Stainless Steel Coil Tube for FP Series Fan Coil Units
Product Reference No.: 1384 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered heat exchange component specifically designed for integration into FP Series Fan Coil Unit (FCU) assemblies. As a critical structural and thermal element, the coil tube serves as the primary medium for heat transfer within hydronic air conditioning systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this product adheres to stringent international standards for dimensional accuracy, corrosion resistance, and thermal conductivity, ensuring reliable performance in both commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications.
The coil tube is fabricated from high-grade stainless steel, forming a continuous helical winding configuration that maximizes the surface area-to-volume ratio for optimal thermal exchange efficiency. This design principle is fundamental to the operation of FP series fan coil units, where the coil tube interacts directly with circulating water or refrigerant to condition air streams passing through the unit's plenum.
2. Material & Properties
2.1 Base Material
- Material Grade: SUS304 (ASTM A240 Type 304) / SUS316 (ASTM A240 Type 316) stainless steel
- Composition: Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%, Carbon (C) ≤ 0.08%, Manganese (Mn) ≤ 2.0%
- SUS316 Variant: Additional Molybdenum (Mo) 2.0–3.0% for enhanced chloride corrosion resistance
- Surface Finish: 2B (cold-rolled and annealed) or No. 4 brushed finish
2.2 Key Physical & Mechanical Properties
| Property | SUS304 Specification | SUS316 Specification |
|---|---|---|
| Thermal Conductivity | 16.3 W/(m·K) at 20°C | 14.6 W/(m·K) at 20°C |
| Tensile Strength | ≥ 520 MPa | ≥ 515 MPa |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ≥ 205 MPa |
| Elongation at Break | ≥ 40% | ≥ 40% |
| Density | 7.93 g/cm³ | 8.00 g/cm³ |
| Operating Temperature Range | −196°C to +870°C | −196°C to +870°C |
| Corrosion Resistance (Pitting) | PRE > 18 | PRE > 24 |
2.3 Surface Treatment
- Pickling & Passivation: Acid pickling followed by chromic or citric acid passivation to restore and enhance the passive chromium oxide film
- Internal Cleaning: High-pressure water jet cleaning to remove manufacturing residues and ensure hydraulic efficiency
- Protective Coating (Optional): Anti-corrosion internal coating available for aggressive fluid environments
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.52 mm (3/8"), 12.7 mm (1/2") | ASME B36.19M |
| Wall Thickness | 0.5 mm – 1.5 mm (customizable) | ASME B36.19M |
| Coil Pitch (Spacing) | 10 mm – 25 mm (configurable per design) | Manufacturer Standard |
| Coil Diameter | 100 mm – 400 mm | — |
| Coil Length (Developed) | Up to 50,000 mm per continuous run | — |
| Dimensional Tolerance | ±0.05 mm (OD), ±10% (wall thickness) | ASTM A778 |
| Hydrostatic Test Pressure | 1.5× Working Pressure (minimum 6.0 MPa) | GB/T 24511 |
| Maximum Working Pressure | 4.0 MPa (at 95°C) | — |
| Thermal Efficiency | ≥ 92% (heat transfer coefficient) | — |
| Welding Method | TIG (Tungsten Inert Gas) / Laser Welding | ASME Section IX |
| Applicable Standards | ASTM A269, ASTM A312, GB/T 12771, EN 10217-7 | — |
| Customization | Non-standard dimensions, bend radii, and configurations available | — |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Inspection: Incoming stainless steel strip/pipe undergoes spectral analysis (PMI — Positive Material Identification) to verify chemical composition and grade certification.
- Slitting & Leveling: Coil stock is slit to precise width and passed through a leveling mill to achieve flatness tolerances of ±0.1 mm/m.
- Forming & Welding: Continuous high-frequency resistance welding or TIG welding forms the pipe seam with full penetration welds. Weld bead height is controlled within 0.1 mm for internal hydraulic smoothness.
- Coiling & Winding: The formed tube is wound into a helical coil configuration using CNC-controlled coil winding equipment, ensuring uniform pitch and consistent bend radius throughout the length.
- Heat Treatment: Solution annealing at 1050–1100°C followed by controlled water quenching to relieve residual stresses and restore full austenitic microstructure.
- Pickling & Passivation: Immersion in mixed acid solution (HNO₃ + H₂SO₄) to remove scale, followed by passivation treatment to establish a minimum 5 μm chromium oxide passive layer.
- Dimensional Inspection: Coordinate Measuring Machine (CMM) verification of OD, wall thickness, pitch uniformity, and overall coil geometry.
- Pressure Testing: 100% hydrostatic pressure testing at 1.5× rated working pressure with minimum 30-second hold time. Leak detection via pressure decay method.
- Final Cleaning & Packaging: Internal flushing with deionized water, end-sealing with protective caps, and vacuum-packaging with desiccant for moisture protection during transit.
4.2 Quality Control Milestones
- In-process inspection at forming, welding, coiling, and heat treatment stages
- Non-Destructive Testing (NDT): Eddy current inspection for weld seam integrity
- Spectroscopic hardness testing (HV scale) to confirm annealed condition
- Batch traceability via heat number and lot code marking
5. Applications
5.1 Primary Applications
- FP Series Fan Coil Units: Primary heat exchange coil for chilled water heating and cooling systems in commercial buildings
- Commercial HVAC Systems: Office buildings, shopping centers, hospitals, and hotels requiring precise temperature and humidity control
- Residential Air Conditioning: Concealed duct-type and cassette-type indoor units
- Industrial Process Cooling: Temperature regulation for manufacturing equipment and clean rooms
5.2 Specialized Applications
- Marine & Offshore Environments: SUS316 grade coil tubes for saltwater-resistant HVAC installations
- Food & Pharmaceutical Processing: Sanitary-grade coil tubes meeting FDA/3-A standards for temperature-controlled processing
- Cooling Coils for Heat Recovery Systems: Integration with energy recovery ventilators (ERV/HRV)
- Refrigeration Condensers & Evaporators: Direct expansion (DX) coil configurations
6. Quality Certifications & Compliance
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Full manufacturing process |
| ISO 14001:2015 | Environmental Management System |
| ASTM A269 / A312 | Material specification for seamless and welded austenitic stainless steel tubing |
| GB/T 12771 | Chinese National Standard — Welded stainless steel seamless and welded tubes for general applications |
| EN 10217-7 | European Standard — Technical delivery conditions for cold-drawn austenitic stainless steel tubes |
| ASME B36.19M | Dimensional standard for stainless steel tubing and pipe |
| ASME Section IX | Welding qualification and procedure standards |
| RoHS / REACH | Restriction of Hazardous Substances / Registration, Evaluation, Authorization and Restriction of Chemicals |
| CE Marking | European Conformity — Machinery Directive compliance for HVAC components |
7. Unique Selling Points
- Superior Corrosion Resistance: Stainless steel construction eliminates the risk of internal corrosion and scaling that plagues copper coil alternatives, extending service life to 20+ years in aggressive water environments.
- Hygienic Internal Surface: Smooth, passivated internal bore prevents bacterial colonization and biofilm formation, making it ideal for potable water heating and food-grade applications.
- High Thermal Efficiency: Optimized coil geometry and pitch design deliver ≥ 92% heat transfer efficiency, reducing energy consumption in fan coil unit operation.
- Customization Capability: Wenzhou Jixing Metal Materials offers full customization of OD, wall thickness, pitch, and coil dimensions to match specific FP series FCU model requirements.
- Full Traceability: Each coil tube batch is traceable from raw material heat number through final inspection, ensuring complete supply chain accountability.
- Environmentally Sustainable: 100% recyclable stainless steel material with zero lead content, compliant with global environmental regulations.
Technical Note: The coil tube described herein is an integral component of FP series fan coil units. Proper installation requires adherence to manufacturer-specified flow rates, pressure drop limits, and connection methods. For optimal performance, coil tubes should be installed with the water flow direction aligned to the unit's designated inlet/outlet orientation.