Stainless Steel Coil Tube — Fan Coil & Capillary Tube Network Applications
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered, continuously wound stainless steel tubing product designed for demanding thermal management applications. This product is specifically engineered to serve as the core heat-exchange element in fan coil units (FCU) and capillary tube network (CTN) combined heat pump systems, particularly those deployed in severe cold regions where extreme low-temperature operation, high corrosion resistance, and long-term structural integrity are critical.
Unlike conventional copper or aluminum coil tubes, the stainless steel coil tube offers superior resistance to low-temperature embrittlement, chemical degradation, and mechanical fatigue under cyclic thermal loading conditions. The continuous coil form factor enables compact installation, efficient heat transfer surface area utilization, and seamless integration into modular building HVAC systems.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, corrosion resistance, and thermal stability across an extreme temperature range.
- Base Material: Austenitic stainless steel (e.g., AISI 304 / AISI 316 / SUS 304 / SUS 316L)
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion due to high chromium (Cr ≥ 18%) and nickel (Ni ≥ 8%) content; 316L grade offers additional molybdenum (Mo ≥ 2%) for enhanced chloride resistance
- Low-Temperature Performance: Maintains ductility and toughness down to −196 °C (cryogenic grade suitability), making it ideal for severe cold region heat pump systems operating at ambient temperatures as low as −40 °C
- Thermal Conductivity: Approximately 14–16 W/(m·K), providing reliable heat transfer while balancing the trade-off against higher-conductivity materials
- Non-Magnetic: Fully austenitic microstructure ensures non-magnetic behavior
- Hygienic: Smooth internal surface finish (Ra ≤ 0.4 μm) prevents biofilm formation and ensures fluid purity
- Non-Toxic: Free of lead, cadmium, and other hazardous heavy metals; complies with food-grade and potable water standards
- Longevity: Service life exceeding 25–30 years under normal operating conditions with negligible degradation
Specifications
| Parameter | Specification / Range | Unit |
|---|---|---|
| Outer Diameter (OD) | 3.0 / 4.0 / 5.0 / 6.0 / 8.0 / 10.0 (customizable) | mm |
| Wall Thickness (WT) | 0.3 / 0.4 / 0.5 / 0.6 / 0.8 (customizable) | mm |
| Inner Diameter (ID) | 2.0 – 9.4 (derived from OD and WT) | mm |
| Coil Winding Diameter | 100 – 500 | mm |
| Coil Length (per roll) | 50 – 300 (customizable) | m |
| Coil Weight | 10 – 80 | kg |
| Surface Finish | BA (Bright Annealed) / 2B / Electropolished | — |
| Surface Roughness (Internal) | ≤ 0.4 | μm (Ra) |
| Tensile Strength (σb) | ≥ 520 (304) / ≥ 550 (316) | MPa |
| Yield Strength (σ0.2) | ≥ 205 | MPa |
| Elongation (A50mm) | ≥ 35 | % |
| Operating Temperature Range | −40 to +200 | °C |
| Maximum Working Pressure | ≤ 1.6 (standard) / ≤ 4.0 (reinforced) | MPa |
| Diameter Tolerance | ±0.05 | mm |
| Wall Thickness Tolerance | ±10% | % |
| Standards Compliance | ASTM A269 / ASTM A270 / GB/T 12771 / EN 10217-7 | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing sequence to ensure dimensional precision, metallurgical integrity, and surface quality:
- Coil Unwinding & Straightening: Stainless steel strip coil (pre-annealed) is unwound and cold-straightened to eliminate residual curvature and ensure flatness within ±0.1 mm/m.
- Precision Forming (Roll Forming): The flat strip is passed through a series of precision-die roll-forming stations that progressively bend the strip into a circular cross-section. This continuous process ensures uniform wall thickness and concentricity.
- Seam Welding (TIG / Laser Welding): The formed strip is seam-welded using either Gas Tungsten Arc Welding (GTAW/TIG) or high-speed laser welding. Laser welding is preferred for thin-wall tubes (< 0.6 mm) to minimize heat-affected zone (HAZ) and maintain mechanical properties.
- Post-Weld Annealing: The welded tube undergoes controlled solution annealing at 1050–1150 °C followed by rapid quenching to restore full austenitic microstructure, relieve welding residual stresses, and ensure non-magnetic properties.
- Internal & External Finishing: Precision internal mandrel drawing and external grinding/polishing achieve the target surface roughness (Ra ≤ 0.4 μm) and dimensional tolerances.
- Coil Winding: The finished straight tube is precisely wound onto a core drum using a CNC-controlled winding machine to produce the final coil tube geometry with controlled pitch and uniform spacing.
- End Sealing & Packaging: Open ends are sealed with protective caps to prevent contamination; coils are wrapped in moisture-barrier film and secured on wooden or steel pallets for transport.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd is engineered for a diverse range of high-performance applications:
- Fan Coil Units (FCU) in Severe Cold Regions: Serves as the evaporator/condenser coil in fan coil units integrated with air-source or ground-source heat pump systems. The stainless steel construction prevents frost damage and low-temperature cracking that commonly affects copper coils in sub-zero environments (−40 °C to −20 °C ambient).
- Capillary Tube Networks (CTN): Functions as the embedded heating/cooling circuit in capillary tube network radiant systems. The small-bore coil tubes are embedded in wall or ceiling panels to provide uniform surface temperature distribution with minimal thermal stratification.
- Combined Heat Pump Systems: Enables hybrid configurations where fan coil units handle sensible heat loads while capillary networks manage latent loads, optimizing Coefficient of Performance (COP) in variable-climate scenarios.
- Commercial & Industrial HVAC: Suitable for hospital cleanrooms, pharmaceutical facilities, food processing plants, and data centers requiring hygienic, corrosion-resistant heat exchange components.
- Geothermal & Solar Thermal Systems: Used in ground-coupled heat exchangers and solar collector loops where long-term exposure to deionized water, brine solutions, or glycol mixtures demands superior corrosion resistance.
- Marine & Coastal Applications: The 316L grade coil tube provides excellent resistance to saltwater and marine atmosphere corrosion in coastal HVAC installations.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality assurance framework to ensure product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification ensuring consistent manufacturing quality and process control
- ISO 14001 — Environmental Management System certification for sustainable manufacturing practices
- ISO 45001 — Occupational Health and Safety Management System
- CE Marking — Conformity with European Union directives for construction products and mechanical safety
- NSF/ANSI 61 — Drinking Water System Components (where applicable for potable water contact)
- GB/T 12771 — Chinese national standard for welded austenitic stainless steel tubes for general application
- ASTM A269 / ASTM A270 — American standards for seamless and welded austenitic stainless steel tubes
- EN 10217-7 — European standard for welded austenitic stainless steel tubes
- Third-Party Testing: Each production batch undergoes independent verification including chemical composition analysis (OES/Spectroscopy), mechanical testing (tensile, hardness, impact), dimensional inspection (CMM), hydrostatic pressure testing, and X-ray/eddy current seam weld integrity inspection
Unique Selling Points
- Extreme Cold Resilience: Unlike copper or aluminum alternatives, the austenitic stainless steel coil tube maintains full ductility and structural integrity at temperatures as low as −40 °C, eliminating the risk of low-temperature embrittlement and thermal shock cracking in severe cold region heat pump systems.
- 25–30 Year Service Life: The inherent corrosion resistance of 304/316 stainless steel ensures a dramatically longer operational lifespan compared to conventional materials, reducing lifecycle maintenance costs and replacement frequency.
- Hygienic & Food-Grade: Non-toxic, non-leaching surface suitable for applications in healthcare, pharmaceutical, and food-grade environments where material safety is paramount.
- Continuous Coil Form Factor: Enables compact, modular installation with maximum heat transfer surface area per unit volume — ideal for space-constrained fan coil and capillary network architectures.
- Full Customization: OD, wall thickness, coil diameter, and coil length are customizable to meet specific system design parameters and project requirements.
- Weld-Free Integration: The continuous coil design minimizes the number of field welds required, reducing installation labor time and potential leak points.
Note: All specifications listed are representative values. Actual product dimensions, material grades, and performance characteristics may vary based on specific project requirements. Wenzhou Jixing Metal Materials Co., Ltd provides engineering consultation and custom fabrication services to ensure optimal product-to-application matching. For detailed material certifications, mill test reports (MTR), and batch-specific quality documentation, contact the manufacturer directly.