Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchanger component specifically designed for integration into radiant cooling/heating systems and Fan Coil Unit (FCU) with fresh air supply systems. This product serves as a critical thermal transfer medium in combined HVAC (Heating, Ventilation, and Air Conditioning) configurations, where it facilitates efficient heat exchange between circulating fluids and ambient air.
Unlike conventional carbon steel coil tubes, the stainless steel variant offers superior corrosion resistance, extended service life, and enhanced hygienic performance—making it particularly suitable for demanding environments such as hospitals, cleanrooms, food processing facilities, and commercial buildings requiring high indoor air quality (IAQ).
2. Material & Properties
2.1 Base Material
- Grade 304 (AISI 304 / SUS304): Standard austenitic stainless steel with 18% Chromium (Cr) and 8% Nickel (Ni), providing excellent general corrosion resistance and formability.
- Grade 316 (AISI 316 / SUS316): Enhanced austenitic stainless steel with the addition of 2–3% Molybdenum (Mo), offering superior resistance to pitting and crevice corrosion in chloride-rich environments.
- Grade 316L (AISI 316L / SUS316L): Low-carbon variant of 316 with carbon content ≤0.03%, ideal for welded applications where intergranular corrosion resistance is critical.
2.2 Mechanical Properties
- Tensile Strength (UTS): ≥520 MPa (Grade 304); ≥570 MPa (Grade 316)
- Yield Strength (0.2% offset): ≥205 MPa (Grade 304); ≥240 MPa (Grade 316)
- Elongation at Break: ≥40% (minimum)
- Hardness: ≤92 HRB (annealed condition)
- Operating Temperature Range: −196°C to +870°C (Grade 304); −196°C to +870°C (Grade 316)
2.3 Corrosion Resistance
- Excellent resistance to atmospheric corrosion, fresh water, and mild chemical environments
- Grade 316/316L demonstrates superior performance in marine atmospheres, chemical processing, and acidic conditions
- Passive chromium oxide film (Cr₂O₃) provides self-healing surface protection
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.35 mm, 8.0 mm, 9.53 mm, 12.7 mm, 15.88 mm (customizable) |
| Wall Thickness (WT) | 0.5 mm – 1.5 mm (typical range for coil tube) |
| Coil Pitch / Spacing | 10 mm – 25 mm (adjustable per heat exchanger design) |
| Coil Length | Up to 50 m per continuous coil (custom lengths available) |
| Surface Finish | BA (Bright Annealed), 2B, or No.4 Brushed |
| Surface Roughness (Ra) | ≤0.4 μm (BA finish); ≤0.8 μm (2B finish) |
| Pressure Rating | Up to 1.6 MPa (standard); 2.5 MPa (reinforced) |
| Fluid Medium Compatibility | Water, glycol solutions, refrigerants, light oils |
| Winding Tolerance | ±0.2 mm (diameter); ±1 mm (pitch) |
| Maximum Operating Pressure | 1.6 MPa (standard configuration) |
| Hydrostatic Test Pressure | 2.4 MPa (1.5× working pressure) |
| Standards Compliance | ASTM A269, ASTM A270, GB/T 12771, EN 10216-5 |
4. Manufacturing Process
4.1 Raw Material Selection
High-purity stainless steel wire rod is sourced from certified mills, undergoing incoming inspection for chemical composition (via Optical Emission Spectrometry, OES) and mechanical properties verification.
4.2 Cold Drawing & Forming
- Wire rod is cold-drawn through precision dies to achieve the required tube diameter and wall thickness
- Multi-stage drawing ensures dimensional accuracy and surface integrity
- Intermediate annealing may be performed to relieve residual stresses
4.3 Coil Winding
- Tubes are precisely wound onto helical or spiral coil forms using CNC-controlled winding machinery
- Coil pitch and diameter are maintained within tight tolerances to ensure uniform heat transfer performance
- Supporting fins or structural elements are integrated during the winding process
4.4 Surface Treatment
- Bright Annealing (BA): Performed in a controlled atmosphere (vacuum or nitrogen) to produce a clean, oxide-free surface with superior hygienic properties
- Pickling & Passivation: Removal of mill scale and formation of a stable chromium oxide passive layer
- Electropolishing: Available upon request for ultra-smooth surfaces (Ra ≤0.2 μm) in pharmaceutical and food-grade applications
4.5 Quality Inspection
- Dimensional Inspection: Laser micrometry for OD, wall thickness, and coil geometry verification
- Visual Inspection: 100% surface examination for defects, scratches, or discoloration
- Pressure Testing: Hydrostatic or pneumatic testing per ASTM standards
- Chemical Analysis: Spectrometric verification of alloy composition
- Intergranular Corrosion Testing: ASTM A262 Practice No.1E (for welded components)
5. Applications
5.1 Fan Coil Unit (FCU) Systems
The coil tube serves as the primary heat exchanger element within fan coil units, where it transfers thermal energy between the circulating fluid (hot water, chilled water, or refrigerant) and the air stream generated by the integrated fan. This enables precise temperature regulation in individual zones of commercial and residential buildings.
5.2 Radiant Cooling/Heating Systems
Integrated with radiant panels, the coil tube facilitates indirect heat exchange through embedded piping networks, providing comfortable, low-velocity thermal comfort with minimal noise generation.
5.3 Combined System Applications
- Hospital & Healthcare Facilities: Sterile environments requiring hygienic, corrosion-resistant components
- Pharmaceutical Manufacturing: Cleanroom HVAC systems demanding high-purity stainless steel (316L)
- Food Processing & Beverage Plants: CIP (Clean-In-Place) compatible systems with smooth surface finishes
- Commercial Office Buildings: VAV (Variable Air Volume) systems with energy-efficient heat recovery
- Hotel & Hospitality Industry: Zone-based climate control with silent operation
- Industrial Facilities: Process cooling/heating where chemical resistance is paramount
5.4 Unique Selling Points
- Superior Corrosion Resistance: Eliminates rust-related failures common with carbon steel alternatives, extending system lifespan by 3–5×
- Hygienic Performance: Smooth, non-porous surface prevents bacterial colonization—critical for healthcare and food-grade applications
- Thermal Efficiency: High thermal conductivity of austenitic stainless steel ensures rapid heat transfer with minimal temperature differential losses
- Low Maintenance: Resistant to scaling, fouling, and chemical degradation—reducing lifecycle maintenance costs
- Environmental Sustainability: Fully recyclable material with minimal environmental footprint; contributes to LEED and Green Building certification targets
- Design Flexibility: Customizable coil geometry, pitch, and dimensions to match specific heat load calculations and system configurations
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing consistency |
| ISO 14001:2015 | Environmental Management System compliance |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing |
| ASTM A270 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipe |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transportation |
| EN 10216-5 | European Standard for Welded Circular Hollow Sections of Stainless Steel for Pressure Purposes |
| ASME B31.9 | Pressure Piping—Refrigeration Piping and Heat Transfer Components |
| NSF/ANSI 61 | Drinking Water System Components—Health Effects (available upon request) |
| CE Marking | European Conformity for pressure equipment compliance (PED 2014/68/EU) |
| Material Test Report (MTR) | Full chemical and mechanical property documentation per heat lot |
7. Technical Support & Engineering Services
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive engineering support including:
- Thermal load calculations and coil tube sizing optimization
- Custom coil geometry design tailored to specific heat exchanger configurations
- Finite Element Analysis (FEA) for stress and deformation prediction
- System integration guidance for FCU and radiant system combinations
- Lifetime technical consultation and replacement part availability
Note: All specifications are subject to verification based on specific project requirements. Custom engineering solutions are available upon submission of detailed technical drawings, heat load data, and operating condition parameters. Please contact the engineering department for project-specific quotations and technical documentation.