Economizer

—An arrangement of tubes placed in the uptake or flues of a boiler serving as a feed water heater, thus effecting economy by extracting further heat from the furnace gases after they have pa ed through the boiler itself and before they are discharged by the chimney. In connection with stationary boilers, the tubes of the economizer are vertical; they are kept clean by ring scrapers continually traveling up and down them, a small engine being provided for driving the scraper mechanism. In certain water tube boilers, the economizer consists of a series of elements similar to that of the boiler proper, so that it really constitutes a second boiler.