Steam boilers

Normand water tube marine steam boiler

A marine water-tube boiler employing an upper steam drum connected by banks of inclined tubes to two lower waterdrums. All the tubes discharge below the water level in the upper drum. Larges downcomers are mounted outside the furnace. The furnace is placed between the lower waterdrums and the flue gases flows between the tubes on both sides of the steam drum.
The main difference between the Normand boiler and the Yarrow boiler is that the external downcomers.