In a D-type boiler, the downcomers connect which two components?

In a D-type boiler, the downcomers connect which two components?

• A. Water drum to feedwater heater
• B. Steam drum to furnace
• C. Steam drum to water drum
• D. Furnace to water drum

Answer: (C)

Downcomers are the downward legs of the natural circulation loop in a water-tube boiler. In a D-type boiler, they connect the steam drum at the top to the water drum at the bottom. Their job is to carry feedwater from the steam drum down to the lower water drum, forming the return path that feeds the furnace waterwalls and risers. As water is heated in the lower drum and through the furnace, it rises through the risers to the steam drum where steam is separated; the cycle then continues with the downcomers returning water to the lower drum.

Downcomers are the downward legs of the natural circulation loop in a water-tube boiler. In a D-type boiler, they connect the steam drum at the top to the water drum at the bottom. Their job is to carry feedwater from the steam drum down to the lower water drum, forming the return path that feeds the furnace waterwalls and risers. As water is heated in the lower drum and through the furnace, it rises through the risers to the steam drum where steam is separated; the cycle then continues with the downcomers returning water to the lower drum.