Abstract: When the equipment needs thermal insulation for a long time or/and postwelding heat treatment (PWHT) at higher heating temperature, the actual properties of skirt material will be reduced if the skirt cylinder needs PWHT with the equipment. Through analysis, it is considered that when the tempering parameter P is large, the skirt material should be subjected to simulated PWHT or the test sample to verify that the actual properties of skirt material can meet the properties. Local PWHT can also be considered to reduce thermal insulation time.In the case where all the axial stresses of the skirt cylinder are all compressive stresses, the possibility of using the lower heating temperature system used in the intermediate stress relief heat treatment for local postweld heat treatment can be considered if necessary.

Key words: post-welding heat treatment, skirt, mechanical properties