In boilers, several types of pipes and tubes are used, each serving distinct purposes for efficient energy transfer and system integrity:

Water Tubes: These are used in water-tube boilers, where water circulates inside the tubes and is heated by combustion gases outside the tubes. Made typically from carbon steel or alloy steel to withstand high pressure and temperatures, water tubes are essential in generating steam for power.

Fire Tubes: In fire-tube boilers, hot gases pass through tubes surrounded by water. These are generally used in lower-pressure applications and are constructed from materials like mild steel.

Superheater Tubes: These tubes are exposed to extremely high temperatures and are critical for raising the temperature of steam above its saturation point. Often made from heat-resistant alloys like stainless steel (such as TP347 or TP321) to handle the intense thermal conditions.

Economizer Tubes: Used in the economizer section of boilers, these tubes preheat the feedwater, improving efficiency by recovering waste heat from flue gases. Economizer tubes are typically made of carbon steel due to moderate temperature requirements.

Reheater Tubes: These tubes reheat steam that has already passed through part of the turbine, increasing its temperature for higher efficiency. Reheater tubes are made from alloy steels that resist high-temperature scaling.

Each of these tubes is selected based on pressure and temperature conditions, with materials ranging from mild steel to high-temperature alloys to withstand thermal stresses and prevent corrosion.