Stainless Steel Coil Tube — Fan Coil Unit (FCU) Application Series
Product Designation: SS-CoilTube-FCU | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Catalog No.: 1373
1. Product Overview
The Stainless Steel Coil Tube (SS-CoilTube-FCU) is a precision-engineered tubular component specifically designed for integration into Fan Coil Units (FCU) — the core heat exchange assemblies employed in modern hydronic air conditioning and heating systems. Unlike conventional coil tubes fabricated from carbon steel or copper, this product leverages the superior corrosion resistance, thermal conductivity, and mechanical durability of stainless steel to deliver extended service life and enhanced performance in demanding HVAC environments.
Wenzhou Jixing Metal Materials Co., Ltd. has developed this coil tube series through extensive research and design optimization, drawing upon advanced performance testing methodologies for fan coil unit assemblies. The product represents a significant advancement in heat transfer efficiency and long-term reliability for commercial and residential HVAC applications.
Key Innovation: The design and research program behind this coil tube incorporates rigorous performance test device methodology, ensuring that each unit meets stringent thermal-hydraulic performance criteria validated through controlled experimental protocols.
2. Material & Properties
2.1 Base Material
The coil tube is manufactured from high-grade austenitic stainless steel, selected for its optimal balance of corrosion resistance, formability, and thermal performance:
- Primary Grade: SUS304 / AISI 304 (18Cr-8Ni) — the industry-standard austenitic stainless steel offering excellent general corrosion resistance
- Alternative Grade: SUS316 / AISI 316 (18Cr-10Ni-2Mo) — enhanced molybdenum addition for superior resistance to chloride-induced pitting and crevice corrosion
- Surface Finish: Electropolished or mechanical polished, achieving a surface roughness of Ra ≤ 0.4 μm to minimize fouling and biofilm accumulation
2.2 Physical and Mechanical Properties
- Thermal Conductivity: 16.3 W/(m·K) at 20 °C — providing efficient heat transfer between the refrigerant/coolant and the airstream
- Operating Temperature Range: −196 °C to +870 °C
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, water, dilute acids, and organic compounds; superior to carbon steel by a factor of 20–50×
- Yield Strength: ≥ 205 MPa (SUS304), ≥ 240 MPa (SUS316)
- Tensile Strength: ≥ 515 MPa (SUS304), ≥ 585 MPa (SUS316)
- Elongation: ≥ 40% (SUS304), ≥ 35% (SUS316)
- Non-magnetic: In the annealed condition, ensuring compatibility with sensitive instrumentation
2.3 Surface Treatment Options
- Electrolytic Polishing: Removes up to 25 μm of surface layer, passivates the surface, and achieves Ra ≤ 0.2 μm
- Pickling & Passivation: Chemical removal of mill scale followed by passivation treatment to form a protective chromium oxide layer
- Anti-scaling Coating: Optional PTFE (Polytetrafluoroethylene) or ceramic-based internal coating to inhibit mineral scale deposition
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | 6.35 mm, 7.94 mm, 9.53 mm (⅛", ⅜", ⅜" series) | ASME B36.19M |
| Tube Wall Thickness | 0.40 mm – 1.20 mm (selectable) | ASTM A213 / A269 |
| Coil Pitch (Center-to-Center Spacing) | 15 mm – 30 mm (configurable) | ASHRAE 40 |
| Row Depth | 1 – 4 rows (standard), up to 6 rows (custom) | Manufacturer Design |
| Coil Height | 300 mm – 900 mm (configurable) | Manufacturer Design |
| Coil Width | 300 mm – 1,200 mm (configurable) | Manufacturer Design |
| Fins per Inch (FPI) | 8 – 14 fins per inch | ASHRAE 40 |
| Fin Material | Aluminum (standard) / Stainless Steel (special order) | ASTM B209 / A240 |
| Fin Thickness | 0.10 mm – 0.20 mm | Manufacturer Specification |
| Refrigerant / Coolant | Chilled Water (4–12 °C), Hot Water (40–80 °C), Glycol Solutions | ASHRAE 34 |
| Maximum Operating Pressure | 1.6 MPa (standard), 2.5 MPa (reinforced) | EN 12828 |
| Design Pressure | 1.0 MPa (standard), 1.6 MPa (high-pressure variant) | ASME BPVC Section VIII |
| Hydrostatic Test Pressure | 1.5 × Design Pressure | ASME BPVC |
| Cooling Capacity | Up to 5,000 W (depending on configuration and airflow) | ASHRAE 40 |
| Airflow Rate | 500 – 4,500 m³/h | Manufacturer Design |
| Pressure Drop (Air Side) | ≤ 150 Pa (standard configuration) | ASHRAE 40 |
| Pressure Drop (Water Side) | ≤ 30 kPa | Manufacturer Specification |
| Connection Type | Flanged, threaded (G1/2", G3/4"), or brazed | ASME B1.20.1 |
| Weight (Typical, 600×600 mm) | 8 – 12 kg | — |
4. Manufacturing Process
The production of the SS-CoilTube-FCU follows a tightly controlled, multi-stage manufacturing workflow designed to ensure dimensional accuracy, material integrity, and performance consistency:
-
Raw Material Inspection & Certification:
- Stainless steel tubes and strips are procured from certified mills (e.g., Outokumpu, POSCO, Taigang)
- Each batch undergoes chemical composition analysis via Optical Emission Spectrometry (OES) and Positive Material Identification (PMI) testing
- Mechanical property verification through tensile testing per ASTM A370
-
Tube Forming & Coiling:
- Continuous stainless steel tubes are precision-formed into serpentine coil patterns using CNC-controlled bending machines
- Bend radius maintained at ≥ 3× tube diameter to prevent wall thinning and ovality exceeding 2%
- Coil pitch and row alignment verified via laser measurement systems
-
Fin Insertion & Brazing:
- Aluminum or stainless steel fins are inserted between coil rows using automated fin-insertion equipment
- Tube-fin joints are secured through diffusion brazing or expansion fitting to ensure thermal contact resistance ≤ 0.5 m²·K/W
- Brazing temperature maintained at 620 °C – 650 °C in a protective nitrogen atmosphere to prevent oxidation
-
Header Assembly & Connection Fabrication:
- Inlet and outlet headers are fabricated from seamless stainless steel pipe (SUS304/SUS316)
- Headers are welded to coil ends using TIG (Tungsten Inert Gas) welding with argon shielding gas
- Weld joints undergo 100% visual inspection and periodic radiographic testing (RT) per ASME Section V, Article 2
-
Surface Treatment & Finishing:
- Electropolishing to achieve a smooth, corrosion-resistant surface finish
- Pickling and passivation to remove welding discoloration and restore the passive chromium oxide film
- Optional internal anti-scaling coating application
-
Performance Testing & Quality Assurance:
- Hydrostatic pressure testing at 1.5× design pressure with 100% pass rate requirement
- Thermal performance validation using dedicated fan coil unit performance test devices — measuring total cooling/heating capacity, air-side and water-side pressure drops, and temperature effectiveness
- Dimensional inspection using coordinate measuring machines (CMM) with tolerance ≤ ±0.5 mm
- Air-side leak testing via helium mass spectrometry (optional, for critical applications)
-
Packaging & Dispatch:
- Each coil tube is individually wrapped in moisture-proof protective film
- Wooden or steel crate packaging with desiccant packs for export shipments
- Accompanied by material test certificates, dimensional inspection reports, and performance test documentation
5. Applications
The SS-CoilTube-FCU is engineered for a broad spectrum of HVAC applications where reliability, hygiene, and long-term performance are paramount:
5.1 Commercial HVAC Systems
- Office Buildings & Commercial Complexes: Fan coil units integrated with central chilled water or hot water systems for precise indoor climate control
- Hospital & Medical Facilities: The inherent antibacterial and corrosion-resistant properties of stainless steel make this coil tube ideal for cleanroom environments, operating theaters, and pharmaceutical manufacturing areas where microbial contamination must be prevented
- Hotels & Hospitality Venues: Ducted and concealed fan coil units providing quiet, efficient comfort conditioning in guest rooms and public areas
- Shopping Malls & Retail Spaces: High-capacity coil tubes handling large air volumes in open-plan environments
5.2 Industrial Applications
- Food & Beverage Processing: Compliance with FDA and EHEDG standards for food-grade environments; resistance to cleaning chemicals (CIP — Clean-in-Place) and corrosive processing fluids
- Pharmaceutical Manufacturing: GMP (Good Manufacturing Practice) compliant coil tubes for controlled-environment HVAC systems
- Electronics Manufacturing: Precision temperature and humidity control in semiconductor cleanrooms and electronics assembly lines
- Marine & Offshore Platforms: Enhanced SUS316 variant for resistance to saltwater-laden atmospheric conditions and humid marine environments
5.3 Residential & Light Commercial
- High-End Residential HVAC: Concealed ceiling-mounted fan coil units for premium comfort solutions
- Multi-Zone Climate Control: Modular coil tube assemblies enabling individual zone temperature regulation
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management and certification programs ensuring product compliance with international standards:
6.1 Management System Certifications
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health and Safety Management Systems
6.2 Product & Performance Standards
- ASHRAE 40 — Standard for the Performance Rating of Air-Cooled and Water-Cooled Heat Exchangers
- ASHRAE 15 — Safety Standard for Refrigeration Systems (applicable to refrigerant-side connections)
- EN 12828 — Heating Systems in Buildings — Water Heating Systems and Their Components
- ASTM A213 / A269 — Specifications for Seamless Austenitic Stainless Steel Tubing and Pipe
- ASME BPVC Section VIII — Pressure Vessel Code (for header and pressure-containing components)
- GB/T 14976 — Chinese National Standard for Seamless Stainless Steel Tubes
6.3 Testing & Verification
- 100% hydrostatic pressure testing per ASME BPVC requirements