Optimum heating of pressure components of steam boilers with regard to thermal stresses

Abstract

ABSTRACTA method for determining time–optimum fluid temperature changes is presented. In contrast to current standards, stepwise fluid temperature changes are allowed. The optimum fluid temperature changes are assumed in the form of a simple time function. It is possible to increase the fluid temperature stepwise, and then the fluid temperature can be increased with a constant rate at the beginning of the heating process. The permissible rates of the fluid temperature change determined by the proposed method are smaller than those obtained by boiler standards. But, due to the abrupt increase in fluid temperature, the heating time of a thick-walled component is of the same order as in the case of calculations according to EN 12952-3 European Standard. However, the total circumferential stresses on the edge of the hole do not exceed the allowable value.