🔍 Key Concepts

• Water-tube boiler construction – how tubes carry water/steam between drums • What happens to trapped water or steam in a closed space when it is heated • Why a sagged tube is damaged and what plugging the tube actually does

💭 Think About

• If you plug both ends of a damaged tube without opening it, what is left inside that tube as the boiler heats and cools? • How do volume and pressure of a fluid (especially water turning to steam) change when heating in a sealed space? • Which of the answer choices best matches the main safety risk created by heating fluid in a sealed, damaged tube?

✅ Before You Answer

• Confirm what plugging a tube physically does: does it open the tube or seal it off from both ends? • Think about whether sagging alone causes the main danger, or if the danger comes from changes in pressure/temperature inside that damaged tube • Match the risk you’ve identified with the most directly related choice among the four options