Question 210Steam Plants - 1st Asst/Chief

The correct answer is C) downcomer. In a boiler, the downcomer is a tube or pipe that carries the cooler, denser water from the steam drum to the bottom of the boiler, where it can be recirculated back up through the water walls or tubes to be heated and turned into steam. The arrow labeled "E" in the illustration SG-0008 is pointing to a downcomer, which is responsible for ensuring proper water circulation within the boiler. The other answer choices are incorrect because they do not accurately describe the component indicated by the arrow. A support tube is a structural element, a recirculating tube is used for water recirculation but not specifically a downcomer, and a water wall tube is part of the heating surface of the boiler, not the water circulation system.