Stainless Steel Coil Tube for Fan Coil Unit (FCU) Systems
Product Overview
The Stainless Steel Coil Tube (Catalog No. 1694) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tube component specifically designed for integration into Fan Coil Unit (FCU) with Fresh Air Systems. This product serves as a critical heat exchange element within hydronic air distribution systems, facilitating efficient thermal transfer between circulating refrigerant (or heating medium) and the airstream passing over the coil surface.
Unlike conventional copper or aluminum coil assemblies, the stainless steel coil tube leverages the superior corrosion resistance, mechanical strength, and hygienic properties of austenitic stainless steel grades, making it particularly suitable for demanding environments including commercial HVAC installations, food processing facilities, pharmaceutical cleanrooms, and marine applications where long-term reliability and sanitary compliance are paramount.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, typically conforming to the following material specifications:
- Grade 304 (UNS S30400 / 1.4301): General-purpose grade offering excellent corrosion resistance, formability, and weldability. Chromium (Cr) content of 18–20% and Nickel (Ni) content of 8–10.5% provide robust passive film stability.
- Grade 316 (UNS S31600 / 1.4401): Enhanced grade with 2–3% Molybdenum (Mo) addition for superior resistance to chlorides, pitting, and crevice corrosion. Ideal for coastal or chemically aggressive environments.
- Surface Finish: Available in mill finish, electropolished (Ra ≤ 0.4 μm), or passivated finish to ensure hygienic performance and minimize biofilm accumulation.
Mechanical Properties (Typical for Grade 304, Annealed Condition):
- Tensile Strength: ≥ 515 MPa
- Yield Strength: ≥ 205 MPa
- Elongation: ≥ 40%
- Density: 8.0 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 Coiltube) |
| Catalog Number | 1694 |
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (1/4" – 1") |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Pitch (Row Spacing) | 12 mm – 25 mm |
| Tube Length per Row | 300 mm – 1,200 mm |
| Number of Rows | 2 – 6 rows |
| Fin Type | Integral fin, louvered fin, or corrugated surface (stainless steel fin) |
| Fin Density | 10 – 20 fins per inch (FPI) |
| Operating Pressure | Up to 1.6 MPa (232 psi) |
| Operating Temperature Range | -40°C to +150°C |
| Connection Method | Flared, threaded, brazed, or welded (TIG) headers |
| Standard Compliance | ASTM A269, ASTM A270, EN 10217-7, GB/T 14976 |
| Application System | Fan Coil Unit + Fresh Air System (FCU + OA) |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, surface integrity, and mechanical performance:
- Material Selection & Inspection: Raw stainless steel coil stock is sourced from certified mills and subjected to spectrographic analysis (PMI) to verify chemical composition compliance with ASTM/EN specifications.
- Blanking & Slitting: The coil strip is slit to precise width tolerances (±0.1 mm) and cut to required tube length.
- Forming & Welding: Flat strip is formed into tubular geometry using precision roll forming equipment. The longitudinal seam is sealed via High-Frequency Induction Welding (HFW) or Continuous TIG Welding, followed by internal bead grinding to achieve a smooth, leak-tight seam.
- Coiling & Bending: Individual tubes are coiled into serpentine or helical configurations using CNC-controlled bending machines with precise angle and pitch control (±0.5° angular accuracy, ±0.2 mm pitch tolerance).
- Fin Integration: Integral fins are formed during the coiling process, or discrete stainless steel fins are mechanically crimped onto the tube surface using specialized finning equipment.
- Header Assembly: Tube ends are brazed or welded to stainless steel distribution headers, forming a complete coil pack assembly.
- Hydrostatic Pressure Testing: Each coil assembly undergoes 100% hydrostatic testing at 1.5× the maximum operating pressure to verify leak integrity.
- Surface Treatment: Optional electropolishing and passivation treatment is applied to enhance corrosion resistance and achieve hygienic surface quality (Ra ≤ 0.4 μm).
- Final Inspection & Packaging: Dimensional verification, visual inspection, and protective packaging in moisture-barrier materials.
Applications
The stainless steel coil tube is engineered for deployment in Fan Coil Unit (FCU) with Fresh Air Systems, which represent a prevalent HVAC architecture in commercial and institutional buildings. Key application domains include:
- Commercial HVAC: Office buildings, hotels, hospitals, and retail spaces requiring precise temperature and humidity control with independent zone regulation.
- Pharmaceutical & Biotechnology: Cleanroom environments (ISO Class 5–8) where sanitary-grade, non-contaminating heat exchange surfaces are mandatory per GMP guidelines.
- Food Processing & Dairy Industry: Facilities requiring resistance to aggressive cleaning agents (CIP systems) and compliance with FDA/3-A sanitary standards.
- Marine & Offshore: Shipboard HVAC systems where chloride-induced corrosion of conventional materials is a primary failure mode.
- Data Centers & Telecommunications: High-density cooling applications demanding long service life and minimal maintenance intervals.
- Residential High-End: Luxury apartments and private residences where silent, compact, and corrosion-free cooling/heating solutions are preferred.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management infrastructure ensuring that every coil tube product meets international standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System, demonstrating commitment to sustainable manufacturing practices.
- CE Marking (EU Conformity): Compliance with relevant European directives including Machinery Directive (2006/42/EC) and Pressure Equipment Directive (PED 2014/68/EU).
- ASTM International Standards: Full compliance with ASTM A269 (welded austenitic stainless steel tubing) and ASTM A270 (seamless and welded austenitic stainless steel tubing).
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes for general application.
- NACE MR0175 / ISO 15156 — Compliance for sour service environments (applicable for Grade 316 variants).
- Mill Test Reports (MTR): Third-party certified chemical composition and mechanical property documentation provided with each batch shipment.
Unique Selling Points
- Exceptional Corrosion Resistance: Stainless steel construction eliminates the risk of internal rust and external degradation that plagues copper and carbon steel alternatives, extending service life beyond 25 years in demanding environments.
- Hygienic Surface Integrity: Electropolished finish with Ra ≤ 0.4 μm prevents microbial colonization and facilitates CIP (Clean-in-Place) protocols, meeting the most stringent sanitary requirements.
- Superior Mechanical Durability: High yield strength and fatigue resistance ensure dimensional stability under cyclic thermal loading, preventing fin-tube separation and maintaining heat transfer efficiency over the product lifecycle.
- Chemical Compatibility: Inert surface chemistry resists degradation from ammonia refrigerants, glycol-based heat transfer fluids, and aggressive cleaning chemicals.
- Full Traceability: Each production batch is linked to raw material certifications, manufacturing parameters, and inspection records, enabling complete quality traceability from mill to installation.
- Custom Engineering Capability: Wenzhou Jixing Metal Materials Co., Ltd offers bespoke coil configurations tailored to specific FCU design requirements, including custom tube diameters, fin geometries, row arrangements, and header configurations.
Design Note: In Fan Coil Unit + Fresh Air System architecture, the stainless steel coil tube functions as the primary heat exchange surface where conditioned water (chilled or hot) transfers thermal energy to/from the airstream. The coil's thermal performance is characterized by its U-value (overall heat transfer coefficient, typically 60–90 W/m²·K for stainless steel coil configurations), air-side pressure drop, and water-side flow resistance. Optimal design balances these parameters against the system's total cooling/heating load, air velocity constraints, and noise level requirements (typically ≤ 35 dBA at 1 meter distance).