With the concentric reducers of high-temperature steam pipelines in thermal power plants being the research object

the stress analysis of reducers under theoretical load conditions was carried out

and the stress distribution cha-racteristics of reducers under the action of internal pressure

axial tension

bending moment

and torque were studied respectively.The results were compared with previous similar research so as to verify the correctness of the analysis model.The paper takes a heat pipe reducer of a 660 MW ultra-supercritical unit as the research object to establish a local finite element three-dimensional analysis model comprising a reducer

45-degree forged triplet

and straight pipeline to study the stress distribution of the 45-degree forged triplet and reducer under service condition.The results show that the forged triplet is inferior in overall stress level

there is a local stress concentration area at the shoulder of its acute angle in the thermal state

and the main stress concentration area of the reducer is located at the bending angle

although the stress concentration areas in the hot and cold states are different.