Cause Analysis And Prevention Measures Of Water-wall Tube Burst Accident Of The First Stage Boiler Of Huaneng Dalian Power Plant

The boiler water wall is the most powerful part in all the heating surfaces of the boiler,which is the key to the steam circulation of the boiler.Its internal bearing high temperature and high pressure of working medium,external bearing flue gas erosion and coal ash particle wear erosion and corrosion,it is easy to happen pipe burst and leakage problems.Once the water wall tube burst and leakage happen to the boiler,it is generally unable to be overhauled in operation,which increases the number of unplanned downtime and maintenance workload,virtually increases the operation cost and safety hidden danger,and seriously affects the safety and economy of the thermal power plant.Therefore,it is of great practical significance to study the high temperature corrosion of water wall of boiler.Through the detailed introduction of the first-phase unit of Huaneng Dalian Power Plant,including equipment specifications,design conditions,heating area,water volume volume of pressure components,technical parameters and design characteristics of the unit,it provides technical reference for the analysis of the water-wall tube burst accident of the first-phase boiler of Huaneng Dalian Power Plant.Statistics are made on the "four pipe" blowout of the first phase unit of Huaneng Dalian Power Plant.It can be seen from the statistics table and figure that the main boiler accident is the water-cooled wall blowout pipe.Through the inspection and analysis of the mechanical properties,microstructure,chemical composition and working environment of the failed waterwall pipe,it is found that the reason of the water-wall pipe burst is hydrogen corrosion.The leakage fragments of water wall were studied on macroscopic and microscopic scale,and the cause of hydrogen corrosion was analyzed.In the process of operation,the temperature of the water-wall tube facing the fire surface is high,and the oxide film is prone to rupture under the condition of overtemperature.The copper and its oxides from the upstream condenser leak deposit in the fluid stable area of the water-wall tube,forming the corrosion environment under scale.Under the combined action of many corrosion factors,hydrogen corrosion occurs to the material,and finally leads to the burst.According to the cause of hydrogen damage,the preventive measures and prolonging the service life of water wall are put forwardt.