Stainless Steel Coil Tube for Fan Coil Unit Systems
Product Overview
The Stainless Steel Coil Tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product designed specifically for use in Fan Coil Unit (FCU) systems, HVAC (Heating, Ventilation, and Air Conditioning) installations, and thermal exchange applications. These coil tubes are formed through a continuous bending process that produces a helical or serpentine configuration, enabling maximum surface area within a compact footprint. The product is engineered to address common operational challenges encountered in fan coil systems, including thermal inefficiency, vibration-induced fatigue, corrosion degradation, and flow resistance issues.
The coil tube serves as the primary heat exchange element within fan coil units, facilitating efficient thermal transfer between the circulating refrigerant or heating medium and the surrounding air stream. Its design prioritizes structural integrity, thermal conductivity, and long-term durability under cyclic thermal loading conditions.
Material & Properties
The coil tubes are fabricated from high-grade stainless steel alloys, selected to deliver optimal performance in demanding thermal and chemical environments. The following materials are available:
- 304 (AISI 304 / SUS 304): General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. Suitable for standard HVAC applications.
- 316 (AISI 316 / SUS 316): Enhanced austenitic grade with molybdenum addition, providing superior resistance to pitting and crevice corrosion in aggressive or marine environments.
- 316L (AISI 316L / SUS 316L): Low-carbon variant of 316 grade, minimizing sensitization risk during welding operations.
- 321 (AISI 321 / SUS 321): Titanium-stabilized austenitic steel suitable for elevated-temperature applications.
Key material properties include:
- Thermal conductivity: 14.9–16.3 W/(m·K) at 20°C
- Operating temperature range: −196°C to +870°C (grade-dependent)
- Corrosion resistance: Excellent against atmospheric, aqueous, and mild chemical environments
- Mechanical strength: Yield strength of 205–310 MPa (annealed condition)
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code | 1146 |
| Outer Diameter (OD) | 6.35 mm, 9.52 mm, 12.7 mm, 15.88 mm (custom sizes available) |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Pitch (Bend Spacing) | 6 mm – 25 mm (configurable) |
| Tube Length per Coil | 1.0 m – 10.0 m (customizable) |
| Number of Rows | 1 – 4 rows (arrangement-dependent) |
| Material Grades | SUS 304, SUS 316, SUS 316L, SUS 321 |
| Surface Finish | Bright annealed, polished, or passivated |
| Tolerance (OD) | ±0.05 mm |
| Tolerance (Wall Thickness) | ±10% |
| End Condition | Deburred, beveled, or capped |
| Maximum Operating Pressure | 1.6 MPa – 2.5 MPa (design-dependent) |
| Heat Exchange Medium | Water, glycol solution, refrigerant |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a multi-stage manufacturing sequence designed to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strip or seamless tubing is sourced from certified suppliers and subjected to incoming quality inspection including spectroscopic analysis (PMI testing) for alloy composition verification.
- Tube Forming: Raw material is formed into the required cross-sectional profile through precision cold-drawing or roll-forming operations, achieving tight dimensional tolerances.
- Coil Bending: The formed tubes are fed into CNC-controlled coil bending machines that produce the helical or serpentine configuration with consistent pitch and bend radius. Bending parameters are optimized to prevent ovalization, wrinkling, or wall thinning at bend locations.
- Heat Treatment: Where applicable, coils undergo solution annealing and pickling to relieve residual stresses introduced during forming, restoring full mechanical properties and ensuring corrosion resistance.
- Surface Treatment: Final surface finishing includes mechanical polishing, electropolishing, or chemical passivation to remove contaminants and establish a protective chromium oxide layer.
- Quality Inspection: Each coil tube batch undergoes dimensional verification, hydrostatic pressure testing, surface defect inspection (visual and magnetic particle testing), and material certification verification.
- End Preparation: Tube ends are deburred, beveled for brazing or welding connections, and may be capped or sealed for transport and storage.
Applications
The stainless steel coil tube is integral to a wide range of thermal management and HVAC systems:
- Fan Coil Units (FCU): Primary heat exchange element in commercial and residential air conditioning systems, providing efficient sensible and latent heat transfer.
- Chilled Water Systems: Used in central air conditioning installations where chilled water circulates through coil tubes to cool supply air.
- Heat Pump Systems: Serves as evaporator or condenser coil in air-source and ground-source heat pump applications.
- Industrial Process Cooling: Employed in manufacturing facilities requiring precise temperature control for process streams.
- Food and Pharmaceutical Processing: Utilized in sanitary applications where corrosion resistance and cleanability are critical.
- Marine and Offshore HVAC: Deployed in environments with high humidity and salt spray exposure, leveraging 316/316L grade corrosion resistance.
- Data Center Cooling: Applied in precision cooling systems for server rooms and telecommunications infrastructure.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems and adheres to internationally recognized standards:
- ISO 9001:2015: Quality Management System certification ensuring consistent production quality and continuous improvement.
- ASTM A269 / ASTM A270: Compliance with American standards for seamless and welded austenitic stainless steel tubing.
- EN 10216 / EN 10217: European standards for seamless and welded stainless steel tubes.
- JIS G 3445 / JIS G 3459: Japanese Industrial Standards for austenitic stainless steel tubes.
- GB/T 14976 / GB/T 14977: Chinese National Standards for seamless and welded stainless steel tubes.
- ASME B31.9: Compliance for pressure piping systems in HVAC applications.
- NSF/ANSI 61: Drinking water system component certification (where applicable).
Unique Selling Points
- Superior Corrosion Resistance: Stainless steel construction eliminates the risk of rust and internal scaling common with copper or carbon steel alternatives, extending service life significantly in humid and chemically aggressive environments.
- Enhanced Thermal Performance: Precision coil geometry maximizes heat transfer surface area while minimizing flow resistance, directly addressing the thermal efficiency issues documented in fan coil system troubleshooting literature.
- Structural Durability: Resistance to vibration fatigue and thermal cycling degradation reduces maintenance frequency and operational downtime in continuous-duty applications.
- Hygienic Surface Quality: Passivated stainless steel surfaces resist bacterial growth and facilitate easy cleaning, making them ideal for food-grade and pharmaceutical applications.
- Custom Configuration Capability: Flexible manufacturing allows tailoring of coil geometry, pitch, row arrangement, and dimensions to meet specific system design requirements and performance targets.
- Long Service Life: With proper installation and maintenance, stainless steel coil tubes offer a service life exceeding 25 years, significantly outperforming alternative materials in demanding environments.
Technical Notes on Fan Coil System Integration
Based on extensive field experience and technical literature regarding fan coil system reliability, the following integration considerations are recommended:
- Flow Distribution: Ensure uniform refrigerant or water flow distribution across all coil rows to prevent localized overheating or underutilization, which can lead to uneven thermal performance and accelerated wear.
- Condensate Management: Proper condensate drainage slope and collection tray design are essential to prevent water accumulation, corrosion, and microbial growth around the coil assembly.
- Vibration Isolation: Implement appropriate vibration dampening measures at coil mounting points to prevent fatigue cracking at tube-to-header weld joints.
- Fin Coating Protection: Where coil tubes are combined with aluminum fins, ensure compatible coating systems that prevent galvanic coupling and maintain long-term corrosion resistance.
- Periodic Inspection: Conduct regular visual and pressure testing to detect early signs of tube degradation, particularly at bend radii and connection points.