Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed into a continuous helical or serpentine coil configuration. Designed for demanding thermal exchange and fluid transport applications, this product line integrates the inherent corrosion resistance of austenitic stainless steel with optimized coil geometry to maximize heat transfer surface area within compact installation footprints. The product is particularly suited for integration into fan coil units (Fan Coil Units, FCUs), where variable operating conditions require reliable performance across a wide range of thermal loads and ambient parameters.
Coiltube products from Wenzhou Jixing Metal Materials Co., Ltd. are available in multiple coil configurations including spiral coils, serpentine coils, and custom-wound coil assemblies. Each coil is manufactured to meet stringent dimensional tolerances, ensuring compatibility with standard HVAC (Heating, Ventilation, and Air Conditioning) system components and specialized industrial heat exchanger designs.
Material & Properties
The coil tube product line is fabricated from high-grade austenitic stainless steel grades, selected for their superior resistance to corrosion, mechanical strength, and thermal conductivity. The primary material specifications are as follows:
- Grade 304 (UNS S30400 / AISI 304): The most widely used austenitic stainless steel, offering excellent general corrosion resistance, formability, and weldability. Suitable for non-aggressive industrial environments and general HVAC applications.
- Grade 316 (UNS S31600 / AISI 316): Enhanced corrosion resistance due to the addition of 2–3% molybdenum, providing superior protection against chlorides, acidic environments, and marine atmospheres.
- Grade 321 (UNS S32100 / AISI 321): Titanium-stabilized austenitic stainless steel offering resistance to intergranular corrosion, ideal for high-temperature applications up to 870°C (1598°F).
Key material properties for the standard 304 grade include:
- Density: 8.0 g/cm³ (0.29 lb/in³)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (29.3 BTU·in/(hr·ft²·°F))
- Specific Heat: 500 J/(kg·K) at 20°C
- Tensile Strength: ≥ 515 MPa (74,700 psi)
- Yield Strength: ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40%
- Operating Temperature Range: −196°C to 870°C (−321°F to 1598°F)
Technical Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") |
| Wall Thickness | 0.5 mm – 3.0 mm (0.020" – 0.118") |
| Coil Diameter (Center-to-Center) | 100 mm – 2000 mm (3.9" – 78.7") |
| Coil Pitch | 10 mm – 100 mm (0.39" – 3.94") |
| Coil Length (Total Tube Length) | 1 m – 500 m (3.3 ft – 1,640 ft) per coil assembly |
| Number of Turns | Custom (typically 5 – 500+ turns) |
| Surface Finish | Bright Annealed (BA), Pickled & Passivated (P&P), or Brushed |
| Surface Roughness (Ra) | ≤ 0.8 μm (BA finish); ≤ 1.6 μm (P&P finish) |
| Dimensional Tolerance (OD) | ±0.05 mm (±0.002") |
| Dimensional Tolerance (Wall Thickness) | ±0.03 mm (±0.0012") |
| Coil Straightness Tolerance | ≤ 0.5 mm/m (≤ 0.02"/ft) |
| End Preparation | Plain cut, Beveled, Threaded, or Flanged |
| Available Grades | 304, 316, 321, 304L, 316L, 310S |
| Hydrostatic Test Pressure | 2.5 × Working Pressure (minimum) |
| Standard References | ASTM A269, ASTM A554, EN 10217-7, GB/T 12771 |
Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Selection & Inspection: Certified stainless steel strip or seamless tube blanks are procured from approved suppliers. Incoming materials undergo spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with specified grades.
- Forming & Welding (for welded tube): Cold-rolled stainless steel strip is fed through precision roll-forming dies to create the desired tube cross-section. A high-frequency induction welding (HFW — High Frequency Welding) process joins the seam, followed by internal and external grinding of the weld zone to achieve uniform wall thickness.
- Heat Treatment & Annealing: The formed tube undergoes solution annealing at 1050°C – 1150°C (1922°F – 2092°F) in a protective atmosphere furnace. This process relieves residual stresses, homogenizes microstructure, and restores full corrosion resistance after cold working.
- Pickling & Passivation: Post-annealing tubes are treated with a mixed acid pickling solution (typically HNO₃/HF blend) to remove oxide scale, followed by nitric acid passivation to establish a protective chromium oxide layer (Cr₂O₃) on the surface.
- Coil Winding: The straight tube is fed through precision CNC-controlled coil winding machines that form the tube into the specified helical or serpentine geometry. Winding parameters (coil diameter, pitch, number of turns) are programmatically controlled to meet exact customer specifications.
- Post-Winding Straightening & Inspection: Each coil assembly undergoes dimensional verification using laser measurement systems. Coil straightness, turn uniformity, and overall geometry are validated against drawing specifications.
- Hydrostatic Testing: Completed coil tubes are pressure-tested at 2.5 times the maximum design working pressure to verify weld integrity and absence of porosity or defects throughout the tube length.
- Final Surface Treatment & Packaging: Final passivation treatment ensures maximum corrosion protection. Products are cleaned, dried, and packaged with protective end caps and moisture-absorbing desiccants in export-grade wooden or steel crates.
Applications
The stainless steel coil tube product line serves a diverse range of industrial and commercial applications:
- HVAC Systems: Integration into fan coil units (FCUs), air handling units (AHUs), and chillers where the coil tube serves as the refrigerant or hot water heat exchange element. The coil geometry maximizes heat transfer area while minimizing pressure drop, enabling efficient operation across variable load conditions — including partial load scenarios where cooling capacity calculations must account for differing air and water temperatures.
- Industrial Heat Exchangers: Shell-and-tube heat exchangers, plate-fin heat exchangers, and condenser/evaporator assemblies in chemical processing, pharmaceutical, and food processing industries.
- Automotive & Transportation: Automotive intercoolers, transmission oil coolers, and battery thermal management systems for electric vehicles (EVs).
- Refrigeration & Cryogenics: Evaporator coils for commercial refrigeration systems and cryogenic applications requiring operation at temperatures below −100°C (−148°F).
- Water Treatment & Desalination: Seawater cooling coils and desalination plant heat recovery systems where chloride-resistant grades (316, 316L) are essential.
- Power Generation: Condenser tubes and feedwater heaters in thermal power plants and nuclear power facilities.
- Marine Engineering: Bilge cooling systems, ballast water heat exchangers, and shipboard HVAC coils.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and certifications that validate the performance and reliability of its stainless steel coil tube products:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and customer satisfaction through defined processes and continual improvement.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices and environmental responsibility.
- EN 10204 — Material Test Certificate (MTC) Type 3.1 issued for each production batch, providing independent verification of chemical composition and mechanical properties.
- ASTM / ASME Compliance — Products manufactured in accordance with ASTM A269 (Austenitic Stainless Steel Seamless, Welded, and Heavy-Walled Tube), ASTM A554 (Cold-Wrought Austenitic Stainless Steel Tube for Chemical and Allied Industries), and ASME BPV Code Section I.
- CE Marking (PED 2014/68/EU) — Conformity with the European Pressure Equipment Directive for products intended for pressure vessel and piping applications.
- NSF/ANSI 61 — Certification for water system components ensuring compliance with health-related requirements for materials in contact with potable water.
- Mill Test Reports (MTR) — Traceable documentation from the steel mill confirming grade, heat number, and mechanical test results for raw material.
- Non-Destructive Testing (NDT) — 100% eddy current testing (ECT) and magnetic particle inspection (MPI) performed on welded seams to detect subsurface and surface defects.
Unique Selling Points
- Custom Coil Geometry Engineering: Ability to manufacture coil tubes with bespoke coil diameters, pitches, and turn counts optimized for specific heat transfer requirements, including variable-load fan coil unit designs where cooling capacity varies across different operating conditions.
- Multi-Grade Availability: Comprehensive grade selection from 304 through 310S allows customers to match material properties precisely to their operating environment — from general industrial service to aggressive chloride-rich or high-temperature applications.
- Precision Winding Technology: CNC-controlled coil winding ensures repeatable geometry with turn-to-turn consistency within ±0.5 mm, critical for uniform heat transfer and balanced fluid distribution in multi-pass coil assemblies.
- Full Traceability: Every coil tube assembly is traceable from raw steel mill heat through final inspection, with complete documentation packages including MTCs, NDT reports, hydrostatic test records, and dimensional inspection certificates.
- Integrated Surface Engineering: Advanced pickling and passivation processes produce surface finishes with surface roughness as low as Ra 0.8 μm, reducing fouling potential and maintaining long-term thermal performance in demanding service environments.
Conclusion
The Wenzhou Jixing Metal Materials Co., Ltd. stainless steel coil tube product line represents a synthesis of metallurgical excellence, precision manufacturing, and application-specific engineering. Whether deployed in HVAC fan coil units operating across variable load conditions, or in high-pressure industrial heat exchangers, these coil tubes deliver dependable thermal performance, extended service life, and compliance with the most stringent international quality standards. The company's commitment to continuous process improvement, full product traceability, and customer-specific design support positions it as a trusted supplier of engineered stainless steel coil tube solutions for global industrial markets.