Stainless Steel Coil Tube (Coiltube) — Fan Coil Unit Application Grade
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product No.: 504
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product designed primarily for use in Fan Coil Units (FCU), air handling systems, and heat exchanger assemblies within commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications. This product is supplied in continuous coil form, enabling efficient downstream processing through automated forming, cutting, and welding lines.
The coil tube is engineered to withstand the thermodynamic and fluid-dynamic demands of cooling and heating cycles, maintaining structural integrity and thermal conductivity under variable cold load conditions typical of summer operation scenarios. The product is manufactured to meet the stringent requirements outlined in national and international standards governing stainless steel seamless and welded tubing.
Material & Properties
Material Grades
- 304 (UNS S30400): Austenitic stainless steel with excellent corrosion resistance and formability; the standard grade for general HVAC applications.
- 316L (UNS S31603): Low-carbon austenitic stainless steel with added molybdenum for enhanced resistance to chlorides and aggressive environments.
- 321 (UNS S32100): Stabilized austenitic grade suitable for elevated-temperature service conditions.
Mechanical & Physical Properties
| Property | Grade 304 | Grade 316L | Grade 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 485 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Thermal Conductivity (W/m·K, 20°C) | 16.3 | 14.6 | 16.3 |
| Operating Temperature Range (°C) | −196 to +870 | −196 to +870 | −196 to +900 |
| Corrosion Resistance | Excellent (general) | Superior (chloride-rich) | Excellent (high-temp oxidation) |
Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (customizable) | ± 0.1 mm |
| Wall Thickness (WT) | 0.5 mm – 2.0 mm | ± 10% of nominal |
| Coil Inner Diameter (ID) | 300 mm – 600 mm | ± 10 mm |
| Coil Length per Spool | 50 m – 500 m (standard); up to 1000 m on request | — |
| Surface Finish | No. 1 (hot-rolled), 2B (cold-rolled & annealed), BA (Bright Annealed) | — |
| Surface Roughness (Ra) | ≤ 0.8 μm (BA finish) | — |
| Winding Direction | Right-hand or left-hand (as specified) | — |
| End Condition | Plain cut, beveled, or formed to drawing | — |
| Applicable Standards | GB/T 12771, ASTM A269, ASTM A213, EN 10216-5 | — |
Manufacturing Process
- Raw Material Inspection: Incoming stainless steel strip or billet is verified for chemical composition (via Spectrometer Analysis) and mechanical properties before processing.
- Coil Forming (Tube Milling): Continuous strip is fed through a series of progressive roll stands to form the desired circular cross-section. The coil tube is produced via cold-rolled coil tubing technology for tight dimensional tolerances, or via seamless piercing for larger diameters.
- Welding (if applicable): For welded coil tubes, high-frequency resistance welding (HFRW) or TIG (Tungsten Inert Gas) welding is employed to ensure leak-tight, metallurgically sound seams.
- Annealing & Pickling: The formed tube is subjected to controlled-temperature annealing to relieve residual stresses and restore ductility. Subsequent acid pickling removes oxide scale, yielding a clean, corrosion-resistant surface.
- Surface Finishing: Depending on the specified grade, the tube may undergo mechanical polishing, electrolytic polishing, or bright annealing in a controlled-atmosphere furnace to achieve the required surface quality.
- Coil Winding: The finished tube is wound onto a steel or wooden coil core using automated winding equipment that maintains uniform tension to prevent deformation or kinking.
- Quality Control & Testing: Each coil undergoes dimensional verification (OD, WT via ultrasonic measurement), hydrostatic pressure testing (typically at 1.5× working pressure for ≥ 30 seconds), and visual inspection of the weld seam and surface finish.
- Packaging & Dispatch: Coils are wrapped in moisture-proof film, secured with steel strapping, and labeled with material certificates and traceability markings prior to shipment.
Applications
Primary Application: Fan Coil Units (FCU)
The stainless steel coil tube is the core heat transfer component in fan coil units. Based on performance analysis under varying cooling load conditions during summer operation, the coil tube's geometry, wall thickness, and material grade directly influence:
- Air Supply Temperature: Determined by the heat exchange efficiency between the refrigerant/water circulating through the tube and the ambient air drawn across the coil surface by the fan.
- Air Velocity & Throw: The coil's aerodynamic profile affects the comfort parameters of the supply air, including velocity distribution and turbulence intensity.
- Comfort Performance: Under different cooling loads (from part-load to full-load conditions), the coil tube must maintain stable thermal performance to ensure consistent indoor comfort levels.
Additional Applications
- Air Handling Units (AHU): Cooling coils, heating coils, and evaporator assemblies in commercial HVAC systems.
- Refrigeration & Cryogenic Systems: Evaporators and condensers requiring high thermal conductivity and low-temperature ductility.
- Food & Pharmaceutical Processing: Sanitary-grade heat exchangers and fluid transfer lines where corrosion resistance and cleanability are critical.
- Automotive Radiators & Intercoolers: Lightweight, high-strength tubing for thermal management systems.
- Medical Equipment: Fluid lines and heat exchangers in diagnostic and therapeutic devices.
- Domestic Appliances: Water heaters, air conditioners, and heat pump units.
Quality Certifications & Compliance
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control. |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices. |
| GB/T 12771 | Chinese national standard for stainless steel seamless and welded tubes for general application. |
| ASTM A269 / A213 | Standard specifications for austenitic stainless steel seamless and welded tubing. |
| EN 10216-5 | European standard for austenitic stainless steel tubes for pressure purposes. |
| Mill Test Certificate (MTC) | Provided with each shipment, including chemical analysis, mechanical test results, and heat traceability. |
| CE Marking | Conformity with European machinery and pressure equipment directives where applicable. |
Unique Selling Points
- Precision Dimensional Control: Tight tolerances on OD and wall thickness ensure optimal fit and performance in fan coil unit assemblies, reducing assembly waste and improving heat transfer efficiency.
- Superior Corrosion Resistance: 316L grade options provide exceptional durability in humid, high-chloride, and chemically aggressive environments commonly encountered in HVAC condensate systems.
- High Thermal Conductivity: Maintains efficient heat exchange under variable cooling loads, directly contributing to improved indoor air comfort parameters as documented in seasonal performance studies.
- Full Traceability: Every coil is accompanied by a comprehensive Mill Test Certificate with heat number traceability, enabling complete quality chain verification.
- Customization Capability: Flexible production parameters (OD, WT, coil length, surface finish) accommodate diverse OEM specifications and project-specific requirements.
- Seamless & Welded Options: Both seamless and high-frequency welded coil tubes are available, offering customers the optimal balance of cost, strength, and leak resistance for their specific application.
Note: Wenzhou Jixing Metal Materials Co., Ltd. maintains a rigorous quality assurance framework encompassing incoming material inspection, in-process monitoring, and final product verification. Technical data sheets and sample testing are available upon request for qualified procurement and engineering inquiries.