Stainless Steel Coil Tube for AFCR-04 Fan Coil Units — Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd | Product Catalog No.: 921 | Product Designation: AFCR-04 Coil Tube Assembly
1. Product Overview
The AFCR-04 Stainless Steel Coil Tube is a precision-engineered coiled heat exchange tube designed specifically for integration into AFCR-04 Fan Coil Unit (FCU) systems used in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) applications. This coil tube assembly serves as the core thermal transfer component within the fan coil unit, facilitating efficient heat exchange between the circulating fluid (water or glycol solution) and the ambient air stream.
Manufactured to the highest standards of metallurgical integrity and dimensional precision, this coil tube product leverages the inherent corrosion resistance, thermal conductivity, and mechanical strength of austenitic stainless steel to deliver superior performance longevity, hygiene compliance, and operational reliability in demanding indoor climate control environments.
2. Material & Properties
2.1 Base Material Composition
The coil tube is fabricated from austenitic stainless steel conforming to international material standards. The primary alloy grade utilized is SUS304 (ASTM A213 TP304 / EN 1.4301), with optional availability in SUS316 (ASTM A213 TP316 / EN 1.4401) for enhanced resistance in aggressive chemical or marine environments.
- Carbon (C): ≤ 0.08% (SUS304) / ≤ 0.08% (SUS316)
- Chromium (Cr): 18.0% – 20.0%
- Nickel (Ni): 8.0% – 10.5%
- Molybdenum (Mo): ≤ 0.75% (SUS304) / 2.0% – 3.0% (SUS316)
- Manganese (Mn): ≤ 2.0%
- Silicon (Si): ≤ 1.0%
- Phosphorus (P): ≤ 0.045%
- Sulfur (S): ≤ 0.030%
2.2 Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (SUS304) / ≥ 520 MPa (SUS316)
- Yield Strength (0.2% Proof Stress): ≥ 205 MPa
- Elongation (A50mm): ≥ 40%
- Hardness (HBW): ≤ 217
- Impact Energy (Charpy V-Notch, 20°C): ≥ 47 J
2.3 Thermal & Physical Properties
- Thermal Conductivity (λ, 20°C): 16.3 W/(m·K) (SUS304) / 14.6 W/(m·K) (SUS316)
- Specific Heat Capacity (cp): 0.50 J/(g·K)
- Linear Thermal Expansion Coefficient (α, 20–100°C): 17.3 × 10⁻⁶ /K
- Density (ρ, 20°C): 7.93 g/cm³
- Maximum Service Temperature: 870°C (continuous)
2.4 Corrosion Resistance
The austenitic microstructure provides exceptional resistance to atmospheric corrosion, pitting, crevice corrosion, and intergranular corrosion. The SUS316 variant, enriched with molybdenum, demonstrates superior resistance to chloride-induced pitting and is recommended for coastal installations or applications involving de-icing salts and chemical cleaners.
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (AFCR-04) | — |
| Tube Outer Diameter (OD) | Φ9.52 mm ± 0.10 mm (⅜") | ASTM A213 / GB/T 12771 |
| Tube Wall Thickness | 0.81 mm ± 0.05 mm (minimum) | ASTM A213 |
| Tube Inner Diameter (ID) | 7.90 mm ± 0.10 mm | Calculated |
| Coil Pitch (Center-to-Center Spacing) | 12.7 mm (0.5") | Manufacturer's Design Specification |
| Number of Rows | 2 / 3 / 4 (configurable) | Application-Dependent |
| Tube Length (Per Pass) | 300 mm / 400 mm / 500 mm / 600 mm | Application-Dependent |
| Fin Type | Aluminum L-Fin (Hydroformed or Stamped) | GB/T 19455 |
| Fin Density | 12 FPI – 16 FPI (Fins Per Inch) | Application-Dependent |
| Surface Finish | Mirror Polish (Ra ≤ 0.4 μm) or Brushed (Ra ≤ 1.6 μm) | ASTM A480 |
| Welding Type | TIG (GTAW) or Orbital Welding, Full Penetration | ASME BPVC Section IX |
| Operating Pressure (Design) | 1.6 MPa (16 bar) | EN 12828 |
| Hydrostatic Test Pressure | 2.4 MPa (24 bar) @ 30 min | Manufacturer's QC Protocol |
| Design Cooling Capacity | 2.0 kW – 5.0 kW (depending on configuration) | ASHRAE Standard 90.1 |
| Design Heating Capacity | 2.5 kW – 6.0 kW (depending on configuration) | ASHRAE Standard 90.1 |
| Weight (Typical Assembly) | 1.2 kg – 2.8 kg | Configuration-Dependent |
| Warranty | 5 Years (Material & Workmanship) | Manufacturer's Guarantee |
4. Manufacturing Process
The production of the AFCR-04 Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing workflow designed to ensure metallurgical soundness, dimensional accuracy, and surface integrity at every step.
- Raw Material Procurement & Inspection: Cold-rolled stainless steel strip is sourced from certified mills (e.g., Outokumpu, ThyssenKrupp, Taigang Stainless Steel). Each batch undergoes spectrographic analysis via Optical Emission Spectroscopy (OES) and Positive Material Identification (PMI) testing to verify alloy composition compliance.
- Coil Winding (Tube Forming): Precision CNC-controlled coiling machines form the strip into helical tubes with exact pitch, diameter, and wall thickness tolerances. The coiling process is performed at controlled temperatures to avoid work-hardening and residual stress accumulation.
- Seam Welding: The longitudinal seam is welded using either continuous TIG (Gas Tungsten Arc Welding, GTAW) or laser welding technology. The weld zone is protected with high-purity argon (99.999%) shielding gas to prevent oxidation. Post-weld, the seam is ground flush to ensure hydraulic smoothness and minimize turbulence-induced flow resistance.
- Fin Attachment: Aluminum fins are applied via hydroforming or mechanical stamping. In the hydroformed process, hydraulic pressure is used to mechanically bond the fin to the tube OD, creating a metallurgical-free but mechanically secure joint with minimal thermal contact resistance.
- Header Assembly & Welding: Individual coil tubes are connected to stainless steel header manifolds using full-penetration TIG welds. Each weld joint is inspected via Dye Penetrant Testing (PT) or Radiographic Testing (RT) to verify absence of porosity, cracks, or incomplete fusion.
- Solution Annealing & Pickling: The welded assembly undergoes solution annealing at 1050°C – 1100°C followed by controlled cooling to restore full austenitic microstructure and relieve residual stresses. Subsequent acid pickling and passivation remove scale and form a protective chromium oxide layer on the surface.
- Surface Finishing: The coil tube assembly is polished to the specified surface finish grade using mechanical buffing and/or electropolishing. This step is critical for hygiene-sensitive applications (e.g., pharmaceutical, food processing) and reduces fouling potential.
- Quality Assurance & Testing: Final quality verification includes hydrostatic pressure testing, dimensional inspection using Coordinate Measuring Machine (CMM), surface roughness measurement, and visual inspection. Each unit is serialized for traceability.
5. Applications
The AFCR-04 Stainless Steel Coil Tube is engineered for a broad spectrum of HVAC and thermal management applications, with particular suitability in environments where material durability, hygiene, and corrosion resistance are paramount.
5.1 Primary Applications
- Commercial HVAC Systems: Office buildings, retail centers, hotels, and hospitals where fan coil units provide zoned climate control.
- Industrial Process Cooling: Precision temperature control in manufacturing facilities, electronics assembly, and cleanroom environments.
- Food & Beverage Processing: Chillers, pasteurization lines, and refrigerated storage where hygienic-grade materials are mandatory (SUS316 recommended).
- Pharmaceutical & Biotechnology: GMP-compliant facilities requiring corrosion-resistant, cleanable, and non-contaminating heat exchange surfaces.
- Marine & Coastal Installations: Shipboard HVAC and coastal commercial buildings where salt-laden air necessitates superior corrosion resistance (SUS316 with Mo content ≥ 2.0%).
- Residential High-End Applications: Premium residential HVAC systems requiring long service life and minimal maintenance.
5.2 AFCR-04 Fan Coil Unit Integration
The AFCR-04 coil tube is designed for seamless integration into the AFCR-04 series Fan Coil Unit, which comprises a centrifugal or axial fan, the coil tube heat exchanger, a condensate drain pan, and a control interface. The unit is typically ceiling-mounted or wall-mounted and connected to a central chilled water or hot water loop. The coil tube's high surface-area-to-volume ratio, combined with the aluminum fin enhancement, ensures rapid thermal response and energy-efficient operation with low circulating flow rates.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system ensuring that every AFCR-04 Coil Tube product meets or exceeds international standards and regulatory requirements.
6.1 Certifications
- 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 — European Conformity for HVAC components
- NSF/ANSI 61 — Drinking Water System Components (where applicable)
- EN 10204 3.1 — Material Test Certificate (Mill Test Report)
6.2 Standards Referenced
- ASTM A213 / A213M — Standard Specification for Seamless Austenitic Stainless Steel Tubing for High Temperature Service
- GB/T 12771 — Stainless Steel Seamless Tubes for General Purpose
- GB/T 19455 — Aluminum Fin-Tube Heat Exchangers
- ASME BPVC Section IX — Welding Qualification Standards
- EN 10217-7 — Non-alloy and Alloy Steel Tubes for Mechanical and Thermal Uses
- ASHRAE Standard 90.1 — Energy Standard for Buildings
6.3 Inspection & Testing Protocols
- Incoming material spectrographic verification (OES / PMI)
- In-process dimensional control via CMM and laser gauging
- Non-Destructive Testing (NDT): Dye Penetrant Testing (PT) on all welds; Radiographic Testing (RT) on critical joints
- Hydrostatic pressure testing at 1.5× design pressure for minimum 30 minutes
- Surface roughness verification (Ra measurement per ISO 4287)
- Corrosion testing: Salt Spray Testing (ASTM B117, ≥ 480 hours for SUS316