Stainless Steel Coil Tube (FCU Coil) — Technical Specification Sheet
1. Product Overview
The Stainless Steel Coil Tube, also known as a Fan Coil Unit (FCU) Coil, is a critical heat exchange component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for use in air conditioning, ventilation, and thermal management systems where high-efficiency heat transfer, corrosion resistance, and long service life are paramount. The coil tube is engineered to maximize the surface-area-to-volume ratio, thereby enhancing thermal exchange efficiency between the fluid medium (water, refrigerant, or glycol solution) and the surrounding air stream.
Based on extensive technical analysis of multiple brand fan coil unit characteristics and selection criteria, the design philosophy of this product emphasizes optimal hydraulic performance, minimal pressure drop, and superior fouling resistance. These attributes collectively contribute to improved energy efficiency (EER/SEER) in HVAC applications and reduce total cost of ownership (TCO) over the system lifecycle.
2. Material & Properties
2.1 Tube Material
- Primary Alloy: Austenitic Stainless Steel conforming to ASTM A269 / ASTM A312
- Grade Options:
- 304 (UNS S30400): General-purpose corrosion resistance; ideal for indoor HVAC applications with potable water or treated glycol solutions. Contains 18% Chromium (Cr), 8% Nickel (Ni).
- 316L (UNS S31603): Enhanced corrosion resistance with 2–3% Molybdenum (Mo) addition; recommended for coastal environments, chemical processing, or high-chloride exposure scenarios.
- Surface Finish: Pickled and passivated (2B finish) for optimal chemical stability and resistance to oxidation
2.2 Fin Material
- Alloy: Electrolytic Copper (Cu ≥ 99.9%) or Aluminum (Al 1100/3003) depending on application requirements
- Fin Type: Laminated, micro-channel, or wavy-fin configurations for enhanced turbulence and heat transfer coefficients
- Coating: Optional hydrophilic or anti-corrosion coating (e.g., Chromate-free, RoHS-compliant) for extended durability in humid environments
2.3 Key Material Properties
| Property | 304 Stainless Steel | 316L Stainless Steel |
|---|---|---|
| Thermal Conductivity (W/m·K) | 16.3 | 14.6 |
| Specific Heat Capacity (J/kg·K) | 500 | 500 |
| Density (kg/m³) | 8,000 | 8,000 |
| Yield Strength (MPa, min) | 205 | 170 |
| Tensile Strength (MPa, min) | 515 | 485 |
| Operating Temperature Range (°C) | -196 to +870 | -196 to +870 |
| Corrosion Resistance | Good (indoor, low-chloride) | Excellent (coastal, high-chloride) |
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Catalog No. | 707 |
| Tube Outer Diameter (OD) | 6.35 mm / 9.52 mm / 12.7 mm (1/4" / 3/8" / 1/2") |
| Tube Wall Thickness | 0.5 mm – 1.0 mm (adjustable per application) |
| Tube Length (per coil) | 1.5 m – 12 m (customizable) |
| Fin Pitch | 2.0 mm – 4.5 mm (typical: 2.5 mm for high-efficiency) |
| Fin Height | 10 mm – 25 mm |
| Row Configuration | 2-row, 3-row, 4-row, or multi-row (as specified) |
| Cooling Capacity | 1.5 kW – 25 kW (per unit, depending on configuration) |
| Heating Capacity | 1.5 kW – 30 kW (per unit, depending on configuration) |
| Design Pressure | 1.0 MPa (standard); up to 1.6 MPa (reinforced) |
| Test Pressure | 1.5 × Design Pressure |
| Fluid Velocity (recommended) | 0.5 m/s – 2.0 m/s |
| Pressure Drop (water side) | ≤ 15 kPa at nominal flow rate |
| Connection Type | Flanged, threaded (G1/2", G3/4"), or brazed |
| Coil Configuration | Serpentine, helical, or cross-flow |
| Coating Option | Hydrophilic, anti-corrosion, or bare (as required) |
| Standard Reference | ASTM A269, ASTM A312, EN 10217, JIS G3459 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel coils are verified for chemical composition (via XRF spectroscopy), mechanical properties, and surface quality in accordance with ASTM A269/A312 requirements.
- Coil Slitting: The master coil is slit into precise-width strips using automated slitting lines with ±0.05 mm tolerance control.
- Tube Forming (Cold Rolling & Seamless): Strips are cold-rolled and welded into seamless tubes using high-frequency induction welding (HFW) or orbital TIG welding, ensuring uniform wall thickness and leak-tight joints.
- Fin Forming: Fins are stamped from copper or aluminum sheets using precision die-stamping machines, then formed into laminated or wavy configurations to optimize airflow turbulence.
- Coil Assembly (Fin-to-Tube Bonding): Tubes are arranged in the specified row configuration and brazed or mechanically bonded to the fins using vacuum brazing at 620–680°C under inert gas (Nitrogen, N₂) atmosphere to prevent oxidation.
- Hydrostatic Pressure Testing: Each coil undergoes 100% hydrostatic testing at 1.5 × design pressure for a minimum dwell time of 60 seconds to verify integrity.
- Surface Treatment: Passivation treatment (citric acid or nitric acid-based) is applied to restore the chromium oxide passive layer, ensuring long-term corrosion resistance.
- Final Quality Control (FQC): Visual inspection, dimensional verification, and random destructive testing (wall thickness measurement, tensile sampling) are performed per ISO 9001 protocols.
4.2 Key Process Advantages
- Seamless Tube Construction: Eliminates weld seams that serve as preferential corrosion sites, significantly extending service life.
- Vacuum Brazing: Ensures uniform, oxidation-free joints with superior thermal and mechanical integrity compared to conventional flux brazing.
- Automated Coiling: Computer-controlled coiling ensures consistent tube pitch and coil geometry, reducing pressure drop variance between units.
5. Applications
5.1 Primary Application Domains
- Commercial HVAC Systems: Fan Coil Units (FCU) for office buildings, shopping malls, hotels, and hospitals — providing precise temperature and humidity control.
- Residential Air Conditioning: Concealed ducted and cassette-type indoor units for high-end residential applications.
- Industrial Process Cooling/Heating: Chilled water coils for process equipment, clean rooms, and pharmaceutical manufacturing.
- Marine & Coastal Applications: 316L-grade coils for marine HVAC systems where saltwater corrosion is a primary concern.
- Food Processing & Dairy Industry: Hygienic-grade coils for pasteurization, cooling, and thermal processing equipment (compliant with FDA/3-A standards).
- Data Center Thermal Management: High-efficiency cooling coils for server room precision cooling systems.
5.2 Selection Guidelines
Based on comparative analysis of multiple brand fan coil unit technical characteristics, the following selection criteria are recommended:
- Indoor, Low-Chloride Environment: 304 Stainless Steel coil with 2.5 mm fin pitch — optimal balance of cost and performance.
- Coastal / High-Chloride Environment: 316L Stainless Steel coil with hydrophilic coating — superior resistance to chloride-induced pitting corrosion.
- High-Pressure Systems (> 1.0 MPa): Reinforced wall thickness (≥ 0.8 mm) with 4-row configuration for enhanced structural integrity.
- Low-Noise Requirements: Wider fin pitch (4.0–4.5 mm) to reduce airflow resistance and fan power consumption.
- Space-Constrained Installations: Compact 2-row coil with micro-channel fins for maximum heat transfer in minimal footprint.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — covers design, manufacturing, and inspection processes |
| ISO 14001:2015 | Environmental Management System — ensures environmentally responsible production |
| ASTM A269 / A312 | Material specifications for stainless steel welded and seamless tubes |
| EN 10217-7 | European standard for stainless steel tubes for heat exchangers |
| JIS G3459 | Japanese Industrial Standard for seamless stainless steel tubes for heat exchangers |
| ASME B31.5 | Pressure piping code for hydronic heating and cooling systems |
| RoHS 2.0 (EU 2011/65/EU) | Restriction of Hazardous Substances — ensures compliance with EU environmental regulations |
| CNAS / CNAS-CL01 | China National Accreditation Service for Conformity Assessment — laboratory testing accreditation |
| SGS Testing Report | Independent third-party verification of material composition, mechanical properties, and corrosion resistance |
7. Unique Selling Points
- Extended Service Life: Stainless steel construction provides 2–3× the service life of conventional copper tube coils, reducing replacement frequency and maintenance costs.
- Superior Corrosion Resistance: Particularly with 316L grade, the coil withstands aggressive water chemistry, chloride environments, and biological fouling without degradation.
- Hygienic & Food-Grade Compliance: Smooth, non-porous inner surfaces prevent bacterial adhesion and biofilm formation, meeting FDA and 3-A sanitary standards.
- Energy Efficiency: Optimized fin geometry and tube configuration minimize pressure drop while maximizing heat transfer coefficients, contributing to lower fan power consumption and improved COP (Coefficient of Performance).
- Customizable Configurations: Full range of tube diameters, fin pitches, row counts, and coil geometries available to match specific system design parameters.
- 100% Hydrostatic Testing: Every unit undergoes complete pressure testing, ensuring zero-defect delivery and eliminating field failure risk.
- Sustainable Manufacturing: