An analysis of problems arising during operation of the perm district power plant 800-MW power unit at sliding pressure

Abstract

The occurrence of cracks at locations in which bottoms are welded to the high-pressure heaters’ headers was revealed during planned repairs of the Perm district power plant units. Specialists of the All-Russia Thermal Engineering Institute carried out investigations aimed at obtaining more detailed data on the effect the loading cyclicity and sliding-pressure operating modes have on the reliability of power-generating equipment. Another aim of those investigations was to elaborate recommendations for achieving more reliable operation of power-generating equipment under the conditions of cyclic variation of its load. The state of the main and auxiliary equipment of the Perm district power plant units is analyzed for determining the possibility and advisability of their further operation in sliding-pressure modes. The results obtained from calculating the permissible number of load variation cycles for the headers used in the Perm district power plant units operating under the conditions of startup–shutdown modes are analyzed, and the headers’ residual cyclic service life is estimated. The results obtained from a metallographic investigation of the high-pressure header’s bottom in the welded joint of which a through crack was revealed are presented. Recommendations for examining the header bottoms and for modifying their design in order to improve their operational reliability are given.