Reason Analysis of Cracking of Liquid Level Gauge Pipe in Acid Gas Separator Tank of Sulfur Plant
An obvious cracking leak occurred at the bottom weld of the liquid level gauge tube of an acid gas separation tank in a sulfur plant.The results of macroscopic and low-power analysis,material analysis,metallographic inspection and electron microscope analysis of the liquid level gauge show that the material of the liquid level gauge tube and flange are S20430 stainless steel(200 series).The metal structures of the liquid level gauge tube,flange and weld are austenite,sensitized austenite,as-cast austenite and a small amount of ferrite,respectively.The cracking failure property of the liquid level gauge tube is stress corrosion,which is mainly transgranular expansion.The main reason for the cracking of the welding between the liquid level pipe and the flange is that the liquid level pipe and the flange are both made of materials that are more sensitive to stress corrosion,there is residual stress in the welding area of the two,and the bottom of the liquid level pipe is a closed area with acidic medium(H2S solution and H2CO3 solution).
sulfur plantacid gas separator tankliquid level gauge tubestress corrosion cracking
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