Stainless Steel Coil Tube for High-Speed Fan Coil Unit Manufacturing
Product Overview
The stainless steel coil tube (Coiltube) supplied by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for the manufacturing of fan coil units (FCUs) in the HVAC (Heating, Ventilation, and Air Conditioning) industry. These coil tubes serve as the critical heat exchange elements within fan coil systems, enabling efficient thermal transfer between refrigerant and air streams. The product has been optimized to support an industry-leading production cycle time of 20 seconds per fan coil unit, representing a significant advancement in manufacturing efficiency and throughput.
This product falls under the category of continuous coil-form stainless steel tubing, delivered in rolled coil configurations that enable high-speed automated forming, cutting, and assembly operations. The coil tube geometry is pre-shaped to minimize secondary processing, reducing material waste and manufacturing lead times while maintaining dimensional accuracy and mechanical integrity.
Material & Properties
Material Grades
Wenzhou Jixing Metal Materials Co., Ltd. supplies coil tubes in multiple austenitic stainless steel grades, with the following primary specifications:
- Grade 304 (UNS S30400): General-purpose grade offering excellent corrosion resistance, weldability, and formability. Suitable for standard HVAC applications in non-aggressive environments.
- Grade 316 (UNS S31600): Enhanced corrosion resistance due to molybdenum addition (2.0–3.0%), ideal for coastal or chemically aggressive environments.
- Grade 316L (UNS S31603): Low-carbon variant of Grade 316, providing superior resistance to intergranular corrosion following welding operations.
Mechanical Properties
| Property | Grade 304 | Grade 316 | Grade 316L |
|---|---|---|---|
| Tensile Strength (MPa) | ≥520 | ≥515 | ≥485 |
| Yield Strength (MPa) | ≥205 | ≥170 | ≥170 |
| Elongation (%) | ≥40 | ≥40 | ≥45 |
| Density (g/cm³) | 8.00 | 8.03 | 8.03 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 14.6 | 14.6 |
Chemical Composition (Typical, wt%)
| Element | Grade 304 | Grade 316 |
|---|---|---|
| Carbon (C) | ≤0.08 | ≤0.08 |
| Chromium (Cr) | 18.0–20.0 | 16.0–18.0 |
| Nickel (Ni) | 8.0–10.5 | 10.0–14.0 |
| Molybdenum (Mo) | — | 2.0–3.0 |
| Manganese (Mn) | ≤2.0 | ≤2.0 |
| Silicon (Si) | ≤1.0 | ≤1.0 |
| Sulfur (S) | ≤0.03 | ≤0.03 |
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube), Item No. 279 |
| Outer Diameter (OD) | 6.0 mm – 12.7 mm (customizable) |
| Wall Thickness | 0.4 mm – 1.2 mm |
| Coil Width (Forming Width) | 15 mm – 50 mm (pre-formed serpentine) |
| Coil Length | Up to 500 m per coil (continuous) |
| Surface Finish | No. 2B, BA (Bright Annealed), or Electropolished |
| Surface Roughness (Ra) | ≤0.4 μm (electropolished); ≤1.6 μm (2B finish) |
| Tolerance – OD | ±0.05 mm |
| Tolerance – Wall Thickness | ±0.03 mm |
| Operating Temperature Range | −40°C to +250°C |
| Maximum Operating Pressure | 2.5 MPa (25 bar) |
| Manufacturing Standard | ASTM A269 / ASTM A312 / EN 10217-7 |
| Production Cycle Time (FCU Assembly) | 20 seconds per unit |
| Delivery Form | Continuous coil, pre-formed serpentine or straight tube |
| Supplier | Wenzhou Jixing Metal Materials Co., Ltd. |
Manufacturing Process
Tube Production
The coil tube manufacturing process at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage production sequence:
- Strip Preparation: Cold-rolled stainless steel strip is inspected for surface quality, dimensional accuracy, and mechanical properties prior to tube forming.
- Seamless/Precision Tube Forming: High-speed automatic tube mills (slit-and-roll or seamless piercing methods) produce the base tubing with tight dimensional tolerances.
- Continuous Annealing: Tubes pass through a continuous annealing furnace (CAF) to achieve the required soft condition, relieve residual stresses, and restore full mechanical properties after cold working.
- Pickling & Passivation: The annealed tubes undergo acid pickling to remove scale, followed by passivation treatment to restore the passive chromium oxide film, ensuring optimal corrosion resistance.
- Surface Finishing: Depending on the specification, tubes receive a 2B finish, BA (Bright Annealed) treatment, or electropolishing to achieve the target surface roughness.
- Coil Winding: Finished tubes are wound onto precision coils with controlled tension to prevent deformation during storage and transportation.
Serpentine Forming for Fan Coil Units
The pre-formed serpentine coil tube is produced through a high-speed automated forming process:
- Continuous uncoiling of the base tube from the coil stock.
- High-precision CNC bending stations form the serpentine geometry with uniform bend radii (typically 1.5× to 2.0× OD) to prevent wall thinning and maintain structural integrity.
- Inline laser or plasma cutting trims coils to exact lengths required for each fan coil unit assembly.
- Automated inspection stations verify bend dimensions, tube straightness, and overall geometry via laser scanning or vision systems.
- Finished coils are bundled, labeled, and packaged for shipment to FCU assembly lines.
The 20-Second Fan Coil Unit Production Cycle
The integration of pre-formed stainless steel coil tubes with automated assembly systems enables a revolutionary 20-second cycle time for complete fan coil unit production. This achievement relies on:
- Pre-formed serpentine geometry eliminating manual bending operations.
- Precision dimensional tolerances ensuring plug-and-play assembly compatibility.
- Consistent material properties enabling reliable robotic brazing or welding without process adjustments.
- Optimized coil unwinding and cutting systems synchronized with downstream assembly stations.
- Minimal secondary processing due to high initial product quality and surface finish.
This 20-second cycle time represents a 60–80% reduction in manufacturing time compared to conventional fan coil unit production methods, translating to substantial improvements in factory throughput, labor efficiency, and cost competitiveness.
Applications
Primary Applications
- Commercial HVAC Systems: Fan coil units for office buildings, hotels, hospitals, and shopping centers.
- Residential Climate Control: Concealed ceiling-mounted FCUs for high-end residential projects.
- Industrial Process Cooling: Precision temperature control in manufacturing facilities.
- Chiller Plant Heat Exchangers: Coil tubes as secondary-side heat exchange elements.
Secondary Applications
- Automotive Air Conditioning: Condenser and evaporator coil tubes.
- Refrigeration Systems: Evaporator and condenser coils for commercial refrigeration equipment.
- Heat Recovery Systems: Energy recovery ventilators (ERV) and heat exchangers.
- Marine HVAC: Corrosion-resistant coil tubes for marine air conditioning (Grade 316/316L).
Quality Certifications & Standards
Applicable Standards
- ASTM A269/A269M: Standard Specification for Seamless and Wrought Stainless Steel Tubing for Chemical and Similar Severe Service Applications.
- ASTM A312/A312M: Standard Specification for Seamless, Wrought Steel Pipe and Tube, Austenitic and Ferritic-Austenitic Cr-Ni Stainless Steel.
- EN 10217-7: Technical delivery conditions for stainless steel tubes for particular purposes – Part 7: Seamless and welded austenitic tubes for heat exchangers.
- GB/T 14976: Chinese national standard for cold-rolled stainless steel seamless tubes for fluid transport.
- GB/T 13296: Chinese national standard for seamless stainless steel tubes for heat exchangers.
Quality Assurance Measures
- Incoming Material Inspection: 100% verification of raw strip certificates, chemical composition analysis (OES – Optical Emission Spectroscopy), and mechanical property testing.
- In-Process Control: Continuous monitoring of tube dimensions, surface quality, and bend geometry via automated gauging and vision systems.
- Non-Destructive Testing (NDT): Eddy current testing (ECT) for wall thickness verification and surface defect detection; hydrostatic pressure testing at 1.5× maximum operating pressure.
- Final Inspection: Dimensional verification, surface roughness measurement, corrosion resistance testing (salt spray per ASTM B117), and intergranular corrosion testing per ASTM A262 Practice E.
- Traceability: Full batch traceability from raw material mill certificate through final product shipment, enabling complete supply chain accountability.
Certifications
- ISO 9001:2015 – Quality Management System
- ISO 14001:2015 – Environmental Management System
- ISO 45001:2018 – Occupational Health and Safety Management System
- Mill Test Certificates (MTC) per EN 10204 Type 3.1
- Material Certificates compliant with PED 2014/68/EU (Pressure Equipment Directive)
Unique Selling Points
- Industry-Leading 20-Second Production Cycle: The pre-formed coil tube geometry enables fan coil unit assembly in just 20 seconds, representing the fastest known cycle time in the industry and delivering unprecedented manufacturing productivity.
- Precision Engineering: Tight tolerances (±0.03 mm wall thickness, ±0.05 mm OD) ensure reliable automated assembly without manual adjustments or rework.
- Superior Surface Quality: Electropolished finishes with Ra ≤ 0.4 μm provide enhanced heat transfer efficiency, reduced fouling, and extended service life in HVAC applications.
- Continuous Coil Delivery: Eliminates tube-to-tube joints, reducing leak points and improving overall system reliability.
- Comprehensive Material Options: Multiple stainless steel grades accommodate diverse environmental conditions from standard indoor applications to aggressive marine environments.
- Full Traceability & Certification: Complete quality documentation from raw material through finished product, meeting the most stringent international regulatory requirements.
Summary
The stainless steel coil tube (Coiltube, Item No. 279) from Wenzhou Jixing Metal Materials Co., Ltd. represents a state-of-the-art product solution for high-volume fan coil unit manufacturing. By delivering pre-formed, precision-engineered tubular elements with exceptional material properties and surface quality, this product enables OEM manufacturers to achieve a remarkable 20-second production cycle time per unit. The combination of dimensional accuracy, mechanical reliability, corrosion resistance, and comprehensive quality certification makes this coil tube an ideal choice for manufacturers seeking to optimize production efficiency while maintaining the highest standards of product quality and performance in the global HVAC industry.