Stainless Steel Coil Tube for Fan Coil Unit Heat Exchangers
Product Overview
The Stainless Steel Coil Tube (Product No. 1692) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping component specifically designed for integration into Fan Coil Unit (FCU) air conditioning systems. These coil tubes serve as the primary heat transfer medium in air-side heat exchange assemblies, facilitating efficient thermal energy exchange between circulating coolant (or refrigerant) and ambient air drawn across the coil surface by axial or centrifugal fans.
Unlike conventional copper or aluminum tube-and-fin heat exchangers, stainless steel coil tubes offer superior corrosion resistance, extended service life, and enhanced hygiene performance—making them particularly suitable for applications in healthcare facilities, food processing environments, clean rooms, and high-moisture industrial settings where material degradation and microbial contamination are critical concerns.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, with the primary material grades being:
- AISI 304 (UNS S30408) — The standard grade offering excellent general corrosion resistance, formability, and weldability. Suitable for most indoor HVAC applications.
- AISI 316 (UNS S31608) — Enhanced grade with added Molybdenum (Mo) content (2.0–2.5%) providing superior resistance to chlorides and aggressive chemical environments. Recommended for coastal installations and industrial applications.
- AISI 316L (UNS S31603) — Low-carbon variant of 316 grade, designed to prevent intergranular corrosion during welding operations.
Key material properties include:
- Non-magnetic (in annealed condition)
- Non-toxic and food-safe (compliant with FDA and EU 1935/2004 regulations)
- Excellent resistance to pitting, crevice, and stress corrosion cracking
- Thermal conductivity: 14.9–16.3 W/(m·K) (at 25°C for 304 grade)
- Linear thermal expansion coefficient: 16.0–17.3 × 10⁻⁶ /°C
- Operating temperature range: −196°C to +870°C
Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 12.7 mm (¼" – ½") | ±0.15 mm |
| Wall Thickness | 0.3 mm – 1.0 mm | ±0.05 mm |
| Coil Inner Diameter | 50 mm – 200 mm | ±2 mm |
| Coil Length per Roll | 10 m – 50 m | ±0.5 m |
| Pitch (Row Spacing) | 2.0 mm – 5.0 mm | ±0.1 mm |
| Bend Radius | ≥ 1.5 × OD (minimum) | — |
| Surface Finish | 2B / BA (Bright Annealed) / Electropolished | Ra ≤ 0.4 μm (electropolished) |
| End Condition | Plain / Flared / Burred / Formed | Per drawing |
| Hydrostatic Test Pressure | 1.5 × working pressure | — |
| Maximum Working Pressure | 1.6 MPa (standard) / 2.5 MPa (heavy wall) | — |
| Material Grade | SUS304 / SUS316 / SUS316L | Per ASTM/EN standards |
| Surface Roughness (internal) | Ra ≤ 0.8 μm | — |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, material integrity, and consistent performance:
- Raw Material Procurement & Verification — Stainless steel strip or seamless tube stock is sourced from certified mills (e.g., Outokumpu, Voestalpine, or domestic equivalent) with full mill test certificates (MTC) confirming chemical composition and mechanical properties per ASTM A213 / ASTM A269 / EN 10216-5 specifications.
- Coil Forming / Bending — Precision CNC-controlled coiling machines form the tube into the specified helical geometry. Computerized bending algorithms ensure uniform bend radii and consistent pitch throughout the entire coil length, minimizing residual stress concentrations.
- Heat Treatment & Annealing — Post-forming annealing at 1050°C–1100°C followed by controlled cooling relieves internal stresses, restores ductility, and ensures the material is in a fully solution-annealed condition. This step is critical for maintaining corrosion resistance after cold working.
- Pickling & Passivation — The coiled tubes undergo acid pickling (HNO₃/HF mixture) to remove scale and oxide films, followed by nitric acid passivation to establish a stable, protective chromium oxide passive layer on the surface.
- Hydrostatic Testing — Each coil is pressure-tested to 1.5 times the rated working pressure to verify weld integrity and absence of defects. Digital pressure gauges with data logging ensure traceability.
- Dimensional Inspection & Non-Destructive Testing (NDT) — Final inspection includes OD/wall thickness measurement via ultrasonic gauging, visual surface examination, and eddy current testing to detect subsurface defects.
- Packaging — Coils are wrapped in anti-corrosion protective film, secured on wooden pallets or steel drums, and labeled with batch traceability information.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. are deployed across a wide spectrum of thermal management and fluid distribution systems:
- HVAC Fan Coil Units (FCUs) — Primary application; coil tubes serve as the air-side heat exchanger in comfort cooling and heating systems for commercial buildings, hospitals, hotels, and residential complexes.
- Chilled Water Distribution — Coil assemblies integrated into air handling units (AHUs) for precise temperature control in large-scale ventilation systems.
- Food & Beverage Processing — Sanitary-grade heat exchange coils in pasteurization equipment, dairy processing lines, and beverage cooling systems where hygiene compliance is mandatory.
- Pharmaceutical & Biotechnology — Clean room air conditioning coils and process heat exchangers in GMP-compliant manufacturing environments.
- Marine & Offshore — Corrosion-resistant coil heat exchangers for shipboard HVAC and marine air conditioning systems exposed to saltwater atmospheres.
- Industrial Process Cooling — Heat recovery coils in industrial exhaust systems and process air conditioning for electronics manufacturing, data centers, and semiconductor fabrication facilities.
- Refrigeration Systems — Evaporator and condenser coil tubes in commercial refrigeration units and cold storage systems.
Unique Selling Points
- Superior Corrosion Resistance — Stainless steel coil tubes outperform copper and aluminum alternatives by 5–10× in terms of service life in corrosive environments, significantly reducing maintenance frequency and total cost of ownership (TCO).
- Hygienic Surface Finish — Electropolished surfaces with Ra ≤ 0.4 μm prevent bacterial adhesion and biofilm formation, meeting the stringent requirements of food-grade and pharmaceutical applications.
- Design Flexibility — Available in multiple OD, wall thickness, and coil geometry configurations to accommodate diverse heat exchanger designs and thermal performance requirements.
- Full Traceability — Each production batch is accompanied by a comprehensive material traceability dossier including mill certificates, chemical analysis reports, mechanical test data, and NDT results.
- Energy Efficiency Contribution — Precision manufacturing tolerances ensure optimal fin-to-tube contact and uniform coolant distribution, contributing to improved Coefficient of Performance (COP) in FCU applications.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and standard conformances:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| ASTM A213 / A269 | Material specification for stainless steel tube |
| EN 10216-5 | European standard for austenitic stainless steel tubes |
| GB/T 12771 | Chinese national standard for stainless steel seamless tubes |
| ASME B31.5 | Piping and piping components for refrigeration and air conditioning |
| NSF/ANSI 61 | Drinking water system components (where applicable) |
| EU 1935/2004 & EC 1935/2004 | Food-contact materials compliance |
Every coil tube shipment is accompanied by a Certificate of Conformance (CoC) and a Material Test Certificate (MTC) in accordance with EN 10204 Type 3.1, providing independent third-party verification of chemical composition and mechanical properties. Customers may request additional testing protocols including spectrometric analysis, salt spray testing (ASTM B117, 1000-hour minimum), and cryogenic impact testing as required for specific project specifications.
Note: All specifications listed above represent standard configurations. Customized coil geometries, material grades, surface finishes, and dimensional tolerances are available upon request through Wenzhou Jixing Metal Materials Co., Ltd.'s engineering support team. Technical data sheets and sample submissions are provided prior to bulk order placement to ensure full alignment with the end-user's design requirements.