Stainless Steel Helical Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Helical Coil Tube (hereinafter referred to as "Coiltube") manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for advanced heat exchange, fluid transport, and process engineering applications. Unlike conventional straight pipes, the helical coil geometry provides significantly enhanced surface-area-to-volume ratios, superior convective heat transfer coefficients, and compact spatial footprint, making it an indispensable component in high-performance thermal management systems.
This product line encompasses both cold-formed and hot-formed helical coils, available in a wide range of stainless steel grades including 304 (UNS S30400), 316L (UNS S31603), 321 (UNS S32100), 347 (UNS S34700), and duplex stainless steels (e.g., 2205/UNS S32205). The coils are supplied in continuous lengths suitable for integration into shell-and-coil heat exchangers, reactor internals, and specialized process equipment.
Unique Selling Points
- Superior Heat Transfer Performance: The helical geometry induces secondary Dean flow, which disrupts the boundary layer and increases the Nusselt number (Nu) by up to 1.5–2.0 times compared to equivalent straight tubes.
- Compact Design: Achieves high heat transfer capacity within minimal footprint, reducing equipment weight and installation space requirements.
- Flow-Induced Vibration (FIV) Resilience: Engineered with optimized coil pitch and curvature radius to mitigate vortex-induced vibrations (VIV) and fluidelastic instabilities in high-velocity fluid environments, including water and liquid metal coolants.
- Corrosion Resistance: High-grade austenitic and duplex stainless steels provide exceptional resistance to pitting, crevice corrosion, and intergranular corrosion in aggressive chemical environments.
- Customizable Geometric Parameters: Coil diameter, pitch, tube outer diameter, and wall thickness can be tailored to specific application requirements.
Material & Properties
The Coiltube product range utilizes certified stainless steel strip and bar stock conforming to international standards including ASTM A213, ASTM A269, EN 10217-7, and GB/T 14976. The following table summarizes the mechanical and physical properties of the primary material grades offered:
| Property | 304 / 304L (UNS S30400/S30403) | 316L (UNS S31603) | 321 (UNS S32100) | 2205 Duplex (UNS S32205) |
|---|---|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa | ≥ 485 MPa | ≥ 515 MPa | ≥ 550 MPa |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ≥ 170 MPa | ≥ 205 MPa | ≥ 450 MPa |
| Elongation (%) | ≥ 40% | ≥ 40% | ≥ 35% | ≥ 25% |
| Density (g/cm³) | 8.00 | 8.03 | 8.00 | 7.81 |
| Thermal Conductivity (W/m·K, 20°C) | 16.3 | 14.6 | 16.3 | 14.8 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 | 300 |
| Pitting Resistance (PREN) | 18–20 | 24–26 | 18–20 | 33–38 |
Chemical Composition (Typical, wt%):
| Grade | C (Max) | Cr | Ni | Mo | Ti | N |
|---|---|---|---|---|---|---|
| 304 | 0.08 | 18.0–20.0 | 8.0–10.5 | — | — | — |
| 316L | 0.03 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | — |
| 321 | 0.08 | 17.0–19.0 | 9.0–12.0 | — | 5×(C+0.02)–0.70 | — |
| 2205 | 0.03 | 22.0–23.0 | 4.5–6.5 | 2.5–3.5 | — | 0.14–0.20 |
Specifications
The following table presents the standard dimensional and geometric parameters available for the Coiltube product line:
| Parameter | Range / Options | Unit |
|---|---|---|
| Tube Outer Diameter (OD) | 6.0 – 50.8 | mm |
| Tube Wall Thickness | 0.5 – 3.0 | mm |
| Coil Mean Diameter (CMD) | 100 – 1200 | mm |
| Coil Pitch (Center-to-Center Spacing) | 15 – 100 | mm |
| Helix Angle | 0° – 45° (adjustable) | ° |
| Tube Length (Uncoiled Equivalent) | 5 – 500 | m |
| End Form | Plain / Beveled / Threaded / Flanged | — |
| Surface Finish | Ra ≤ 0.8 μm (polished) / Ra ≤ 1.6 μm (electropolished) | μm |
| Surface Condition | Pickled & Passivated (P&P) / Bright Annealed (BA) | — |
| Coil Count per Bundle | 1 – 200 (assembled) | — |
Tolerance Standards
- OD Tolerance: ±0.10 mm (≤ 12.7 mm OD); ±0.15 mm (> 12.7 mm OD)
- Wall Thickness Tolerance: ±10%
- Coil Diameter Tolerance: ±0.5% of nominal CMD
- Pitch Tolerance: ±0.5 mm
- Straightness (per unit length): ≤ 1.0 mm/m (for straightened segments)
Manufacturing Process
The production of high-quality stainless steel helical coil tubes involves a multi-stage process chain that ensures dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement: Certified stainless steel strip or seamless tube stock is sourced from approved mills, with full mill test certificates (MTC) per EN 10204 Type 3.1 or ASTM equivalents.
- Coil Winding (Helical Forming): Straight tube is wound around a mandrel using CNC-controlled coil-winding machines. The mandrel diameter, winding speed, and feed rate are precisely controlled to achieve target coil diameter and pitch. For cold-forming, the tube is bent at room temperature; for hot-forming (required for larger diameters or thicker walls), the tube is heated to 900–1100°C prior to bending.
- Welding (if applicable): For welded coil construction, longitudinal welds are performed via TIG (Tungsten Inert Gas) welding per ASME Section IX or EN ISO 3834. Orbital TIG welding is preferred for circumferential joints to ensure uniform weld quality.
- Solution Heat Treatment (Annealing): Cold-worked coils undergo solution annealing at 1010–1120°C followed by rapid quenching to restore full austenitic microstructure, eliminate cold-work hardening, and maximize corrosion resistance.
- Pickling & Passivation: The coil surface is treated with a mixed acid solution (HNO₃/HF) to remove scale and oxide layers, followed by passivation to form a stable chromium oxide film (Cr₂O₃) that provides the passive corrosion barrier.
- Dimensional Inspection: Post-manufacturing verification includes OD/wall thickness measurement (ultrasonic or micrometer), coil diameter verification, pitch measurement, and visual inspection for surface defects.
- Non-Destructive Testing (NDT): Eddy current testing (ECT) per ASTM E309, ultrasonic testing (UT) per ASTM E213, and penetrant testing (PT) per ASTM E165 are performed to detect subsurface and surface discontinuities.
- Hydrostatic/Pneumatic Pressure Testing: Each coil is pressure-tested to a minimum of 1.5× design pressure (or per applicable standard) to verify leak-tightness.
- Final Inspection & Packing: Coils are inspected for dimensional conformity, surface quality, and marking. They are then protected with desiccant packaging, VCI (Vapor Corrosion Inhibitor) wrap, and wooden or steel cradles for shipment.
Applications
The Coiltube product is widely deployed across multiple industrial sectors where compact heat exchange, corrosion resistance, and thermal efficiency are critical:
- Nuclear Power & Advanced Reactors: Used in lead-bismuth eutectic (LBE) cooled reactor systems, where the coil geometry provides effective heat removal while withstanding the aggressive liquid metal environment. Flow-induced vibration characteristics are specifically engineered for LBE coolant conditions.
- Chemical Processing: Shell-and-coil heat exchangers for exothermic reaction temperature control, distillation column reboilers, and condensers in petrochemical and pharmaceutical plants.
- Oil & Gas: Subsea heat exchangers, gas coolers, and separators in offshore platforms where space is constrained and corrosion resistance is paramount.
- Power Generation: Economizers, superheaters, and air preheaters in waste heat recovery systems and combined cycle plants.
- Food & Beverage Processing: Pasteurization units, sterilization equipment, and condensate recovery systems requiring hygienic-grade (Ra ≤ 0.4 μm) surfaces.
- Heat Pump & Refrigeration Systems: Compact evaporator and condenser coils for industrial heat pump applications.
- Research & Development: Helical coil test sections for fluid dynamics research, including flow-induced vibration (FIV) studies in water and liquid metal coolants, as documented in academic literature.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring traceability and compliance with international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification |
| ISO 3834 | Welding quality requirements for structural welding |
| EN 10204 Type 3.1 | Inspection certificates — specific inspection (product-by-product) |
| ASME BPV Code Section VIII | Pressure vessel and heat exchanger construction (where applicable) |
| ASTM A213 | Standard specification for austenitic stainless steel seamless, wrought austenitic stainless steel, and heat-resistant alloy steel boiler, superheater, and heater tubes |
| ASTM A269 | Standard specification for wrought austenitic stainless steel tubing, seamless and welded |
| EN 10217-7 | Heat-resistant and superalloy steel tubes — Technical delivery conditions for seamless austenitic steel tubes |
| GB/T 14976 | Chinese national standard for seamless stainless steel tubes for fluid transport |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance for EU market |
| NB Registration | National Board registration for ASME-stamped products |
Quality Assurance Measures
- Full Material Traceability: Each coil is marked with heat number, production batch, and serial identification enabling complete traceability from raw material to finished product.
- In-Process Inspection: Critical process parameters (winding tension, coil diameter, pitch, welding parameters) are monitored and recorded in real time.
- Final Product Testing: Includes dimensional verification, surface roughness measurement, hydrostatic testing, and NDT as specified above.
- Third-Party Inspection: Available upon customer request through recognized inspection bodies (e.g., TÜV, SGS, Lloyd's).
- Documentation Package: Each shipment is accompanied by MTC, test reports, dimensional drawings, and certificates of compliance.
Technical Note on Flow-Induced Vibration (FIV): Research published in the