Stainless Steel Coil Tube for Fan Coil Unit Air Conditioners
Product Overview
The Stainless Steel Coil Tube (Coiltube, Product No. 1609) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping component designed specifically for integration into room fan coil air conditioning systems. This product complies with the Chinese national standard GB/T 19232 — Room Fan Coil Air Conditioners, which governs the design, performance, and safety requirements for fan coil units (FCUs) used in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications.
Coil tubes serve as the critical heat exchange medium within fan coil units, facilitating the transfer of thermal energy between circulating refrigerant or hydronic fluid and the indoor air stream. The stainless steel construction of this coil tube provides superior corrosion resistance, mechanical durability, and long-term thermal efficiency compared to conventional carbon steel or copper alternatives, making it an ideal material for demanding HVAC environments.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, formability, and thermal conductivity. The primary material grades utilized include:
- 304 (UNS S30400 / AISI 304) — The most widely used austenitic stainless steel grade, offering excellent general corrosion resistance with 18% Chromium (Cr) and 8% Nickel (Ni) content.
- 316 (UNS S31600 / AISI 316) — Enhanced corrosion resistance due to the addition of 2–3% Molybdenum (Mo), suitable for aggressive chemical environments and coastal applications.
- 316L (UNS S31603 / AISI 316L) — Low-carbon variant of 316 with improved weldability and resistance to intergranular corrosion.
Key material properties of the coil tube include:
- Corrosion Resistance: Excellent resistance to oxidation, pitting, and crevice corrosion under normal HVAC operating conditions, including exposure to condensate and humid air environments.
- Thermal Conductivity: Approximately 16.3 W/(m·K) for Grade 304, providing efficient heat transfer performance within the coil assembly.
- Operating Temperature Range: Suitable for continuous operation from −196°C to +870°C (−321°F to +1,598°F), well beyond typical HVAC operating ranges of −20°C to +120°C.
- Mechanical Strength: Yield strength of approximately 205 MPa (Grade 304) with tensile strength exceeding 515 MPa, ensuring structural integrity under internal pressure loads.
- Formability: High ductility and elongation (≥40%) enabling precise coiling without cracking or deformation.
- Hygienic Surface: Non-toxic, non-leaching surface suitable for potable water and HVAC applications, meeting food-grade standards where applicable.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Product Number | 1609 | — |
| Material Grade | 304 / 316 / 316L (Austenitic Stainless Steel) | ASTM A213 / GB/T 12771 |
| Outer Diameter (OD) | 6.35 mm / 9.53 mm / 12.70 mm (¼" / ⅜" / ½") | ASME B36.19M |
| Wall Thickness | 0.80 mm – 1.65 mm (0.031" – 0.065") | ASME B36.19M |
| Coil Diameter | Customizable, typically 100 mm – 300 mm | GB/T 19232 |
| Coil Length | Customized per FCU design requirements (typically 2 m – 10 m) | GB/T 19232 |
| Surface Finish | Mill finish / Brushed / Polished (Ra ≤ 0.8 μm) | ASTM A403 |
| Operating Pressure | Up to 1.6 MPa (232 psi) standard; 2.5 MPa (363 psi) on request | GB/T 19232 |
| Operating Temperature | −20°C to +120°C (−4°F to +248°F) | GB/T 19232 |
| Heat Transfer Medium | Water / Glycol-Water Mixture / Refrigerant | GB/T 19232 |
| Tolerance on OD | ±0.10 mm (±0.004") | ASTM A213 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| Joining Method | TIG (Tungsten Inert Gas) Welding / Brazing / Flare Connection | ASME B31.9 |
| Applicable Standard | GB/T 19232 — Room Fan Coil Air Conditioners | Chinese National Standard |
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, material integrity, and consistent performance:
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Raw Material Procurement and Inspection:
High-purity austenitic stainless steel wire rod is sourced from certified mills, subjected to spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition, and inspected for surface defects and mechanical properties prior to processing.
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Wire Drawing:
The stainless steel wire rod is drawn through a series of progressively reducing dies to achieve the target wire diameter with tight tolerances. This cold-drawing process enhances the grain structure, improving mechanical strength and surface finish.
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Tube Forming (Seamless or Welded):
The drawn wire is formed into tubular geometry through either a seamless extrusion process or a precision longitudinal welding technique. For seamless tubes, the material is heated and extruded through a die to produce a continuous tube without weld seams, ensuring uniform wall thickness and superior pressure resistance.
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Heat Treatment:
Formed tubes undergo solution annealing at temperatures between 1010°C and 1150°C, followed by rapid quenching, to relieve internal stresses, restore full austenitic microstructure, and ensure optimal corrosion resistance and ductility.
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Precision Coiling:
Using computer-controlled coiling machinery, the straight tube is wound into a precise helical coil geometry with uniform pitch and diameter. The coiling process is designed to avoid work hardening, distortion, or surface damage. CNC (Computer Numerical Control) systems ensure repeatable dimensional accuracy.
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Surface Treatment:
Depending on the application requirements, the coil tube may undergo pickling and passivation (acid cleaning) to remove mill scale and oxide layers, followed by passivation treatment to form a protective chromium oxide film on the surface, enhancing long-term corrosion resistance.
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Quality Inspection and Testing:
Finished coil tubes undergo comprehensive quality assurance testing including:
- Hydrostatic pressure testing to verify integrity under operating pressure conditions
- Dimensional measurement using laser gauges and micrometers
- Visual inspection for surface defects, weld quality, and geometric accuracy
- Chemical composition verification via XRF (X-ray Fluorescence) analysis
- Corrosion resistance testing (salt spray testing per ASTM B117)
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Packaging and Delivery:
Inspected and approved coil tubes are carefully packaged with protective wrapping and moisture barriers to prevent surface damage and corrosion during transit. Each shipment is accompanied by a mill test certificate (MTC) and quality documentation.
Applications
The Stainless Steel Coil Tube (Coiltube, Product No. 1609) is specifically designed for use in fan coil unit air conditioning systems and finds broad application across multiple sectors:
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Commercial HVAC Systems:
Primary heat exchange coil in room fan coil air conditioners (FCUs) for office buildings, hotels, hospitals, shopping malls, and educational facilities. Compliant with GB/T 19232 performance requirements for cooling capacity, heating capacity, air flow, and noise levels.
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Residential Air Conditioning:
Used in residential FCU units and concealed ceiling-mounted systems, providing reliable and long-lasting thermal performance in domestic environments.
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Industrial Process Cooling:
Applicable in industrial environments requiring corrosion-resistant heat exchange coils, including chemical processing plants, food and beverage production facilities, and pharmaceutical manufacturing.
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Refrigeration Systems:
Suitable for refrigerant circulation in commercial refrigeration units and cold storage systems where stainless steel's corrosion resistance provides extended service life.
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Hydronic Heating Systems:
Effective in radiant heating and hydronic heating coil applications where glycol-water mixtures are used as heat transfer media.
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Specialized Environments:
Recommended for coastal, marine, and high-humidity environments where conventional copper or carbon steel coils would suffer accelerated corrosion.
Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure that all stainless steel coil tube products meet or exceed international and national standards:
- GB/T 19232 — Room Fan Coil Air Conditioners: Full compliance with the Chinese national standard governing the design, performance testing, and safety requirements for room fan coil air conditioning systems. This standard specifies requirements for cooling/heating capacity, air flow rate, noise level, power consumption, and structural integrity.
- ISO 9001:2015 — Quality Management Systems: Certified quality management system ensuring consistent product quality, process control, and continuous improvement throughout the manufacturing lifecycle.
- ASTM A213 / A269: Compliance with American Society for Testing and Materials (ASTM) standards for seamless and welded austenitic stainless steel tubing.
- GB/T 12771: Compliance with Chinese national standards for stainless steel seamless tubes for general use.
- CE Marking: Conformity with European Union directives for products sold in the European Economic Area, including machinery safety and electromagnetic compatibility requirements.
- MTC (Mill Test Certificate): Each batch of coil tube is accompanied by a detailed mill test certificate documenting chemical composition, mechanical properties, heat treatment parameters, and test results.
- NSF / FDA Compliance: Available upon request for applications involving potable water systems, ensuring the material is non-toxic and meets public health standards.
Unique Selling Points
- Superior Corrosion Resistance: Austenitic stainless steel construction provides dramatically longer service life compared to copper or carbon steel alternatives, particularly in humid, corrosive, or chemically aggressive HVAC environments.
- Extended Service Life: Expected operational lifespan exceeding 25–30 years under normal HVAC conditions, significantly reducing maintenance frequency and total cost of ownership (TCO).
- Hygienic and Food-Safe: Non-reactive surface prevents contamination of air streams, making the coil tube ideal for hospital, pharmaceutical, and food processing applications.
- Customizable Geometry: Coil diameter, pitch, length, and tube dimensions can be tailored to specific FCU design requirements, enabling optimized heat transfer performance for each application.
- Environmental Sustainability: Stainless steel is 100% recyclable, contributing to sustainable manufacturing practices and reduced environmental impact throughout the product lifecycle.
- Standard Compliance: Full adherence to GB/T 19232 and international standards ensures seamless integration into certified fan coil unit systems and regulatory compliance in global markets.
Note: All specifications are subject to revision based on the latest version of applicable standards. Customers are advised to consult Wenzhou Jixing Metal Materials Co., Ltd. for the most current product data and technical documentation prior to procurement. Custom specifications and non-standard configurations are available upon request with appropriate lead time allowances.