A complete finite element model for boiler drum

which is based on the actual boiler drum structure size

was established by pre-processor of ANSYS

to study the effects of hot start-up speed on stresses in boiler drum.Combining with the hot start-up curves given by operation rules and five hot start-up curves at different temperature rising rates

the transient stress field of the boiler drum was investigated.The results indicate that

during the hot start-up

the maximum mechanical stress intensity and the maximum total stress intensity locate at the inner joint corner of drum shell and downcomer in the longitudinal cross section.The maximum thermal stress intensity locates at the inner joint corners of drum shell and risers which are in contact with the normal water line in the horizontal cross section.As the temperature rising rate increases from 2 ℃/min to 5℃/min

the hot start-up speed has no effect on the maximum mechanical stress intensity of the most dangerous point on the boiler drum

but the maximum thermal stress intensity increases with the temperature rising rate.In the latter stage of hot start-up process

the thermal stress is not going to work.The total stress is largely driven by the mechanical stress.So the maximum total stress intensity is the same as the maximum mechanical stress intensity

and they don't change with the temperature rising rate but with the pressure in the drum.Therefore

the boiler drum can suffer a higher temperature rising rate during the hot start-up

compared with the value given by the operation rule.