This paper introduces a novel method for effectively mitigating high thermal stresses caused during local postweld heat treatment (PWHT) of welds in pressure vessels on which traditional heating method such as bull's eye heating arrangement has been proven difficult in meeting Code requirements for avoiding “harmful” temperature gradients. The method involves the use of a secondary heat band (SHB) that strategically positioned at some distance away from primary PWHT heat band (HB) in terms of vessel characteristic length parameter , where is vessel radius and wall thickness. The basic principles associated with the SHB based technique are first demonstrated on a simple straight pipe girth weld configuration. Then, applications for treating nozzle welds in more complex spherical vessel, cylindrical vessel, and at end of cylindrical vessel are presented. Finally, a set of recommended guidelines are provided for defining both the SHB size and location for performing local PWHT on welds in three major nozzle/vessel weld configurations.
A Thermal Stress Mitigation Technique for Local Postweld Heat Treatment of Welds in Pressure Vessels
Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received September 2, 2014; final manuscript received October 31, 2014; published online February 27, 2015. Assoc. Editor: Haofeng Chen.
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Nie, C., and Dong, P. (October 1, 2015). "A Thermal Stress Mitigation Technique for Local Postweld Heat Treatment of Welds in Pressure Vessels." ASME. J. Pressure Vessel Technol. October 2015; 137(5): 051404. https://doi.org/10.1115/1.4029097
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