Stainless Steel Coil Tube — Fan Coil Unit (FCU) Series
Product Overview
The Stainless Steel Coil Tube (Model No. 1008) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tubing product designed for integration into Fan Coil Unit (FCU) systems and centralized HVAC (Heating, Ventilation, and Air Conditioning) control networks. This product line represents a critical component in modern building climate management infrastructure, where thermal transfer efficiency, corrosion resistance, and long-term reliability are paramount requirements.
The coil tube is fabricated from high-grade austenitic stainless steel and formed into continuous helical configurations optimized for maximum heat exchange surface area within compact spatial envelopes. It serves as the primary heat transfer medium in both hydronic and refrigerant-based fan coil unit assemblies, enabling precise temperature regulation across commercial, industrial, and institutional facilities.
Material & Properties
The coil tube is produced using premium austenitic stainless steel grades, selected for their exceptional combination of mechanical integrity, thermal conductivity, and resistance to environmental degradation.
- Base Material: Austenitic Stainless Steel (SAE 304 / SAE 316L)
- Chemical Composition (Typical — SAE 304): Carbon (C) ≤ 0.08%, Manganese (Mn) ≤ 2.0%, Chromium (Cr) 18.0–20.0%, Nickel (Ni) 8.0–10.5%, Silicon (Si) ≤ 1.0%
- Chemical Composition (Typical — SAE 316L): Carbon (C) ≤ 0.03%, Molybdenum (Mo) 2.0–3.0%, Chromium (Cr) 17.0–19.0%, Nickel (Ni) 10.0–14.0%
- Tensile Strength: ≥ 520 MPa (SAE 304); ≥ 485 MPa (SAE 316L)
- Yield Strength: ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +870°C
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and intergranular attack; SAE 316L grade offers enhanced resistance to chlorides and acidic media
- Surface Finish: No. 4 Brushed Finish or Electropolished (Ra ≤ 0.4 μm) for hygienic applications
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube — FCU Series (No. 1008) |
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (¼" – 1") |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Diameter (BD) | 150 mm – 600 mm (configurable) |
| Coil Length | Up to 30 meters per continuous coil |
| Number of Turns | 3 – 20 turns (application-dependent) |
| Material Grade | SAE 304 / SAE 316L / SAE 321 (on request) |
| Maximum Operating Pressure | 1.6 MPa (standard); 2.5 MPa (reinforced) |
| Heat Transfer Coefficient | 800 – 1,200 W/(m²·K) (water-side) |
| Surface Treatment | Pickled & Passivated / Electropolished |
| Connection Type | Flared, Soldered, Brazed, or Compression Fittings |
| Applicable Standards | ASTM A269 / ASTM A213 / GB/T 12771 / EN 10216-5 |
| Color / Appearance | Metallic Silver (natural stainless finish) |
| Packaging | Wooden crate with moisture-absorbent desiccant; individual coil protection |
Manufacturing Process
The production of the Stainless Steel Coil Tube for FCU applications follows a rigorously controlled multi-stage manufacturing sequence:
- Material Selection & Incoming Inspection: Certified stainless steel strip or seamless tube stock is sourced from accredited mills. Each batch undergoes spectrographic analysis (OES), mechanical testing, and visual inspection to verify compliance with ASTM and GB/T standards.
- Slitting & Straightening: The raw coil material is slit to the required width and then cold-straightened to achieve uniform flatness tolerances of ±0.1 mm/m.
- Cold Forming / Helical Winding: Precision CNC-controlled forming machines wind the flat stock into helical coil configurations. The forming process is performed under controlled lubrication to prevent surface deformation and maintain dimensional accuracy within ±0.05 mm tolerance.
- Welding (if applicable): Longitudinal seams are welded using Automatic Submerged Arc Welding (SAW) or Laser Welding technology. Weld bead geometry is controlled to minimize stress concentration and ensure structural continuity.
- Heat Treatment & Annealing: Coils are solution-annealed at 1050–1150°C followed by controlled cooling (air or water quench) to restore full austenitic microstructure, relieve residual stresses, and optimize corrosion resistance.
- Pickling & Passivation: The formed coils are immersed in nitric/hydrofluoric acid baths to remove oxide scale and form a protective chromium oxide passive layer, ensuring long-term corrosion protection.
- Dimensional Inspection & Pressure Testing: Each coil undergoes dimensional verification (OD, wall thickness, coil diameter, turn count) using calibrated gauges and CMM (Coordinate Measuring Machine) systems. Pneumatic or hydraulic pressure testing is conducted at 1.5× the maximum operating pressure for a minimum hold time of 10 minutes.
- Final Inspection & Packaging: Visual and dimensional final inspection is performed. Approved coils are individually wrapped, labeled with traceability documentation, and packed in export-grade wooden crates.
Applications
The Stainless Steel Coil Tube (FCU Series) is designed for integration into centralized Fan Coil Unit control systems, as documented in comprehensive engineering technical summaries for large-scale building HVAC installations. Primary applications include:
- Commercial Building HVAC Systems: Office towers, hotels, shopping malls, and hospitals where precise, zoned temperature control is required through distributed FCU terminals connected to a centralized control system.
- Industrial Process Cooling & Heating: Pharmaceutical manufacturing facilities, food processing plants, and semiconductor cleanrooms requiring hygienic-grade heat transfer components resistant to chemical corrosion.
- Residential High-End Systems: Luxury residential complexes and multi-family housing developments utilizing mini-split or air-source heat pump systems with stainless steel coil terminal units.
- Centralized Control Integration: The coil tube is engineered to interface seamlessly with Building Management Systems (BMS) and centralized FCU control platforms, supporting automated temperature regulation, flow metering, and energy monitoring protocols.
- Marine & Offshore Environments: SAE 316L grade coils provide reliable performance in high-humidity, salt-laden atmospheres where carbon steel alternatives would rapidly corrode.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring that every coil tube product meets international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Compliance with European Union Machinery and Pressure Equipment Directives
- SGS / BV Third-Party Inspection — Independent material verification and product conformity testing
- Mill Test Reports (MTR) — Provided with every shipment, documenting chemical composition, mechanical properties, and heat treatment records
- NACE SP0169 Compliance — For corrosion-resistant coating and passivation procedures
Unique Selling Points
- Enhanced Heat Transfer Efficiency: The helical coil geometry maximizes surface-area-to-volume ratio, delivering superior thermal performance compared to straight-tube alternatives in FCU heat exchanger assemblies.
- Exceptional Durability & Service Life: Austenitic stainless steel construction ensures a design life exceeding 25 years under normal operating conditions, significantly reducing lifecycle replacement costs in centralized control system installations.
- Corrosion-Resistant Passive Layer: The pickled and passivated surface provides self-healing oxide protection, eliminating the need for supplemental anti-corrosion treatments in aggressive chemical environments.
- Centralized Control System Compatibility: Designed with standardized connection interfaces and dimensional tolerances that ensure plug-and-play integration with modern BMS-driven FCU control architectures.
- Hygienic Grade Available: Electropolished surface finish (Ra ≤ 0.4 μm) meets FDA and 3-A sanitary standards for pharmaceutical and food-grade applications.
- Full Traceability: Each coil carries a unique batch identifier linked to mill certificates, process parameters, and inspection records, enabling complete supply chain traceability.
Engineering Note: The integration of these stainless steel coil tubes within a centralized FCU control system—as documented in comprehensive technical project summaries—enables optimized thermal zoning, reduced energy consumption through variable flow control, and predictive maintenance capabilities via real-time sensor monitoring. The material selection and manufacturing precision of this product line directly contribute to the overall reliability and efficiency of the building's HVAC infrastructure.