Stainless Steel Coil Tube for Fan Coil Units (FCU)
Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Coiled Tubing) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered product specifically designed for integration into Fan Coil Units (FCU) and related HVAC (Heating, Ventilation, and Air Conditioning) systems. This product complies with the standards discussed in the technical literature titled "Discussion on Standards Related to Fan Coil Units" and represents a critical heat exchange component in modern building climate control infrastructure.
Coil tubes serve as the primary heat transfer medium in FCU systems, enabling efficient thermal energy exchange between refrigerant or water circuits and ambient air. The coiled configuration maximizes the surface area-to-volume ratio, thereby optimizing heat dissipation and absorption performance within compact installation footprints.
Material and Properties
The coil tube is fabricated from high-grade stainless steel, ensuring superior corrosion resistance, mechanical strength, and long-term structural integrity under demanding operating conditions.
- Base Material: Austenitic stainless steel (e.g., AISI 304 / AISI 316), conforming to ASTM A269 / ASME SA-269 standards for seamless stainless steel tubes
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, chemical attack, and condensation-induced degradation common in HVAC environments
- Thermal Conductivity: Suitable thermal properties for efficient heat exchange, with values typically ranging from 14 to 16 W/(m·K) for 304 grade
- Mechanical Strength: High tensile strength (≥ 515 MPa for 304 annealed) and yield strength (≥ 205 MPa), ensuring dimensional stability under pressure cycling
- Temperature Range: Operational capability from −196 °C to +870 °C, accommodating extreme thermal cycling in commercial and industrial applications
- Hygienic Surface: Smooth internal bore finish (Ra ≤ 0.4 μm available) to minimize fouling and pressure drop
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Material Grade | 304 / 316 / 316L / 2205 (Duplex) | ASTM A269 / ASME SA-269 |
| Outer Diameter (OD) | 3.0 mm – 25.4 mm (customizable) | GB/T 14976 / EN 10217 |
| Wall Thickness | 0.3 mm – 2.0 mm | GB/T 14976 |
| Coil Pitch | 6 mm – 50 mm (application-dependent) | Custom engineering |
| Coil Diameter | 50 mm – 600 mm | Custom engineering |
| Surface Finish | Polished / Brushed / Matte / Mirror (Ra ≤ 0.2 μm) | ASTM A270 |
| Pressure Rating | Up to 4.0 MPa (tested at 1.5× working pressure) | EN 12235 / ISO 4126 |
| Length per Coil | 3 m – 50 m (continuous) | — |
| Connection Type | Flared / Threaded / Brazed / Welded / Flanged | ASME B16.11 / ISO 7-1 |
| Standards Compliance | GB/T 14976, ASTM A269, EN 10217, JIS G3459 | Multi-standard |
| Testing Methods | Hydrostatic, Eddy Current, Helium Leak, Visual | ASTM E309 / ISO 9712 |
Manufacturing Process
The production of high-quality stainless steel coil tubes for fan coil unit applications involves a rigorous, multi-stage manufacturing process that ensures dimensional accuracy, material homogeneity, and functional reliability.
- Raw Material Selection and Verification: Certified stainless steel billets or seamless pipe blanks are procured from approved suppliers. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition and mechanical property certification per ASTM A269.
- Pipe Drawing and Forming: Seamless tubes are cold-drawn or hot-finished to the specified outer diameter and wall thickness. The drawing process ensures uniform wall thickness and tight dimensional tolerances (± 0.05 mm).
- Coiling Operation: The formed tube is precisely coiled using CNC-controlled coiling machines. Coil pitch, coil diameter, and turn count are controlled within ± 0.5 mm tolerance to ensure uniform heat transfer performance and compatibility with FCU housing dimensions.
- Heat Treatment (Annealing): Where required, the coil tube undergoes solution annealing at 1010–1150 °C followed by controlled cooling to achieve the desired austenitic microstructure, relieve residual stresses, and optimize corrosion resistance.
- Surface Treatment and Finishing: The coil tube surface is polished, passivated, or chemically cleaned to remove scale, contaminants, and oxidation. Passivation enhances the passive chromium oxide layer, improving long-term corrosion resistance.
- Quality Inspection and Testing: Each coil tube batch undergoes comprehensive non-destructive testing (NDT), including eddy current inspection for wall thickness verification, hydrostatic pressure testing at 1.5× the rated pressure for 30 seconds, and visual inspection for surface defects. Helium leak testing is performed for critical-seal applications.
- Packaging and Traceability: Finished coil tubes are packaged in moisture-proof containers with individual batch traceability documentation, including mill test certificates (MTC), dimensional inspection reports, and compliance declarations.
Applications
The stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd finds extensive application across multiple HVAC and industrial sectors:
- Fan Coil Units (FCU): Primary heat exchange coils in commercial and residential FCU systems for heating, cooling, and dehumidification
- Air Handling Units (AHU): Heating and cooling coils within large-scale air handling systems in commercial buildings and industrial facilities
- Chilled Water Systems: Heat transfer coils in chilled water distribution networks for temperature regulation
- Heat Pump Systems: Evaporator and condenser coils in air-source and water-source heat pump installations
- Refrigeration Systems: Evaporator coils in commercial refrigeration, cold storage, and display equipment
- Industrial Process Cooling: Precision temperature control in pharmaceutical, food processing, and semiconductor manufacturing environments
- Marine HVAC: Corrosion-resistant coil tubes for shipboard and offshore HVAC systems (316/316L grade)
Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring that all coil tube products meet or exceed international and national standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO/IEC 17025 — Laboratory Competence for testing and calibration
- CE Marking — Conformity with European Union directives for HVAC components
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes
- ASTM A269 / ASME SA-269 — American standard for seamless austenitic stainless steel tubing
- EN 10217 — European standard for seamless stainless steel tubes for heat exchangers
- JIS G3459 — Japanese Industrial Standard for austenitic stainless steel tubes
- Mill Test Certificate (MTC) / EN 10204 3.1 — Provided with every shipment for full traceability
Unique Selling Points
1. Standards-Aligned Engineering: Products are developed and validated in accordance with the comprehensive standards framework discussed in "Discussion on Standards Related to Fan Coil Units," ensuring seamless integration with FCU systems and regulatory compliance across global markets.
2. Precision Coiling Technology: CNC-controlled coiling delivers consistent pitch and diameter tolerances, guaranteeing uniform heat transfer performance and reduced pressure drop across the coil assembly.
3. Multi-Grade Material Availability: Flexible material options (304, 316, 316L, 2205) accommodate diverse application environments, from standard commercial HVAC to highly corrosive marine and chemical processing installations.
4. Comprehensive NDT Protocol: Multi-method non-destructive testing (eddy current, hydrostatic, helium leak) ensures zero-defect delivery and eliminates latent failure modes in critical heat exchange applications.
5. Full Traceability: Every coil tube batch is accompanied by complete documentation including MTC, dimensional reports, and chemical analysis, enabling full supply chain traceability and facilitating OEM quality audits.