Causes of dry gas sealing disc stud fracture of centrifugal compressor in ethylene plant

The dry gas seal disc stud of a centrifugal compressor was broken. The causes of stud fracture were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, hardness test, scanning electron microscopy and energy spectrum analysis. The results show that the carbon element content of 304 stainless steel stud was high, the material was sensitized during high temperature service, and the corrosion resistance of the stud decreased. The water－containing corrosive medium entered the gap between the butt flanges and contacted the polished rod position in the middle of the sensitized double－headed stud, causing local micro－corrosion on the surface of the material. Under the combined action of the fastening stress of the stud, the stress corrosion crack initiated from the corrosion position and propagated along the radial intergranular direction, eventually leading to the fracture of the stud.