Studded tubes, also known as nail-head tubes, pin tubes, or studded fin tubes, are high-efficiency extended-surface heat transfer elements. Our ASTM A106 Gr.B carbon steel studded tubes consist of a seamless base tube manufactured to ASTM A106 / ASME SA106 Grade B, with solid carbon steel (CS) studs resistance-welded onto the outer surface. These tubes significantly increase the external heat transfer area, typically 2–3 times that of a bare tube, while maintaining excellent mechanical strength and resistance to fouling and aggressive cleaning. They are widely used in high-temperature, high-pressure, and corrosive flue-gas environments in the petrochemical, power generation, and process industries.
The structure comprises three key elements:
Base Tube – Seamless carbon steel pipe conforming to ASTM A106 Gr.B / ASME SA106 Gr.B, designed for high-temperature service.
Studs (Fins) – Solid cylindrical (or occasionally elliptical/lens-shaped) carbon steel pins.
Bonding Process – Fully automatic electrical resistance welding (also called resistance stud welding or forge welding). High current and pressure create a true metallurgical forge weld with full penetration and minimal heat-affected zone. No filler metal is used. The process is PLC-controlled for precise stud height, diameter, pitch, and circumferential density.
This welding method produces a bond stronger than the parent materials, allowing the tubes to withstand severe mechanical cleaning (high-pressure water jetting, shot blasting) and thermal cycling without stud detachment.
The chemical composition of the ASTM A106 / ASME SA106 Grade B base tube is as follows:
| Element | Requirement |
|---|---|
| Carbon (C) | ≤ 0.30 |
| Manganese (Mn) | 0.29 – 1.06 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.035 |
| Silicon (Si) | ≥ 0.10 |
| Chromium (Cr) | ≤ 0.40 |
| Molybdenum (Mo) | ≤ 0.15 |
| Nickel (Ni) | ≤ 0.40 |
| Copper (Cu) | ≤ 0.40 |
| Vanadium (V) | ≤ 0.08 |
The mechanical properties of the base tube are as follows:
| Property | Requirement |
|---|---|
| Tensile Strength, min | 415 MPa (60,000 psi) |
| Yield Strength, min | 240 MPa (35,000 psi) |
| Elongation in 50 mm, min | 30% |
| Hardness, max | 197 HBW |
The studded tube design and manufacturing parameters are summarized below:
| Parameter | Specification |
|---|---|
| Base Tube Material | ASTM A106 Gr.B / ASME SA106 Gr.B |
| Stud Material | Carbon Steel (CS) |
| Base Tube OD | 25 – 219 mm (1″ – 8″ NPS) |
| Wall Thickness | 3.5 – 20 mm (Sch 40 – Sch 160) |
| Stud Diameter | 6 – 25.4 mm (0.25″ – 1″) |
| Stud Height | 10 – 38 mm |
| Stud Pitch (Spacing) | 8 – 30 mm |
| Stud Shape | Cylindrical, elliptical, or lens-shaped |
| Tube Length | Up to 15 – 28 m (customizable) |
| Operating Temperature Range | –29°C to 565°C |
| Stud Density | Typically 2–3 times the surface area of a bare tube |
The manufacturing process of ASTM A106 Gr.B studded tubes involves fully automatic electrical resistance welding. The key steps include:
Raw Material Inspection – Base tubes and studs are inspected for chemical composition, dimensions, and surface quality.
Tube Preparation – Tubes are cleaned and prepared to ensure proper bonding.
Stud Welding – Studs are automatically welded to the tube surface using a PLC-controlled resistance welding machine. The welding parameters, including stud height, diameter, pitch, and circumferential density, are precisely controlled.
Quality Control – Weld integrity is verified through visual inspection and mechanical testing.
ASTM A106 Gr.B studded tubes are widely used in applications requiring high heat transfer efficiency in demanding environments:
Steam Reforming Furnaces – Convection section tubes for hydrogen and syngas production.
Waste Heat Recovery Systems – Heat recovery from flue gas and exhaust streams in petrochemical and power plants.
Fired Heaters – Convection chamber heating in refinery and petrochemical furnaces.
Boilers – High-pressure boilers for power generation and industrial heating.
Heat Exchangers – Shell and tube heat exchangers in chemical and petrochemical industries.
Air Preheaters – Combustion air preheating in industrial furnaces.
Economizers – Flue gas waste heat recovery for boiler feed water preheating.
Superheaters – Steam superheating in power generation and process industries.
Each studded tube undergoes inspection and testing in accordance with applicable standards and customer specifications:
Hydrostatic Test – Performed on the base tube per ASTM A106 requirements.
Non-Destructive Examination (NDE) – Ultrasonic Testing (UT) and Eddy Current Testing (ET) as specified.
Dimensional Inspection – Verification of tube OD, wall thickness, stud height, stud diameter, stud pitch, and overall length.
Material Verification – Positive Material Identification (PMI) and full traceability to mill certificates.
Visual Inspection – Surface finish, weld quality, and stud integrity.
Welding Process Control – PLC-controlled welding parameters ensure consistent stud attachment quality.
Each shipment is supplied with complete documentation including:
Mill Test Certificates (EN 10204 Type 3.1)
Hydrostatic test reports
NDE reports (if applicable)
Dimensional inspection reports
Welding procedure specifications (WPS) and procedure qualification records (PQR)
Quantity (number of pieces or weight)
Base tube outside diameter, wall thickness, and length
Stud material, height, diameter, and pitch/spacing
Finned length and unfinned sections (bare ends)
End preparation (plain ends or beveled ends)
Delivery period required
