Which of the following problems can occur...

🔍 Key Concepts

• Heat transfer surface area in water screen tubes and its effect on boiler operation • Relationship between heat absorption in the furnace/waterwalls and temperatures/pressures in the superheater and drum • Difference between temperature changes and pressure changes in a controlled boiler system

💭 Think About

• If many water screen tubes are plugged and can no longer absorb heat, where does that heat go instead? How would that affect the steam flowing to the superheater? • In a properly controlled boiler, which variable is more directly controlled by the firing rate and feedwater system: drum pressure or superheater outlet temperature? • Think about whether plugging tubes changes the boiler pressure setpoint, or changes how intensely remaining heating surfaces are exposed to the same heat load.

✅ Before You Answer

• Compare which choices deal with temperature versus pressure changes and decide which is more likely to be directly affected by loss of water screen tube cooling. • Ask yourself whether plugging tubes would make the remaining gas path hotter or cooler, and what that would do to steam temperature. • Verify which components (drum vs. superheater outlet) are usually kept at relatively constant pressure by controls, and which parameter tends to vary when heat absorption patterns change.

Which of the following problems can occur when an excessive number of water screen tubes are plugged?

Superheater outlet temperature will rise.

Steam pressure leaving the drum will increase.

Steam temperature in the drum will decrease.

Superheater outlet pressure will rise.

🔍 Key Concepts

💭 Think About

✅ Before You Answer