Stainless Steel Coil Tube for Fan Coil Units (FCU)
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component specifically designed for large temperature difference, high static pressure fan coil unit (FCU) applications. This coil tube product is fabricated from high-grade austenitic stainless steel and is formed into a serpentine or spiral configuration to maximize heat exchange surface area within a compact envelope. The coil tube serves as the core heat transfer element in air handling systems, enabling efficient thermal energy exchange between the circulating fluid (water or refrigerant) and the ambient air stream.
Based on the research and development experience documented in the study titled "Development of Large Temperature Difference High Static Pressure Fan Coil Unit", this product has been optimized for scenarios requiring significant temperature differentials (ΔT) between supply and return fluid, as well as high static pressure conditions that demand robust structural integrity and low-flow-resistance geometry.
2. Material & Properties
The coil tube is constructed from premium-grade stainless steel, selected for its outstanding corrosion resistance, thermal conductivity, and mechanical durability under demanding HVAC (Heating, Ventilation, and Air Conditioning) operating conditions.
- Base Material: Austenitic stainless steel (commonly Grade 304 or Grade 316L per ASTM A213 / EN 10217-7)
- Corrosion Resistance: Excellent resistance to chloride-induced pitting and general atmospheric corrosion, particularly in Grade 316L configurations
- Thermal Conductivity: 14.9 – 16.3 W/(m·K) at 20 °C, providing reliable heat transfer performance
- Tensile Strength: ≥ 515 MPa (Grade 304); ≥ 485 MPa (Grade 316L)
- Yield Strength: ≥ 205 MPa (0.2% offset)
- Operating Temperature Range: −196 °C to +870 °C
- Surface Finish: Pickled and passivated (2B finish) or mechanically polished to achieve low surface roughness (Ra ≤ 0.8 μm)
- Weldability: High; suitable for TIG (Tungsten Inert Gas) and orbital welding without pre- or post-heat treatment
3. Specifications
| Parameter | Specification / Value | Standard / Reference |
|---|---|---|
| Product Category | Coil Tube (Serpentine / Spiral) | Internal Classification #786 |
| Outer Diameter (OD) | Ø6.0 – Ø19.0 mm (customizable) | ASTM A213 / EN 10217-7 |
| Wall Thickness (WT) | 0.5 – 1.5 mm | — |
| Bend Radius | 2D – 5D (minimum bend radius, where D = OD) | — |
| Coil Pitch / Spacing | 10 – 40 mm (adjustable per FCU design) | — |
| Row Configuration | 2-row, 3-row, 4-row, or multi-row | — |
| Design Static Pressure | Up to 250 Pa (high static pressure rating) | — |
| Maximum Temperature Differential (ΔT) | Up to 20 °C (large ΔT capability) | — |
| Operating Pressure | Up to 1.6 MPa (gauge) | EN 12156 |
| Hydrostatic Test Pressure | 1.5× operating pressure | EN 12156 |
| End Connection | Soldered, brazed, or welded headers | — |
| Corrosion Protection | Passivation treatment; optional coating | ASTM A380 |
| Applicable Standards | EN 12156, ISO 5152, GB/T 14976 | — |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Selection & Inspection: Stainless steel seamless or welded pipe (per ASTM A213 or EN 10217-7) is procured and subjected to incoming quality control (IQC), including chemical composition verification (OES analysis), mechanical property testing, and visual inspection.
- Cutting & Deburring: Pipe lengths are cut to specified dimensions using precision sawing or laser cutting. All burrs and sharp edges are removed to prevent flow obstruction and stress concentration.
- Forming / Bending: The tube is cold-bent into the desired serpentine or spiral coil geometry using CNC-controlled bending machines. The bend radius is carefully controlled (minimum 2D) to avoid ovalization, wrinkling, or cracking. Mandrel-assisted bending ensures uniform cross-sectional integrity.
- Header Fabrication: Inlet and outlet headers are fabricated from matching stainless steel material and welded to the coil tube ends using TIG welding or orbital welding. Weld joints are inspected for continuity and porosity.
- Welding & Brazing: Multi-row coil configurations are joined to headers and intermediate manifolds using appropriate joining techniques. Post-weld passivation ensures the weld zones maintain corrosion resistance equivalent to the base material.
- Surface Treatment: The completed coil tube undergoes pickling (acid cleaning) and passivation to remove oxide scale and form a protective chromium oxide layer, enhancing long-term corrosion performance.
- Quality Testing: Final product testing includes hydrostatic pressure testing, dimensional verification, visual NDT (Non-Destructive Testing), and optional eddy current inspection for wall thickness uniformity.
5. Applications
The stainless steel coil tube is specifically engineered for high-performance thermal management systems and finds extensive application in the following domains:
- Large Temperature Difference Fan Coil Units (FCU): Primary application — designed for FCU systems where supply and return fluid temperatures exhibit significant differentials (up to 20 °C), requiring enhanced heat transfer efficiency and thermal stress resistance.
- High Static Pressure HVAC Systems: Suitable for air handling units (AHU) and fan coil units operating under elevated static pressure conditions (up to 250 Pa), where structural rigidity and low flow resistance are critical.
- Commercial & Industrial Building HVAC: Office buildings, hotels, hospitals, shopping malls, and industrial facilities requiring reliable, low-maintenance air conditioning and heating solutions.
- Cleanroom & Pharmaceutical Environments: The stainless steel construction ensures hygienic, corrosion-free operation in environments with strict contamination control requirements.
- Marine & Coastal Applications: Grade 316L coil tubes provide superior resistance to chloride-rich marine atmospheres.
- Food Processing & Dairy Equipment: Compliant with food-grade sanitary standards due to the inert nature of austenitic stainless steel.
- Refrigeration & Chilled Water Systems: Efficient heat exchange in chiller loops, cooling towers, and refrigeration condensers.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and service processes
- ISO 14001:2015 — Environmental Management System, ensuring sustainable and eco-conscious production practices
- EN 12156 — Compliance with European standard for heat exchanger tubes and pipes, including dimensional tolerances and pressure testing protocols
- ISO 5152 — Conformity with international standard for seamless and welded austenitic stainless steel tubes and pipes for heat exchangers
- GB/T 14976 — Chinese national standard for cold-rolled seamless stainless steel tubes
- CE Marking — Conformity with European directives for CE-marked HVAC components
- Material Traceability: Full batch traceability from raw material mill certificates (MTC, EN 10204 3.1) through final product inspection reports
7. Unique Selling Points
Engineered for Large ΔT and High Static Pressure: Unlike conventional coil tubes, this product is specifically optimized based on research in large temperature difference, high static pressure fan coil unit development. The geometry, material selection, and structural design collectively address the unique thermal and mechanical demands of these challenging operating conditions.
- Superior Corrosion Durability: Austenitic stainless steel construction eliminates concerns of rust, scale formation, or internal corrosion — critical for long service life in water-carrying HVAC systems.
- High Thermal Efficiency: Optimized coil geometry (pitch, row count, bend radius) maximizes heat transfer coefficient while minimizing flow resistance, improving COP (Coefficient of Performance) of the overall FCU system.
- Low Maintenance & Long Service Life: The inherent corrosion resistance and structural robustness result in minimal maintenance requirements and extended operational lifespan (20+ years under normal conditions).
- Customizable Design: Wenzhou Jixing Metal Materials offers flexible customization of tube dimensions, coil configurations, and header designs to match specific FCU unit requirements.
- Hygienic & Food-Grade Compatible: Suitable for demanding sanitary applications without risk of material leaching or contamination.
- Environmentally Friendly: Stainless steel is 100% recyclable, supporting sustainable building practices and reducing lifecycle environmental impact.
Note: All specifications are subject to confirmation based on specific project requirements. Custom engineering solutions are available upon request. For detailed technical data sheets and material certificates, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly.