The Research on Rupture Failure Reason of Fll Main Steam Pipe

摘要

The main steam pipe of unit 2 in the upper straight part of the flowing orifice near the platform of deaerator was broken, making the unit shutdown, at 3:46, on llth,June, 1998, in Laiwu Power Plant of shandong Province. (See figure 1) The unit (125MW) was first put into operating in 1973, it had been running for 158400 hours until the failure occurred. The design material of main steam pipe is Fll (X20CrMoWV121), the design parameter is Φ273X 25(mm), the design temperature is 555 ℃,and the design pressure is 13.7MPa, and the main pipe has two side of pipe lines. From 1986, the unit loaded down the main steam changed from 555 ℃ to 540 ℃, the pressure kept the same. The highest main steam temperature is 565℃,the time that beyond the design time is not longer than 1 minute and average 3-4 times each year.