Cause analysis and Countermeasures for tube explos

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#Cause analysis and Countermeasures for tube explosion of division platen superheater of boiler 2 at 20:22 on July 2, a serious tube explosion occurred in the division platen superheater of 2 boiler of Pingdian company. The huge leakage shook the whole boiler, and a harsh sound was heard tens of meters outside the boiler. At that time, the unit load was 560MW. At 21:00, the load of the unit was reduced, at 22:19, the unit was disconnected, the scaffold in the boiler was erected and maintained at 8:30 on the 4th, the maintenance was completed at 16:08 on the 5th, and the unit was combined at 4:31 on the 6th. The shutdown time of the unit was 78.2 hours, the preparation time for shutdown was 34.18 hours, the first-aid repair time was 31.63 hours, and the startup time was 12.39 hours

1 on site inspection and maintenance conditions

(1) pipe explosion position: separation screen 4 screen front component outlet section 2 pieces, el:50mm above the 55.6m welded junction, 2.1m from the screen bottom

constitute a complete product service system

(2) conditions of adjacent heating surfaces: the steam leaked from pipe explosion has blown damage to the adjacent pipe wall. In fiscal 2016, the operating revenue reached 1.3040 trillion yen. The steam corrodes the outer wall of the pipe in the area in the high-temperature flue gas, but they are all light. The 3 ring lower elbow was actually flattened due to the deformation of the 2 root of the burst leakage due to the large steam impulse. The outer walls of adjacent 3, 4, 5 and 6 root canals are overheated and oxidized, and there is obvious oxide skin at higher places. What is more serious is that the outlet sections 2, 3, 4, 5 and 6 of the rear assembly on the opposite side are severely deformed at a higher place. The deformation is caused by overheating, and there is thick oxide skin on the outer wall of the pipe. The front end of the fluid cooling spacer tube of the front assembly collided with the cushion block, and the tube wall was worn by 2mm

(3) field treatment: replace 2 lower elbows and 8m long rising section with 4 welds in total when 2 test pieces are brittle fracture; Replace the flattened 3 ring elbow

2 burst tube sample

tube: 12Cr1MoV, specification: Ф fifty-seven × 9。

burst: prismatic, diagonal 120 × 51. The thickness of the burst edge is 2mm, and oxide skin is formed on the inner and outer walls. Within 100mm above the burst, the pipe is expanded into Ф 61, the expansion rate is 6.56%, and the pipe wall hardness is 119hb; Within 100 ~ 200mm from the blasting opening, the pipe is expanded into Ф 59,, the expansion rate is 3.5%, the pipe wall hardness is 109hb, and the pipe is expanded into Ф 60.5, and the expansion rate is 6.14%. The hardness at the crater is 116hb, and the hardness at the side and back of the crater is 112/98hb

there are a large number of longitudinal cracks on the outer wall of the pipe within 1.5 meters above and 0.4 meters below the crater, and the oxide skin on the pipe wall is thick. Due to the great reaction force of the leaked steam, a nearly 90 ° elbow has been formed at the explosion opening, which has expanded the explosion opening, and the pipe wall at the edge of the explosion opening has been thinned and torn

structure introduction of 3 partition superheater

structure diagram of inlet tee partition platen superheater

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