🔍 Key Concepts

• Waterside scale forms on the water side (inside) of boiler tubes and acts like insulation, not a conductor • Think about what happens to metal temperature if heat cannot easily pass from the hot gas, through the tube wall, into the water/steam • Distinguish between waterside problems (inside tube, water side) and fireside problems (gas side, combustion side)

💭 Think About

• If scale reduces heat transfer from metal to water, what happens to the tube metal when the burner keeps putting the same heat in? Cooler or hotter? • Which choice clearly describes a waterside effect inside the tube, versus something that would more likely occur on the gas/combustion side? • Look for the option that matches the idea of insulation building up on the water side and the consequences of poor cooling of the tube wall.

✅ Before You Answer

• Confirm that scale is an insulating layer, not something that improves heat transfer • Identify which option is clearly a fireside phenomenon and eliminate it • Ask yourself: which choice describes the direct consequence of tube metal not being properly cooled by the water/steam on the inside?