Boiler draught control: damper function Statement: The damper in a steam boiler is provided to control the draught (rate of flow of air and flue gases) and thus regulate the rate of steam generation.

Introduction / Context:
Draught—the flow of air for combustion and flue gases through the boiler and chimney—is a key determinant of firing rate and heat transfer. Dampers are adjustable flow-restricting devices used in natural and mechanical draught systems to modulate this flow, thereby affecting furnace pressure, flame intensity, and steam production rate.

Given Data / Assumptions:

• Boiler with flue gas passages and either natural or fan-assisted draught.
• Manual or automatic damper actuation tied to firing controls.
• Safe operating practices observed to avoid excessive furnace pressure fluctuations.

Concept / Approach:
Opening the damper reduces flow resistance and increases draught; closing it increases resistance and reduces draught. Through combustion control, the damper works with fuel valves and fans to match heat input to steam demand, stabilizing steam pressure and temperature.

Step-by-Step Solution:
Demand rises ⇒ controller opens damper (and fuel), increasing air and flue flow.Higher draught elevates combustion rate and heat release.More heat to water/steam circuit ⇒ higher steam generation rate.Opposite actions occur when demand falls, preventing pressure overshoot.

Verification / Alternative check:
Boiler control schematics show damper or fan speed as primary manipulated variables for air/gas flow; operators routinely track damper position with steam demand.

Why Other Options Are Wrong:
Limiting truth to specific boiler types or loads is unnecessary; the principle applies widely across natural and mechanical draught systems.

Common Pitfalls:
Over-throttling causing high excess air or unstable flames; ignoring interlocks between fuel and air during damper adjustments.

Final Answer:
Correct