Stainless Steel Coil Tube (Coiltube) — HVAC Fan Coil Unit Application Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled stainless steel tubing product specifically designed for thermal exchange applications in Fan Coil Unit (FCU) with Fresh Air System air conditioning installations. This product serves as a critical heat transfer component in both heating and cooling cycles, particularly under winter operating conditions where the system must efficiently manage latent and sensible loads during low-ambient-temperature environments.
The coil tube is supplied in continuous coiled form, enabling seamless integration into heat exchanger assemblies for commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems. Its design ensures optimal thermal conductivity while maintaining structural integrity under repeated thermal cycling and corrosive condensate environments typical of fan coil unit operation.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for superior corrosion resistance, mechanical strength, and thermal performance in demanding HVAC service conditions.
- Material Grade: SUS304 / SUS316L (AISI 304 / 316L) austenitic stainless steel
- Corrosion Resistance: Excellent resistance to condensation corrosion, chloride-induced pitting (316L grade), and general atmospheric degradation
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (SUS304), providing efficient heat transfer between the refrigerant/water circuit and ambient air
- Operating Temperature Range: −40°C to +200°C, accommodating both winter heating and summer cooling cycles
- Mechanical Properties: Tensile strength ≥520 MPa; elongation ≥40% (as per ASTM A213)
- Hygienic Surface: Food-grade surface finish with low roughness (Ra ≤0.4 μm) minimizing fouling and facilitating condensate drainage
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm, 8.0 mm, 9.52 mm, 12.0 mm (customizable) | ASTM A213 / GB/T 14976 |
| Wall Thickness | 0.5 mm – 1.5 mm (±0.1 mm tolerance) | ASME B36.19M |
| Coil Inner Diameter (ID) | 300 mm – 1200 mm | Manufacturer specification |
| Coil Length per Roll | 50 m – 500 m (customizable per order) | — |
| Surface Finish | Bright annealed / Pickled & passivated (2B finish) | ASTM A479 |
| End Condition | Plain cut / Beveled / Threaded / Flanged (upon request) | — |
| Pressure Rating | Up to 1.6 MPa (PN16) at operating temperature | EN 10217-7 |
| Fin Compatibility | Compatible with aluminum fins (clad or discrete) for extended surface heat exchangers | — |
| Winding Tolerance | ±2 mm on coil diameter; ±5 mm on coil length | Internal QC standard |
| Packaging | Wooden pallet with moisture-proof wrapping; coil secured with steel straps | ISO 11607 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical soundness, and surface integrity:
- Raw Material Selection: Certified stainless steel strip or seamless tube billet conforming to ASTM A269 / A213 chemical composition requirements.
- Hot Rolling / Extrusion: Initial forming of seamless tube or ERW (Electric Resistance Welded) tube from rolled stock.
- Cold Drawing & Sizing: Precision cold-drawing through calibrated dies to achieve exact OD and wall thickness tolerances.
- Heat Treatment (Solution Annealing): Annealing at 1040°C–1150°C followed by rapid quenching to restore full austenitic structure and eliminate cold-work stresses.
- Pickling & Passivation: Acid pickling to remove oxide scale, followed by passivation treatment to establish a stable chromium oxide protective layer.
- Coiling: Continuous coiling on precision winders with controlled tension to prevent deformation, kinking, or surface scratches.
- Quality Inspection: 100% ultrasonic testing (UT) for internal defects; visual and dimensional inspection; hydrostatic pressure testing at 1.5× working pressure.
- Final Packaging: Protective wrapping and secure palletization for transport and storage.
Applications
The coil tube is purpose-engineered for the following primary applications:
- Fan Coil Units (FCU) — Winter Operating Conditions: Serves as the core heat exchange element in FCU systems where hot water or steam circulates through the coil tube to provide space heating during cold weather. The stainless steel construction ensures long-term resistance to condensate and corrosion under dehumidification conditions.
- Fan Coil Unit + Fresh Air System Integration: Compatible with combined indoor/outdoor air-handling systems where the coil tube manages both sensible and latent heat loads, maintaining indoor air quality (IAQ) standards.
- Commercial HVAC Heat Exchangers: Used in plate-fin and shell-and-tube heat exchanger assemblies for commercial buildings, hotels, hospitals, and cleanrooms.
- Industrial Process Cooling/Heating: Applicable in food processing, pharmaceutical, and chemical industries where hygienic and corrosion-resistant tubing is mandated.
- Refrigeration Circuits: Suitable for refrigerant-side tubing in vapor-compression systems requiring high pressure and temperature cycling resistance.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management and holds the following certifications and complies with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Compliance with European Economic Area directives for construction products and machinery
- ASTM A213 / A269 — Specification for seamless austenitic stainless steel boiler, heat exchanger, and similar heat-transfer tubing
- GB/T 14976 — Chinese national standard for cold-rolled stainless steel seamless tubes for fluid transport
- EN 10217-7 — European standard for welded stainless steel tubes for pressure purposes
- NACE MR0175 / ISO 15156 — Compliance for sour service environments (316L grade)
- Third-Party Inspection: Available SGS / BV / TÜV inspection upon buyer request
Unique Selling Points
- Superior Winter Performance: Engineered specifically for efficient heat exchange under low-ambient-temperature conditions, ensuring reliable heating output in fan coil unit winter operating cycles.
- Extended Service Life: Austenitic stainless steel construction provides 2–3× the service life compared to carbon steel alternatives in corrosive condensate environments.
- Customizable Dimensions: Flexible production capability accommodating non-standard OD, wall thickness, and coil length to meet specific OEM heat exchanger designs.
- Hygienic Grade Surface: Passivated surface finish minimizes microbial growth and fouling, reducing maintenance frequency and ensuring consistent thermal performance over the system lifecycle.
- Seamless Supply Chain: Integrated manufacturing from raw material to finished coil tube ensures traceability, dimensional consistency, and reduced lead times for HVAC OEMs.