Stainless Steel Coil Tube (盘管 / Coiltube) — Technical Product Specification
Product Code: 557 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Stainless Steel Pipe & Tube Products — Coil Tube Series
This technical specification provides a comprehensive academic-level description of the stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. The product is engineered to meet the rigorous demands of HVAC (Heating, Ventilation, and Air Conditioning), heat exchange, and industrial fluid transport applications, with particular emphasis on energy efficiency in fan coil unit (FCU) systems.
1. Product Overview
The stainless steel coil tube is a continuous, helically wound tubular product fabricated from austenitic stainless steel grades. Unlike straight-segment pipe, the coil tube is produced in a continuous spiral configuration, which eliminates the need for welding joints along the length of the tube. This seamless, joint-free architecture provides superior pressure containment, eliminates potential leak paths, and ensures uniform thermal conductivity across the entire coil assembly.
The coil tube is particularly critical in the construction of fan coil units (FCU), where it serves as the primary heat exchange medium. In fan coil unit environments, the coil tube facilitates efficient heat transfer between a circulating refrigerant (or hot water) and the ambient air drawn by the axial or centrifugal fan. The energy-saving performance of such systems is directly correlated to the geometric precision, surface finish, and material integrity of the coil tube used.
Based on academic research into energy-efficient fan coil unit systems, the coil tube's design parameters — including tube diameter, wall thickness, coil pitch, and bend radius — significantly influence the overall thermal efficiency (Coefficient of Performance, COP) of the air-conditioning system. Wenzhou Jixing Metal Materials Co., Ltd. produces coil tubes optimized for maximum heat transfer surface area while maintaining low hydraulic resistance.
2. Material & Properties
2.1 Material Grades
The coil tube is manufactured from the following austenitic stainless steel grades, each selected for specific application requirements:
- SUS304 / AISI 304 (UNS S30400): The most widely used grade, offering excellent general corrosion resistance, good formability, and weldability. Suitable for HVAC, food processing, and chemical applications.
- SUS316 / AISI 316 (UNS S31600): Enhanced pitting and crevice corrosion resistance due to 2–3% Molybdenum (Mo) content. Ideal for marine environments, chemical processing, and high-chloride applications.
- SUS321 / AISI 321 (UNS S32100): Titanium-stabilized grade with superior resistance to intergranular corrosion at elevated temperatures (450–850°C). Suitable for high-temperature heat exchange applications.
- SUS304L / AISI 304L (UNS S30403): Low-carbon variant of 304 with improved weldability and reduced sensitization risk. Preferred for welded coil assemblies.
2.2 Mechanical Properties
| Property | SUS304 | SUS316 | SUS321 |
|---|---|---|---|
| Tensile Strength (抗拉强度), MPa | ≥ 520 | ≥ 520 | ≥ 520 |
| Yield Strength (屈服强度), MPa (0.2% offset) | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (伸长率), % (min, 50 mm gauge) | ≥ 40 | ≥ 40 | ≥ 40 |
| Density (密度), g/cm³ | 8.0 | 8.0 | 8.0 |
| Thermal Conductivity (热导率), W/(m·K) at 100°C | 16.3 | 14.6 | 14.2 |
| Specific Heat (比热容), J/(kg·K) at 25°C | 500 | 500 | 500 |
2.3 Chemical Composition (wt%)
| Element | C (Carbon) | Si (Silicon) | Mn (Manganese) | P (Phosphorus) | S (Sulfur) | Cr (Chromium) | Ni (Nickel) | Mo (Molybdenum) | Ti (Titanium) |
|---|---|---|---|---|---|---|---|---|---|
| SUS304 | ≤ 0.08 | ≤ 1.00 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 18.0–20.0 | 8.0–11.0 | — | — |
| SUS316 | ≤ 0.08 | ≤ 1.00 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| SUS321 | ≤ 0.08 | ≤ 1.00 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 17.0–19.0 | 9.0–12.0 | — | 5 × (C × 5) |
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD, 外径) | Φ6.0 mm – Φ38.0 mm (custom sizes available) | ASTM A213 / EN 10216-5 |
| Wall Thickness (WT, 壁厚) | 0.3 mm – 2.0 mm | ASTM A213 / EN 10216-5 |
| Coil Pitch (盘管节距) | 8.0 mm – 50.0 mm (adjustable per application) | Manufacturer's Standard |
| Coil Diameter (盘管直径) | Φ100 mm – Φ600 mm (custom) | Manufacturer's Standard | Bend Radius (弯曲半径) | R ≥ 1.5 × OD (minimum) | ASTM A213 |
| Tube Length per Coil (单盘管长度) | 3 m – 200 m (continuous) | Manufacturer's Standard |
| Dimensional Tolerance (尺寸公差) | OD: ±0.1 mm; WT: ±0.05 mm | EN 10216-5 Class 2 |
| Surface Finish (表面光洁度) | Ra ≤ 0.8 μm (polished); Ra ≤ 1.6 μm (standard) | ASTM A270 |
3.2 Common Size Designations (for HVAC/FCU Applications)
| Model Designation | OD (mm) | WT (mm) | Typical Application |
|---|---|---|---|
| CT-6×0.5 | 6.0 | 0.5 | Compact FCU heat exchangers |
| CT-8×0.6 | 8.0 | 0.6 | Medium-duty FCU / Chiller coils |
| CT-10×0.7 | 10.0 | 0.7 | Industrial heat exchangers |
| CT-12×0.8 | 12.0 | 0.8 | Large-capacity FCU / Process cooling |
| CT-16×1.0 | 16.0 | 1.0 | High-pressure process coils |
| CT-19×1.2 | 19.0 | 1.2 | Heavy-duty industrial heat exchange |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Procurement (原材料采购): Cold-rolled stainless steel strip (冷带) of certified grade is sourced from approved mills. Incoming material undergoes spectroscopic analysis (光谱分析) to verify chemical composition compliance.
- Coil Winding & Forming (盘管成型): The cold-rolled strip is fed into a precision winding machine (精密绕管机) where it is helically wound around a mandrel (芯轴) at controlled tension. The winding parameters — including pitch, tension, and rotational speed — are precisely calibrated to ensure uniform geometry and prevent material distortion.
- Welding (焊接): For seamless coil tubes, the strip edges are joined via Automated TIG (Tungsten Inert Gas) Welding or Laser Welding (激光焊接) during the winding process. The weld seam is continuously monitored using inline optical inspection systems to detect porosity, lack of fusion, or undercut defects.
- Heat Treatment (热处理): The welded coil tube undergoes solution annealing (固溶退火) at 1010–1150°C followed by rapid quenching in water or air. This process dissolves carbide precipitates, restores full austenitic microstructure, and maximizes corrosion resistance.
- Pickling & Passivation (酸洗钝化): The annealed surface is cleaned via hydrochloric acid (HCl) or citric acid pickling to remove oxide scale. A subsequent passivation treatment with nitric acid (HNO₃) or citric acid forms a protective chromium oxide (Cr₂O₃) passive film on the surface.
- Surface Finishing (表面处理): Depending on application requirements, the coil tube may undergo electropolishing (电解抛光), mechanical polishing (机械抛光), or brushing (拉丝) to achieve the specified surface roughness (Ra值).
- Quality Inspection (质量检验): Final inspection includes dimensional verification (尺寸检测), hydrostatic pressure testing (水压试验), visual examination of weld seams (焊缝目视检验), and surface finish measurement (表面光洁度测量).
- Packaging & Shipping (包装发货): The coil tubes are packaged in moisture-proof wrapping with protective end caps to prevent mechanical damage and moisture-induced staining during transit.
4.2 Key Process Parameters
| Process Stage | Parameter | Typical Value |
|---|---|---|
| Solution Annealing (固溶退火) | Temperature / Duration | 1050–1120°C / 1–3 hours |
| TIG Welding (TIG焊接) | Current / Speed | 80–200 A / 30–100 mm/min |
| Hydrostatic Testing (水压试验) | Test Pressure / Duration | 1.5 × Design Pressure / 5 min hold |
| Coil Winding (盘管绕制) | Winding Tension | 50–200 N (size-dependent) |
5. Applications
5.1 HVAC & Fan Coil Unit Systems (暖通空调及风机盘管系统)
The primary application of the stainless steel coil tube is in the construction of heat exchangers for fan coil units (FCU). In these systems, the coil tube serves as the refrigerant-side heat exchange medium. Academic research on energy-efficient FCU systems has demonstrated that the geometric design of the coil tube — including tube diameter, coil pitch, and number of passes — directly influences the system's Coefficient of Performance (COP) and seasonal energy efficiency ratio (SEER).
In classroom and commercial building environments, demand-controlled ventilation (需求化新风) systems integrated with fan coil units rely on precisely manufactured coil tubes to maintain indoor air quality (IAQ) while minimizing energy consumption. The seamless construction of the coil tube eliminates micro-leakage pathways that could compromise refrigerant containment and system efficiency.
5.2 Additional Applications
- Industrial Heat Exchangers (工业热交换器): Shell-and-tube heat exchangers, plate-fin heat exchangers, and evaporator coils in chemical processing, pharmaceutical, and food processing industries.
- Refrigeration & Air Conditioning (制冷与空调): Evaporator and condenser coils in commercial refrigeration units, chiller plants, and rooftop HVAC units.
- Process Cooling Systems (工艺冷却系统): Cooling coils for injection molding machines, CNC machining centers, and industrial laser systems.
- Food & Beverage Industry (食品饮料行业): Heat exchange coils in pasteurization systems, brewing equipment, and dairy processing equipment (SUS316 grade for high hygiene requirements).
- Medical Equipment (医疗设备): Heat exchange coils in medical imaging systems (MRI, CT scanner cooling circuits) and sterilization equipment.
- Marine & Offshore (海洋与 offshore): Seawater cooling coils in marine HVAC systems and offshore platform cooling circuits (SUS316 grade for chloride resistance).