The #4 boiler of Anshun Power Plant is DG1025/18.2--Ⅱ10 type W-flame boiler produced with Dongfang-Foster Wheeler technologies. Each boiler is equipped with two blowers. The #4 boiler was put into production in 2003 and has been running for near 11 years. During the operation process, the blower had many faults.

Blowers in Anshun Power Plant are axial-flow fans with adjustable moving blades produced with the exclusive VARIAX technology of Denmark NOVENCO, featuring adjustable blade angle and high fan efficiency during operation. The fan is assembled on site mainly with rotor assembly, bearing set, air intake box, main air cylinder, diffuser cylinder, and the automatic control system. It is equipped with a stall probe. The rotor assembly part includes the wheel hub, blade, hydraulic adjustment mechanism and the adjustment drive.

Technical data of the blower:

Model: ASN-2180/1000    Flow: 611578m3/h

Full pressure: 4716 Pa    Speed: 1490 r/min    Efficiency: 85.3%

On October 26, 2012, the metal impact sound suddenly appeared in the blower A of #4 unit, and the temperature of the thrust bearing on the CRT screen rose rapidly from 45℃ to 107℃. The blower A coupler bolts were all cut off, and A coal mill was stopped emergently to maintain stable combustion, with the load reduced from 300MW to 210MW.

Our vibration expert arrived at the Plant and investigated and analyzed the fault, learning that no abnormality was discovered before the fan trip, with all parameters being normal, the blade opening 45%, the same as opening of the blower on B side. Inspections in the fan showed that all 17 moving blades were broken from the roots, the moving blade adjustment mechanism was damaged, all the three oil pipes were broken, the main shaft of the fan was slightly bent, and bearings on the thrust side and the supporting side were damaged. The six fixing bolts of all the blades were intact.

The alloy detector was used for checking and analysis, concluding that the cause of the accident was that poor material of the blower blade. One blade suddenly broke during operation, collided with other blades and caused all 17 blades to break. If the Power Plant could build a precision diagnosis platform, equipped with BCT102, the large rotating equipment online monitoring system of BKC, it can prevent the occurrence of accidents and thereby save huge economic losses for the Power Plant.