Overview of advanced methods of boiler tubes erosion protection

Abstract

Based on the analysis of the exploitation behavior of domestic thermal power plants it was concluded that the failures on the boiler tubing systems is due to erosion by flying ashes and that it is the main cause for the boiler tube failure especially in the evaporator and economiser surfaces. Current boiler tube erosion protection methods can be classified into three basic categories: a) welding overlay; b) thermal spraying (metallization) and c) mechanical protection. Welding overlay and thermal spraying procedures are successfully implemented on the clean boiler tubings prior to installation, although the same procedure with qualitative preparation (cleaning) can effectively be used even with the boiler tubings that were in the operation for a period of time. On modern thermal power plants in the world, thermal spraying method is widely used for the protection against erosion, abrasion and corrosion. Despite being inexpensive, mechanical protection methods are generally not used in the modern systems because of limited lifetime, difficulties during dismantling and reduced heat transfer on the protected tubings. In order to reduce the number of outages (direct material saving) and thus improve the operational reliability, availability and competitiveness, the use of modern erosion protection methods is of high priority.