In a D-type boiler, downcomers connect the steam drum to the water drum.

In a D-type boiler, downcomers connect the steam drum to the water drum.

• A. They transfer steam from the steam drum to the water drum
• B. Water drum to steam drum
• C. Drain from the steam drum to the furnace
• D. Steam drum to water drum

Answer: (D)

Downcomers form the downward path in boiler circulation, carrying water from the steam drum back down to the water drum. In a D-type boiler, water circulates by a loop: cooler water returns from the steam drum through the downcomers to the lower drum, then moves through the furnace tubes where it is heated, rises as steam in the riser sections, and returns to the steam drum. This downward flow is essential to sustain continuous circulation and proper boiler operation. So, downcomers are the connections that move water from the steam drum to the water drum, not steam, not water in the opposite direction, and not drains.

Downcomers form the downward path in boiler circulation, carrying water from the steam drum back down to the water drum. In a D-type boiler, water circulates by a loop: cooler water returns from the steam drum through the downcomers to the lower drum, then moves through the furnace tubes where it is heated, rises as steam in the riser sections, and returns to the steam drum. This downward flow is essential to sustain continuous circulation and proper boiler operation.

So, downcomers are the connections that move water from the steam drum to the water drum, not steam, not water in the opposite direction, and not drains.