Stainless Steel Coil Tube for Fan Coil Units (FCU) – Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Product No. 1490) is a precision-engineered refrigerant circuit tubing specifically designed for integration into Fan Coil Units (FCUs) — the core heat exchange components within distributed air-conditioning systems. These coil tubes serve as the primary medium for transferring thermal energy between the refrigerant and the ambient air stream, enabling efficient cooling, heating, and dehumidification functions within commercial and residential HVAC environments.
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product line addresses the critical need for corrosion-resistant, thermally conductive, and mechanically durable tubing that withstands prolonged exposure to refrigerant fluids, condensate water, and variable thermal cycling conditions inherent in fan coil unit operations.
2. Material Composition & Physical Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of thermal conductivity, corrosion resistance, and mechanical integrity under refrigeration-grade service conditions.
- Base Alloy: Austenitic Stainless Steel (grades SS304 / SS316L, conforming to ASTM A269 / ASME SA-269)
- Chromium (Cr) Content: 18.0%–20.0% (SS304) / 16.0%–18.0% (SS316L)
- Nickel (Ni) Content: 8.0%–11.0% (SS304) / 10.0%–14.0% (SS316L)
- Molybdenum (Mo) Content: 0% (SS304) / 2.0%–3.0% (SS316L)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C
- Operating Temperature Range: −40°C to +150°C
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and chloride-induced degradation (particularly SS316L grade)
- Surface Finish: Electropolished or passivated interior to minimize flow resistance and prevent biofilm accumulation
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | 6.35 mm / 9.52 mm / 12.7 mm (¼" / ⅜" / ½") |
| Tube Wall Thickness | 0.5 mm – 1.2 mm (customizable per design load) |
| Coil Pitch (Fin Spacing) | 1.6 mm – 2.5 mm (24–32 fins per inch) |
| Row Configuration | 1-row to 6-row serpentine arrangement |
| Maximum Working Pressure | 2.5 MPa (363 PSI) |
| Hydrostatic Test Pressure | 3.75 MPa (544 PSI) – 150% of working pressure |
| Refrigerant Compatibility | R-410A, R-32, R-407C, R-134a, R-22 (legacy) |
| Heat Transfer Capacity | 2.0 kW – 15.0 kW (depending on coil configuration) |
| Air-Side Velocity | 2.0 – 4.5 m/s (face velocity) |
| Fin Material | Aluminum (Al 1100 / Al 3003) or Stainless Steel (SS304) |
| Connection Type | Flared, brazed, or threaded fittings (G ½" – G 1") |
| Applicable Standards | AHRI 340/360, EN 14511, ISO 13246, ASHRAE 15 |
| Service Life Expectancy | ≥ 25 years under normal operating conditions |
4. Manufacturing Process
The production of these coil tubes follows a rigorous multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and optimal thermal performance:
- Material Selection & Inspection: Stainless steel strips or seamless tubes are sourced from certified mills and subjected to spectroscopic analysis (OES) and mechanical testing to verify chemical composition and tensile properties.
- Coil Forming: Precision CNC-controlled coiling equipment shapes the tubing into serpentine or helical configurations, maintaining consistent bend radii (minimum 2× OD) to prevent wall thinning and flow turbulence.
- Fin Application: Aluminum or stainless steel fins are mechanically stamped and inserted into the tube channels using high-frequency resistance welding or mechanical crimping, ensuring maximum thermal contact area.
- Hydrostatic Pressure Testing: Each coil assembly undergoes 100% hydrostatic testing at 3.75 MPa for a minimum dwell time of 30 seconds to verify weld integrity and structural soundness.
- Leak Testing: Helium mass spectrometry or nitrogen bubble testing confirms zero-leak performance at the molecular level.
- Surface Treatment: Interior passivation (citric acid or nitric acid treatment) removes scale and oxide layers, enhancing corrosion resistance and fluid dynamics.
- Final Inspection & Packaging: Dimensional verification via coordinate measuring machine (CMM), visual inspection for surface defects, and protective packaging for shipment.
5. Applications
The stainless steel coil tube for fan coil units is deployed across a broad spectrum of HVAC applications:
- Commercial Buildings: Office towers, hotels, retail complexes, and hospitals requiring precision temperature and humidity control
- Residential HVAC: High-end residential units with concealed or cassette-type fan coil installations
- Industrial Processes: Clean rooms, laboratories, and pharmaceutical facilities demanding high-purity air and corrosion-resistant heat exchange media
- Marine & Coastal Environments: SS316L-grade coil tubes resist chloride-induced pitting in humid coastal or offshore installations
- Energy-Efficient Systems: Variable refrigerant flow (VRF) systems and heat pump configurations where thermal cycling is frequent and aggressive
6. Quality Certifications & Standards Compliance
This product line is manufactured under a certified quality management system and complies with the following international standards and certifications:
- ISO 9001:2015 – Quality Management System certification
- AHRI 340/360 – Air-Conditioning and Refrigeration Institute standard for unitary air-conditioner rating
- EN 14511 – European standard for small refrigerating units (safety and performance)
- ASME SA-269 / ASTM A269 – Standard specification for seamless austenitic stainless steel tubing
- CE Marking – Conformity with European Machinery Directive and Pressure Equipment Directive (PED 2014/68/EU)
- RoHS & REACH – Compliance with restrictions on hazardous substances and chemical regulation
- Third-Party Testing: Certified by SGS, Bureau Veritas, or TÜV for material compliance and performance verification
7. Unique Selling Points
Engineering Excellence for Superior Thermal Performance:
- Enhanced Corrosion Resistance: Unlike conventional copper-aluminum coil assemblies, the stainless steel construction eliminates galvanic corrosion risks and extends service life by up to 40% in aggressive environments.
- Superior Thermal Efficiency: Optimized coil geometry and fin density achieve EER (Energy Efficiency Ratio) values exceeding 3.5, reducing operational energy costs.
- Refrigerant Compatibility: Full compatibility with next-generation low-GWP refrigerants (R-32, R-410A), ensuring future-proof integration with evolving environmental regulations.
- Hygienic Design: Electropolished interiors prevent microbial growth and condensate contamination, critical for hospital and food-processing applications.
- Modular Configurability: Available in 1-row through 6-row configurations to match diverse cooling/heating load requirements from 2 kW to 15 kW.
- Comprehensive Traceability: Each unit is serialized with full material traceability documentation, enabling lifecycle maintenance and recall management.
8. Analysis & Performance Evaluation Summary
Based on the technical study referenced in "Analysis and Evaluation of Fan Coil Units" (风机盘管机组的分析与评价), the stainless steel coil tube demonstrates measurable advantages over traditional copper-tube/aluminum-fin (CTAF) alternatives in terms of:
- Long-term reliability and reduced maintenance frequency
- Resistance to acid condensate corrosion (pH 4.0–6.5 range)
- Consistent heat transfer coefficients across extended operational cycles
- Reduced total cost of ownership (TCO) over a 25-year service horizon
These findings validate the product's positioning as a premium-grade thermal exchange solution for demanding HVAC applications where reliability, hygiene, and energy efficiency are non-negotiable requirements.