Stainless Steel Coil Tube for Fan Coil Unit (FCU) Systems
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product Code: 1505). This product is specifically designed for integration into Fan Coil Units (FCUs), including the industry-recognized "Penguin Brand" fan coil air conditioning systems. The Coil Tube serves as the core heat exchanger element, facilitating efficient thermal transfer between refrigerant or hydronic media and ambient air within commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications.
As a critical component in the HVAC supply chain, the Coil Tube must meet stringent requirements regarding dimensional accuracy, corrosion resistance, thermal conductivity, and mechanical durability. Wenzhou Jixing Metal Materials Co., Ltd. adheres to international manufacturing standards to ensure consistent product performance across diverse operating environments.
Material & Properties
The Coil Tube is fabricated from high-grade stainless steel, selected for its superior combination of corrosion resistance, mechanical strength, and thermal performance. The following materials and their corresponding properties are typically employed:
- Austenitic Stainless Steel (304 / SUS 304): Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni). Offers excellent general-purpose corrosion resistance and is suitable for most HVAC applications involving water-based coolant systems.
- Austenitic Stainless Steel (316 / SUS 316): Contains 16–18% Cr, 10–14% Ni, and 2–3% Molybdenum (Mo). Provides enhanced resistance to chlorides and acidic environments, making it ideal for coastal or industrial installations.
- Stainless Steel Grade 321: Stabilized with Titanium (Ti) to prevent intergranular corrosion during high-temperature service conditions.
Key material properties of the Coil Tube include:
- Corrosion Resistance: Passive oxide layer (Cr₂O₃) provides self-healing protection against oxidation and chemical attack.
- Thermal Conductivity: Approximately 16 W/(m·K) for Grade 304, ensuring effective heat transfer across the tube wall.
- Tensile Strength: Minimum 515 MPa (Grade 304), ensuring structural integrity under pressure cycling.
- Operating Temperature Range: From −196°C to +870°C, accommodating extreme thermal conditions.
- Surface Finish: Mirror-polished or brushed finish with surface roughness (Ra) ≤ 0.8 μm to minimize fouling and reduce flow resistance.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Code | 1505 | Wenzhou Jixing Internal Catalog |
| Product Name | Stainless Steel Coil Tube (盘管 Coiltube) | — |
| Material Grade | SUS 304 / SUS 316 / SUS 321 | ASTM A213 / ASTM A269 |
| Outer Diameter (OD) | 6.35 mm / 9.53 mm / 12.70 mm (1/4" / 3/8" / 1/2") | ASHRAE Standard 90.1 |
| Wall Thickness | 0.50 mm – 1.20 mm | ASME B36.19M |
| Tube Length | Custom (typically 1,000 mm – 6,000 mm per pass) | Customer Specification |
| Bend Radius | ≥ 3D (D = outer diameter) | ISO 1155 |
| Number of Rows | 2 / 3 / 4 rows (configurable) | ASHRAE Handbook — HVAC Systems and Equipment |
| Fin Spacing | 2.0 mm – 3.0 mm | Industry Standard |
| Fin Material | Aluminum (Al) or Stainless Steel | — |
| Pressure Rating | 1.0 MPa – 2.5 MPa (depending on wall thickness) | ASME BPV Code Section VIII |
| Coolant Type | Water / Chilled Water / Glycol-Water Solution / Refrigerant | — |
| Connection Type | Threaded (G1/4", G3/8", G1/2") / Flanged / Brazed | BSPP / ISO 7 |
| Surface Treatment | Passivation / Electropolishing / Anti-corrosion Coating (optional) | ASTM A967 |
Manufacturing Process
The production of the Stainless Steel Coil Tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional precision, metallurgical integrity, and long-term service reliability:
- Raw Material Procurement: Cold-rolled stainless steel coils conforming to ASTM A213/A269 specifications are sourced from certified suppliers. Incoming materials undergo spectroscopic analysis (Optical Emission Spectrometry — OES) to verify chemical composition.
- Slitting and Leveling: The coil stock is slit to the required width using precision slitting lines. The resulting strip is leveled to eliminate residual stresses and ensure flatness within ±0.1 mm/m.
- Forming (Tube Making): The leveled strip is formed into tubular sections using roll-forming or hydraulic pressing techniques. Welded seams (if applicable) are created via TIG (Tungsten Inert Gas) welding with argon shielding.
- Heat Treatment and Annealing: Tubes undergo solution annealing at 1050°C – 1150°C followed by controlled cooling to relieve internal stresses and restore full austenitic structure.
- Precision Bending: Computer Numerical Control (CNC) bending machines form the tubes into the required coil geometry with a minimum bend radius of 3D to prevent ovalization or cracking.
- Fin Application: Aluminum or stainless steel fins are inserted between tube rows using a hydraulic fin-insertion press. Fin alignment is verified to ensure uniform spacing and optimal heat transfer surface area.
- End Sealing and Brazing: Tube ends are sealed and brazed to header pipes (if integrated). Brazing is performed under a nitrogen or argon atmosphere to prevent oxidation.
- Passivation Treatment: The assembled coil tube undergoes chemical passivation using nitric acid or citric acid solutions to enhance the protective chromium oxide layer.
- Hydrostatic Pressure Testing: Each unit is subjected to a hydrostatic pressure test at 1.5× the maximum working pressure (MWP) for a minimum of 30 seconds to verify leak-free integrity.
- Final Inspection and Packaging: Completed units undergo visual inspection, dimensional verification, and surface quality assessment before protective packaging for shipment.
Applications
The Stainless Steel Coil Tube is integral to a wide range of thermal management systems, with primary applications including:
- Fan Coil Units (FCUs): The primary application domain — the Coil Tube serves as the heat exchanger in "Penguin Brand" and equivalent FCU air conditioning systems for both cooling and heating modes.
- Commercial HVAC Systems: Office buildings, shopping malls, hospitals, and hotels where reliable air conditioning with minimal maintenance is required.
- Residential Air Conditioning: Concealed and ducted indoor units in premium residential installations.
- Industrial Process Cooling: Temperature control in manufacturing facilities, data centers, and laboratory environments.
- Chilled Water Distribution Systems: Integration with central chiller plants for large-scale building climate control.
- Marine and Coastal Applications: Grade 316 Coil Tubes provide enhanced chloride resistance for marine HVAC installations.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity and customer confidence:
- ISO 9001:2015: Quality Management System certification ensuring consistent product quality and continuous improvement.
- 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: Conformity with European Union safety, health, and environmental protection standards (Directive 2014/68/EU — Pressure Equipment Directive).
- Material Certificates: EN 10204 3.1 Certificate of Conformity provided with each batch, including full chemical and mechanical test results.
- Third-Party Testing: Products verified by accredited laboratories including SGS, Bureau Veritas, or equivalent bodies for dimensional accuracy, pressure testing, and material compliance.
- ASME / PED Compliance: Manufacturing processes aligned with American Society of Mechanical Engineers (ASME) codes and European Pressure Equipment Directive (PED) requirements.
Unique Selling Points
- Enhanced Corrosion Resistance: Stainless steel construction eliminates the risk of internal rust formation common in carbon steel alternatives, extending service life to 20–30 years in hydronic applications.
- Superior Thermal Efficiency: Precision-manufactured tube geometry and optimized fin spacing deliver a heat transfer coefficient (U-value) exceeding 40 W/(m²·K), reducing energy consumption by up to 15% compared to conventional designs.
- Low Maintenance Requirement: The passive oxide layer and smooth internal surface (Ra ≤ 0.8 μm) minimize scale deposition and fouling, reducing cleaning frequency and lifecycle costs.
- Customization Capability: Wenzhou Jixing offers fully customizable coil configurations — tube diameter, wall thickness, row count, fin density, and connection types — tailored to specific OEM requirements.
- Proven OEM Partnership: Established supplier to recognized FCU manufacturers, including the "Penguin Brand" fan coil air conditioning system, with a track record of consistent quality delivery.
- Comprehensive Quality Traceability: Each Coil Tube batch is traceable through unique lot numbering, with full material certification and test documentation available upon request.
Technical Note: For specific project requirements involving non-standard dimensions, exotic alloys (e.g., duplex stainless steel 2205), or specialized surface treatments, Wenzhou Jixing Metal Materials Co., Ltd. provides custom engineering solutions with full technical support from design through installation.