Stainless Steel Coil Tube — Radiant & Fan Coil Heating System Component
Product Code: WJX-CT-332 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The WJX-CT-332 Stainless Steel Coil Tube is a precision-engineered coiled tubing product specifically designed for integration into floor radiant heating systems and fan coil unit (FCU) heating/cooling circuits in regions characterized by hot summers and cold winters (夏热冬冷地区). This product addresses the growing demand for efficient, durable, and corrosion-resistant heat exchanger components in HVAC (Heating, Ventilation, and Air Conditioning) applications.
Unlike conventional carbon steel or copper coil tubes, the WJX-CT-332 leverages the superior material properties of austenitic stainless steel to deliver extended service life, minimal maintenance requirements, and consistent thermal performance across diverse operating conditions. The coil geometry provides high surface-area-to-volume ratios, enabling rapid heat transfer while maintaining structural integrity under cyclic thermal and hydraulic loading.
2. Material & Properties
2.1 Base Material
- Grade: SUS304 / SUS316L (austenitic stainless steel)
- Standard Composition (SUS304): Cr 18–20%, Ni 8–10.5%, C ≤ 0.08%, Mn ≤ 2.0%, Si ≤ 1.0%
- Standard Composition (SUS316L): Cr 17–19%, Ni 10–14%, Mo 2–3%, C ≤ 0.03%
2.2 Key Mechanical & Physical Properties
| Property | SUS304 | SUS316L |
|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 485 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 |
| Elongation at Break (%) | ≥ 40 | ≥ 45 |
| Density (g/cm³) | 7.93 | 8.00 |
| Thermal Conductivity (W/m·K, at 20°C) | 16.3 | 16.3 |
| Operating Temperature Range (°C) | -196 to +870 | -196 to +870 |
| Corrosion Resistance (Salt Spray, hours) | ≥ 200 | ≥ 500 |
2.3 Unique Selling Points
- Exceptional Corrosion Resistance: The passive chromium oxide layer provides inherent protection against scaling, pitting, and crevice corrosion — critical for long-term operation in humid, chemically aggressive environments typical of floor heating circuits.
- Thermal Stability: Maintains dimensional accuracy and mechanical properties across repeated heating and cooling cycles, preventing fatigue-induced failure common in carbon steel alternatives.
- Hygienic Surface Finish: Electropolished or brushed internal surfaces (Ra ≤ 0.4 μm) minimize biofilm formation and scale adhesion, ensuring sustained heat transfer efficiency over decades of service.
- Full Recyclability: 100% recyclable without degradation of material properties, supporting green building certification standards (LEED, BREEAM).
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ8 mm, Φ10 mm, Φ12 mm, Φ14 mm, Φ16 mm (customizable) |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Inner Diameter (ID) | Φ100 mm – Φ300 mm |
| Coil Length per Spool | 50 m – 500 m (standard); up to 2000 m (special order) |
| Surface Finish | 2B / BA (Bright Annealed) / Electropolished (Ra ≤ 0.4 μm) |
| Pressure Rating | ≤ 1.6 MPa (PN16) at 95°C working temperature |
| Tolerance on OD | ±0.1 mm |
| Tolerance on Wall Thickness | ±10% of nominal |
| Standard Length Options | 50 m, 100 m, 200 m, 500 m |
| End Treatment | Plain cut / Beveled / Threaded (optional) |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection & Inspection: Hot-rolled stainless steel strip is sourced from certified mills. Incoming material undergoes spectroscopic composition verification and mechanical property testing per ASTM A240 / GB/T 3280 standards.
- Cold Rolling & Annealing: The strip is cold-rolled to precise thickness tolerances (±10%) followed by controlled annealing in a protective atmosphere to restore ductility and achieve the desired grain structure.
- Surface Treatment: Pickling and passivation remove scale and oxide layers. Optional electropolishing achieves mirror-quality internal surfaces for hygienic applications.
- Coil Forming: Precision roll-forming equipment shapes the strip into seamless coil tubes with uniform coil diameter and pitch. The forming process is computer-controlled to maintain dimensional consistency.
- Welding (if applicable): Longitudinal welds, where used, are performed via TIG (Tungsten Inert Gas) welding with argon shielding to ensure full-penetration welds free of porosity or lack of fusion.
- Pressure Testing: Each coil is hydrostatically tested at 1.5× the maximum working pressure for a minimum dwell time of 30 minutes to verify leak-tightness.
- Final Inspection & Packaging: Visual inspection, dimensional verification, and material certification are completed. Coils are wrapped in protective film and secured on steel pallets for shipping.
4.2 Quality Control Measures
- In-line ultrasonic thickness measurement at 100% coverage
- Random sampling for tensile testing and impact testing (Charpy V-notch) per ISO 14577
- Positive Material Identification (PMI) via XRF (X-ray Fluorescence) analysis
- Dye penetrant or magnetic particle inspection for surface and subsurface defect detection
5. Applications
5.1 Floor Radiant Heating Systems
The WJX-CT-332 coil tube serves as the primary heat distribution medium in hydronic floor radiant heating systems. Its corrosion resistance eliminates the risk of internal scale buildup that degrades flow capacity over time, while its thermal conductivity ensures efficient heat transfer from the circulating water to the floor surface. The coil geometry facilitates uniform spacing during installation, promoting even floor temperature distribution.
5.2 Fan Coil Unit (FCU) Heat Exchangers
In fan coil applications, the coil tube forms the core of the air-side heat exchanger. The high surface-area-to-volume ratio of the coiled configuration maximizes convective heat exchange between the circulating fluid and the passing air stream. Stainless steel construction prevents degradation from condensation, humidity, and potential chemical exposure in commercial and residential HVAC systems.
5.3 Additional Applications
- District heating network distribution loops
- Solar thermal energy collector manifolds
- Industrial process heating circuits
- Geothermal heat exchange well casings
- Chilled water distribution in commercial cooling systems
6. Quality Certifications & Standards Compliance
| Certification / Standard | Applicable Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14577 | Stainless steel tubes and fittings — Seamless tubes |
| GB/T 3280 | National standard for cold-rolled stainless steel strips and plates |
| ASTM A269 | Austenitic stainless steel seamless tubing |
| EN 10216-5 | Seamless and welded stainless steel tubes for pressure purposes |
| CE Marking | Compliance with EU Pressure Equipment Directive (PED 2014/68/EU) |
| RoHS / REACH | Restriction of hazardous substances compliance |
Wenzhou Jixing Metal Materials Co., Ltd. maintains a fully traceable supply chain with mill test certificates (MTC) provided for every batch. Third-party inspection by SGS or BV (Bureau Veritas) is available upon customer request. All products carry a minimum 10-year warranty against material defects and corrosion perforation under normal operating conditions.