Stainless Steel Coil Tube for Fan Coil Water Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for hydronic heating, cooling, and ventilation (HVAC) applications, with particular emphasis on fan coil water systems in commercial and institutional buildings. This product is supplied in continuous coil (spool) form, enabling efficient downstream forming, bending, and installation processes. The coil tube serves as the core heat exchange and fluid conveyance medium in fan coil units (FCUs), providing reliable thermal transfer performance while maintaining long-term corrosion resistance in water-based circulation systems.
The product has been validated through practical application in large-scale commercial building projects, including the New Hongqiao Tower fan coil water system, where it demonstrated superior performance in installation, commissioning, and long-term operational reliability.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, ensuring excellent corrosion resistance, mechanical strength, and thermal conductivity suitable for water circulation systems.
- Material Grade: AISI 304 / 304L (UNS S30400 / S30403), with optional 316L (UNS S31603) for aggressive environments
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in potable water and glycol-based heat transfer fluids
- Mechanical Strength: Tensile strength ≥ 515 MPa (ASTM A269); yield strength ≥ 205 MPa
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C, facilitating efficient heat exchange in fan coil systems
- Temperature Range: Operational range from −196°C to +870°C, with continuous service suitable for typical hydronic system temperatures (5°C to 95°C)
- Hygienic Performance: Non-toxic, non-tarnishing, and resistant to microbial growth; compliant with potable water contact requirements
- Surface Finish: Cold-rolled (CR) finish with Ra ≤ 0.8 μm; optional electropolished or passivated surface
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | φ12.7 mm / φ15.9 mm / φ19.05 mm / φ21.3 mm (customizable) | ASTM A269 / ASME B36.19M |
| Wall Thickness | 0.8 mm – 2.0 mm (tolerance ±10%) | ASTM A269 |
| Coil Length | 10 m – 500 m per coil (customizable) | — |
| Coil Inner Diameter | φ150 mm – φ600 mm | — |
| Material Grade | AISI 304 / 304L / 316L | ASTM A240 / A269 |
| Manufacturing Method | Cold-drawn seamless tube | ASTM A269 |
| Surface Treatment | Cold-rolled / Passivated / Electropolished | — |
| Pressure Rating | Up to 1.6 MPa (PN16) at 25°C | EN 10217-7 |
| End Condition | Plain end / Beveled / Threaded (on request) | — |
| Minimum Bend Radius | ≥ 3D (D = outer diameter) | — |
| Packaging | Wooden coil stand with moisture-proof wrapping | — |
Manufacturing Process
The stainless steel coil tube is produced through a multi-stage cold-drawn seamless manufacturing process, ensuring dimensional accuracy, uniform wall thickness, and superior surface quality:
- Hot-Rolled Billet Preparation: Stainless steel ingots are cast and hot-rolled into seamless tube blanks with controlled chemical composition and microstructure.
- Piercing & Rolling: Blanks are heated to 1150°C – 1200°C and pierced to form hollow tubes, which are then hot-rolled to approximate dimensions.
- Acid Pickling & Descaling: Hot-rolled scale is removed using a controlled acid bath (HNO₃/HF mixture) to reveal the clean base metal surface.
- Cold Drawing (Multi-Pass): Tubes are cold-drawn through precision tungsten carbide dies in multiple passes to achieve the final OD, wall thickness, and surface finish within tight tolerances.
- Intermediate Annealing: Where necessary, tubes undergo solution annealing at 1050°C – 1150°C followed by controlled cooling to relieve cold-work hardening and restore ductility.
- Final Coiling: Finished tubes are wound onto precision coil stands to maintain consistent curvature and prevent deformation or kinking.
- Passivation Treatment: A final nitric acid passivation cycle enhances the passive chromium oxide layer (Cr₂O₃), maximizing corrosion resistance for water system service.
- Quality Inspection: Each coil undergoes dimensional measurement, hydrostatic pressure testing, surface inspection, and chemical composition verification.
Applications
The stainless steel coil tube is specifically engineered for the following applications:
- Fan Coil Unit (FCU) Water Systems: Primary application in hydronic heating and cooling systems within commercial office buildings, hospitals, hotels, and educational facilities. The coil tube forms the water-side heat exchange circuit within fan coil units, circulating chilled water or hot water to regulate indoor air temperature.
- Chilled Water Distribution Piping: Used as secondary distribution tubing in central air conditioning (CAC) systems, connecting the chiller plant to terminal units through compact, space-efficient coil routing.
- Heat Recovery Systems: Deployed in total heat exchangers and plate-fin coil assemblies for energy-efficient air handling units (AHUs).
- Commercial Building HVAC Retrofit: Ideal for upgrading legacy fan coil systems due to its superior corrosion resistance and extended service life compared to carbon steel alternatives.
- Industrial Process Cooling: Applicable in food processing, pharmaceutical manufacturing, and semiconductor fabrication facilities where hygienic and corrosion-resistant tubing is mandated.
Field Validation — New Hongqiao Tower Project
The stainless steel coil tube was successfully installed, commissioned, and operated in the fan coil water system of the New Hongqiao Tower. Post-installation performance evaluation confirmed:
- Seamless integration with existing hydronic piping infrastructure
- Zero leakage incidents during the full commissioning cycle
- Stable thermal performance with minimal pressure drop across the coil circuit
- Long-term operational reliability with no signs of internal or external corrosion
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and product compliance with the following standards and certifications:
- ISO 9001:2015 — Quality Management System (QMS) certification
- ISO 14001:2015 — Environmental Management System (EMS) certification
- ASTM A269 / A270 — Standard specification for austenitic stainless steel seamless, cold-drawn tube and pipe
- ASME B36.19M — Welded and seamless wrought stainless steel pipe dimensions
- EN 10217-7 — Technical delivery conditions for stainless steel tubes for pressure purposes
- GB/T 12771 — Chinese national standard for seamless stainless steel tubes for fluid transport
- Hydrostatic Testing: Every coil is pressure-tested at 1.5× the maximum operating pressure to ensure structural integrity
- Material Traceability: Full mill test certificates (MTC) and heat number traceability provided with each shipment
Unique Selling Points
- Extended Service Life: Stainless steel construction provides a design life exceeding 25 years in hydronic systems, significantly outperforming galvanized steel and carbon steel alternatives (typically 8–12 years).
- Superior Corrosion Resistance: The passive chromium oxide layer self-heals in the presence of oxygen, protecting against internal scaling and external corrosion even in aggressive water chemistries.
- Hygienic & Non-Toxic: Compliant with potable water and food-grade contact requirements, making it suitable for healthcare and pharmaceutical facilities.
- Compact Coil Form Factor: Supplied in continuous coil format for efficient storage, transportation, and on-site installation, reducing labor costs and installation time compared to straight-length tubing.
- Low Maintenance: Requires no internal lining, cathodic protection, or chemical water treatment, reducing total cost of ownership (TCO) over the system lifecycle.
- Customizable Specifications: Available in a range of diameters, wall thicknesses, and coil lengths to meet project-specific design requirements.