Stainless Steel Coil Tube — Fan Coil Unit Integration Product
Product Overview
The Stainless Steel Coil Tube (Product No. 1257) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tubing product designed primarily for integration into Fan Coil Units (FCUs) and similar hydronic heat exchange systems. Unlike conventional carbon steel or copper coil assemblies, this product leverages the superior corrosion resistance, thermal conductivity, and mechanical integrity of stainless steel to deliver extended service life, reduced maintenance costs, and enhanced system reliability in demanding HVAC (Heating, Ventilation, and Air Conditioning) environments.
This product line addresses critical performance challenges identified in domestic fan coil unit applications, including premature corrosion, heat transfer degradation over time, and inconsistent coil geometry — issues that have historically plagued lower-grade coil tube solutions in the Chinese HVAC market.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its optimal balance of corrosion resistance, formability, and thermal performance.
- Primary Material Grade: SUS 304 / AISI 304 (18/8 Stainless Steel — 18% Chromium, 8% Nickel)
- Alternative Grade Available: SUS 316 / AISI 316L (with Molybdenum addition for enhanced chloride resistance)
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, condensation water (including mildly acidic condensate), and general industrial atmospheres
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 25°C — sufficient for efficient hydronic heat exchange while maintaining long-term structural integrity
- Operating Temperature Range: −196°C to +870°C (well beyond typical FCU operating parameters of 0°C to +90°C)
- Surface Finish: Bright annealed (2B finish) or electropolished for reduced surface roughness and enhanced heat transfer
- Hygienic Properties: Non-toxic, non-tarnishing, and resistant to biofilm formation — advantageous for indoor air quality (IAQ)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) | — |
| Product Number | 1257 | Internal Catalog |
| Tube Outer Diameter (OD) | 6.35 mm (1/4") / 9.52 mm (3/8") / 12.70 mm (1/2") | ASTM A269 / ASTM A213 |
| Tube Wall Thickness | 0.5 mm – 1.0 mm (typical) | ASTM A269 |
| Coil Inner Diameter (ID) | 50 mm – 300 mm (configurable) | Custom per application |
| Coil Height | 50 mm – 500 mm (configurable) | Custom per application |
| Number of Rows | 1 – 6 rows | ASHRAE 15 / ISO 5189 |
| Fin Type | Aluminum lamination / Hydrophilic coated aluminum fins | Custom |
| Fin Pitch | 1.2 mm – 2.5 mm | ASHRAE 15 |
| Material Grade | SUS 304 / SUS 316L | ASTM A269 / JIS G4304 |
| Surface Treatment | Bright annealed (2B) / Electropolished / Passivated | ASTM A967 |
| Pressure Rating | Up to 1.6 MPa (232 psi) working pressure | ASME B31.5 |
| Tolerance on OD | ±0.05 mm | ASTM A269 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A269 |
| End Condition | Plain ends / Beveled ends / Flared ends | Custom per application |
| Maximum Length per Coil | Up to 50 m (configurable) | — |
| Applicable Standards | ASTM A269, ASTM A213, ASHRAE 15, ISO 5189, EN 10217 | See individual references |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection and Inspection: Stainless steel seamless or welded tube stock is procured in compliance with ASTM A269 and ASTM A213 specifications. Each batch undergoes incoming quality control (IQC) including chemical composition analysis (via Spark OES), mechanical property verification, and visual surface inspection.
- Cutting and Deburring: Tube stock is precision-cut to specified lengths using cold-cutting or sawing methods. Burrs and sharp edges are removed to prevent fluid turbulence and potential damage during downstream processing.
- Coiling (Cold Forming): The straight tube is cold-coiled to the required coil geometry (inner diameter, height, and number of turns) using specialized CNC-controlled coiling machinery. This process maintains the solution-annealed condition of the stainless steel while achieving tight dimensional tolerances.
- Fin Application: Aluminum fins are laminated onto the coiled tube using a fin-coil rolling process. The fins are typically aluminum alloy (1100 or 3003) and may receive a hydrophilic coating to enhance condensate drainage and heat transfer efficiency.
- Welding and Brazing (if applicable): Inlet and outlet headers are attached to the coil assembly using silver brazing (Sn-Ag-Cu brazing alloy) or TIG (Tungsten Inert Gas) welding. All joints are inspected for integrity.
- Surface Treatment: The completed assembly undergoes pickling and passivation treatment per ASTM A967 to remove scale, restore chromium oxide passivation layer, and enhance long-term corrosion resistance.
- Pressure Testing: Each coil assembly is subjected to hydrostatic pressure testing at 1.5× the maximum working pressure to verify weld and joint integrity.
- Final Inspection and Packaging: Completed products undergo final dimensional verification, visual inspection, and performance testing before protective packaging for shipment.
Applications
The Stainless Steel Coil Tube (Product No. 1257) is engineered for a broad spectrum of hydronic heat exchange applications, with particular emphasis on fan coil unit integration:
- Commercial HVAC Systems: Chilled water coils and hot water coils for commercial fan coil units in office buildings, retail spaces, and hospitality facilities.
- Residential and Light Commercial Heating/Cooling: Radiator-style fan coil units and cassette-type FCUs for residential apartments, hotels, and small commercial spaces.
- Industrial Process Cooling/Heating: Heat exchangers for chemical processing, food and beverage production, and pharmaceutical manufacturing where corrosion resistance is critical.
- Marine and Coastal Environments: HVAC systems in coastal or marine applications where chloride-laden air accelerates corrosion of carbon steel alternatives.
- High-Humidity Environments: Data centers, laboratories, clean rooms, and other facilities where condensate management and corrosion prevention are paramount.
- Chiller and Boiler Circuits: Integration with central chiller plants and boiler systems as terminal heat exchange elements.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework to ensure consistent product performance and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and service processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- CE Marking — Compliance with European Directive requirements for safety, health, and environmental protection.
- ASME Stamp (where applicable) — Pressure vessel and piping component compliance for applications requiring ASME certification.
- Material Traceability: Each production batch is accompanied by a Mill Test Report (MTR) / Certificate of Analysis (CoA) documenting chemical composition, mechanical properties, and heat treatment status.
- Third-Party Testing: Periodic verification of corrosion resistance (salt spray testing per ASTM B117), mechanical properties (tensile testing per ASTM E8), and dimensional accuracy (CMM measurement) by accredited independent laboratories.
Unique Selling Points
1. Superior Corrosion Longevity: Unlike carbon steel coil tubes that corrode within 3–5 years in typical HVAC condensate environments, the SUS 304/316L stainless steel construction provides a service life exceeding 15–25 years, dramatically reducing replacement frequency and total cost of ownership (TCO).
2. Enhanced Indoor Air Quality (IAQ): The non-reactive, non-tarnishing surface of stainless steel prevents the growth of bacteria, mold, and biofilm that commonly develops on corroded carbon steel coils — a critical factor in preventing sick building syndrome (SBS).
3. Dimensional Precision via CNC Coiling: Automated CNC coiling ensures consistent coil geometry, uniform fin-to-tube contact pressure, and optimal heat transfer surface area — directly translating to improved energy efficiency (COP) of the integrated FCU system.
4. Full Traceability and Documentation: Every coil assembly is accompanied by complete material documentation, enabling OEM integrators to satisfy regulatory and client audit requirements with confidence.
5. Customizable Engineering: Flexible configurability across tube diameter, wall thickness, coil geometry, fin type, and end conditions allows seamless integration into diverse OEM fan coil unit designs without compromise on material quality.
Note: This technical specification is based on the product knowledge documented under Product No. 1257 in the Wenzhou Jixing Metal Materials Co., Ltd catalog. Specific dimensional and performance parameters should be confirmed with the manufacturer for each individual order, as configurations may vary based on application requirements and customer specifications.