Stainless Steel Coil Tube for Radiant Ceiling Systems (Three-Constant System)
Product Overview
The Stainless Steel Coil Tube (盘管 Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing product designed for integration into structural floor slabs and ceiling assemblies within advanced building climate control systems. This product is specifically developed for the Three-Constant System (三恒系统), which maintains constant temperature, constant humidity, and constant indoor air quality (IAQ) through a combination of radiant heating/cooling and precision air distribution.
Coil tubes serve as the primary heat exchange medium in radiant ceiling panels, circulating heated or chilled water through embedded serpentine or serpentine-loop tube configurations to achieve uniform thermal distribution across the conditioned space. The product is supplied in continuous coil form to facilitate on-site installation without field welding, minimizing the risk of thermal bridging and ensuring long-term hydraulic integrity.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, and mechanical durability in demanding architectural applications.
- Base Material: Austenitic Stainless Steel (typically Grade 304 / S30408 or Grade 316L / S31603)
- Corrosion Resistance: Excellent resistance to chloride-induced pitting and crevice corrosion, ensuring service life exceeding 25 years in humid indoor environments
- Thermal Conductivity: Approximately 16.3 W/(m·K) for Grade 304, providing efficient heat transfer between the circulating fluid and the radiant surface
- Mechanical Properties: Tensile strength ≥ 520 MPa; elongation ≥ 40%; suitable for bending radii as small as 3× the outer diameter without wall-thinning
- Operating Temperature Range: −40°C to +120°C (compatible with low-temperature radiant cooling at 16–18°C supply water and high-temperature heating at 40–60°C)
- Operating Pressure: Rated for working pressures up to 1.0 MPa (10 bar) with a safety factor of 2.0
- Surface Finish: Interior surface roughness Ra ≤ 0.8 μm to minimize flow resistance and inhibit biofilm formation
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 8 mm / 10 mm / 12 mm / 15 mm / 16 mm (custom available) |
| Wall Thickness | 0.8 mm / 1.0 mm / 1.2 mm / 1.5 mm |
| Tube Length (Coil) | 50 m – 500 m per coil (continuous, no joints) |
| Bending Radius (Minimum) | ≥ 3 × OD (factory pre-formed); ≥ 5 × OD (on-site forming) |
| Coil Forming Diameter | 1.0 m – 2.0 m (adjustable per project requirement) |
| Tolerance on OD | ± 0.1 mm |
| Tolerance on Wall Thickness | ± 10% of nominal |
| Surface Treatment | Pickled and passivated (optional: electropolished interior) |
| End Finishing | Deburred, chamfered, and protected with plastic end caps |
| Standards Compliance | ASTM A269 / ASTM A270; GB/T 12771; EN 10216-5 |
| Hydraulic Testing | 100% hydrostatic pressure test at 2.0 × working pressure |
Manufacturing Process
- Raw Material Procurement: Cold-rolled stainless steel strip (coil) is sourced from certified mills with full chemical composition and mechanical property traceability.
- Coil Winding & Forming: The strip is wound into a continuous coil using CNC-controlled forming machinery, maintaining precise dimensional tolerances throughout the entire length.
- Seam Welding: Where required, the tube is formed into a circular cross-section via resistance seam welding (RSW) or automatic orbital TIG welding, followed by internal and external grinding to eliminate weld protrusion.
- Pickling & Passivation: The welded tube undergoes acid pickling (HNO₃/HF mixture) to remove oxide scale, followed by passivation treatment to restore the protective chromium oxide film.
- Hydrostatic Testing: Every coil is subjected to a 100% hydrostatic pressure test (minimum 2.0 MPa hold for 10 seconds) to verify structural integrity and absence of leaks.
- Coil Packaging: Tested coils are wound onto protective spools, wrapped in moisture-barrier film, and labeled with batch identification, material certification, and test data.
Applications
Primary Application: Three-Constant System Radiant Ceilings
The coil tube is embedded within structural floor slabs or suspended ceiling assemblies as part of the Three-Constant System (恒温、恒湿、恒氧 — Constant Temperature, Constant Humidity, Constant Oxygen). The system integrates:
- Radiant Heating/Cooling: The coil tube circulates conditioned water to provide zone-level thermal comfort via infrared radiation and natural convection.
- Hybrid Air Handling: Complemented by dedicated fresh air systems to maintain constant IAQ and relative humidity within ±5% of setpoint.
Typical Building Types
- High-end commercial office towers and corporate headquarters
- Healthcare facilities (hospitals, clinics, laboratories)
- Education institutions (university buildings, research centers)
- Luxury residential complexes with premium comfort specifications
- Cultural venues (museums, galleries, auditoriums)
Quality Certifications & Standards
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| CE Marking (EU) | Compliance with Construction Products Regulation (CPR) 305/2011 |
| ASTM A269 | Welded Austenitic Stainless Steel Tubes — General Requirements |
| GB/T 12771-2019 | Chinese National Standard for Welded Stainless Steel Tubes (Hydraulic/Pneumatic) |
| EN 10216-5 | European Standard for Non-Alloy Steel Tubes (Stainless Steel Edition) |
| Mill Test Certificate (MTC) | Full EN 10204 3.1 Certificate with chemical analysis and mechanical test data |
Unique Selling Points
- Continuous Coil Supply: Delivered as a single uninterrupted length, eliminating field welds and reducing installation labor by up to 40% compared to straight pipe segments.
- Structural Integration: Designed for direct embedding within reinforced concrete floor slabs, serving as both the radiant element and a structural composite component.
- Corrosion-Free Service Life: Austenitic stainless steel construction ensures zero internal corrosion or scaling, maintaining consistent thermal performance over decades of operation.
- Low-Flow-Resistance Design: Ultra-smooth interior surface (Ra ≤ 0.8 μm) reduces pumping energy consumption by 15–20% compared to carbon steel alternatives.
- Full Traceability: Each coil is batch-coded with complete material certification, dimensional inspection data, and hydrostatic test results for project documentation and warranty purposes.
- Custom Configuration: Wenzhou Jixing Metal Materials Co., Ltd. offers project-specific customization of tube diameter, wall thickness, coil length, and forming geometry to match architectural design requirements.
Installation & Integration Notes
When embedding coil tubes within structural floor slabs for Three-Constant System radiant ceilings, the following engineering considerations must be observed:
- Minimum concrete cover over the tube crown: 30 mm to ensure adequate load transfer and crack resistance.
- Tube spacing (pitch): Typically 100–200 mm center-to-center, determined by thermal load calculation and desired surface temperature differential.
- Expansion joints must be provided at structural movement joints to prevent stress concentration on the coil tube.
- All connections (manifolds, risers) shall be made using butt-weld or orbital TIG weld methods to maintain system integrity.
- Pre-commissioning: System shall be pressure-tested at 1.5 × design pressure for a minimum of 24 hours prior to slab pour.
Conclusion
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. represents a state-of-the-art solution for high-performance radiant ceiling systems within the Three-Constant System paradigm. By combining the inherent advantages of austenitic stainless steel with precision coil manufacturing technology, this product delivers exceptional thermal efficiency, mechanical reliability, and service longevity—making it the preferred choice for architects, MEP engineers, and building owners demanding uncompromising indoor environmental quality.