On a wreck that we have been diving are two big round(about 5-6 feet in diameter) and about 10 feet long structures. The first is mostly smashed away, but the second has a grate about 3 feet in one side and a series of pipes that run lengthwise of the thing from the grate to the end. Does this sound like some sort of boiler or condenser? It is made of iron that is riveted. There is lots of iron plate around and some big timbers close by. Is there any good pics of old boilers? thanks bell