Stainless Steel Floor Coil Tube for Radiant Heating Systems
Product Overview
The Stainless Steel Floor Coil Tube (盘管 / Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coil tube product specifically designed for underfloor radiant heating (UFH) and underfloor radiant cooling systems. As a critical component in modern hydronic heating and cooling infrastructure, this coil tube serves as the primary heat exchanger medium embedded within concrete or screed layers of residential, commercial, and industrial floor structures.
Unlike conventional plastic piping solutions, the stainless steel coil tube offers superior mechanical strength, thermal stability, and long-term service life, making it the preferred choice for high-performance radiant floor systems where durability, corrosion resistance, and dimensional accuracy are paramount. The coil tube is supplied in continuous coiled configurations to facilitate efficient installation with minimal joints, thereby reducing potential leak points and enhancing system reliability.
Material Composition & Physical Properties
Material Grade
The coil tube is fabricated from high-purity austenitic stainless steel, conforming to the following material standards:
- Primary Grade: AISI 304 / SUS 304 / ASTM A269 TP304 (06Cr19Ni10)
- Alternative Grade: AISI 316 / SUS 316 / ASTM A269 TP316 (06Cr17Ni12Mo2) — for aggressive environments
- Surface Treatment: Pickled and Passivated (酸洗钝化), achieving a surface roughness of Ra ≤ 0.4 μm
Key Physical and Mechanical Properties
| Property | Specification / Value | Test Standard |
|---|---|---|
| Density (密度) | 7.93 g/cm³ | ASTM A269 |
| Thermal Conductivity (导热系数) | 16.3 W/(m·K) at 20°C | ASTM E153 |
| Thermal Expansion Coefficient (热膨胀系数) | 17.3 × 10⁻⁶ /°C (20–100°C) | ASTM E228 |
| Tensile Strength (抗拉强度) | ≥ 520 MPa (0.2% offset) | ASTM A269 |
| Yield Strength (屈服强度) | ≥ 205 MPa | ASTM A269 |
| Hardness (硬度) | ≤ 200 HB (Brinell) | ASTM E10 |
| Operating Temperature Range (工作温度范围) | −196°C to +600°C | — |
| Corrosion Resistance (耐腐蚀性) | PASS per ASTM A967 Passivation Test | ASTM A967 |
| Maximum Working Pressure (最大工作压力) | 1.6 MPa (standard); 2.5 MPa (enhanced) | EN 12828 |
| Service Life (使用寿命) | ≥ 50 years (design life) | EN 12828 |
Detailed Specifications
| Parameter (参数) | Specification | Applicable Standard |
|---|---|---|
| Outer Diameter (外径, OD) | 15 mm, 16 mm, 20 mm, 22 mm, 25 mm, 28 mm, 32 mm (customizable) | ASTM A269 / GB/T 12771 |
| Wall Thickness (壁厚, WT) | 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 2.0 mm (customizable) | ASTM A269 / GB/T 12771 |
| Coil Diameter (盘管外径) | 1.0 m, 1.5 m, 2.0 m (customizable) | — |
| Coil Length (盘管长度) | 20 m, 30 m, 50 m, 100 m, or as required | — |
| Bending Radius (最小弯曲半径) | ≥ 5 × OD (no kinking or flattening) | EN 10217-7 |
| Surface Finish (表面质量) | Mirror polished or matte pickled finish; Ra ≤ 0.4 μm | ASTM A240 |
| End Preparation (端部处理) | Flat cut with deburred edges; optional threaded or flanged ends | — |
| Tolerance — OD (外径公差) | ±0.15 mm | ASTM A269 |
| Tolerance — WT (壁厚公差) | ±10% of nominal | ASTM A269 |
| Hydrostatic Test Pressure (水压试验压力) | 3 × Maximum Working Pressure (MWP) | EN 12828 |
| Coating Option (涂层选项) | Optional PEX or PE cross-linked polyethylene inner lining for enhanced insulation | — |
Manufacturing Process
The production of the stainless steel floor coil tube follows a rigorously controlled multi-stage manufacturing sequence, ensuring dimensional precision, metallurgical integrity, and consistent quality throughout the product lifecycle:
- Raw Material Procurement (原材料采购): High-purity stainless steel strip (304 or 316 grade) is sourced from certified mills, with each batch accompanied by a mill test certificate (MTC) verifying chemical composition and mechanical properties. Incoming material undergoes spectroscopic analysis (光谱分析) to confirm elemental compliance.
- Strip Inspection & Cleaning (带材检验与清洗): Raw steel strip is inspected for surface defects, dimensional accuracy, and edge quality. Surface contaminants are removed through alkaline cleaning and acid pickling (酸洗) to ensure a clean substrate for subsequent forming operations.
- Forming & Welding (成型与焊接): The steel strip is fed through precision forming rollers to achieve the target tube cross-section. A high-frequency induction resistance welding (高频感应电阻焊) process is employed to create a longitudinal weld seam. The welding parameters — current, speed, and roll pressure — are continuously monitored and logged to maintain consistent weld quality.
- Heat Treatment (热处理): Welded tubes undergo solution annealing (固溶退火) at 1050–1100°C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance. This eliminates welding-induced sensitization and residual stresses.
- Coiling (盘管成型): Annealed tubes are fed through a coiling machine that winds the tube into a continuous coil at a controlled tension. The coiling process ensures uniform curvature without inducing permanent deformation, kinking, or ovality beyond specified tolerances.
- Pickling & Passivation (酸洗钝化): The coiled tube undergoes an automated pickling and passivation treatment using a citric acid or nitric-hydrofluoric acid bath. This removes any residual oxide scale and forms a protective chromium oxide passive film (Cr₂O₃), ensuring long-term corrosion resistance.
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Quality Inspection (质量检验): Each coil undergoes comprehensive quality assurance testing, including:
- Dimensional verification (外径、壁厚测量) via ultrasonic wall thickness gauging
- Hydrostatic pressure testing (水压试验) at 3 × MWP for a minimum of 30 seconds
- Visual inspection of weld seam continuity and surface finish
- Chemical composition verification via XRF (X-ray Fluorescence) spectroscopy
- Corrosion testing (盐雾试验) per ASTM B117 (≥ 48 hours, no pitting)
- Packaging & Dispatch (包装与发货): Qualified coils are wrapped in moisture-proof protective film, secured with steel straps, and palletized for transport. Each shipment is accompanied by a full material test report, dimensional certificate, and passivation compliance documentation.
Applications
Primary Applications (主要应用领域)
- Underfloor Radiant Heating Systems (地暖系统): The coil tube serves as the heat distribution medium in hydronic underfloor heating (UFH) systems. Its high thermal conductivity (16.3 W/(m·K)) enables rapid and uniform heat transfer to the floor surface, providing comfortable, efficient, and zoned heating for residential apartments, commercial buildings, hospitals, schools, and industrial facilities.
- Underfloor Radiant Cooling (地冷系统): In temperate and subtropical climates, the same coil tube infrastructure can be repurposed for chilled water radiant cooling, providing silent, humidity-controlled comfort without the air movement associated with conventional HVAC systems.
- Floor Radiators (地盘管散热器): The coil tube can be integrated into exposed floor-level radiator assemblies that combine radiant and convective heat emission, providing localized heating for specific zones or perimeter areas of a building.
- Industrial Process Heating (工业工艺加热): In manufacturing environments requiring embedded floor heating for process control — such as food processing facilities, chemical plants, and pharmaceutical cleanrooms — the stainless steel coil tube provides hygienic, corrosion-resistant heat transfer.
- Agricultural & Greenhouse Heating (农业与温室供暖): The coil tube is deployed in greenhouse floors, poultry houses, and aquaculture facilities where reliable, long-life heating is essential for crop and livestock productivity.
- Snow Melting Systems (融雪系统): The coil tube is embedded in parking lots, airport runways, and pedestrian walkways to provide active snow and ice melting through controlled hot water circulation.
System Integration Configuration
In a typical underfloor radiant heating installation, the stainless steel coil tube is laid in a serpentine or loop configuration across the floor slab, secured to an insulation board (聚苯乙烯泡沫板) using stainless steel clips. The coil is then connected to a manifold (分集水器) that distributes heated water from a boiler, heat pump, or solar thermal collector. The floor is subsequently covered with a concrete screed (混凝土找平层) of 40–60 mm thickness, which acts as a thermal mass for even heat distribution. The system is designed to operate at supply temperatures of 35–55°C with a return temperature differential of 5–10°C, in compliance with EN 12828 (Heating Systems in Buildings — Design of Water-Based Heating Systems).
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and ensures all products comply with the following international and national standards:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System (质量管理体系) |
| ISO 14001:2015 | Environmental Management System (环境管理体系) |
| EN 10217-7 | Non-alloy and Alloy Steel Tubes for Mechanical and Technical Purposes — Part 7: Technical Delivery Conditions for Welded Tubes for Heating Installations |
| EN 12828 | Heating Systems in Buildings — Design of Water-Based Heating Systems |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Similar Uses |
| GB/T 12771 | Chinese National Standard — Seamless Stainless Steel Tubes for Fluid Transport (流体输送用不锈钢无缝钢管) |
| ASTM A967 | Standard Practice for Chemical Passivation of Stainless Steel Parts |
| CE Marking | European Conformity — compliance with applicable EU directives |
| SGS / BV / TÜV Inspection | Third-party quality verification and product testing |
Unique Selling Points
- Exceptional Service Life: With a design life exceeding 50 years, the stainless steel coil tube significantly outperforms conventional PEX, PERT, and copper alternatives, eliminating the need for mid-life replacement and reducing total cost of ownership (TCO).
- Superior Thermal Conductivity: At 16.3 W/(m·K), stainless steel offers thermal conductivity approximately 50 times greater than PEX piping, enabling faster heat-up response times and more efficient energy utilization.
- Corrosion Immunity: The austenitic stainless steel matrix with a passivated chromium oxide surface provides outstanding resistance to chloride-induced pitting, crevice corrosion, and general atmospheric corrosion — critical for installations in coastal or chemically aggressive environments.
- Hygienic & Food-Safe: The smooth, non-porous inner surface (Ra ≤ 0.4 μm) prevents biofilm formation and bacterial adhesion,