Failure Analysis On Clutch Bolt Of Extruder At High-Pressure Polyethylene Plant

Extruder is an important equipment in petrochemical plant,the failure of bolt in the extruder results in the shut-down and maintenance of industrial equipment,and even leads to heavy casualties.Therefore,it is essential to analyze the reason and mechanism of bolt failure.This paper views the failure of the coupling bolt of high pressure polyethylene unit as the research object,and presents a systematic study of the cause and the mechanism of bolt failure in an extruder by referencing to Brook's failure analytical procedures and ASM failure analytical procedures.The following works will be carried out this thesis.1.Using tensile test,blow test and hardness test,we evaluated the mechanical properties of two materials,38 Cr Mo Al and 40 Cr Ni Mo A.Then,the chemical characters of those materials were studied using Sequential X-Ray Fluorescence spectrometer,while surface profile of the fracture Nick rent was studied using scanning electron microscope.2.The static intensity was checked,the tightening torque and the friction force of the joint face were calculated.Through theoretical and experimental analysis,it shows that the fracture of bolt wasn't caused by pulling stress or shearing stress;though the obvious fatigue striation were not found,according to many crack initiations found in the bottom of thread and macroscopic analysis of plane of fracture,we can draw a conclusion that the fluctuating load produced by friction force of composition face leads to the fatigue fracture.Upon the above conclusion,we propose that the bolt fracture can be avoided by controlling bolt pretension,using high-strength material,ensuring the bolt grade is 10.9 or12.9 and keeping neutral when the clutch is working.