(under subclass 412) Miscellaneous subject matter wherein the feed water is heated in a water tube boiler, whether the water be heated outside or inside the water space of the boiler.
SEE OR SEARCH THIS CLASS, SUBCLASS:
347, and 365, for disclosures of feed water heating devices within the steam and water drum of a water tube boiler.
477, for combinations of feed heaters and superheaters.
