Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
1. Product Overview
The Stainless Steel Coil Tube (Product No. 1567) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tube specifically designed for integration into Fan Coil Unit (FCU) systems. These coil tubes serve as the critical heat exchange medium in hydronic air distribution systems, facilitating efficient thermal transfer between circulating coolant/hot water and ambient air. The product is engineered to meet the stringent performance parameters required for fresh air treatment terminal systems, ensuring optimal temperature and humidity control in commercial and industrial HVAC applications.
This coil tube product represents a specialized component within the broader stainless steel pipe family, distinguished by its continuous spiral geometry, which maximizes surface area per unit volume while maintaining structural integrity under cyclic thermal and pressure loads.
2. Material & Properties
The coil tubes are fabricated from high-purity austenitic stainless steel, selected for exceptional corrosion resistance, thermal conductivity, and long-term mechanical stability under repeated heating and cooling cycles.
- Primary Alloy Grades: AISI 304 (UNS S30408), AISI 316L (UNS S31603)
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in aqueous environments
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, ensuring efficient heat exchange performance
- Mechanical Properties: Tensile strength ≥ 520 MPa; elongation ≥ 40% (AISI 304); yield strength ≥ 205 MPa
- Temperature Range: Continuous operation from −196°C to +870°C
- Surface Finish: Electropolished or passivated, Ra ≤ 0.8 μm for reduced flow resistance
- Hygienic Compliance: Free of lead, cadmium, and other toxic leachables
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (1/4" – 1") | ASTM A269 / EN 10217 |
| Wall Thickness | 0.5 mm – 2.0 mm | ASTM A269 |
| Coil Diameter | 200 mm – 1200 mm | Custom per application |
| Coil Length | Up to 500 m per continuous coil | — |
| Pressure Rating | Up to 1.6 MPa (PN16) | EN 10217-2 |
| Operating Temperature | −20°C to +120°C (standard); up to +250°C (special) | — |
| Dimensional Tolerance | OD: ±0.1 mm; Wall: ±10% | ASTM A269 |
| Surface Roughness | Ra ≤ 0.8 μm (electropolished) | ISO 4287 |
| Weld Seam Type | Continuous longitudinal weld (butt-welded) | ISO 14286 |
| Packaging | Wooden crate / PE-film wrapped coil stand | ISO 4180 |
4. Manufacturing Process
The production of these stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical quality, and functional performance:
- Steel Coil Procurement: Cold-rolled stainless steel strip sourced from certified mills, verified via mill test certificates (MTC) per EN 10204 Type 3.1.
- Forming & Welding: Precision roll-forming to achieve target OD and wall thickness, followed by continuous high-frequency induction welding or TIG (Tungsten Inert Gas) welding to produce a seamless-quality longitudinal seam.
- Heat Treatment: Solution annealing at 1050–1150°C with rapid quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Coiling: Controlled-diameter coiling on mandrels to achieve uniform coil geometry with minimal residual stress.
- Surface Treatment: Acid pickling and passivation (or electropolishing) to remove scale and establish a protective chromium oxide passive film.
- Quality Inspection: Ultrasonic testing (UT), eddy current inspection (ECI), hydrostatic pressure testing at 1.5× working pressure, and dimensional verification via laser measurement systems.
- Packaging & Dispatch: Protective wrapping, moisture barrier packaging, and labeling with traceability documentation.
5. Applications
The coil tubes are purpose-engineered for the following critical applications:
- Fan Coil Unit (FCU) Systems: Primary heat exchanger coils for residential, commercial, and industrial HVAC terminal units
- Fresh Air Treatment Systems: Precise thermal conditioning of incoming outdoor air to meet terminal parameter requirements (temperature, dew point, enthalpy)
- Chilled Water Distribution: Low-temperature hydronic circuits in radiant cooling and air handling units (AHU)
- Heat Recovery Systems: Plate-fin and tube-fin heat exchangers in energy recovery ventilators (ERV)
- Industrial Process Cooling: Heat exchange in pharmaceutical, food processing, and semiconductor manufacturing cleanroom environments
- Marine & Offshore HVAC: Corrosion-resistant coil solutions for shipboard climate control systems
6. Quality Certifications & Standards Compliance
All products manufactured by Wenzhou Jixing Metal Materials Co., Ltd. conform to internationally recognized quality and safety standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification |
| ISO 14001:2015 | Environmental Management System |
| ASTM A269/A269M | Standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel tube |
| EN 10217-2 | Heat-resistant, hydrogen-resistant, and non-oxidizing steel tubes — technical delivery conditions |
| GB/T 14976 | Chinese national standard for seamless steel tubes for cold-rolled steel pipes |
| ASME B31.9 | Pressure piping for refrigeration and air-conditioning systems |
| NACE MR0175 / ISO 15156 | Susceptibility to sulfide stress cracking (where applicable for 316L grade) |
| RoHS / REACH | Restriction of Hazardous Substances compliance |
| CE Marking | European conformity for pressure equipment directive (PED 2014/68/EU) |
7. Unique Selling Points
- Optimized Thermal Performance: Continuous coil geometry with uniform wall thickness ensures consistent heat transfer coefficients across the entire coil length, minimizing thermal bypass and improving system COP (Coefficient of Performance).
- Extended Service Life: Austenitic stainless steel construction provides a design life exceeding 25 years without degradation of mechanical or thermal properties under normal operating conditions.
- Zero-Maintenance Hygiene: Electropolished interior surfaces inhibit microbial growth and scale formation, critical for pharmaceutical and food-grade HVAC applications.
- Precision Dimensional Consistency: Laser-monitored production ensures ±0.1 mm OD tolerance, enabling reliable integration with fin-tube assemblies and brazed headers without field modification.
- Full Traceability: Each coil is accompanied by a complete mill test certificate (MTC) with chemical composition, mechanical test results, and heat number for full supply chain traceability.
- Customizable Configurations: Flexible manufacturing capability supports custom OD, wall thickness, coil diameter, and length specifications to match specific OEM requirements for fan coil unit terminal systems.
Note: The selection of appropriate coil tube specifications for fan coil unit systems requires careful consideration of terminal parameter targets—including supply air temperature, dew point depression, and enthalpy change—to ensure the coil tube geometry and material properties align with the designed fresh air treatment process. Wenzhou Jixing Metal Materials Co., Ltd. provides technical consultation services to assist system designers in matching coil tube specifications to specific HVAC design conditions.