Stainless Steel Coil Tube for Fan Coil Units
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing product specifically designed for integration into Fan Coil Units (FCUs) and air-conditioning terminal systems. This coil tube serves as the core heat exchange medium within fan coil assemblies, where it undergoes continuous thermal cycling between cooling and heating modes. The product is engineered to meet the stringent requirements of the cooling and heating capacity conversion equations governing FCU performance, ensuring accurate thermal energy transfer under variable operating conditions.
The coil tube is produced in continuous coil form to facilitate automated winding into multi-circuit heat exchanger configurations, enabling high surface-area-to-volume ratios essential for efficient latent and sensible heat exchange in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, selected for its exceptional combination of thermal conductivity, corrosion resistance, and mechanical durability under prolonged thermal stress.
- Material Grade: SUS304 (UNS S30400) / SUS316 (UNS S31600) — selected based on application-specific corrosion requirements
- Thermal Conductivity: 16.3 W/(m·K) at 25°C (SUS304), providing reliable heat transfer efficiency across the operational temperature range of −20°C to +120°C
- Corrosion Resistance: Superior resistance to chlorides, condensate water, and dehumidification-related moisture environments typical in FCU operation
- Mechanical Strength: Tensile strength ≥ 520 MPa; yield strength ≥ 205 MPa — ensuring structural integrity during coil winding and operational pressure cycling
- Surface Finish: Interior surface roughness Ra ≤ 0.8 μm to minimize flow resistance and fouling; exterior surface Ra ≤ 1.6 μm for optimal fin adhesion
- Operating Pressure: Rated for up to 1.6 MPa (PN16) water-side pressure, accommodating high-pressure hydronic loop designs
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Material | SUS304 / SUS316 Austenitic Stainless Steel | ASTM A213 / GB/T 14976 |
| Outer Diameter (OD) | 6.35 mm (⅛"), 9.53 mm (⅜"), 12.7 mm (½") | ASTM B816 |
| Wall Thickness | 0.5 mm / 0.8 mm / 1.0 mm | — |
| OD Tolerance | ±0.05 mm | ISO 4287 |
| Wall Thickness Tolerance | ±0.03 mm | ISO 4287 |
| Coil Winding Diameter | 50 mm – 200 mm (configurable per FCU design) | — |
| Coil Length per Spool | 50 m – 300 m (continuous coil) | — |
| Operating Temperature Range | −20°C to +120°C | — |
| Maximum Working Pressure | 1.6 MPa (PN16) | EN 10226 |
| Hydrostatic Test Pressure | 2.4 MPa (1.5× working pressure) | ASTM A213 |
| Surface Treatment | Pickled & Passivated (P&P) | ASTM A967 |
| Delivery Form | Coiled (Coiltube) — ready for automatic bending/winding | — |
| Traceability | Full heat number traceability per spool | ISO 9001:2015 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical integrity, and surface quality suitable for high-performance heat exchange applications:
- Raw Material Sourcing: High-purity stainless steel strip or seamless tube stock is procured from certified mills with verified chemical composition (C ≤ 0.08%, Ni ≥ 8.0%, Cr ≥ 18.0% for SUS304).
- Hot Rolling & Annealing: The base material undergoes controlled hot rolling followed by solution annealing at 1050°C – 1100°C to achieve a uniform austenitic microstructure free of residual stresses.
- Cold Drawing & Sizing: Precision cold drawing through calibrated dies achieves the target OD and wall thickness with tight tolerances (±0.05 mm OD, ±0.03 mm wall thickness).
- Intermediate Annealing: Controlled recrystallization annealing restores ductility after cold working, preventing cracking during subsequent forming operations.
- Precision Coiling: The finished tube is wound into coils using CNC-controlled coiling equipment, ensuring uniform coil geometry, consistent layer-to-layer contact pressure, and absence of kinks or deformations.
- Pickling & Passivation: The coiled tube undergoes acid pickling (HNO₃/HF mixture) to remove mill scale and oxidation, followed by passivation treatment to form a protective chromium oxide layer (Cr₂O₃) on the surface.
- Quality Inspection: Each coil is subjected to dimensional verification (OD/wall thickness), visual surface inspection, hydrostatic pressure testing, and chemical composition analysis (spectrometry).
- Packaging & Labeling: Coils are wrapped in moisture-proof film, secured on protective spools, and labeled with full traceability information including heat number, material grade, dimensions, and certification data.
Applications
The stainless steel coil tube is specifically engineered for the following application domains:
- Fan Coil Units (FCUs): Primary application — serves as the water-side heat exchange coil in commercial FCU systems, where accurate cooling and heating capacity conversion is critical for maintaining indoor thermal comfort. The coil tube's thermal conductivity and corrosion resistance ensure consistent performance across both cooling (dehumidification) and heating modes.
- Chilled Water & Hot Water Distribution Systems: Suitable for hydronic piping loops delivering conditioned water to terminal units in large commercial buildings, hospitals, and data centers.
- Industrial Process Cooling: Used in process cooling applications requiring corrosion-resistant heat exchange tubing in chemical, pharmaceutical, and food processing industries.
- Heat Pump Systems: Integrated into the evaporator and condenser sections of air-source and water-source heat pumps operating within the −20°C to +120°C temperature envelope.
- Marine & Coastal HVAC: SUS316 grade coil tube provides enhanced resistance to chloride-induced pitting corrosion in coastal and marine HVAC installations.
Quality Certifications & Standards Compliance
All products manufactured by Wenzhou Jixing Metal Materials Co., Ltd. comply with the following international and national standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
- ASTM A213 — Specification for seamless austenitic stainless steel tubing
- ASTM A269 — Specification for seamless and welded austenitic stainless steel tubing
- ASTM A967 — Standard practice for chemical cleaning and passivation of stainless steel parts
- GB/T 14976 — Chinese national standard for stainless steel seamless tubes
- EN 10216-5 — European standard for stainless steel cold-drawn seamless tubes
- ISO 4287 — Surface texture roughness measurement and evaluation
- ISO 1143 — Welding consumables and welding quality standards
Unique Selling Points
- Precision Dimensional Control: Tight tolerances (±0.05 mm OD, ±0.03 mm wall thickness) ensure reliable fin-tube interference fit in heat exchanger assembly, maximizing thermal contact efficiency.
- FCU-Optimized Design: Coil tube geometry and material properties are specifically calibrated to meet the thermal performance requirements defined by fan coil unit cooling/heating capacity conversion equations, ensuring predictable and consistent output across operating conditions.
- Corrosion-Resistant Longevity: SUS304/SUS316 austenitic stainless steel provides a service life exceeding 20 years in standard HVAC environments, significantly outperforming carbon steel alternatives in condensate-rich conditions.
- Continuous Coil Form: Delivered in continuous coil format, enabling high-speed automated winding and reducing labor costs and installation time in FCU manufacturing lines.
- Full Traceability: Complete heat number and batch traceability from raw material to finished coil, supporting compliance with critical industry audits and warranty claims.
- Surface Quality: Pickled and passivated finish with Ra ≤ 0.8 μm interior surface minimizes flow resistance, reducing pumping energy consumption and preventing biofilm fouling in water-side applications.
Note: This product specification is based on the technical framework established by Wenzhou Jixing Metal Materials Co., Ltd. for stainless steel coil tube products intended for fan coil unit heat exchange applications. Custom dimensions, material grades, and coil configurations are available upon request to meet specific OEM requirements.