Stainless Steel Coil Tube (Fan Coil Tube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Fan Coil Tube" or "Coil Tube") is a precision-engineered heat exchange component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 565). This product is specifically designed for integration into Fan Coil Units (FCUs), which are widely deployed in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems. The coil tube serves as the primary heat transfer medium within the fan coil unit, facilitating efficient thermal exchange between circulating refrigerant or hot water and the ambient air stream.
Wenzhou Jixing Metal Materials Co., Ltd. has accumulated extensive expertise in stainless steel tube fabrication, addressing critical industry challenges such as condensation formation (dew point condensation) on fan coil unit surfaces — a well-documented problem that leads to microbial growth, structural corrosion, and degraded indoor air quality. This product incorporates design and material solutions specifically targeted at mitigating these issues.
2. Material and Properties
2.1 Base Material
- Primary Alloy: Austenitic Stainless Steel, conforming to ASTM A213 / ASTM A269 specifications
- Standard Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), SUS321 (UNS S32100)
- Alternative Grades (upon request): SUS304L (UNS S30403), SUS316L (UNS S31603) — low-carbon variants for enhanced weldability and corrosion resistance
2.2 Mechanical Properties (Typical Values for SUS304)
| Property | Symbol | Value | Unit | Standard Reference |
|---|---|---|---|---|
| Tensile Strength | UTS (Rm) | ≥ 520 | MPa | ASTM A213 |
| Yield Strength (0.2% offset) | Re0.2 | ≥ 205 | MPa | ASTM A213 |
| Elongation (after fracture) | A | ≥ 35 | % | ASTM A213 |
| Hardness (Rockwell B) | HBR | ≤ 95 | HRB | ASTM A262 |
| Density | ρ | 7.93 | g/cm³ | — |
| Thermal Conductivity (at 20°C) | λ | 16.3 | W/(m·K) | ASME |
| Specific Heat Capacity (at 20°C) | cp | 0.50 | kJ/(kg·K) | ASME |
| Linear Thermal Expansion Coefficient (20–100°C) | α | 17.3 × 10-6 | 1/K | ASME |
2.3 Chemical Composition (SUS304 — Typical)
| Element | C | Si | Mn | P | S | Cr | Ni | N |
|---|---|---|---|---|---|---|---|---|
| Maximum (%) | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | — | — | 0.10 |
| Range (%) | — | — | — | — | — | 18.0–20.0 | 8.0–10.5 | — |
2.4 Key Material Advantages
- Superior Corrosion Resistance: The high chromium (18–20%) and nickel (8–10.5%) content provides excellent resistance to atmospheric corrosion, condensation-induced pitting, and general chemical attack.
- Condensation Mitigation: The smooth surface finish (Ra ≤ 0.4 μm) minimizes nucleation sites for water droplet formation, directly addressing the condensation problem identified in fan coil unit operation.
- Hygienic Surface: The non-porous, passivated surface inhibits microbial adhesion and biofilm formation, ensuring compliance with indoor air quality standards.
- Thermal Stability: Maintains mechanical integrity across operating temperatures ranging from −196°C to 870°C.
3. Specifications
| Parameter | Specification / Range | Standard / Note |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Fan Coil Tube) | — |
| Product No. | 565 | Wenzhou Jixing Catalog |
| Tube Outer Diameter (OD) | 6.35 mm, 9.53 mm, 12.7 mm (custom available) | ASTM B751 / EN 10216 |
| Wall Thickness (WT) | 0.5 mm – 2.0 mm | ±10% tolerance |
| Tube Length (as coiled) | 5 m – 50 m per coil (standard); up to 100 m (custom) | — |
| Coil Inner Diameter (ID) | 300 mm – 600 mm | — |
| Coil Outer Diameter (OD) | 600 mm – 1200 mm | — |
| Surface Finish | No. 4 Brushed / Mirror Polish (Ra ≤ 0.4 μm) / Passivated | ASTM A967 |
| End Condition | Open ends / Flared / Threaded / Brazed (custom) | — |
| Fin Configuration (if finned) | Integral stamped fins / Loose-fit aluminum fins | Fin pitch: 2.0–3.5 mm |
| Operating Temperature Range | −40°C to +200°C | — |
| Maximum Operating Pressure | 1.6 MPa (16 bar) | — |
| Hydrostatic Test Pressure | 2.4 MPa (24 bar) — 100% tested | ASTM A213 |
| Coil Pitch (winding spacing) | 15 mm – 30 mm (adjustable per application) | — |
| Material Certification | EN 10204 Type 3.1 / MTR (Mill Test Report) | — |
| Packaging | Wooden pallet / Export-grade plywood crate with moisture barrier | ISPM 15 compliant |
4. Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
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Raw Material Selection and Inspection:
Virgin stainless steel coils are procured from certified mills and subjected to incoming inspection including chemical composition analysis (spectroscopic verification), dimensional measurement, and visual surface examination.
-
Pipe Forming (Cold Roll Forming / Seamless Extrusion):
Flat stainless steel strip is cold-rolled into tubular form using precision roll-forming machines. For seamless variants, the tube is produced via hot or cold extrusion from solid billets. The forming process is carefully controlled to minimize work hardening and maintain uniform wall thickness.
-
Welding (for welded variants):
Welded tubes are joined using Automatic TIG (Tungsten Inert Gas) welding with argon gas shielding (99.99% purity). Weld seam quality is verified via 100% visual inspection and periodic X-ray radiography or ultrasonic testing (UT) in accordance with EN ISO 17637.
-
Heat Treatment and Solution Annealing:
Tubes undergo solution annealing at 1050–1150°C followed by controlled cooling (air or water quench) to dissolve carbides, restore full austenitic structure, and maximize corrosion resistance. The grain structure is verified by metallographic examination.
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Coiling / Winding:
Finished tubes are wound into coils using CNC-controlled coiling machines that maintain consistent pitch spacing and minimize mechanical deformation. The coiling parameters (inner diameter, outer diameter, pitch) are programmed to match the specific fan coil unit housing dimensions.
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Surface Finishing and Passivation:
Tubes undergo mechanical surface finishing (brushing or polishing) followed by chemical passivation treatment using nitric acid or citric acid solutions (ASTM A967) to remove surface contaminants and establish a protective chromium oxide layer. This step is critical for condensation resistance performance.
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Quality Testing:
Every production lot undergoes comprehensive testing including hydrostatic pressure testing, dimensional verification (OD, WT, coil diameter), surface roughness measurement, and corrosion testing (salt spray test per ASTM B117, minimum 480 hours without pitting for SUS304; 1000 hours for SUS316).
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Packaging and Dispatch:
Finished coils are wrapped in moisture-proof polyethylene film, secured on export-grade wooden pallets, and packed in ISPM 15-certified plywood crates for international shipment.
5. Applications
The Stainless Steel Coil Tube (Fan Coil Tube) is a versatile component with broad application across multiple industries:
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Commercial HVAC Systems:
Primary heat exchange element in fan coil units used in office buildings, shopping malls, hotels, hospitals, and educational institutions. The corrosion-resistant stainless steel construction eliminates the condensation-related degradation problems commonly associated with carbon steel alternatives.
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Industrial Process Cooling:
Used in process air handling units, industrial dehumidifiers, and specialized cooling loops where chemical resistance and long service life are critical.
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Pharmaceutical and Food Processing:
Hygienic-grade coil tubes (SUS316L) are employed in cleanroom HVAC systems, pharmaceutical drying rooms, and food processing facilities where sanitary standards (FDA, EU 1935/2004) mandate non-toxic, non-porous materials.
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Marine and Offshore HVAC:
SUS316 and SUS316L variants provide superior resistance to chloride-induced pitting and crevice corrosion in marine environments, making them suitable for shipboard HVAC systems and offshore platform climate control.
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Data Center Cooling:
High-efficiency coil tubes are integrated into precision air handling units for server room cooling, where consistent thermal performance and minimal maintenance are essential for continuous operation.
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Automotive and Transportation HVAC:
Custom coil tube configurations are used in train air conditioning units, bus HVAC systems, and automotive heat exchangers requiring compact form factors and high thermal efficiency.
6. Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliances:
| Certification / Standard | Description |
|---|