The 4094-D is the largest fireless steam locomotive ever built and was originally built for the Hammermill Paper Company in Erie.

a "Fireless" type locomotive, often described as a giant thermos bottle. Fireless locomotives were used in industrial plants that had steam generating equipment for other purposes. They received and stored steam, and were able to run for a number of hours in switching duties.

http://forums.steves-digicams.com/olympus-dslr/192716-more-locomotives-gearheads.html#b