimensional solid model of crankshaft,I have carried out numerical simulation of finite element strength of crankshaft under normal operating conditions and abnormal conditions.As a result,the crankshaft maximum stress value is small,which will rarely cause fatigue fracture under normal operating conditions.While under abnormal operating conditions,as the maximum stress of the crankshaft which occurs at the bottom of the crankshaft shaft key groove increases dramatically.Actually,such position is consistent with the actual fracture position of the crankshaft.The main reason why the crankshaft fracture failure occurs under abnormal conditions is that the crankshaft shaft keyway passes a large torque,resulting in a large peak stress at inner thread,with the fatigue cracks occurring from the bottom of the keyway and extending to the outside,finally causing crankshaft fracture;(4)Having summarized the main reason for the failure of crankshaft fracture,I have proposed an improved scheme for crankshaft structures,making the numerical simulation of intensity.Meanwhile,I have figure out the improved crankshaft finite element model.By comparing structure before and after improvement,the maximum stress position of the crankshaft has not changed,but the maximum stress value is drastically reduced,thus avoiding the crankshaft fracture failure accident occurring.