Stainless Steel Coil Tube (Coiltube) for Fan Coil Unit Applications
Product Overview
The Stainless Steel Coil Tube (Product No. 1508) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tube component specifically designed for integration into Fan Coil Units (FCUs). This product represents a critical heat exchange element within HVAC (Heating, Ventilation, and Air Conditioning) systems, where it serves as the primary conduit for water circulation between the chiller/boiler and the terminal air-handling unit. The coil tube assembly is engineered to maximize thermal transfer efficiency while minimizing hydraulic resistance (water resistance), ensuring optimal performance across residential, commercial, and industrial air conditioning installations.
Material & Properties
The coil tube is fabricated from high-grade stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity. The material composition ensures long-term durability in environments exposed to moisture, condensation, and chemical agents commonly encountered in HVAC systems.
- Material Grade: Austenitic stainless steel (e.g., SUS304 / SUS316L), providing superior resistance to pitting and crevice corrosion in aqueous environments.
- Corrosion Resistance: Demonstrates excellent performance against chlorides, condensate water, and treatment chemicals used in closed-loop hydronic systems.
- Mechanical Strength: Maintains structural integrity under operational pressures up to 1.6 MPa (232 psi) and beyond, depending on wall thickness.
- Thermal Conductivity: Optimized for efficient heat exchange between the circulating water and the surrounding air stream in fan coil unit applications.
- Temperature Range: Suitable for continuous operation from −40°C to +200°C, accommodating both heating and cooling cycles.
- Hygienic Properties: Non-toxic, non-flavoring, and resistant to bacterial growth, making it ideal for air distribution systems serving occupied spaces.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product No. | 1508 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Material | SUS304 / SUS316L Stainless Steel |
| Outer Diameter (OD) | 6 mm – 16 mm (customizable) |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Pitch | 12 mm – 25 mm (adjustable per design) |
| Coil Length | Up to 50 m continuous coil |
| Operating Pressure | ≤ 1.6 MPa (standard); ≤ 2.5 MPa (reinforced) |
| Working Temperature | −40°C to +200°C |
| Surface Finish | Ba & Be / No. 4 / Mirror Polish |
| Surface Roughness (Ra) | ≤ 0.4 μm (hygienic grade) |
| Water Resistance | Optimized low-pressure-drop design (ΔP minimized per unit length) |
| Heat Exchange Efficiency | Enhanced by fin attachment compatibility and smooth internal bore |
| Compliance Standards | ASTM A269 / GB/T 12771 / EN 10217 |
| Customization | Available — dimensions, coil geometry, and finish per customer requirements |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strip is sourced from certified mills with full chemical composition traceability and mechanical property documentation.
- Slitting & Leveling: The strip is slit to precise width and leveled to eliminate residual stresses, ensuring uniform coil geometry.
- Forming (Coiling): High-precision rotary forming machines shape the flat strip into a continuous helical coil with controlled pitch, diameter, and wall thickness. Computer Numerical Control (CNC) systems maintain tolerances within ±0.1 mm.
- Welding (if applicable): Longitudinal welds are produced using Automated Submerged Arc Welding (SAW) or Gas Metal Arc Welding (GMAW), followed by internal grinding to achieve a smooth, obstruction-free bore.
- Heat Treatment: Solution annealing and stress-relief annealing are performed to restore full austenitic microstructure, eliminate forming-induced residual stresses, and ensure corrosion resistance.
- Pickling & Passivation: The coil tube undergoes acid pickling to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide film on the surface.
- Surface Finishing: Mechanical polishing or chemical polishing achieves the specified surface roughness, critical for minimizing water resistance and preventing biofilm accumulation.
- Quality Inspection: Each batch undergoes dimensional verification, hydraulic pressure testing, surface defect inspection (visual + eddy current), and chemical composition analysis.
Applications
The Stainless Steel Coil Tube (No. 1508) is primarily engineered for the following application domains:
- Fan Coil Units (FCUs): The principal application — serving as the water-circulation heat exchange coil within terminal air-handling units for commercial buildings, hospitals, hotels, and office complexes.
- Hydronic Heating & Cooling Systems: Integration into radiant floor systems, wall-mounted convector units, and under-desk FCU installations.
- Industrial Process Cooling: Use in process water cooling circuits where corrosion resistance and hygiene are critical.
- Food & Pharmaceutical HVAC: Deployment in cleanroom environments requiring hygienic-grade stainless steel components.
- Marine & Coastal HVAC: Suitable for installations in high-chloride environments where carbon steel alternatives would suffer premature corrosion.
- Refrigeration Systems: Utilization in evaporator and condenser coil assemblies for medium-temperature refrigeration applications.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd adheres to internationally recognized quality management and product standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001 — Environmental Management System compliance for sustainable manufacturing practices.
- ASTM A269 / A270 — Standard specifications for welded austenitic stainless steel tubing.
- GB/T 12771 — Chinese national standard for welded stainless steel tubing and pipe.
- EN 10217 — European standard for welded stainless steel tubes.
- CE Marking — Conformity with European health, safety, and environmental protection standards.
- Mill Test Certificates (MTC) — Provided with each shipment, documenting chemical composition, mechanical properties, and heat treatment records.
Unique Selling Points
Optimized Water Resistance Design: The coil geometry and internal surface finish are specifically engineered to minimize hydraulic resistance (pressure drop), reducing pumping energy consumption and extending the service life of circulating pumps in FCU installations.
- Superior Corrosion Longevity: Unlike carbon steel coil tubes requiring internal coatings or cathodic protection, the stainless steel construction provides inherent, maintenance-free corrosion resistance throughout the product lifecycle — eliminating the need for sacrificial anodes or chemical inhibitors.
- Hygienic Interior Surface: The polished internal bore (Ra ≤ 0.4 μm) prevents sediment accumulation and biofilm formation, ensuring consistent thermal performance over time and compliance with sanitary HVAC requirements.
- Design Flexibility: Custom coil pitch, diameter, and length configurations allow seamless integration into diverse FCU designs, from compact concealed ceiling units to large-volume industrial air handlers.
- Full Traceability: Each production batch is traceable from raw material mill certificates through final inspection, providing complete quality documentation for project compliance and warranty purposes.
- Energy Efficiency Contribution: The combination of high thermal conductivity, low water resistance, and corrosion-resistant smooth surfaces directly contributes to improved Coefficient of Performance (COP) in HVAC systems, reducing operational energy costs.
- Structural Reliability: The coil tube maintains dimensional stability under thermal cycling, mechanical vibration from fan operation, and sustained hydraulic pressure — ensuring leak-free operation over decades of service.
Installation Considerations
Based on the technical study of "Fan Coil Unit Structure, Installation, and Water Resistance", the following installation guidelines are recommended for the Stainless Steel Coil Tube:
- Support & Vibration Isolation: The coil assembly must be mounted on vibration-dampening supports to prevent fatigue cracking at soldered or brazed joints during fan operation.
- Piping Configuration: Inlet and outlet connections should incorporate expansion loops or flexible connectors to accommodate thermal expansion of the coil tube during heating/cooling cycles.
- Flow Direction: Water flow should enter from the bottom and exit from the top (or as specified by the FCU manufacturer) to ensure complete coil filling and prevent air pocket formation.
- Pressure Testing: A hydrostatic pressure test at 1.5× the maximum operating pressure should be performed post-installation, held for a minimum of 30 minutes with zero leakage tolerance.
- Water Treatment: Even with stainless steel, closed-loop water treatment (inhibitors, pH control) is recommended to prevent chloride-induced stress corrosion cracking in specific environmental conditions.
- Drainage Provision: A low-point drain valve must be installed to facilitate system flushing and winterization, preventing freeze damage.
Conclusion
The Stainless Steel Coil Tube (Product No. 1508) from Wenzhou Jixing Metal Materials Co., Ltd represents a premium-grade solution for fan coil unit heat exchange applications. Its combination of corrosion resistance, optimized hydraulic performance, hygienic surface quality, and full manufacturing traceability makes it an ideal choice for designers and engineers seeking reliable, energy-efficient, and long-service-life HVAC components. The product's adherence to international standards and customizable geometry ensures compatibility with a wide range of system designs and installation environments.