The real thermal displacement of rear downcomer in boiler of 300 MW unit in one power plant is somewhat small

having comparatively large diferrence with the designed value. After the external factors being eliminated through rectification

the internal reasons have been found by using the stresscalculating method. Summing up results of field inspection

as well as of calculation and analysis for the static force of pipelines

it is believed that the variation of steadiness concerning constant force hanger to be the main cause leading to that the thermal displacement of the hanging point can’t reach the designed value.