Local Heating Treatment for Main and Auxiliary Heating of the Tubesheet's Girth Weld on High-pressure Liquid Ammonia Preheater
The local heat treatment of tubesheet's girth weld means great to the service safety of high-pressure liquid ammonia preheaters.Both uneven temperature distribution and large tubesheet constraint in traditional local heat treatment make it difficult to eliminate residual stress.Therefore,the local heat treat-ment method for main and auxiliary heating was adopted,and the effectiveness of this method in the high-pressure liquid ammonia preheater was verified.Both calculation and test results show that,the traditional local heat treatment only reduces the axial and circumferential residual stress of the outer surface,while the axial stress of the inner surface increases slightly and the circumferential stress decreases slightly.The local heat treatment for the main and auxiliary heating can reduce the axial stress of the inner surface from 283 MPa to less than 100 MPa,a decrease of about 64%,and the circumferential stress from 324 MPa to 206 MPa,a decrease of about 37%,which can significantly reduce the sensitivity to stress corrosion cracking on the equipment's inner surface.
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