Stainless Steel Coil Tube (盘管) — Model No. 1012
Product Overview
The Stainless Steel Coil Tube (Model No. 1012) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tube product designed primarily for hydronic heating and cooling applications, with particular emphasis on low-temperature floor radiant heating systems (Low-Temperature Floor Radiant Heating, LTFRH) in large-span architectural structures. The coil tube is supplied in continuous coiled form, enabling flexible on-site installation through various laying configurations — including serpentine (蛇形) and double-return (回字形) patterns — to optimize thermal comfort and heat distribution efficiency across expansive floor areas.
This product represents a specialized segment within the stainless steel pipe industry, combining the inherent corrosion resistance and mechanical strength of austenitic stainless steel with the geometric flexibility required for radiant floor heating systems. The coiled configuration eliminates the need for field welding or soldering, significantly reducing installation time and ensuring leak-free performance over the service life of the system.
Material & Properties
Base Material
The coil tube is fabricated from high-grade austenitic stainless steel, typically conforming to UNS S30408 (AISI 304) or UNS S31603 (AISI 316L) specifications, depending on the application environment. The material selection ensures:
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and intergranular corrosion in aqueous heating media, including glycol-based antifreeze solutions.
- Mechanical Strength: High tensile strength (≥ 520 MPa for Grade 304) and yield strength (≥ 205 MPa), providing resistance to mechanical deformation under floor loading conditions.
- Thermal Stability: Maintains structural integrity across operating temperature ranges from −40 °C to +150 °C, suitable for both heating and cooling applications.
- Hygienic Surface: Smooth inner surface finish (Ra ≤ 0.4 μm) minimizes flow resistance and prevents biofilm accumulation.
- Long Service Life: Expected operational lifespan exceeding 50 years under normal hydronic heating conditions, far surpassing conventional PEX or copper alternatives.
Key Performance Characteristics
- Thermal Conductivity: 16.3 W/(m·K) — enabling efficient heat transfer to the surrounding concrete screed and ultimately to the room space.
- Linear Expansion Coefficient: 17.3 × 10⁻⁶ /K — requiring appropriate expansion joint provisions in long-run installations.
- Non-Magnetic: Austenitic microstructure ensures no magnetic interference with adjacent equipment.
- Recyclability: 100% recyclable material, contributing to sustainable construction practices and compliance with green building standards.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Model | 1012 | Internal Catalog |
| Product Name | Stainless Steel Coil Tube (盘管 / Coil Tube) | — |
| Outer Diameter (OD) | 8 mm / 10 mm / 12 mm / 16 mm (selectable) | GB/T 12771 — 2019 |
| Wall Thickness | 0.5 mm / 0.8 mm / 1.0 mm / 1.5 mm (selectable) | GB/T 12771 — 2019 |
| Coil Length per Spool | 50 m / 100 m / 150 m (customizable) | Manufacturer Specification |
| Coil Inner Diameter | ≥ 500 mm (standard packaging) | ISO 15491 |
| Material Grade | 304 / 304L / 316L (austenitic stainless steel) | ASTM A269 / GB/T 12771 |
| Surface Finish | Industrial passivated (standard) / Electropolished (optional) | ASTM A967 |
| Operating Pressure | ≤ 1.6 MPa (standard) / ≤ 2.5 MPa (thick-wall option) | ASME B31.9 |
| Operating Temperature | −40 °C to +150 °C | Material Data Sheet |
| Hydrostatic Test Pressure | 2.5 × working pressure, held for 30 s minimum | GB/T 12771 — 2019 |
| Connection Method | Press-fit fittings / Threaded fittings / Flanged joints (per system design) | ISO 15492 |
| Minimum Bending Radius | ≥ 5 × OD (cold bending without special tooling) | Manufacturer Recommendation |
| Applicable Standards | GB/T 12771, ASTM A269, EN 10217-7, JIS G 3459 | — |
| Coating / Protection | None (bare stainless steel) / PE outer coating (optional for soil burial) | ISO 21809-3 |
Manufacturing Process
The production of the Stainless Steel Coil Tube (Model 1012) follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Hot Rolling & Annealing: Stainless steel slabs are hot-rolled into seamless tube blanks or welded from precision-cut coil strip, followed by solution annealing at 1050–1150 °C in a controlled atmosphere furnace to achieve uniform austenitic grain structure.
- Cold Drawing / Cold Forming: The tube is cold-drawn through precision tungsten carbide dies to achieve exact outer diameter and wall thickness tolerances (± 0.05 mm for OD, ± 0.05 mm for wall thickness). This process induces beneficial work hardening while maintaining ductility.
- Intermediate Annealing: Periodic annealing at 850–950 °C relieves accumulated cold work stresses, preventing cracking during subsequent forming operations.
- Coil Winding: The finished tube is wound onto precision-mandrel coils using an automated winding system that controls tension to prevent ovality or kinking. Each coil is inspected for geometric uniformity.
- Pickling & Passivation: The coil tube undergoes chemical pickling (HNO₃/HF mixed acid bath) to remove mill scale and surface contaminants, followed by passivation treatment to establish a protective chromium oxide (Cr₂O₃) film. This step is critical for ensuring long-term corrosion resistance.
- Non-Destructive Testing (NDT): 100% eddy current inspection and hydrostatic pressure testing are performed on every coil to detect internal and external defects, ensuring zero-leak integrity.
- Final Inspection & Packaging: Coils are visually inspected, dimensionally verified, and packaged with protective end caps and moisture-absorbing desiccants to prevent corrosion during storage and transport.
Applications
Primary Application: Low-Temperature Floor Radiant Heating (LTFRH)
The primary design application of Model 1012 is in low-temperature floor radiant heating systems for large-span architectural spaces, including:
- Commercial Buildings: Shopping malls, exhibition halls, airports, and convention centers requiring uniform floor-level thermal comfort over expansive areas.
- Industrial Facilities: Manufacturing plants, warehouses, and cold storage facilities where floor heating is critical for worker comfort and process requirements.
- Public Infrastructure: Stadiums, sports facilities, and transportation hubs with high foot traffic and large floor areas.
- Residential High-Rise: Multi-unit residential buildings utilizing hydronic floor heating for zoned comfort control.
Installation Configurations
Research on thermal comfort in large-space buildings has demonstrated that the laying configuration (敷设方式) of the coil tube significantly affects indoor thermal comfort performance. Model 1012 is designed to accommodate multiple installation patterns:
- Serpentine (蛇形) Layout: Continuous back-and-forth path maximizing floor coverage with minimal pipe length; suitable for rectangular spaces with uniform heating demand.
- Double-Return / Spiral (回字形) Layout: Concentric looping pattern that provides more uniform temperature distribution and reduces thermal stratification; preferred for large open spaces.
- Hybrid Configuration: Combination of serpentine and spiral patterns to address differential heating loads within a single space (e.g., perimeter zones vs. core zones).
Secondary Applications
- Underfloor Cooling Systems: Chilled water radiant cooling for energy-efficient HVAC in moderate climates.
- Heat Exchanger Coils: Custom-formed coils for industrial heat exchangers and process heating systems.
- Marine & Offshore Systems: Corrosion-resistant piping in marine environments where 316L grade is specified.
- Food & Pharmaceutical Processing: Hygienic-grade piping for clean-in-place (CIP) systems.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product reliability and regulatory compliance:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering manufacturing, inspection, and traceability processes. |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices. |
| GB/T 12771 — 2019 | Chinese National Standard for welded stainless steel tubes and pipes — dimensional, mechanical, and chemical requirements. |
| ASTM A269 / A270 | American standards for austenitic stainless steel seamless and welded tubes — fully compliant. |
| EN 10217-7 | European standard for austenitic stainless steel seamless and welded tubes — applicable for European market compliance. |
| CE Marking | Conformity with European Construction Products Directive (CPD) for building services applications. |
| Pressure Vessel / Piping Code | Compliant with ASME B31.9 (Building Services Piping) for hydronic heating system applications. |
| Material Traceability | Full mill certification (EN 10204 Type 3.1) provided with each batch, including chemical composition, mechanical properties, and heat treatment records. |
Unique Selling Points
1. Engineered for Large-Space Thermal Comfort: Model 1012 is specifically optimized for low-temperature floor radiant heating in large-span architectural structures, informed by research into thermal comfort characteristics and optimal coil laying configurations. The product delivers uniform floor surface temperatures and consistent indoor air temperatures, minimizing thermal stratification in high-ceiling spaces.
2. Weld-Free Installation: The continuous coil form eliminates field welding joints, the primary failure point in conventional stainless steel piping systems. This ensures leak-free performance throughout the 50+ year service life and dramatically reduces installation labor costs.
3. Superior Corrosion Performance: The 304/316L austenitic stainless steel construction provides exceptional resistance to corrosion in glycol-water heating media, eliminating the need for water treatment chemicals and reducing maintenance costs compared to carbon steel alternatives.
4. Flexible Configuration: The coil tube's inherent flexibility (minimum bending radius of 5 × OD without special tooling) allows adaptation to various installation patterns — serpentine, spiral, and hybrid — enabling system designers to optimize thermal comfort for specific architectural geometries.
5. Sustainability & Lifecycle Advantage: 100% recyclable stainless steel, minimal embodied carbon relative to copper alternatives, and a service life exceeding conventional plastic piping (PEX, PERT) by 3–5×, resulting in superior total lifecycle cost performance.
6. Full Traceability & Quality Assurance: Every coil is accompanied by comprehensive mill certification, hydrostatic test records, and dimensional inspection reports, ensuring complete quality traceability from raw material to final installation.
Technical Notes for System Design
- When designing LTFRH systems with Model 1012 coil tubes, the recommended pipe spacing (管间距) should be determined based on the required heat flux (typically 80–150 W/m²), floor construction type, and desired surface temperature limits (≤ 29 °C for habitable rooms per GB 50195).
- For large-span spaces exceeding 100 m² per zone, the double-return spiral layout is recommended to achieve more uniform floor temperature distribution, as demonstrated in thermal comfort studies of large-space buildings.
- Expansion joints or compensating loops should be provided for continuous runs exceeding 15 m to accommodate thermal expansion of the stainless steel tube.
- The recommended design flow velocity within the coil tube is 0.3–0.8 m/s to ensure adequate heat transfer while minimizing pressure drop and erosion risk.