Studded Finned Tube ASME SA335 P9 with Alloy Steel Studs for Heater and Furnace

A studded finned tube is a type of heat exchanger tube that has been enhanced with studs to improve its ability to transfer heat between two mediums, typically fluids and gases. The presence of studs increases the surface area without significantly enlarging the footprint of the tube. The increased surface area allows for more efficient heat transfer, since there is more material available to absorb heat from the hot medium and transfer it to the cooler one.

The studs are usually arranged in a uniform pattern and are welded to the outside of the tube. In heat exchangers, the fluid runs through the tube while the gas flows around the outside, passing over the studs. As the gas transfers its heat to the studs, the heat is then conducted into the tube and to the fluid inside.

Notes: The 9% Cr-1% Mo composition provides high-temperature strength and oxidation resistance. Low carbon content helps with weldability.

Notes:

• Heat Treatment: Usually supplied in normalized & tempered condition for optimal strength and ductility.
• High-Temperature Performance: Retains strength up to ~650 °C (1200°F).
• Weldability: Requires preheating (~200 -300°C) and post-weld heat treatment (PWHT) to avoid cracking.

• P9 has higher Cr than P11 (1.25% Cr) but lower than P91 (9% Cr with Nb/V).
• Better oxidation resistance than P22 (2.25% Cr) but less creep resistance than P91.

Instead of helical fins, this tube has alloy steel studs welded radially onto the outer surface.

• Material: Studs are often made of alloy steel (e.g., similar to P9 or other high-temperature alloys) for compatibility and durability.
• Purpose: Increases the heat transfer surface area, improving thermal efficiency in gas-to-liquid or gas-to-steam applications.

• Better erosion/corrosion resistance in harsh environments (e.g., flue gas, fluidized beds).
• Reduced risk of fin breakage compared to thin, continuous fins.
• Enhanced turbulence for improved heat transfer.

• Increased Surface Area: The studs significantly increase the surface area in contact with the heat-carrying medium (usually gases), thus facilitating more heat transfer.
• Compact Design: Studded tubes maximize the surface area for heat transfer without taking up as much space as traditional finned tubes, allowing for a more compact design.
• High-Temperature Applications: Studded tubes are resilient and capable of withstanding extreme temperatures, which is beneficial for heat recovery in combustion or high-temperature process applications.
• Reduced Fouling: The design of studded tubes can help reduce fouling because of the smooth surface of the studs, which is less prone to the buildup of deposits compared to other fin types.

• Heat Recovery Steam Generators (HRSGs) - Recovers waste heat from gas turbines to produce steam.
• Fluidized Bed Boilers (FBC Boilers) - Resists abrasion from bed materials (sand, ash).
• Superheaters & Reheaters - Withstands high-pressure steam (up to 650°C).

• Fired Heaters & Process Furnaces - Efficient heat transfer in crude oil refining.
• Catalytic Cracking Units (FCCU) - Handles corrosive flue gases.
• Coker Units - Resists fouling and thermal stress.

• Waste-to-Energy Plants - Handles aggressive flue gases (HCl, SO₂).
• Air Preheaters (APH) - Recovers heat from exhaust gases.

• Sulfuric Acid & Ammonia Plants - Resists acid dew point corrosion.
• Syngas Coolers - Cools high-temperature synthesis gas.

• Clinker Coolers - Recovers heat from cement kilns.
• Blast Furnace Gas Ducts - Withstands erosive dust-laden gases.