Stainless Steel Coil Tube (Coil Tube) — Fan Coil Unit Application Series
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing product designed primarily for use in fan coil unit (FCU) air conditioning systems and related HVAC (Heating, Ventilation, and Air Conditioning) applications. These coil tubes are formed from high-grade stainless steel wire or strip through a continuous coil-forming process, producing a helical or serpentine tube configuration that maximizes heat exchange surface area within a compact footprint. The product is engineered to withstand prolonged exposure to water, refrigerant, and corrosive atmospheric conditions while maintaining dimensional stability and structural integrity over extended service life.
This product line is particularly suited for integration with multi-speed, low-noise single-phase capacitor motor assemblies used in fan coil unit systems, where reliable heat transfer, minimal pressure drop, and acoustic performance are critical operational parameters.
Material & Properties
The coil tubes are fabricated from austenitic stainless steel grades selected for their superior corrosion resistance, thermal conductivity, and mechanical durability. The primary material specifications are as follows:
- Material Grade: SUS304 / SUS316L (ASTM A213 / ASTM A269 equivalent)
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and atmospheric oxidation; suitable for both potable water and closed-loop refrigerant circuits
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, providing efficient heat transfer performance
- Operating Temperature Range: −196°C to +870°C (depending on grade), accommodating extreme thermal cycling conditions
- Mechanical Strength: Tensile strength ≥ 520 MPa (SUS304) / ≥ 485 MPa (SUS316L); yield strength ≥ 205 MPa
- Surface Finish: Bright annealed (BA) or polished finish with surface roughness Ra ≤ 0.4 μm, minimizing fouling and pressure loss
- Hygienic Compliance: Suitable for food-grade and pharmaceutical applications where cleanability and non-toxicity are mandated
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 12.7 mm (1/4" – 1/2") | ASTM A213 / ASTM A269 |
| Wall Thickness | 0.3 mm – 1.0 mm | GB/T 14976 |
| Coil Pitch (Turn Spacing) | 8.0 mm – 25.0 mm (configurable) | Custom / OEM Specification |
| Coil Diameter (Bundle Diameter) | 100 mm – 600 mm | Customer-Specific Design |
| Tube Length (Uncoiled) | Up to 50 m continuous | — |
| Number of Turns | 5 – 200 turns (configurable) | — | Material Grade | SUS304, SUS316L, SUS321 | ASTM A213 / GB/T 12771 |
| Surface Treatment | Bright Annealed, Electropolished, or Passivated | — |
| End Preparation | Plain end, beveled, or socket-weld ready | ASME B31.9 |
| Pressure Rating | Up to 2.5 MPa (working pressure, depending on OD/WT) | GB/T 14976 |
| Heat Transfer Coefficient | Improved 20–40% over bare tube equivalents | — |
| Weight (Approximate) | 0.8 kg – 15.0 kg per coil bundle | — |
Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical quality, and surface integrity:
- Raw Material Selection: Certified stainless steel wire rod or cold-rolled strip is sourced from approved mills with full traceability documentation including mill test certificates (MTC) and chemical composition analysis.
- Tube Forming: The raw material is processed through seamless or welded tube forming operations. Seamless tubes are produced via hot or cold piercing and subsequent cold drawing; welded tubes undergo high-frequency resistance welding (HFW) with full-penetration weld inspection.
- Heat Treatment: Tubes undergo solution annealing at 1050–1150°C followed by controlled water quenching to achieve a fully austenitic microstructure with maximum ductility and corrosion resistance.
- Coil Forming: Annealed tubes are fed through precision coil-forming machines equipped with CNC-controlled bending heads. The bending process utilizes mandrel-assisted tooling to prevent ovalization, ensuring uniform bend radius and consistent coil geometry.
- Surface Finishing: Tubes receive bright annealing in a controlled atmosphere furnace (reducing atmosphere, dew point ≤ −60°C) to remove scale and restore surface luster. Optional electropolishing or passivation treatments are applied for enhanced hygienic performance.
- Quality Inspection: Each coil bundle undergoes dimensional verification (OD, wall thickness, pitch, coil diameter), visual surface inspection, and hydrostatic pressure testing at 1.5× working pressure with minimum 10-second hold time. Non-destructive testing (NDT) including eddy current testing is performed on weld seams where applicable.
- End Preparation & Packaging: Tube ends are cut square, deburred, and beveled to ASME B31.9 standards. Bundles are packaged in protective foam-lined wooden crates or shrink-wrapped for shipment.
Applications
The stainless steel coil tube product line is designed for a broad spectrum of industrial and commercial applications:
- Fan Coil Unit (FCU) Systems: Primary application — coil tubes serve as the heat exchange core in fan coil units, where water or refrigerant circulates through the coil while air is blown across the tube surfaces by low-noise fan motors. The compact helical geometry maximizes heat transfer area per unit volume.
- HVAC Chilled Water Systems: Used in air handlers, unitary cooling systems, and precision temperature control environments including data centers, cleanrooms, and laboratories.
- Refrigeration & Heat Pump Systems: Suitable for evaporator and condenser coils in commercial refrigeration units and heat pump systems operating with environmentally friendly refrigerants (R-410A, R-32, R-134a).
- Food & Beverage Processing: Hygienic-grade coil tubes are employed in pasteurization, pasteurization, sterilization, and thermal processing equipment where CIP (Clean-In-Place) compatibility is required.
- Pharmaceutical Manufacturing: Used in GMP-compliant heat exchange systems, sterile water loops, and process heating/cooling circuits.
- Chemical & Petrochemical Industry: Corrosion-resistant coil tubes handle aggressive chemical media, acidic solutions, and chlorinated environments.
- Marine & Offshore Applications: SUS316L-grade coil tubes provide enhanced pitting and crevice corrosion resistance in seawater-cooled heat exchangers.
- Power Generation: Applied in steam generators, condensers, and waste heat recovery systems in thermal and nuclear power plants.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certification portfolio to ensure compliance with international standards and regulatory requirements:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- ISO 45001:2018 — Occupational Health and Safety Management System certification
- CE Marking — Compliance with European Directive requirements for product safety
- EN 10216-5 — European standard for welded austenitic stainless steel tubes
- ASTM A213 / A269 — American Society for Testing and Materials standards for seamless and welded austenitic stainless steel tubes
- GB/T 14976 — Chinese national standard for fluid transport stainless steel seamless tubes
- GB/T 12771 — Chinese national standard for fluid transport stainless steel welded tubes
- ASME B31.9 — Code for Building Services Piping, ensuring pressure vessel and piping system integrity
- NSF/ANSI 61 — Drinking water system components certification (where applicable for potable water applications)
- 3-A Sanitary Standards — Dairy and food industry hygienic design certification (where applicable)
Unique Selling Points
- Superior Corrosion Resistance: Austenitic stainless steel construction provides exceptional longevity in corrosive environments, significantly reducing maintenance frequency and replacement costs compared to carbon steel or copper alternatives.
- Enhanced Heat Transfer Efficiency: The helical coil geometry combined with precision surface finishing delivers 20–40% improved heat transfer coefficients over conventional straight-tube configurations, enabling more compact and energy-efficient system designs.
- Low-Noise Compatibility: Designed for seamless integration with multi-speed low-noise single-phase capacitor motor assemblies, ensuring acoustic performance meets stringent indoor environment quality (IEQ) standards.
- Customizable Geometry: Flexible coil pitch, diameter, and turn count configurations allow OEM-specific optimization for diverse system requirements and space constraints.
- Full Traceability: Every coil bundle is accompanied by complete material traceability documentation, including mill test certificates, chemical analysis reports, and process heat treatment records.
- Hygienic Design: Electropolished and passivated surfaces with Ra ≤ 0.4 μm finish meet the most demanding sanitary requirements in food, pharmaceutical, and medical applications.
- Wide Operating Envelope: Capable of withstanding extreme temperature and pressure conditions, ensuring reliable performance across diverse industrial applications.
Note: All specifications listed are representative values based on standard product configurations. Custom specifications, dimensional tolerances, and material grades are available upon request through direct consultation with the Wenzhou Jixing Metal Materials Co., Ltd. engineering team. Product performance should be verified against specific application requirements and applicable local codes and standards.