Complex sentence: She had 56 corrugated furnaces heating six double-ended and two single-ended boilers that had a combined heating surface of and supplied steam at 215 lb f/in 2 to her two quadruple-expansion steam engines.
Split into simpler sentences: She had 56 corrugated furnaces heating six double-ended and two single-ended boilers that had a combined heating surface of. These supplied steam at 215 lb f/in 2 to her two quadruple-expansion steam engines.