In a D-type steam boiler, downcomers are used to transfer water from the water drum to the steam drum.

In a D-type steam boiler, downcomers are used to transfer water from the water drum to the steam drum.

• A. True
• B. False
• C. They transfer steam from the steam drum to the water drum
• D. They transfer water from steam drum to water drum

Answer: (B)

Downcomers form the downward leg of the boiler’s natural circulation. In a D-type water-tube boiler, water moves up through risers from the lower drum to the steam drum where it becomes steam, then the liquid water returns down through the downcomers back to the lower drum. They carry water downward, not steam, and not upward from the water drum to the steam drum. So the statement that downcomers transfer water from the water drum to the steam drum is false. The correct description is that they transfer water from the steam drum to the water drum, completing the circulation loop.

Downcomers form the downward leg of the boiler’s natural circulation. In a D-type water-tube boiler, water moves up through risers from the lower drum to the steam drum where it becomes steam, then the liquid water returns down through the downcomers back to the lower drum. They carry water downward, not steam, and not upward from the water drum to the steam drum. So the statement that downcomers transfer water from the water drum to the steam drum is false. The correct description is that they transfer water from the steam drum to the water drum, completing the circulation loop.