The causes leading to tube-burst failures on high-temperature superheater of supercritical 670 MW unit in Huadian Weifang Power Generation Co Ltd have been analysed

the macroscopic examination metallographic test

and mechanical test of bursted tube sections and tube-sections on same location of the neighbouring tube pannels being carried out.Results show that the bad tube-bending technology has made the flow-pasage area at both ends of the bend to be reduced

affecting the flow of steam

leading to serious ageing of pipes due to overtemperature in long-terms

further resulting in occurrence of tube-burst.For this

countermeasures

such as all the bends on inner circle of the high-temperature superheater have to be replaced

the steam and tube-wall temperature of heating surface has to be strictly controlled in the course of operation

the difference of steam temperature at outlet of high-temperature superheater shouldn't be greater than 5 ℃ at left and right side

etc.

have been put forword.After implementation

the tube-burst failures haven't occurred again.