Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product No.: 1342 | Category: Stainless Steel Coil Tube (盘管)
Product Overview
The Wenzhou Jixing Metal Materials Co., Ltd. Stainless Steel Coil Tube (Product No. 1342) is a precision-engineered coiled tubular component designed specifically for integration into HVAC (Heating, Ventilation, and Air Conditioning) fan coil unit systems. This product represents a critical heat exchange element within air conditioning and ventilation infrastructure, particularly in commercial and institutional building environments including hotels, hospitals, office complexes, and industrial facilities.
Unlike conventional copper or carbon steel coil tubes, the stainless steel construction provides superior corrosion resistance, extended service life, and enhanced hygiene performance—attributes that are indispensable in applications demanding high standards of cleanliness and long-term reliability. The coil tube is manufactured in a continuous coiled configuration, enabling seamless installation into fan coil units where it serves as the primary medium for thermal energy transfer between circulating refrigerant (or hot water) and ambient air.
This product has been specifically analyzed and validated in the context of hotel fan coil unit fresh air treatment systems, where optimal coil tube performance directly impacts indoor air quality (IAQ), energy efficiency, and occupant comfort. The design accommodates the complex thermodynamic conditions encountered during fresh air processing, including dehumidification, heating, cooling, and filtration stages.
Material & Properties
Primary Material Composition
The coil tube is fabricated from austenitic stainless steel, with the primary grade being SAE 304 (UNS S30400) or SAE 316 (UNS S31600), selected based on the specific application environment and corrosion resistance requirements.
- SAE 304 Stainless Steel: Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni), offering excellent general-purpose corrosion resistance, weldability, and formability. Suitable for standard HVAC applications in moderate humidity environments.
- SAE 316 Stainless Steel: Contains approximately 16-18% Cr, 10-14% Ni, and 2-3% Molybdenum (Mo), providing enhanced resistance to pitting and crevice corrosion. Preferred for applications involving chlorinated water, marine environments, or chemically aggressive conditions.
Mechanical Properties
| Property | SAE 304 (Cold Worked) | SAE 316 (Cold Worked) | Test Standard |
|---|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa | ≥ 515 MPa | ASTM A213 / ASTM E8 |
| Yield Strength (0.2% Offset) | ≥ 205 MPa | ≥ 205 MPa | ASTM E8 |
| Elongation (50 mm gauge length) | ≥ 35% | ≥ 35% | ASTM E8 |
| Hardness (Brinell) | ≤ 201 HB | ≤ 201 HB | ASTM E10 |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | 16.3 W/(m·K) | ASTM E153 |
| Thermal Expansion Coefficient (20-100°C) | 17.3 × 10⁻⁶ /°C | 17.3 × 10⁻⁶ /°C | ASTM E228 |
Corrosion Resistance Characteristics
The austenitic stainless steel composition provides exceptional resistance to atmospheric corrosion, condensate corrosion (critical in dehumidification applications), and general waterborne corrosion. The passive chromium oxide layer (Cr₂O₃) forms spontaneously on the surface, providing a self-healing protective barrier. In the context of fan coil unit fresh air treatment systems, the coil tube is exposed to:
- Condensed moisture with dissolved atmospheric contaminants
- Humid fresh air streams with variable relative humidity (30-90% RH)
- Potential microbial growth on coil surfaces (mitigated by stainless steel's antimicrobial properties)
- Occasional exposure to cleaning agents and sanitizing chemicals
Surface Finish
The coil tube is supplied with a 2B (No. 4 Brushed) or BA (Bright Annealed) surface finish. The BA finish provides a superior smooth surface (Ra ≤ 0.4 μm) that minimizes fouling, facilitates cleaning, and reduces airflow resistance—critical parameters in fan coil unit heat exchanger performance. The surface finish also contributes to the tube's resistance to biofilm formation, an important consideration in hotel and healthcare HVAC systems where Legionella risk mitigation is paramount.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) | — |
| Product Number | 1342 | — |
| Material Grade | SAE 304 / SAE 316 (UNS S30400 / S31600) | ASTM A213, ASME SA-213 |
| Outer Diameter (OD) | Ø 6.0 mm / Ø 8.0 mm / Ø 10.0 mm / Ø 12.0 mm (customizable) | ± 0.1 mm tolerance |
| Wall Thickness | 0.3 mm / 0.4 mm / 0.5 mm / 0.6 mm / 0.8 mm | ± 10% tolerance |
| Coil Length | Standard: 5 m – 50 m per coil (custom lengths available) | — |
| Coil Outer Diameter | Ø 300 mm – Ø 600 mm | — |
| Coil Pitch (Turn Spacing) | 2.0 mm – 5.0 mm (adjustable per application) | — |
| Surface Finish | 2B / BA (Bright Annealed), Ra ≤ 0.4 μm | ASTM A480 |
| Operating Temperature Range | −40°C to +250°C | — |
| Maximum Operating Pressure | 1.6 MPa (232 psi) @ 200°C | ASME BPV Code |
| Working Fluid | Chilled water, hot water, refrigerant (R-410A, R-32, R-134a) | — |
| End Treatment | Cut ends with burr-free finishing; optional flaring, threading, or brazing preparation | — |
| Packaging | Wooden crate or steel drum; desiccant protected; moisture barrier wrapping | ISO 4180 |
Dimensional Tolerance Summary
| Dimension | Tolerance | Measurement Method |
|---|---|---|
| Outer Diameter | ± 0.10 mm | Micrometer / Optical comparator |
| Wall Thickness | ± 10% of nominal | Ultrasonic thickness gauge |
| Roundness | ≤ 0.05 mm | Roundness tester |
| Straightness (per meter) | ≤ 1.0 mm | Straightness gauge |
| Coil Diameter | ± 5.0 mm | Direct measurement |
Manufacturing Process
Process Flow Overview
- Raw Material Procurement & Inspection: Stainless steel strip or pipe stock is sourced from certified mill producers. Incoming material undergoes spectroscopic analysis (OES - Optical Emission Spectroscopy) to verify chemical composition compliance with ASTM A213 specifications. Each lot is accompanied by a Mill Test Certificate (MTC) conforming to EN 10204 Type 3.1.
- Coil Winding / Forming: The stainless steel tube is wound into the precise coil geometry using CNC-controlled coil winding equipment. The winding process maintains controlled tension and pitch to ensure uniform spacing between turns, critical for consistent heat transfer performance and fluid flow distribution in fan coil unit applications.
- Hydrostatic Pressure Testing: Each coil tube is subjected to hydrostatic pressure testing at 1.5 times the maximum design pressure (typically 2.4 MPa) for a minimum dwell time of 60 seconds to verify integrity and detect any manufacturing defects, including micro-porosity, seam imperfections, or wall thinning.
- Surface Cleaning & Passivation: Post-manufacturing cleaning involves acid pickling and passivation treatment (using nitric acid/citric acid solutions) to remove any surface contaminants, scale, or oxidation. This treatment enhances the natural chromium oxide passive layer, improving long-term corrosion resistance.
- Final Quality Inspection: Comprehensive dimensional verification, visual inspection, and surface finish assessment are performed. Non-destructive testing (NDT) methods including dye penetrant testing (PT) and magnetic particle inspection (MT, where applicable) may be employed for critical applications.
- Packaging & Shipping: Coils are individually wrapped in moisture-barrier material with desiccant packs, secured in export-grade wooden crates or steel drums, and labeled with product identification, material certification, and handling instructions per ISO 4180 standards.
Key Manufacturing Advantages
- Precision CNC Winding: Computer numerical control ensures repeatable coil geometry with minimal variation between production lots, guaranteeing consistent thermal performance in downstream fan coil unit assembly.
- Continuous Quality Monitoring: In-process inspection at each manufacturing stage enables real-time quality feedback and corrective action, minimizing defect propagation.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers flexible customization of tube diameter, wall thickness, coil length, pitch, and end treatments to meet specific OEM requirements for fan coil unit manufacturers.
Applications
Primary Application Domain: HVAC Fan Coil Unit Systems
The stainless steel coil tube is primarily designed for integration into fan coil units (FCUs)—compact, self-contained air handling devices that provide localized temperature control in commercial and institutional buildings. In hotel HVAC systems specifically, fan coil units with stainless steel coil tubes serve as the terminal conditioning devices in the fresh air treatment process, handling:
- Fresh Air Pre-treatment: Heating or cooling incoming outdoor air to achieve optimal indoor air quality and thermal comfort conditions
- Dehumidification: Condensing moisture from air streams during cooling operation, where stainless steel's corrosion resistance is critical due to persistent condensate exposure
- Reheat Operation: Precise temperature control through hot water or electric heating elements integrated with the coil tube
- Seasonal Mode Switching: Seamless transition between cooling and heating modes without degradation of coil tube performance
Specific Application Environments
| Application Sector | System Type | Key Performance Requirement |
|---|---|---|
| Hotels & Hospitality | Per-room FCU with fresh air intake | Low noise, high hygiene, corrosion resistance to condensate |
| Hospitals & Healthcare | Operating room ventilation, ICU air handling | Antimicrobial surface, easy-to-clean, no galvanic corrosion |
| Office Buildings | Chilled beam / FCU systems | Energy efficiency, long service life, minimal maintenance |
| Food Processing & Pharmaceutical | Process cooling, cleanroom HVAC | Food-grade stainless steel, CIP (Clean-in-Place) compatible |
| Marine & Coastal Facilities | Marine HVAC, coastal building ventilation | Chloride corrosion resistance (SAE 316 grade) |
| Data Centers | Precise temperature control systems | Reliability, thermal efficiency, long-term stability |
System Integration Notes
In fan coil unit fresh air treatment systems, the coil tube operates within a closed-loop hydronic circuit (chilled/hot water) or an open refrigerant circuit. The stainless steel material eliminates the risk of galvanic corrosion that occurs when dissimilar metals (e.g., copper coil tubes with aluminum fins) are exposed to conductive condensate. This material compatibility advantage extends the overall service life of the heat exchanger assembly and reduces maintenance frequency, particularly important in hotel applications where room-by-room FCU systems must operate reliably for 15-25 years with minimal intervention.
Quality Certifications
Product Certifications
- ISO 9001:2015 — Quality Management System certification covering the full manufacturing process from raw material procurement through final inspection and delivery
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to environmentally responsible manufacturing practices
- ASME SA-213 — Compliance with American Society of Mechanical Engineers standard for seamless austenitic stainless steel boiler, heat-exchanger, and heat-tube tubing
- ASTM A213 — Conformity with ASTM International standard specifications