Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered continuous tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. The product is supplied in a coiled configuration, offering flexibility in downstream processing, installation, and integration into complex systems. Unlike straight-length tubing, the coil form factor eliminates the need for field welding or joint assembly, significantly reducing installation time and enhancing system reliability.
This product is specifically designed for use in Fan Coil Units (FCU) — a critical component in modern HVAC (Heating, Ventilation, and Air Conditioning) systems. The coil tube serves as the heat exchange medium, facilitating thermal transfer between a circulating fluid (water or refrigerant) and ambient air. Its performance characteristics directly influence the efficiency, durability, and service life of the entire fan coil unit assembly.
The stainless steel coil tube represents a superior alternative to traditional carbon steel or copper coil tubes, offering exceptional resistance to corrosion, high-temperature oxidation, and mechanical fatigue in demanding engineering environments.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its optimal combination of mechanical strength, corrosion resistance, and formability. The primary material grades include:
- SUS304 / AISI 304 (UNS S30408) — The most widely used austenitic stainless steel, containing 18% Chromium (Cr) and 8% Nickel (Ni). Provides excellent general corrosion resistance and weldability.
- SUS316 / AISI 316 (UNS S31608) — Enhanced grade with 2–3% Molybdenum (Mo) addition, offering superior resistance to pitting and crevice corrosion, particularly in chloride-containing environments.
- SUS316L / AISI 316L (UNS S31603) — Low-carbon variant of 316, suitable for applications requiring post-weld heat treatment avoidance and maximum corrosion resistance.
Key Material Properties
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, industrial pollution, and most dilute organic and inorganic acids. The passive chromium oxide film (Cr₂O₃) self-repairs in the presence of oxygen, providing long-term protection.
- Thermal Conductivity: Approximately 15–16 W/(m·K) for SUS304, providing adequate heat transfer performance while maintaining structural integrity at elevated temperatures.
- Operating Temperature Range: −196 °C to +870 °C (SUS304); −196 °C to +925 °C (SUS316), ensuring reliability across extreme thermal cycles.
- Mechanical Strength: Tensile strength of 520–720 MPa (annealed condition); yield strength ≥ 205 MPa; elongation ≥ 40%.
- Non-magnetic: Austenitic microstructure ensures non-magnetic behavior, critical for applications sensitive to electromagnetic interference (EMI).
- Hygienic Surface: Food-grade surface finish with Ra (Surface Roughness) ≤ 0.8 μm available upon request, suitable for pharmaceutical and food processing applications.
3. Specifications
The following table summarizes the standard dimensional and performance specifications for the Stainless Steel Coil Tube product line:
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6 mm – 51 mm (custom sizes available) | ASTM A213 / GB/T 14976 |
| Wall Thickness | 0.5 mm – 4.0 mm | ASTM A269 / GB/T 12771 |
| Coil Inner Diameter (Coil ID) | 200 mm – 800 mm | Manufacturer specification |
| Coil Length (per coil) | 15 m – 100 m (continuous) | — |
| Surface Finish | 2B (Cold Rolled & Annealed), BA (Bright Annealed), No.4 Brushed | ASTM A480 |
| Tolerance on OD | ±0.1 mm – ±0.3 mm | ISO 1128 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| End Form | Plain cut, beveled, or threaded (upon request) | — |
| Maximum Operating Pressure | Up to 2.5 MPa (design dependent) | ASME B31.9 |
| Heat Transfer Coefficient | ≥ 800 W/(m²·K) (water-to-air) | ASHRAE Handbook |
| Service Life (expected) | ≥ 25 years (indoor HVAC application) | — |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous, multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and surface quality:
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Raw Material Procurement & Inspection:
Hot-rolled stainless steel strip or wire rod is sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with the specified grade.
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Cold Drawing / Cold Forming:
Hot-rolled stock is cold-drawn through a series of progressively reduced dies to achieve the target outer diameter and wall thickness. This process induces work hardening, improving mechanical strength while maintaining ductility for subsequent forming.
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Seam Welding (if applicable):strong>
For seamless coil tubes, the drawn tube is formed into a helical coil through precision bending. For welded variants, a continuous longitudinal seam is created via TIG (Tungsten Inert Gas) welding or laser welding, followed by internal and external grinding to eliminate weld imperfections.
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Heat Treatment (Annealing):
The formed coil tube undergoes solution annealing at 1010–1150 °C followed by controlled cooling (air or water quench depending on grade). This eliminates residual stresses, restores full austenitic microstructure, and ensures maximum corrosion resistance.
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Pickling & Passivation:
Annealed surfaces are treated with a pickling acid solution (typically a mixture of nitric acid and hydrofluoric acid) to remove oxide scale, followed by passivation to establish a stable chromium oxide protective layer.
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Surface Finishing:
Depending on the application, the tube may undergo additional surface treatment including electropolishing, mechanical polishing, or brushing to achieve the specified surface roughness and appearance.
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Dimensional Inspection & Testing:
Finished coil tubes are subjected to comprehensive quality control including dimensional measurement (OD, wall thickness, coil diameter), hydrostatic pressure testing, and visual inspection. Non-destructive testing (NDT) methods such as eddy current testing and ultrasonic testing may be employed for weld integrity verification.
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Packaging & Dispatch:
Coil tubes are wrapped in protective film or paper, placed in wooden crates or pallets with moisture-absorbing desiccants, and prepared for shipment according to international packaging standards.
5. Applications
The stainless steel coil tube finds extensive application across multiple industrial sectors:
5.1 HVAC Systems — Fan Coil Units (FCU)
This is the primary application domain. The coil tube is installed within the air handler section of fan coil units, where it serves as the heat exchanger core. In cooling mode, chilled water circulates through the coil tube, absorbing heat from passing air. In heating mode, hot water transfers thermal energy to the airstream. The coil tube's corrosion resistance is critical, as it is continuously exposed to condensation (particularly in cooling mode), which can be mildly acidic and corrosive over time.
5.2 Chiller & Condenser Systems
Used in shell-and-tube heat exchangers within industrial chiller plants and refrigeration condensers, where the tube forms the inner tube bundle facilitating refrigerant-to-water or water-to-water heat exchange.
5.3 Pharmaceutical & Biotechnology
Employed in CIP (Clean-in-Place) and SIP (Sterilize-in-Place) systems for pharmaceutical processing equipment. The hygienic surface finish and resistance to aggressive cleaning chemicals (acids, alkalis, peracetic acid) make stainless steel coil tubes ideal for sanitary applications governed by FDA and EU GMP (Good Manufacturing Practice) regulations.
5.4 Food & Beverage Industry
Utilized in pasteurization systems, brewing equipment, dairy processing lines, and beverage cooling systems where product contact requires adherence to food safety standards (NSF, 3-A Sanitary Standards).
5.5 Marine & Offshore
SUS316 and SUS316L grade coil tubes are specified for marine HVAC systems, shipboard condensers, and offshore platform cooling circuits, where resistance to saltwater (marine atmosphere and seawater spray) is paramount.
5.6 Chemical & Petrochemical
Applied in process cooling circuits, heat recovery systems, and utility piping where exposure to corrosive process fluids necessitates high-grade stainless steel construction.
5.7 Energy & Power Generation
Used in nuclear power plant cooling circuits (specific grades), solar thermal systems, and geothermal heat exchange applications requiring long-term thermal cycling resistance.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity with international standards:
- ISO 9001:2015 — Quality Management System (QMS) certification, demonstrating systematic commitment to customer satisfaction and continuous improvement.
- ISO 14001:2015 — Environmental Management System (EMS) certification, ensuring environmentally responsible manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- ASTM A213 / ASTM A269 Compliance — Product specifications conform to American Society for Testing and Materials (ASTM) standards for seamless and welded austenitic stainless steel tubing.
- EN 10216-5 / EN 10217-7 Compliance — European standard conformity for stainless steel tubes for general and pressure purposes.
- GB/T 14976 / GB/T 12771 — Chinese national standard compliance for seamless and welded stainless steel tubes.
- MILL TEST CERTIFICATE (MTC) — Each batch is accompanied by a mill test certificate (EN 10204 Type 3.1) documenting chemical composition, mechanical properties, and heat treatment data.
- Third-Party Inspection — Available upon request through recognized inspection bodies (SGS, Bureau Veritas, TÜV, Lloyd's Register).
7. Unique Selling Points
Superior Corrosion Longevity: Compared to conventional carbon steel or copper coil tubes, the stainless steel coil tube offers a service life exceeding 25 years in indoor HVAC applications — significantly reducing lifecycle replacement costs and minimizing maintenance downtime.
Coil Configuration Advantage: The continuous coil form eliminates field joints, reducing potential leak points by up to 90% compared to straight-tube assemblies requiring multiple welded or brazed connections. This translates to enhanced system reliability and reduced installation labor costs.
Thermal Performance Retention: The passive oxide layer on stainless steel does not degrade thermal conductivity over time, unlike copper which may suffer from oxidation-related fouling. This ensures consistent heat transfer efficiency throughout the operational lifecycle.
Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil tube specifications including outer diameter, wall thickness, coil inner diameter, surface finish, and material grade, tailored to specific engineering requirements.
Environmental Sustainability: Stainless steel is 100% recyclable without degradation of material properties. The coil tube's extended service life and recyclability contribute to reduced material consumption and carbon footprint over the product lifecycle.
8. Conclusion
The Stainless Steel Coil Tube (Coiltube) from Wenzhou Jixing Metal Materials Co., Ltd. represents a technologically advanced, standards-compliant product solution for heat exchange applications. Its integration into Fan Coil Units (FCU) and related HVAC systems delivers proven benefits in terms of energy efficiency, system reliability, and total cost of ownership. The product embodies the principles of precision metallurgy and engineered design, meeting the rigorous demands of modern industrial and commercial engineering.