Cause Analysis And Solution Of Tube Burst Caused By Oxide Skin Peeling On A Supercritical Boiler

With the ever-increasing development of electric power construction in China and capacity of power units, supercritical boiler and ultra-supercritical boiler is fast establishing themselves as a first-team regular. As parameters have been improved, oxide skin has more pronounced effects on the safe running of the boiler and steam turbine.Oxide skin is analyzed on formation mechanism and influencing factors in this paper. With some practical examples in domestic power plants, the paper particularly analyzes harms caused by oxide skin peeling. For corrosion of solid particles in steam turbine, the theoretical work focuses on corrosion mechanism, influencing factor and preventive measures.To solve the problem in JinWan power plant, we analyzes from various aspects, including boiler design, operation, metal material, characteristics of oxide skins, law of metal oxide skins peeling and field measurements data of metal oxide skins. The major cause of tube burst in the heating surface was that the final superheater use a large quantity of T23 materials, which overheated for a long time, and T23 overheating caused the peeling and deposit of metal oxide skins of T23 inner wall. The clogging in the lower elbow whose workmanship is inferior can reduce the streaming area. The level of the material of inner ring tubes is the low, and the temperature margin is small. The above two factors cause the tube overheating for a long time, accelerate the formation and peeling of oxide skins, and lead to a tube burst eventually.In terms of combustion adjustment, equipment modification and optimization of startup mode, a comprehensive solution is presented to relieve the formation of metal oxide and prevent metal oxide skin peeling. According to on-site experience, the preventive solution, which has been implemented, reduces effectively the harms of metal oxide skin peeling on boiler in JinWan power plant. The remolding solution, which remains to be implemented, can eradicate the problems of metal oxide skin peeling.