Design and Application of the Protection Casing in Boiler of Power Plant

Abstract

Based on the load characteristics and failure mode of the protective casing in boiler in power plant, its design principle and management strategy were put forward. The protective casing shall be configured in the areas with different temperature medium mixing, such as boiler drum water supply pipe, recycling pipe, balance vessel pipe, superheater and desuperheater header, desuperheater spray pipe, etc. The structure and material of the casing shall be able to avoid the thermal stress directly acting on the component body. In terms of application management, visual inspection and nondestructive surface testing shall be carried out for the casing and its connecting areas in which the key parts of inspection included stress concentration areas, such as welding joints, grooves, hole edges and welding defects during equipment maintenance. Different methods such as grinding and welding and reaming and replacement and others are used to deal with casing defects according to its severity. The feasibility and reliability of the above design principles and application and management strategies were proved by several engineering examples.