Stainless Steel Coil Tube (盘管) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product takes the form of a continuous stainless steel tube wound into a compact helical coil configuration, offering an optimized surface-area-to-volume ratio that maximizes thermal exchange efficiency. The coil tube is primarily designed for integration into solar thermal systems, heat exchangers, fluid circulation loops, and industrial process piping where space-constrained environments demand high-performance heat transfer solutions.
As a critical component in coil-tube-type solar water heaters (盘管型太阳能热水器), this product facilitates efficient heat absorption from solar collectors and subsequent transfer to the water storage system through a closed-loop circulation mechanism. The helical geometry ensures laminar-to-turbulent flow transitions that enhance convective heat transfer coefficients, making it a superior alternative to straight-tube designs in compact thermal applications.
2. Material & Properties
The stainless steel coil tube is fabricated from high-grade austenitic stainless steel, predominantly conforming to the following material specifications:
- 304 (AISI 304 / UNS S30408): General-purpose grade with excellent corrosion resistance, weldability, and formability. Suitable for most solar thermal and domestic water applications.
- 316 (AISI 316 / UNS S31608): Enhanced molybdenum content provides superior resistance to pitting and crevice corrosion, ideal for aggressive chemical environments and marine applications.
- 321 (AISI 321 / UNS S32108): Titanium-stabilized grade offering improved resistance to intergranular corrosion at elevated temperatures, suitable for high-temperature process applications.
Key Material Properties:
- Operating temperature range: −196°C to 870°C (depending on grade)
- Corrosion resistance: Excellent resistance to atmospheric, aqueous, and mild chemical corrosion
- Mechanical strength: Tensile strength of 515–750 MPa; yield strength of 205–310 MPa
- Thermal conductivity: 14.9–16.3 W/(m·K) at 20°C
- Surface finish: Annealed and pickled (2B finish) or polished (BA finish), with optional electropolishing for food-grade applications
- Hygienic surface: Ra ≤ 0.5 μm achievable for pharmaceutical and food-grade coil assemblies
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) |
| Material Grade | AISI 304 / 316 / 321 (Custom grades available) |
| Outer Diameter (OD) | 6 mm – 50.8 mm (¼" – 2") |
| Wall Thickness | 0.3 mm – 2.0 mm |
| Coil Diameter (Pitch) | 50 mm – 500 mm (customizable) |
| Coil Length per Spool | 5 m – 500 m (configurable) |
| Coil Turn Spacing | 3 mm – 25 mm |
| End Configuration | Plain ends, threaded ends, or custom fittings |
| Surface Treatment | 2B Annealed / BA Bright Annealed / Electropolished |
| Pressure Rating | Up to 4.0 MPa (dependent on OD and wall thickness) |
| Standards Compliance | ASTM A213 / A269, EN 10217, GB/T 12771 |
| Minimum Order Quantity | 50 kg (negotiable) |
| Customization | Available for coil geometry, end fittings, and surface finish |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and consistent performance:
- Raw Material Selection: Cold-rolled stainless steel strip or seamless tube blanks are sourced from certified suppliers, with each batch accompanied by a mill test certificate (MTC) documenting chemical composition and mechanical properties.
- Cutting & Forming: Precision slitting and cutting operations produce strips or tubes of exact nominal dimensions. For welded coil tubes, the strip is formed into a circular cross-section using a high-precision roll-forming machine.
- Welding (if applicable): Helical or longitudinal TIG (Tungsten Inert Gas) welding is performed under controlled argon shielding to produce a clean, oxide-free weld seam with minimal heat-affected zone (HAZ).
- Coil Winding: The formed tube is wound onto a precision-controlled mandrel using a CNC-guided coil winding machine. Parameters such as coil diameter, pitch, turn spacing, and winding tension are programmatically controlled to achieve the target geometry with tolerances of ±1 mm.
- Heat Treatment: Post-forming annealing is conducted at 1050°C – 1100°C in a protective atmosphere (nitrogen or argon) to relieve residual stresses, restore full annealed microstructure, and achieve the required mechanical properties.
- Pickling & Passivation: The coil tube undergoes acid pickling (HNO₃/HF blend) to remove surface oxides and scale, followed by nitric acid passivation to establish a stable chromium oxide passive film for maximum corrosion resistance.
- Quality Inspection: Final products undergo dimensional verification (caliper, micrometer, laser measurement), visual inspection, hydrostatic pressure testing, and, where required, ultrasonic or radiographic testing of weld seams.
5. Applications
The stainless steel coil tube is a versatile component utilized across multiple industrial and commercial sectors:
- Solar Thermal Systems: Primary application in coil-tube-type solar water heaters (盘管型太阳能热水器), where the coil serves as the heat exchange element between the solar collector and the water storage tank, enabling efficient closed-loop heat transfer.
- Heat Exchangers: Compact spiral heat exchangers for HVAC systems, district heating networks, and industrial process cooling/heating circuits.
- Automotive & Marine: Engine cooling loops, exhaust aftertreatment systems, and marine engine heat exchange circuits.
- Food & Beverage Industry: Pasteurization coils, condensate recovery loops, and sanitary fluid transfer in breweries, dairy processing, and pharmaceutical manufacturing.
- Chemical Processing: Reactor cooling coils, distillation column condensers, and corrosive fluid handling systems where 316/321 grades provide essential chemical resistance.
- Refrigeration & Air Conditioning: Evaporator and condenser coils for commercial refrigeration units and precision cooling systems.
- Oil & Gas: Subsea production coils, subsea heat exchangers, and offshore platform utility loops.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing quality and continuous improvement processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices and environmental stewardship.
- ISO 45001:2018 — Occupational Health and Safety Management System certification for workplace safety and risk management.
- CE Marking (EU Conformity) — Compliance with European Directive requirements for product safety and performance.
- ASME (American Society of Mechanical Engineers) — Certification for pressure-containing components where applicable.
- Mill Test Certificates (MTC / EN 10204 3.1) — Each batch is accompanied by a full material test certificate documenting chemical analysis, mechanical testing results, and traceability information.
- Hydrostatic Pressure Testing — All coil tubes are pressure-tested to 1.5× the design pressure to verify structural integrity and weld seam quality.
7. Unique Selling Points
Optimized Thermal Performance: The helical coil geometry provides a significantly higher heat transfer surface area per unit volume compared to straight-tube alternatives, enabling compact system designs without sacrificing thermal efficiency. The continuous curvature also promotes favorable flow dynamics that minimize dead zones and reduce fouling tendencies.
- Full Customization Capability: Coil diameter, pitch, turn spacing, tube dimensions, and end configurations are all customizable to meet specific engineering requirements, ensuring seamless integration into existing system architectures.
- Multi-Grade Material Availability: Offering AISI 304, 316, and 321 grades provides flexibility for diverse application environments, from standard domestic water systems to aggressive chemical processing.
- End-to-End Traceability: From raw material mill certificates through final product inspection, every coil tube is fully traceable, supporting compliance with stringent industry regulations.
- Cost-Effective Solution: The coil configuration reduces material usage and installation footprint compared to equivalent straight-tube heat exchange assemblies, delivering lower lifecycle costs for system integrators.
For detailed technical inquiries, custom specification requests, or sample evaluations, please contact Wenzhou Jixing Metal Materials Co., Ltd directly.