Stainless Steel Coil Tube for Low-Temperature Radiant Floor Heating Systems
Product Overview
The Stainless Steel Coil Tube (Product No. 705) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for low-temperature hot water radiant floor heating (Low-Temperature Radiant Floor Heating, LTRFH) applications. This coil tube is engineered to operate within laminar flow states within pumped foamed cement pad layers, ensuring uniform heat dissipation, superior thermal conductivity, and long-term hydraulic reliability in underfloor heating circuits. The product embodies advanced metallurgical processing techniques combined with rigorous dimensional control, making it an ideal choice for residential, commercial, and industrial radiant heating installations.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, primarily conforming to ASTM A269 / A270 and GB/T 12771 standards. The material composition ensures exceptional corrosion resistance, mechanical strength, and thermal stability under prolonged exposure to hot water media.
- Grade: 304 (06Cr19Ni10) or 316L (022Cr17Ni12Mo2) austenitic stainless steel
- Corrosion Resistance: Superior resistance to chloride-induced pitting and general corrosion in aqueous heating media
- Thermal Conductivity: ~16 W/(m·K), ensuring efficient radiant heat transfer through the floor assembly
- Operating Temperature Range: -40°C to +120°C (continuous service)
- Operating Pressure: Up to 1.6 MPa (16 bar) at rated temperature
- Surface Finish: Electropolished interior (Ra ≤ 0.4 μm) to minimize flow resistance and prevent scale deposition
- Chemical Composition (304): C ≤ 0.08%, Cr 18–20%, Ni 8–10.5%, Mn ≤ 2.0%, Si ≤ 1.0%
- Chemical Composition (316L): C ≤ 0.03%, Cr 16–18%, Ni 10–14%, Mo 2–3%
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 12 mm, 14 mm, 16 mm, 17 mm, 20 mm (customizable) | GB/T 12771 / ASTM A269 |
| Wall Thickness | 0.8 mm – 1.5 mm | GB/T 12771 |
| Bending Radius | ≥ 30 mm (minimum, without crimping or collapse) | Internal specification |
| Coil Length | 100 m – 300 m per coil (adjustable) | — |
| Dimensional Tolerance (OD) | ±0.1 mm | GB/T 12771 |
| Dimensional Tolerance (Wall Thickness) | ±10% | GB/T 12771 |
| Hydrostatic Test Pressure | 2.5 MPa (25 bar), zero leakage | Internal QC protocol |
| Flow Regime | Laminar flow (Reynolds number Re < 2300) at design conditions | ISO 5167 |
| Design Service Life | ≥ 50 years (corrosion allowance included) | EN 12817 |
| Heat Dissipation Efficiency | ≥ 95% radiant heat transfer ratio through cementitious pad layer | EN 1264 |
| Maximum Flow Velocity | ≤ 1.0 m/s (laminar flow maintenance) | ISO 5167 |
Manufacturing Process
The production of the stainless steel coil tube follows a multi-stage, precision-controlled manufacturing sequence:
- Strip Sourcing & Inspection: High-purity stainless steel strip (coil) is procured from certified mills and subjected to spectroscopic analysis for chemical composition verification.
- Cold Forming & Welding: The strip is cold-formed into tubular shape using precision rolls, followed by automatic orbital TIG (Tungsten Inert Gas) welding to produce a seamless-grade weld seam with full penetration and uniform bead geometry.
- Internal Electropolishing: A specialized electropolishing process is applied to the tube interior, reducing surface roughness to Ra ≤ 0.4 μm. This critical step minimizes frictional losses in laminar flow conditions and prevents biofilm or scale accumulation.
- Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1050–1100°C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Precision Coiling: The finished tube is coiled at controlled radii using automated coiling machinery to prevent ovalization, kinking, or plastic deformation. Each coil is inspected for dimensional conformity.
- Hydrostatic Testing: Every coil undergoes 100% hydrostatic pressure testing at 2.5 MPa to verify weld integrity and structural soundness.
- Final Inspection & Packaging: Non-destructive testing (NDT) including eddy current inspection is performed. Coils are wrapped in protective film and packed in wooden cases for shipment.
Applications
This stainless steel coil tube is purpose-engineered for the following application domains:
- Low-Temperature Radiant Floor Heating (LTRFH): The primary application, where the coil tube is embedded within pumped foamed cement pad layers (Foamed Concrete Slab, FCS) to provide uniform radiant floor heating at supply water temperatures of 35–55°C.
- Laminar Flow Hydraulic Circuits: Designed to maintain laminar flow conditions within the cementitious matrix, ensuring predictable pressure drops, minimal turbulence noise, and energy-efficient pumping.
- Commercial & Industrial Heating: Large-scale radiant floor systems in shopping centers, hospitals, schools, and sports facilities requiring durable, maintenance-free heating circuits.
- HVAC Radiant Systems: Integration into combined heating and cooling radiant panels where stainless steel's thermal stability accommodates both heating and cooling modes.
- Food & Pharmaceutical Processing: Where sanitary-grade 316L stainless steel coil tubes are required for process heating loops and cleanroom floor heating.
Unique Selling Points
- Laminar Flow Optimization: The electropolished interior surface (Ra ≤ 0.4 μm) is specifically engineered to sustain laminar flow regimes within pumped foamed cement pad layers, reducing pumping energy consumption by up to 30% compared to standard-grade tubing.
- 50-Year Service Life: Austenitic stainless steel construction with comprehensive corrosion allowance ensures a design life exceeding 50 years without replacement, significantly outperforming conventional PEX or copper alternatives.
- Seamless-Grade Weld Integrity: Orbital TIG welding with 100% hydrostatic testing guarantees zero-leakage performance under sustained thermal cycling.
- Thermal Efficiency: High thermal conductivity of stainless steel combined with the radiant floor assembly achieves ≥95% heat transfer efficiency through the cementitious pad layer.
- Chemical Inertness: Complete resistance to corrosion from heating water additives, antifreeze solutions, and cementitious alkaline environments.
- Customizable Coil Configuration: Flexible coil lengths (100–300 m) and diameters to match diverse floor plan geometries and heating load calculations.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certifications aligned with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Conformity with European Construction Products Directive (CPD 305/2011/EU) for heating system components
- EN 12817 — Space heating equipment — Requirements and tests for underfloor heating systems
- EN 1264 — Space heating equipment — Radiant heating systems — Terminology and definitions
- GB/T 12771 — Chinese national standard for seamless stainless steel tubes for fluid transport
- GB 50494 — Chinese national standard for design code of radiant floor heating systems
- ASTM A269 / A270 — American standard specifications for austenitic stainless steel tubing
- SUS 304 / 316L — Japanese Industrial Standard (JIS G4305) compliance for austenitic stainless steel
Note: All product specifications are subject to verification against the latest revision of the referenced standards. Custom specifications and project-specific engineering support are available upon request from Wenzhou Jixing Metal Materials Co., Ltd.