Stainless Steel Coil Tube for Fan Coil Unit Systems — Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product Code: No. 1290 | Classification: HVAC Coil Tube Components
1. Product Overview
The Stainless Steel Coil Tube (盘管Coiltube) is a precision-engineered tubular component designed specifically for integration into Fan Coil Unit (FCU) systems used in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) applications. These coil tubes serve as the primary heat exchange media within fan coil assemblies, facilitating efficient thermal transfer between the circulating refrigerant or hot water and the ambient air stream.
Wenzhou Jixing Metal Materials Co., Ltd. supplies high-grade stainless steel coil tubes that meet rigorous international standards, ensuring long-term durability, corrosion resistance, and optimal thermal performance in demanding HVAC environments. The technical and economic evaluation of fan coil unit systems has demonstrated that the selection of appropriate coil tube materials is a critical determinant of overall system efficiency, lifecycle cost, and reliability.
2. Material & Properties
The coil tubes are manufactured from austenitic stainless steel grades, primarily SAE 304 (UNS S30400) and SAE 316L (UNS S31603), selected for their superior combination of mechanical strength, weldability, and resistance to corrosion.
- SAE 304 (UNS S30400): Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni). Ideal for general HVAC applications where moderate corrosion resistance is required. Offers excellent formability and weldability.
- SAE 316L (UNS S31603): Enhanced grade with 2–3% Molybdenum (Mo) addition and reduced Carbon (C) content. Provides superior resistance to pitting and crevice corrosion, making it suitable for humid, coastal, or chemically aggressive environments.
Key Material Properties:
- Thermal Conductivity (λ): 16.3 W/(m·K) at 300 K (SAE 304); 14.2 W/(m·K) at 300 K (SAE 316L)
- Density (ρ): 8.0 g/cm³
- Yield Strength (σy): ≥ 205 MPa (SAE 304); ≥ 170 MPa (SAE 316L)
- Tensile Strength (σu): 515–720 MPa
- Operating Temperature Range: −196 °C to +870 °C
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and mild chemical environments
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Material Grade | SAE 304 / SAE 316L | ASTM A269 / ASTM A312 |
| Outer Diameter (OD) | 6.0 mm – 12.7 mm (1/4" – 1/2") | ASTM A751 |
| Wall Thickness | 0.5 mm – 1.2 mm | ASTM A751 |
| Surface Finish | No. 4 Brushed / BA (Bright Annealed) / Mirror Polished (Ra ≤ 0.4 μm) | ASTM A480 |
| Coil Winding Diameter | Custom (typically 300 mm – 800 mm) | Per OEM Specification |
| Tube Length (per coil) | 1.5 m – 12.0 m (customizable) | Per Project Requirement |
| Dimensional Tolerance | OD: ±0.05 mm; Wall Thickness: ±0.03 mm | ISO 3499 |
| Surface Roughness (Ra) | ≤ 0.8 μm (standard); ≤ 0.4 μm (mirror finish) | ISO 4287 |
| Hydrostatic Test Pressure | ≥ 2.5 MPa (minimum burst pressure factor: 3×) | ASTM A269 |
| Heat Treatment | Solution Annealed (1050 °C – 1150 °C) + Water Quenched | ASTM A480 |
| Coating / Treatment | Pickling & Passivation (Nitric Acid / Citric Acid) | ASTM A967 |
| Compliance Standards | GB/T 14976, EN 10217, ISO 13973 | — |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement & Inspection: Hot-rolled stainless steel strip or tube blanks are sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition compliance with ASTM/GB standards.
- Cold Drawing & Forming: The tube blanks are cold-drawn through precision dies to achieve the target outer diameter and wall thickness with tight tolerances. This process enhances mechanical properties through strain hardening.
- Solution Annealing: Drawn tubes are annealed at 1050–1150 °C in a protective atmosphere furnace, followed by rapid water quenching. This eliminates residual stresses, restores ductility, and ensures a fully austenitic microstructure free of carbide precipitation.
- Coil Winding: Annealed tubes are wound into precise spiral coils using CNC-controlled winding machinery. Coil pitch, diameter, and turn count are controlled to within ±1.0 mm to ensure uniform heat exchange surface area and flow distribution.
- Pickling & Passivation: The wound coils undergo acid pickling (HNO₃/HF blend) to remove oxide scale and contaminants, followed by passivation treatment to restore the chromium-rich passive film. This step is critical for long-term corrosion resistance.
- Surface Finishing: Depending on application requirements, coils may receive No. 4 brushed, Bright Annealed (BA), or mirror-polished finishes using automated polishing and buffing equipment.
- Hydrostatic Pressure Testing: Each coil is subjected to hydrostatic pressure testing at ≥2.5 MPa for a minimum dwell time of 60 seconds to verify structural integrity and detect any manufacturing defects.
- Final Quality Control & Packaging: Finished coils undergo dimensional inspection (OD, wall thickness, coil diameter), surface defect examination (visual + eddy current testing), and chemical spot analysis. Approved coils are packaged with protective wrapping and moisture-absorbing desiccants for shipment.
5. Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. are integral components in a broad range of HVAC and thermal management systems:
- Fan Coil Units (FCU): Primary application — coil tubes serve as the heat exchange core in both chilled water and hot water fan coil units used in commercial buildings, hotels, hospitals, and office complexes.
- Air Handling Units (AHU): Used in large-scale air distribution systems for temperature regulation in industrial facilities and commercial spaces.
- Chilled Beam Systems: Integrated into active and passive chilled beam configurations for radiant cooling in high-performance buildings.
- Process Cooling & Heating: Employed in pharmaceutical, food and beverage, and chemical processing industries where hygienic-grade stainless steel is mandated.
- Marine & Offshore HVAC: SAE 316L grade coil tubes are specified for marine air conditioning systems due to their superior resistance to saltwater and chlorinated environments.
- Refrigeration Systems: Used as evaporator and condenser coil elements in commercial refrigeration equipment.
6. 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 all manufacturing operations
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Conformity with European Union Directives for product safety
- GB/T 14976 — Chinese National Standard for seamless stainless steel tubes
- EN 10217 — European Standard for welded stainless steel tubes
- ASTM A269 / A312 — American standards for austenitic stainless steel tubing
- ASME B31.3 / B31.5 — Compliance with piping code requirements for process and refrigeration applications
- Mill Test Reports (MTR) — Available for every batch, documenting chemical composition, mechanical properties, and heat treatment parameters
7. Unique Selling Points
Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself in the competitive HVAC coil tube market through the following value propositions:
- Precision Engineering: Tight dimensional tolerances (±0.05 mm OD) ensure optimal fin-to-tube bonding and uniform airflow distribution, directly contributing to improved COP (Coefficient of Performance) in fan coil units.
- Superior Surface Quality: Mirror-polished finishes (Ra ≤ 0.4 μm) minimize fouling and biofilm accumulation, reducing maintenance intervals and extending service life.
- Material Versatility: Availability in both SAE 304 and SAE 316L grades allows customers to optimize the cost-performance ratio based on specific environmental and application requirements.
- Customization Capability: Full customization of coil diameter, pitch, tube length, and surface finish to match OEM specifications and project-specific thermal load calculations.
- Economic Efficiency: The technical-economic evaluation of fan coil unit systems confirms that high-quality stainless steel coil tubes reduce lifecycle costs by 15–25% through extended operational life, lower energy consumption, and reduced replacement frequency compared to carbon steel alternatives.
- Traceability & Documentation: Complete batch traceability with mill test reports and compliance certificates ensures full supply chain transparency and facilitates regulatory audits.
8. Technical & Economic Evaluation Context
The selection of coil tube material and specification is a pivotal factor in the Technical and Economic Evaluation of Fan Coil Unit Systems. Key evaluation criteria include:
- Initial Capital Cost (CAPEX): Stainless steel coil tubes carry a higher upfront cost than carbon steel alternatives but offer significantly lower lifecycle expenditure.
- Operational Energy Cost (OPEX): Superior thermal conductivity and surface finish of stainless steel coils enhance heat transfer efficiency, reducing fan motor energy consumption by 8–12%.
- Maintenance Cost: Corrosion resistance eliminates periodic replacement and chemical cleaning requirements, saving an estimated 30–40% in maintenance costs over a 10-year service period.
- Return on Investment (ROI): Comprehensive lifecycle analysis demonstrates a positive ROI within 3–5 years for stainless steel coil tube installations compared to conventional materials.
- Environmental Impact: Extended service life and reduced waste generation align with sustainability objectives and green building certification requirements (LEED, BREEAM).
Through rigorous adherence to international standards, advanced manufacturing capabilities, and a commitment to technical excellence, Wenzhou Jixing Metal Materials Co., Ltd. delivers stainless steel coil tubes that represent an optimal balance of performance, durability, and economic value for HVAC system integrators worldwide.