Which boiler design is a water-tube boiler featuring three steam and water drums on the top and a mud drum beneath, interconnected by a large number of water tubes?

• A. Sterling
• B. LaMont
• C. Yarrow
• D. Babcock

Answer: (A)

This item tests recognizing a Sterling three-drum water-tube boiler by its distinctive drum arrangement. The defining feature is three drums on the top that act as steam/water drums, with a mud drum located beneath, all connected by a dense network of water tubes. This layout provides effective steam separation and distribution at the top, while the mud drum at the bottom serves as a reservoir and sediment collection point. The large number of tubes creates a big heat-transfer surface and strong circulation, which is ideal for high-pressure, rapid steam production. That combination—three top drums plus a bottom mud drum linked by many tubes—is what sets the Sterling design apart from other boiler types.