Stainless Steel Coil Tube (Coiltube) — HVAC Fan Coil Unit Application Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed primarily for use in Fan Coil Units (FCUs) and other HVAC (Heating, Ventilation, and Air Conditioning) systems. Unlike straight seamless or welded pipes, coil tubes are supplied in continuous coiled form, which significantly reduces fabrication waste, minimizes thermal stress from bending operations, and enhances manufacturing efficiency in heat exchanger assembly lines.
This product category is particularly associated with advanced control technologies such as Fuzzy Control Technology applied in fan coil air conditioners. The integration of fuzzy logic controllers with high-performance stainless steel coil tubes enables precise modulation of air temperature, humidity, and airflow rates, resulting in superior thermal comfort and energy efficiency in commercial and residential buildings.
Material & Properties
Wenzhou Jixing Metal Materials Co., Ltd. produces coil tubes from premium austenitic and duplex stainless steel grades, selected specifically for their corrosion resistance, formability, and thermal conductivity characteristics essential in HVAC applications.
Available Grades
- 304 / SUS304 (UNS S30400) — General-purpose austenitic grade with excellent corrosion resistance and weldability
- 316 / SUS316 (UNS S31600) — Enhanced molybdenum-bearing grade for aggressive chemical environments
- 316L / SUS316L (UNS S31603) — Low-carbon variant for superior post-welding corrosion resistance
- 321 / SUS321 (UNS S32100) — Titanium-stabilized grade for elevated temperature service
- Duplex 2205 (UNS S32205) — High-strength duplex grade for demanding pressure and corrosion applications
Key Mechanical Properties (Grade 304, Annealed Condition)
- Tensile Strength (抗拉强度): ≥ 515 MPa (75 ksi)
- Yield Strength (屈服强度): ≥ 205 MPa (30 ksi)
- Elongation (伸长率): ≥ 40%
- Hardness (硬度): ≤ 92 HRB (Rockwell B Scale)
- Density (密度): 8.0 g/cm³
- Thermal Conductivity (热导率): 16.3 W/(m·K) at 300 K
- Specific Heat (比热容): 0.50 J/(g·K) at 300 K
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 32.0 mm | ASTM A269 / EN 10217-7 |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm | ASTM A269 / EN 10217-7 |
| Coil Inner Diameter (CID) | 300 mm – 1,000 mm | Manufacturer Specification |
| Coil Length per Piece | 100 m – 500 m (continuous coil) | Manufacturer Specification |
| OD Tolerance | ±0.05 mm (for OD ≤ 12.7 mm); ±0.10 mm (for OD > 12.7 mm) | ASTM A269 |
| Wall Thickness Tolerance | ±10% of nominal (minimum ±0.05 mm) | ASTM A269 |
| Roundness (椭圆度) | ≤ 1% of OD | EN 10217-7 |
| Surface Finish | Mirror polish (Ra ≤ 0.4 μm), Hairline, or Industrial grade | ASTM A269 |
| End Condition | Plain, Beveled, or Threaded | Customer Specification |
| Heat Treatment | Solution Annealed and Pickled | ASTM A269 |
| Maximum Operating Temperature | 870 °C (Grade 304); 870 °C (Grade 316) | ASME Boiler & Pressure Vessel Code |
| Minimum Operating Temperature | −196 °C (cryogenic capable) | ASME Section VIII |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a multi-stage manufacturing process that ensures dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Inspection — Ingot or strip material is verified for chemical composition (via Spark Optical Emission Spectroscopy, OES) and mechanical properties prior to processing.
- Hot Rolling / Cold Rolling — Steel strip is cold-rolled to precise thickness tolerances on multi-stand mills with integrated tension control.
- Coil Slitting & Edge Trimming — Wide strip is slit to exact width specifications for the target tube OD, with burr-free edge preparation.
- Forming & Welding — The strip is formed into a circular cross-section and welded using Argon Arc Welding (TIG) or Laser Welding technology with 100% inert gas backing to prevent internal oxidation.
- Coiling — The continuous welded tube is wound into coils using precision coiling equipment that maintains uniform tension to prevent deformation.
- Solution Annealing & Pickling — Coils undergo solution heat treatment (typically 1050–1150 °C) followed by acid pickling to remove scale, restore corrosion resistance, and achieve the required mechanical properties.
- Hydrostatic Testing — Each coil is subjected to hydrostatic pressure testing to verify weld integrity and wall thickness uniformity.
- Surface Finishing — Optional polishing, passivation, or electropolishing is applied based on customer requirements for specific surface roughness and corrosion performance.
- Final Inspection & Packaging — Dimensional verification, surface inspection, and material certification are completed before protective packaging and shipment.
Applications
The coil tube format offers significant advantages in HVAC manufacturing, particularly in Fan Coil Unit (FCU) production, where it is used for:
- Heat Exchanger Coils — S-shaped or serpentine coil arrangements for air-cooled and water-cooled heat exchangers in commercial FCUs
- Fan Coil Air Conditioners — Integration with Fuzzy Control Technology systems for intelligent temperature and humidity regulation in office buildings, hospitals, and hotels
- Chilled Water & Heating Circuits — Distribution piping in radiant floor heating and cooling systems
- Refrigeration Systems — Condenser and evaporator tubing in industrial and commercial refrigeration units
- Process Cooling — Heat transfer applications in food processing, pharmaceutical manufacturing, and electronics cooling
- Water Treatment & Desalination — Corrosion-resistant tubing in brackish water and seawater applications
Advantages of Coil Tube in Fan Coil Unit Design
The use of pre-coiled stainless steel tubing in FCU manufacturing eliminates the need for on-site bending operations, which reduces manufacturing time by up to 40%, minimizes work-hardening and residual stress in the tube walls, and ensures consistent tube geometry throughout the heat exchanger circuit. When combined with fuzzy control algorithms for variable-speed fan and valve actuation, the system achieves optimal coefficient of performance (COP) with minimal energy consumption.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and holds the following certifications to ensure product reliability and international compliance:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 3.1 Certificate — Third-party material test certification for each production batch
- ASTM Compliance — Full compliance with ASTM A269/A269M for welded austenitic stainless steel tubes
- CE Marking — Conformity with European Union directives for pressure equipment and building services
- Mill Test Reports (MTR) — Provided with every shipment including chemical analysis, mechanical test data, and dimensional inspection records
Unique Selling Points
- Continuous Coil Supply — Reduces fabrication waste by up to 15% compared to straight pipe stock, offering significant cost savings for large-scale FCU production
- Precision Dimensional Control — Tight tolerances on OD and wall thickness ensure reliable fitting of fin tubes and consistent heat transfer performance
- Superior Surface Quality — Smooth internal and external surfaces minimize flow resistance and prevent fouling, extending heat exchanger service life
- Excellent Weldability — Solution-annealed condition ensures reliable TIG and laser welding during heat exchanger assembly without sensitization concerns
- Long-Service Life — Austenitic stainless steel grades provide decades of corrosion-free operation in water-based HVAC systems
- Customizable Specifications — Flexible manufacturing capability for non-standard OD, WT, coil dimensions, and surface finishes tailored to specific OEM requirements
For detailed technical data sheets, material certifications, and quotation inquiries, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Custom engineering support is available for specialized HVAC and heat exchanger applications.