Stainless Steel Coil Tube (Coil Tubing) — Large-Diameter Steam Generator Grade
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed through a continuous cold-drawing and coiling process, designed specifically for high-performance thermal exchange applications. This coil tube product line is distinguished by its large outer diameter, uniform wall thickness, and superior thermal conductivity characteristics, making it an ideal component for large-scale direct-current (DC) steam generators and other industrial heat recovery systems.
The design philosophy of this coil tube is grounded in rigorous thermal performance research, including experimental investigations into the heat transfer characteristics of large-diameter coil steam generators. The resulting product exhibits optimized fluid dynamics within the coiled geometry, ensuring efficient convective heat transfer while maintaining structural integrity under prolonged thermal cycling.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal stability, and mechanical strength across a broad operating temperature range.
- Base Material: Austenitic Stainless Steel (304 / 316L / 321 / Inconel 625, per customer specification)
- Corrosion Resistance: Excellent resistance to oxidation at temperatures up to 870°C (1600°F); outstanding resistance to pitting and crevice corrosion in chlorinated environments (particularly 316L grade)
- Thermal Conductivity: 16–22 W/(m·K) at 25°C, ensuring efficient heat transfer performance in steam generator applications
- Maximum Operating Temperature: Up to 1150°C (2092°F) for 304 grade; up to 1200°C (2192°F) for 321 grade
- Mechanical Properties: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40%
- Surface Finish: 2B / BA (Bright Annealed) / Electropolished, with surface roughness Ra ≤ 0.4 μm for electropolished grade
- Crystal Structure: Fully austenitic (face-centered cubic, FCC), non-magnetic, ensuring consistent thermal expansion behavior
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ19.05 mm – Φ108 mm (0.75" – 4.25") |
| Wall Thickness | 0.5 mm – 6.0 mm (0.020" – 0.236") |
| Coil Diameter | Φ500 mm – Φ3000 mm (adjustable per application) |
| Coil Length | Up to 200 m per coil (continuous) |
| OD Tolerance | ±0.05 mm (precision grade) / ±0.10 mm (standard grade) |
| Wall Thickness Tolerance | ±10% of nominal (standard) / ±5% (precision) |
| Material Grades | ASTM A213 TP304, TP304L, TP316, TP316L, TP321, TP347, TP310S |
| Standard Compliance | ASTM A213 / A269 / ASME SA-213 / EN 10216-5 / GB/T 14976 |
| End Condition | Plain end / Beveled end / Threaded end (per request) |
| Heat Treatment | Solution Annealed (1050°C – 1150°C) followed by water quench |
| Maximum Design Pressure | Up to 4.0 MPa (580 psi), dependent on geometry and grade |
| Operating Temperature Range | −196°C to +1150°C (−320°F to +2092°F) |
Manufacturing Process
The production of large-diameter stainless steel coil tubes follows a rigorously controlled multi-stage manufacturing process to ensure dimensional accuracy, metallurgical soundness, and thermal performance:
- Raw Material Procurement: High-purity stainless steel wire rod or seamless tube blanks are sourced from certified mills, with full chemical composition verification via optical emission spectrometry (OES) and inductively coupled plasma (ICP) analysis.
- Seamless Tube Forming: Hot-rolled or cold-drawn seamless tubes are produced using the Mannesmann piercing or capstan drawing process, ensuring a homogeneous microstructure without weld seams.
- Cold Drawing & Sizing: Tubes are cold-drawn through precision dies to achieve the target outer diameter and wall thickness with tight tolerances. This step also induces beneficial work hardening for improved mechanical properties.
- Intermediate Annealing: Periodic solution annealing is performed during multi-pass drawing to relieve accumulated cold work stresses and restore ductility.
- Coiling Operation: The straightened tube is wound into the desired coil geometry using a CNC-controlled coiling head. The coil diameter and pitch are precisely controlled to ensure uniform curvature radius throughout the length.
- Final Solution Annealing: The completed coil is subjected to a full solution anneal cycle (1050°C – 1150°C, water quench) to achieve a fully recrystallized, stress-free austenitic microstructure.
- Pickling & Passivation: Surface scale is removed via hydrofluoric-nitric acid pickling, followed by passivation treatment to establish a protective chromium oxide film.
- Final Inspection & Testing: Comprehensive quality verification including dimensional measurement, hydrostatic pressure testing, ultrasonic testing (UT), and visual inspection.
Applications
The large-diameter stainless steel coil tube is engineered for demanding thermal exchange and process engineering applications:
- Steam Generators: Primary heating elements in large-scale DC steam generators and waste heat recovery steam generators (WHRSGs), where thermal performance and corrosion resistance are critical.
- Power Generation: Boiler tubes, superheaters, and economizer sections in fossil-fuel and nuclear power plants.
- Chemical Processing: Heat exchangers and reactor coils in petrochemical, pharmaceutical, and polymer manufacturing facilities.
- Food & Beverage Industry: Sterilization coils and pasteurization systems requiring sanitary-grade stainless steel surfaces.
- Marine & Offshore: Heat exchanger coils in shipboard power systems and offshore platform processing units, leveraging superior chloride resistance of 316L grade.
- Aerospace: Fuel heating coils and hydraulic system heat exchangers utilizing high-temperature alloys such as Inconel 625.
- Geothermal Energy: Heat extraction coils for geothermal power plants and district heating systems.
Quality Certifications & Testing
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system aligned with international standards:
- Quality Management: ISO 9001:2015 certified manufacturing system
- Environmental Management: ISO 14001:2015 compliant production processes
- Product Standards: ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 14976
- Material Certification: Mill Test Certificates (MTC) per EN 10204 Type 3.1, including full chemical analysis and mechanical property data
- Non-Destructive Testing (NDT): Ultrasonic testing (UT) per ASTM E127; Eddy current testing (ECT) per ASTM E309; Radiographic testing (RT) per ASTM E94 for weld integrity verification
- Pressure Testing: Hydrostatic pressure testing per ASTM A530 at 1.5× design pressure, with zero-defect acceptance criteria
- Corrosion Testing: Salt spray testing (ASTM B117) exceeding 1000 hours without red rust for 316L grade; Intergranular corrosion testing per ASTM A240 Table 6
- Third-Party Inspection: Available upon request (SGS, Bureau Veritas, TÜV, Lloyd's Register)
Unique Selling Points
1. Research-Driven Thermal Optimization: Product design informed by experimental thermal performance research on large-diameter coil steam generators, ensuring optimal heat transfer coefficients and reduced pressure drop through validated coil geometry parameters.
2. Seamless Integrity: True seamless construction eliminates potential failure points at weld joints, providing superior long-term reliability in high-pressure thermal cycling environments.
3. Precision Coiling: CNC-controlled coiling process ensures uniform curvature radius and consistent coil pitch, critical for predictable thermal performance and simplified installation.
4. Multi-Grade Flexibility: Availability in multiple austenitic and high-alloy grades (304, 304L, 316, 316L, 321, 347, 310S, Inconel 625) allows precise matching of material properties to specific service conditions.
5. Full Traceability: Complete material traceability from raw steel mill to finished coil, with digital documentation of every processing step, ensuring compliance with the most stringent regulatory requirements.
Technical Reference
This product specification incorporates findings from experimental research on the thermal performance characteristics of large-diameter direct-current steam generators, specifically addressing heat transfer enhancement mechanisms, flow distribution uniformity in coiled geometries, and the influence of coil pitch and diameter on overall system efficiency. The manufacturing parameters and quality standards described herein reflect best practices validated through both computational fluid dynamics (CFD) simulation and physical experimental verification.