Study On Cracking Reasons And Reparation Measures Of The Shell Of Three-phase Separator While Setting Roundness

Three-phase separator is the key equipment in the processing of oil and gas, mainly using sedimentation theory for the preliminary separation of oil, gas and water mixture. The three-phase separator which had been designed and manufactured by Lanpec Technologies Limited was the pressure vessel of classification III, and would be exported to the Republic of Turkmenistan used for the ground gathering device of the Nanyueluotan gas field, which was one part of China's "West-East natural gas transmission " Energy Strategy project.A separator shell in the manufacturing process cracked when setting roundness. If this shell was discarded, re-purchasing the shell material needed three months at least, which would seriously affect the product delivery schedule.In this paper, cracking reasons of the shell were studied. The damaged separator vessel's chemical composition, mechanical property and stress state were analyzed. The analysis results show that the cylindrical material is good. Localized mechanical damage in the clad plate caused the failure of the vessel according to the analysis results of the characteristics of cracks. During the setting roundness, the shell was rolled repeatedly and the mechanical damage was rolled repeatedly. Hardening in mechanical damage zone caused the formation of cracks and cracks development took place under the pressure of three-roller coiling.Finally, the shell was repaired by welding in the cracked zone based on the failure reasons.