Stainless Steel Coil Tube for Fan Coil Unit Applications
Product Code: 514 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Classification: Literature Study & Technical Reference
Product Overview
The Stainless Steel Coil Tube (盘管) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed primarily for integration into Fan Coil Units (FCU) and HVAC (Heating, Ventilation, and Air Conditioning) systems. This product is engineered to meet rigorous measurement accuracy requirements, particularly in the context of air volume and input power measurement uncertainty for fan coil unit assemblies.
As a critical heat-exchange element, the coil tube serves as the core thermal transfer medium within fan coil units, facilitating efficient energy exchange between the circulating refrigerant or hot water and the ambient air stream. The product is developed in alignment with simplified calculation methodologies for measurement uncertainty, ensuring that downstream system performance parameters—including airflow volume and electrical input power—can be determined with high confidence intervals.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical durability under cyclic thermal loading conditions.
- Primary Alloy: AISI 304 / 316L austenitic stainless steel, providing superior resistance to chlorides and acidic condensate formed during HVAC operation
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (AISI 304), ensuring efficient heat transfer across the coil surface
- Operating Temperature Range: −196°C to +870°C, accommodating both refrigerant and hot water service conditions
- Surface Finish: Electropolished to Ra ≤ 0.4 μm, minimizing fluid friction losses and reducing fouling potential
- Mechanical Strength: Yield strength ≥ 205 MPa; tensile strength ≥ 515 MPa (AISI 304 annealed condition)
- Non-Magnetic: Fully austenitic microstructure ensures non-magnetic properties essential for electromagnetic compatibility in FCU assemblies
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (盘管Coiltube) | Internal Product Code 514 |
| Material Grade | AISI 304 / 316L | ASTM A213 / A269 |
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (1/4" – 1") | ASME B36.19M |
| Wall Thickness | 0.5 mm – 2.0 mm | ASTM A269 Type 12 |
| Coil Pitch | 10 mm – 50 mm (adjustable) | Custom per application |
| Tube Length per Coil | 3 m – 50 m (configurable) | ASME B31.9 |
| Operating Pressure | Up to 2.5 MPa (362.6 psi) | ASME BPVC Section I |
| Corrosion Resistance | Potential Difference (PD) ≥ 400 mV in 3.5% NaCl | ASTM G102 |
| Measurement Uncertainty Class | Conforms to simplified uncertainty calculation for FCU air volume & input power | ISO/IEC Guide 98-3 (GUM) |
| Surface Treatment | Pickled & passivated / Electropolished | ASTM A967 |
Manufacturing Process
The production of the stainless steel coil tube follows a multi-stage precision manufacturing workflow designed to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Procurement: Cold-rolled stainless steel strip or seamless tube stock is sourced from certified mills, with full material traceability via heat-number documentation and chemical composition verification per ASTM E415 (spectroscopic analysis).
- Coil Forming: High-precision CNC coil winding machines form the tube into the required helical geometry. The winding process is controlled to maintain consistent coil pitch, concentricity (±0.5 mm), and tube surface integrity without inducing plastic deformation or work hardening.
- Welding (if applicable): Butt-welded joints between tube segments are performed using TIG (Tungsten Inert Gas) welding under argon shielding. Weld quality is verified through visual inspection and, where required, dye penetrant testing (DPT) per ASTM E165.
- Heat Treatment: Solution annealing at 1040°C–1120°C followed by rapid water quenching restores the full austenitic microstructure, eliminates welding-induced sensitization, and ensures uniform mechanical properties throughout the coil assembly.
- Pickling & Passivation: The coil tube is immersed in a mixed acid solution (nitric acid/hydrofluoric acid blend) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide layer per ASTM A967.
- Dimensional Inspection: Final quality control includes verification of outer diameter, wall thickness, coil pitch uniformity, and overall length using calibrated measuring instruments. Dimensional tolerance is maintained within ±0.05 mm per relevant standards.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is applicable across a broad spectrum of industries where reliable, corrosion-resistant heat exchange is paramount:
- HVAC Systems: Primary application in fan coil units (FCU) for commercial buildings, hospitals, and cleanrooms, where the coil tube functions as the heat exchanger core transferring thermal energy between air streams and circulating fluid.
- Refrigeration & Air Conditioning: Integration into evaporator and condenser coils for medium- and low-temperature refrigeration systems, leveraging the material's resistance to ammonia and refrigerant corrosion.
- Food Processing & Dairy Industry: Used in heat exchangers for pasteurization, sterilization, and refrigeration circuits where hygienic (food-grade) surfaces are mandated per FDA 21 CFR Part 117.
- Pharmaceutical Manufacturing: Deployed in cleanroom HVAC coils and process cooling systems requiring compliance with GMP (Good Manufacturing Practice) standards.
- Marine & Coastal Applications: Suitable for HVAC coils in offshore platforms and marine vessels due to superior resistance to saltwater and humid environments.
- Data Centers & Server Cooling: Employed in precision cooling units where long-term reliability and low maintenance are critical to uptime.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that every coil tube product meets international and domestic standards:
- ISO 9001:2015 — Quality Management System certification, ensuring consistent process control and continuous improvement
- ISO 14001:2015 — Environmental Management System, covering sustainable manufacturing practices and waste minimization
- ISO/IEC 17025 — Laboratory competence for in-house testing facilities, ensuring measurement traceability and uncertainty evaluation per ISO/IEC Guide 98-3 (GUM — Guide to the Expression of Uncertainty in Measurement)
- CE Marking — Conformity with European machinery and pressure equipment directives
- ASME Stamp (where applicable) — Certification for pressure-containing components manufactured to ASME Boiler and Pressure Vessel Code
- GB/T Standards Compliance — Adherence to Chinese national standards for stainless steel tubes (GB/T 12771, GB/T 21830) and HVAC components
Technical Note: The coil tube product is designed with measurement uncertainty considerations integrated into its manufacturing tolerances and dimensional specifications. This ensures that when the coil tube is installed as part of a fan coil unit assembly, the resulting air volume and input power measurements can be evaluated using simplified uncertainty calculation methodologies, achieving expanded uncertainty (k = 2) within acceptable limits for system performance validation.
Unique Selling Points
- Measurement-Aware Design: Unique integration of dimensional tolerance specifications aligned with simplified uncertainty calculation methods for fan coil unit performance parameters, enabling reliable downstream metrology.
- Premium Material Selection: Use of AISI 316L grade available upon request for enhanced pitting and crevice corrosion resistance in aggressive chemical environments.
- Custom Configurable Geometry: Flexible coil pitch, tube diameter, and length options allow tailoring to specific thermal load requirements of end-use applications.
- Full Traceability: Each production batch is accompanied by mill test certificates, dimensional inspection reports, and surface finish verification documentation.
- Extended Service Life: Corrosion resistance and fatigue durability ensure operational lifetimes exceeding 20 years in standard HVAC duty cycles, significantly reducing total cost of ownership.