Stainless Steel Coil Tube for Fan Coil Unit (FCU) Applications
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchanger component designed primarily for use in Fan Coil Units (FCUs) within central air conditioning (CAC) terminal systems. This product represents a critical element in the thermal exchange mechanism of modern HVAC (Heating, Ventilation, and Air Conditioning) infrastructure. The coil tube is formed into a serpentine or spiral configuration to maximize surface area contact with air streams, enabling efficient heat transfer between the refrigerant or hot water circulating within the tube and the ambient air passing over its exterior.
Designed to meet the rigorous demands of commercial, industrial, and residential climate control systems, this coil tube integrates seamlessly with intelligent controller systems for Fan Coil Unit terminals, enabling precise temperature regulation, energy optimization, and automated operational control. The product embodies the convergence of metallurgical engineering excellence and modern building automation technology.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and long-term durability under cyclic thermal loading conditions.
- Base Alloy: Austenitic stainless steel conforming to ASTM A269 / A213 specifications, typically Grade 304 (UNS S30400) or Grade 316 (UNS S31600) depending on the application environment
- Corrosion Resistance: Superior resistance to oxidation, condensation water, and chemical attack from refrigerants or water treatment additives, critical for long-term operation in humid HVAC environments
- Thermal Conductivity: Approximately 16.3 W/(m·K) for Grade 304, providing reliable heat transfer performance while maintaining structural integrity
- Mechanical Properties: Tensile strength ≥ 515 MPa, yield strength ≥ 205 MPa, elongation ≥ 40% (annealed condition)
- Temperature Range: Operational capability from −196°C to +870°C, with sustained HVAC operating range of −40°C to +120°C
- Surface Finish: Mill finish or electropolished interior to minimize flow resistance and prevent biofilm accumulation
- Hygienic Grade Option: Available in Ra ≤ 0.5 μm finish for pharmaceutical and food-grade HVAC applications
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.52 mm (3/8"), 12.70 mm (1/2"), 15.88 mm (5/8"), 19.05 mm (3/4") | ASTM A269 |
| Wall Thickness | 0.50 mm – 1.50 mm (customizable) | ISO 3506 |
| Bend Radius | ≥ 3D (three times the outer diameter) | Internal Specification |
| Coil Pitch (Row Spacing) | 15 mm – 50 mm (adjustable per design) | ASHRAE 15 |
| Row Configuration | 1-row to 6-row serpentine layout | ASHRAE Guideline 36 |
| Maximum Operating Pressure | 1.6 MPa (standard), 2.5 MPa (reinforced) | ASME B31.5 |
| Maximum Flow Velocity | ≤ 3.0 m/s (water), ≤ 25 m/s (refrigerant) | Internal Specification |
| Heat Transfer Coefficient (U-value) | 250 – 450 W/(m²·K) depending on configuration | ASHRAE Handbook |
| Tolerance (OD) | ±0.05 mm | ASTM A269 |
| Tolerance (Wall Thickness) | ±10% of nominal | ASTM A269 |
| End Treatment | Cut square, beveled, or flanged (per customer requirement) | — |
| Standard Length (Straight) | 2,000 mm – 6,000 mm (pre-coiling) | — |
| Coil Length (Formed) | Custom per FCU design, typically 2.0 m – 12.0 m per pass | — |
| Available Grades | 304, 304L, 316, 316L, 321, 310S | ASTM / EN |
Manufacturing Process
The production of the stainless steel coil tube follows a tightly controlled multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and thermal performance:
- Raw Material Procurement: Selection of certified stainless steel seamless or welded tube from qualified mills, with full material traceability through Heat Number documentation and Mill Test Reports (MTR).
- Incoming Inspection: Verification of chemical composition via X-ray fluorescence (XRF) spectrometry, dimensional measurement, and visual surface inspection per ASTM E162 (visual examination) and ASTM A923 (chemical analysis).
- Cutting & Preparation: Precision sawing to required lengths with burr removal and end-face deburring to ensure leak-free brazing or welding connections.
- Forming & Coiling: Cold bending using CNC-controlled rotary draw bending machines to form the serpentine coil pattern. The bend radius is maintained at ≥ 3D to prevent wall thinning, ovalization, or work-hardening-induced cracking.
- Heat Treatment (if required): Solution annealing at 1050°C – 1150°C followed by water quenching for grades requiring full austenitic restoration after cold working.
- Internal Cleaning: High-pressure water jet or chemical pickling to remove oxide scale, lubricants, and particulate contaminants from the tube interior.
- Fin Attachment (optional): Integration of aluminum or stainless steel fins via roll-bonding or brazing to enhance external heat transfer surface area.
- Pressure Testing: Hydrostatic or pneumatic testing at 1.5× the maximum operating pressure for a minimum of 30 seconds to verify leak tightness.
- Final Inspection & Packaging: Dimensional verification, surface quality assessment, and protective packaging with desiccant for moisture-sensitive applications.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. finds extensive application across multiple sectors where reliable thermal exchange and corrosion resistance are paramount:
- Central Air Conditioning Terminal Units: Primary application in Fan Coil Units (FCUs) for commercial buildings, hotels, hospitals, and office complexes, serving as the core heat exchange element for heating and cooling air distribution.
- Intelligent HVAC Control Systems: Integration with smart controllers and IoT-enabled sensors for real-time monitoring of flow rate, temperature differentials, and energy consumption in building management systems (BMS).
- Commercial Refrigeration: Evaporator and condenser coil tubes in walk-in coolers, freezers, and display cases requiring hygienic-grade stainless steel construction.
- Industrial Process Cooling: Heat exchangers in chemical processing, pharmaceutical manufacturing, and food and beverage production lines where product purity and corrosion resistance are critical.
- Marine & Offshore HVAC: Air conditioning systems in shipping vessels and offshore platforms where saltwater corrosion resistance (Grade 316/316L) is essential.
- Residential High-End HVAC: Premium split-system air handlers and mini-split indoor units requiring silent operation, compact coil configurations, and long service life.
- Clean Room & Laboratory HVAC: Temperature and humidity control systems in semiconductor fabrication, biotechnology, and pharmaceutical clean rooms requiring ultra-low particulate emission.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring compliance with international standards and regulatory requirements:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and process control
- ISO 14001:2015 — Environmental Management System for sustainable manufacturing practices
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 — Material test documentation (Type 2.1 and 3.1 certificates available)
- CE Marking — Conformity with European standards for pressure equipment and HVAC components
- PED 2014/68/EU — Pressure Equipment Directive compliance for components operating above specified pressure thresholds
- NSF/ANSI 61 — Drinking water system components certification (for potable water HVAC systems)
- UL / cUL — Underwriters Laboratories safety certification for electrical and thermal safety in HVAC assemblies
- RoHS & REACH Compliance — Restriction of hazardous substances and chemical safety regulations for global market access
Unique Selling Points
1. Intelligent Integration Capability: The coil tube design accommodates seamless integration with intelligent controller systems for Fan Coil Unit terminals, enabling advanced features such as adaptive temperature modulation, predictive maintenance alerts, and energy consumption optimization through embedded sensor compatibility.
2. Precision Engineering: CNC-controlled forming ensures consistent bend geometry, uniform wall thickness distribution, and minimal ovalization (≤ 2% of nominal OD), resulting in predictable and repeatable thermal performance across production batches.
3. Extended Service Life: The selection of austenitic stainless steel grades with full solution-annealed microstructure provides exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC), ensuring design life exceeding 25 years in typical HVAC duty cycles.
4. Customization Flexibility: Full customization capability including tube diameter, wall thickness, coil geometry, row configuration, and fin arrangement to match specific thermal load calculations and equipment envelope constraints.
5. Complete Traceability: Each production lot is traceable through unique Heat Numbers, batch codes, and digital documentation, supporting regulatory compliance and quality assurance requirements in regulated industries.
Conclusion
The Stainless Steel Coil Tube (Coiltube) from Wenzhou Jixing Metal Materials Co., Ltd. represents a synergistic fusion of metallurgical expertise and modern HVAC engineering. By leveraging high-performance austenitic stainless steel alloys, precision manufacturing processes, and intelligent system integration capabilities, this product delivers superior thermal exchange efficiency, long-term operational reliability, and energy consumption optimization for central air conditioning terminal applications. The product is particularly suited for installations requiring intelligent control integration, where real-time monitoring and adaptive performance management contribute to reduced energy costs and enhanced occupant comfort.