Stainless Steel Coil Tube — Fan Coil Unit & HVAC Application Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for heat exchange and fluid distribution applications within Fan Coil Unit (FCU) and Fresh Air System (FAS) architectures. As a critical component in modern indoor air quality (IAQ) management systems, this coil tube serves as the primary heat transfer medium in fan coil units that regulate indoor temperature, humidity, and particulate matter — particularly PM2.5 (Particulate Matter with aerodynamic diameter ≤ 2.5 micrometers) — in commercial, institutional, and residential environments.
Unlike conventional copper or aluminum coil tubes, the stainless steel variant offers superior resistance to corrosion, microbial growth, and long-term degradation, making it an ideal material choice for applications demanding extended service life, hygienic performance, and compliance with stringent indoor air quality standards.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, primarily conforming to the following alloy specifications:
- Grade 304 (UNS S30400): The standard workhorse alloy offering excellent general corrosion resistance, weldability, and formability. Suitable for most HVAC and ventilation applications where moderate chloride exposure may occur.
- Grade 316 (UNS S31600): Enhanced with 2–3% Molybdenum (Mo) content for superior resistance to pitting and crevice corrosion, particularly in environments with elevated chloride or sulfur compound concentrations.
- Grade 316L (UNS S31603): Low-carbon variant of 316, optimized for welding applications where sensitization and intergranular corrosion must be minimized.
- Grade 321 (UNS S32100): Titanium-stabilized austenitic grade providing enhanced resistance to intergranular corrosion at elevated temperatures.
Key Mechanical and Physical Properties:
- Tensile Strength: 515–720 MPa (depending on grade and condition)
- Yield Strength: ≥ 205 MPa
- Elongation: ≥ 40%
- Thermal Conductivity: 14–16 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +870°C
- Surface Finish: 2B, No.4, or BA (Bright Annealed) per customer specification
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Type | Stainless Steel Coil Tube (Coiltube) | — |
| Material Grade | 304, 316, 316L, 321 | ASTM A213 / A269, EN 10216-5 |
| Outer Diameter (OD) | 6.0 mm – 25.4 mm | Custom ranges available |
| Wall Thickness | 0.5 mm – 2.0 mm | Tolerance: ±0.1 mm |
| Coil Length | 5 m – 50 m (standard); up to 200 m on request | — |
| Coil Inner Diameter (ID) | 300 mm – 600 mm | — |
| Manufacturing Method | Seamless / Welded (TIG / EFW) | ASTM A213, ASTM A269 |
| Surface Treatment | Pickled & Passivated / Polished | — |
| End Condition | Cut to length, beveled, or threaded | — |
| Pressure Rating | Up to 4.0 MPa (working pressure, dependent on OD/WT) | ASME B31.9 |
| Heat Transfer Efficiency | Optimized for FCU radiator and evaporator coil applications | ASHRAE Standard 90.1 |
| Packaging | Wooden pallet with VCI (Vapor Corrosion Inhibitor) wrapping | ISO 17678 |
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:
- Raw Material Procurement & Inspection: Stainless steel ingots or wire rod are sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with specified ASTM/EN grades.
- Hot Rolling & Annealing: Billet or wire rod is hot-rolled to approximate dimensions and subsequently annealed in a controlled atmosphere furnace to relieve residual stresses and achieve the desired austenitic microstructure.
- Piercing / Extrusion (for seamless tubes): For seamless variants, the heated billet is pierced through a mandrel to form a hollow tube. Alternatively, extrusion through a die produces the initial tube geometry.
- Cold Drawing / Cold Pilgering: The tube is drawn through precision dies to achieve exact outer diameter and wall thickness specifications. Cold working imparts improved mechanical properties and surface finish.
- Intermediate Annealing: Periodic annealing cycles are performed during multi-pass cold drawing to restore ductility and prevent cracking.
- Coil Forming / Spooling: The straight tube is fed through a progressive bending system that forms the tube into a continuous coil of specified diameter and length. The bending process is controlled to avoid ovality, kinking, or residual stress concentrations.
- Pickling & Passivation: The coil tube is immersed in a hydrofluoric/nitric acid bath to remove mill scale and surface contaminants. A subsequent passivation treatment forms a protective chromium oxide layer on the surface, enhancing corrosion resistance.
- Quality Inspection: Each coil undergoes hydrostatic pressure testing, dimensional measurement (OD, WT, straightness), and surface inspection. Sampling for mechanical testing (tensile, hardness, impact) is performed per lot.
- Packaging & Shipping: Qualified coils are wrapped with protective film and VCI paper, secured on wooden pallets, and prepared for export or domestic delivery.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. finds extensive application across multiple industries:
HVAC & Indoor Air Quality Systems
- Fan Coil Units (FCUs): The primary heat exchange medium in FCU radiator coils and evaporator coils, facilitating precise temperature control in commercial buildings, hospitals, laboratories, and cleanrooms.
- Fresh Air Systems (FAS) with PM2.5 Filtration: Integrated into hybrid ventilation systems that combine fan coil units with dedicated outdoor air systems and high-efficiency particulate filters (HEPA / ePM1), enabling effective PM2.5 pollution control while maintaining thermal comfort.
- Chilled Water & Hot Water Distribution: Used in secondary loop piping and coil assemblies within central HVAC plants.
Industrial & Process Applications
- Heat Exchangers & Radiators: Coil windings in shell-and-tube and plate-fin heat exchangers for chemical, pharmaceutical, and food processing industries.
- Refrigeration & Cryogenic Systems: Evaporator and condenser coils where stainless steel's resistance to ammonia, brine, and refrigerant-induced corrosion is critical.
- Automotive & Aerospace: Fuel lines, hydraulic lines, and exhaust systems requiring high-temperature and corrosion resistance.
Domestic & Commercial
- Water Heater & Boiler Systems: Internal heating coils and heat transfer elements.
- Solar Thermal Collectors: Absorber tube coils in evacuated tube and flat plate solar collectors.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that all coil tube products meet or exceed international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering all manufacturing and quality assurance processes. |
| ISO 14001:2015 | Environmental Management System certification demonstrating commitment to sustainable manufacturing practices. |
| ISO 45001:2018 | Occupational Health and Safety Management System certification. |
| CE Marking | Compliance with European Union directives for machinery and pressure equipment safety. |
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-temperature Service. |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Other General Purposes. |
| EN 10216-5 | European standard for welded austenitic stainless steel tubes for general purposes. |
| ASME B31.9 | Pressure Piping, Refrigeration and Air-Conditioning — compliance with safety and design requirements. |
| SGS Testing | Independent third-party verification of material composition, mechanical properties, and dimensional accuracy. |
Unique Selling Points
- Exceptional Corrosion Resistance: Austenitic stainless steel construction provides outstanding resistance to oxidation, pitting, and crevice corrosion, ensuring service life exceeding 25 years even in aggressive environments — a significant advantage over copper or aluminum alternatives in chloride-rich or humid conditions.
- Hygienic Surface Integrity: The smooth, non-porous surface of stainless steel prevents microbial colonization and biofilm formation, making it ideal for healthcare facilities, pharmaceutical manufacturing, and food-grade HVAC applications.
- Superior PM2.5 Control Compatibility: Designed for seamless integration into Fan Coil Unit plus Fresh Air System architectures that achieve indoor PM2.5 concentrations below 35 μg/m³, meeting WHO (World Health Organization) Air Quality Guidelines for indoor environments.
- Full Traceability: Every coil tube batch is accompanied by a Material Test Certificate (MTC) / Certificate of Conformity (CoC) with full heat number traceability, chemical composition reports, and mechanical test data.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers tailored OD, wall thickness, coil length, surface finish, and end treatment configurations to meet specific project requirements.
- Energy Efficiency Contribution: The optimized geometry and thermal properties of the coil tube contribute to improved heat transfer coefficients, reducing fan energy consumption and enhancing overall system COP (Coefficient of Performance) in compliance with ASHRAE 90.1 energy efficiency standards.
Conclusion
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. represents a premium solution for demanding HVAC, industrial heat exchange, and indoor air quality applications. Its combination of metallurgical excellence, dimensional precision, and compliance with international quality standards positions it as the preferred choice for engineers and specifiers seeking reliable, long-life, and hygienic heat transfer components in modern building systems.