🔍 Key Concepts

• Difference between natural circulation and controlled/forced circulation in water-tube boilers • What having one or more water drums tells you about the boiler’s basic construction • How header-type vs drum-type boilers are identified in marine engineering terminology

💭 Think About

• Ask yourself: In a natural circulation boiler, what actually causes the water/steam to move through the tubes—pumps or density difference? Which option names that correctly? • Which of the choices specifically refers to the presence of water drums as a main identifying feature of the boiler? • Does “header-type” usually mean multiple small headers feeding tubes rather than large drums, or the other way around?

✅ Before You Answer

• Identify which option’s name clearly connects to the phrase "one or more water drums" in the question • Confirm that natural circulation in the stem matches the circulation type implied by your chosen option • Eliminate any option that implies forced/controlled circulation using pumps rather than natural thermal circulation