Spiral Coil Tube (Coiltube) for Heat Transfer Furnace Systems
1. Product Overview
The Spiral Coil Tube (Coiltube) is a precision-engineered stainless steel tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for high-temperature heat transfer and combustion applications within industrial furnace systems. This product is formed by continuously winding seamless stainless steel tubing into a helical (spiral) coil geometry, creating an efficient heat exchange surface area while maintaining structural integrity under extreme thermal and mechanical loading conditions.
The spiral coil configuration provides superior heat transfer performance compared to straight-tube designs, owing to the induced secondary flow patterns (Dean vortices) that enhance turbulent mixing within the tube interior. This geometric advantage allows for compact furnace designs with maximized thermal efficiency, making the product particularly suitable for helical coil heat transfer furnaces (螺旋盘管式导热炉) used in petrochemical, power generation, and industrial process heating applications.
2. Material & Properties
The Spiral Coil Tube is fabricated from high-grade austenitic and austenitic-ferritic stainless steel grades selected for exceptional resistance to oxidation, thermal cycling, and corrosive combustion environments. The material selection is guided by the operating temperature range, combustion atmosphere composition, and mechanical stress requirements of the target application.
2.1 Available Material Grades
- ASTM A213 TP304 / TP304L — General-purpose austenitic stainless steel with excellent corrosion resistance and formability; suitable for moderate-temperature heat transfer applications (up to 870°C / 1600°F).
- ASTM A213 TP310 / TP310S — High-chromium, high-nickel austenitic grade offering outstanding resistance to oxidation and thermal cycling; suitable for severe furnace environments (up to 1150°C / 2100°F).
- ASTM A213 TP321 / TP321H — Columbium-stabilized austenitic grade providing resistance to intergranular corrosion and scale formation; ideal for sustained high-temperature service.
- ASTM A213 TP347 / TP347H — Columbium-stabilized grade with enhanced creep strength and thermal stability for long-duration furnace operation.
- ASTM A213 TP316 / TP316L — Molybdenum-bearing austenitic grade with superior resistance to pitting and crevice corrosion in aggressive chemical environments.
- ASTM A213 TP904L — Super austenitic grade for extreme oxidation and corrosion resistance in the most demanding furnace applications.
2.2 Key Mechanical Properties (Representative — TP310S at Room Temperature)
| Property | Specification |
|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa (75 ksi) |
| Yield Strength (屈服强度) | ≥ 205 MPa (30 ksi) |
| Elongation (延伸率) | ≥ 40% |
| Thermal Conductivity (热导率, at 100°C) | 16.3 W/(m·K) |
| Thermal Expansion Coefficient (热膨胀系数, 20–800°C) | 17.2 × 10⁻⁶ /°C |
| Maximum Continuous Service Temperature | 1150°C (2100°F) |
3. Technical Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Spiral Coil Tube / Coiltube (盘管) |
| Product Code | 331 |
| Outer Diameter (OD) | 6.35 mm – 168.3 mm (¼" – 6½") |
| Wall Thickness | 0.5 mm – 12.7 mm (0.020" – 0.500") |
| Coil Diameter (Centerline) | 200 mm – 6000 mm (8" – 236") |
| Coil Length (per piece) | Custom, up to 200 m (656 ft) per coil |
| Helix Pitch (螺距) | 10 mm – 150 mm (adjustable per design) |
| Surface Finish | Mill finish (2B), Pickle & Passivate, or Polished (Ra ≤ 0.4 μm) |
| End Preparation | Plain end, Beveled (45°), Threaded (BSW/NPT), or Flanged |
| Applicable Standards | ASTM A213, ASTM A269, EN 10216-5, GB/T 14976, JIS G3459 |
| Heat Treatment | Solution Annealing (1040–1120°C), Stress Relief (optional) |
| Maximum Operating Pressure | Up to 15.0 MPa (2175 psi) — dependent on wall thickness |
| Operating Temperature Range | −196°C to +1150°C (−321°F to +2100°F) |
| Coil Tolerance (OD) | ±0.15 mm or ±0.05", whichever is greater |
| Coil Tolerance (Wall Thickness) | ±10% of nominal |
4. Manufacturing Process
The production of the Spiral Coil Tube involves a multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and uniform heat transfer performance across the entire coil length.
4.1 Process Flow
- Raw Material Procurement & Inspection: Seamless stainless steel tube stock is sourced from certified mills and subjected to incoming quality inspection including chemical composition analysis (spectrometry), mechanical testing, and visual surface examination.
- Tube Straightening & Cutting: Straightened tube stock is cut to the required coil length using precision sawing or laser cutting, with end faces ground smooth to prevent flow disturbances.
- Helical Coiling (螺旋盘绕): The tube is wound onto a precision-machined coiling mandrel using a CNC-controlled coiling machine. The coiling parameters (diameter, pitch, tension) are programmatically controlled to maintain uniform helical geometry and avoid work-hardening or plastic deformation of the tube wall.
- Welding & Joining: Where multi-section coils are required, butt-welded or orbital-welded joints are performed in a controlled argon atmosphere to maintain the corrosion resistance of the weld zone. Weld seams undergo radiographic testing (RT) or ultrasonic testing (UT) for full volumetric inspection.
- Heat Treatment: The completed coil is solution-annealed in a protective atmosphere (vacuum or inert gas) at 1040–1120°C followed by controlled cooling to restore full austenitic microstructure, relieve residual stresses from coiling, and optimize corrosion resistance.
- Surface Treatment: Pickle and passivate treatment is applied to remove scale and oxide layers formed during heat treatment, restoring the passive chromium oxide film essential for long-term corrosion protection.
- Final Dimensional Inspection: The finished coil is inspected for coil diameter tolerance, pitch uniformity, OD/wall thickness compliance, and surface finish quality.
- Packaging & Dispatch: Coils are wrapped in protective film, secured with strapping, and packed for shipment with accompanying material test certificates (MTC) and quality documentation.
4.2 Key Process Controls
- Coiling Tension Control: Real-time monitoring of tensile stress during winding ensures the coil retains its helical shape without springback or permanent deformation.
- Atmosphere Control during Annealing: Dew point maintained below −60°C to prevent re-oxidation and decarburization of the tube surface.
- Weld Quality Assurance: 100% visual inspection plus random RT/UT sampling (minimum 10% per production lot) for weld seam integrity.
5. Applications
The Spiral Coil Tube is engineered for demanding thermal applications where efficient heat transfer, corrosion resistance, and structural reliability are critical.
5.1 Primary Application Domains
- Helical Coil Heat Transfer Furnaces (螺旋盘管式导热炉): The coil serves as the primary heat transfer surface in process gas or liquid heating systems, where combustion flue gases transfer thermal energy to the working fluid flowing through the coiled tube. Numerical simulation studies (CFD and conjugate heat transfer modeling) have confirmed that the spiral geometry enhances the Nusselt number (Nu) by 20–40% compared to straight-tube configurations due to Dean vortex-induced turbulence.
- Petrochemical Process Heating: Used in reformer tubes, waste heat boilers, and process heaters for hydrocarbon vaporization and cracking operations in refineries and chemical plants.
- Power Generation: Employed in superheater and reheater sections of boiler systems, as well as in heat recovery steam generators (HRSG) for combined cycle power plants.
- Industrial Process Heating: Applied in polymer processing, food and beverage pasteurization, pharmaceutical manufacturing, and paper/pulp production where precise temperature control and hygiene-grade materials are required.
- Combustion Chamber Liners & Burner Systems: The coil tube can be configured as a fuel injection manifold or burner tube assembly, distributing combustion gases uniformly across the furnace chamber.
- Oil & Gas Downhole Equipment: Resistant to high-temperature, high-pressure (HTHP) environments in wellbore heat tracing and chemical injection systems.
5.2 Performance in Combustion Environments
Numerical simulation research on spiral coil heat transfer furnaces has demonstrated that the helical coil configuration provides several distinct advantages in combustion-driven heating systems:
- Enhanced Convective Heat Transfer: The curvature of the coil induces centrifugal forces that generate Dean vortices, promoting radial fluid mixing and significantly increasing the internal heat transfer coefficient (h_i). This effect is characterized by the Dean number (De = Re · √(d/D_c)), where Re is the Reynolds number, d is the tube diameter, and D_c is the coil centerline diameter.
- Uniform Temperature Distribution: The continuous helical winding ensures a uniform heat flux distribution along the tube length, minimizing hot spots and thermal stress concentrations that could lead to premature tube failure.
- Compact Furnace Footprint: The coil geometry maximizes heat transfer surface area within a constrained volume, reducing overall furnace dimensions and capital expenditure.
- Improved Combustion Efficiency: The coil arrangement facilitates optimized flue gas flow patterns within the furnace chamber, promoting complete fuel combustion and reducing NOx and CO emissions.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a rigorous quality management system and holds the following certifications and complies with the following standards:
6.1 Quality Management System Certifications
- ISO 9001:2015 — Quality Management Systems certification covering all manufacturing and quality assurance processes.
- ISO 14001:2015 — Environmental Management Systems certification for environmentally responsible production practices.
- ISO 45001:2018 — Occupational Health and Safety Management Systems certification.
6.2 Product Compliance Standards
- ASTM A213 — Standard Specification for Seamless Ferritic, Austenitic, and Austenitic-Ferritic (Duplex) Stainless Steel Tubing for High Temperature Service.
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Chromium-Chromium-Nickel Stainless Steel Tubing for Chemical and Similar Severe Service Applications.
- EN 10216-5 — Non-ferrous metallic tubes — Technical delivery conditions — Part 5: Austenitic stainless steel tubes for general purposes.
- GB/T 14976 — Chinese National Standard for cold-rolled stainless steel seamless tubes for fluid transport.
- JIS G3459 — Japanese Industrial Standard for austenitic stainless steel tubing for boiler, heat exchanger, and similar heat transfer uses.
6.3 Testing & Inspection Protocols
- Hydrostatic Testing (水压试验): 100% of coils tested at 1.5× maximum operating pressure for minimum 30 seconds with zero leakage tolerance.
- Chemical Analysis (化学成分分析): Spectrometric verification of alloy composition for every production lot.
- Mechanical Testing (力学性能试验): Tensile and hardness testing per ASTM E8 and ASTM E18.
- Non-Destructive Testing (无损检测): Eddy current testing (ECT) for surface and near-surface defect detection; radiographic testing (RT) for weld seam volumetric inspection.
- Intergranular Corrosion Testing (晶间腐蚀试验): ASTM A262 Practice 1A (Acetic Acid–Formic Acid Test) for stabilized grades.
- Material Test Certificate (MTC):