Stainless Steel Coil Tube for Underfloor Heating Systems — Waterproof-Resistant Grade
Product Overview
The Stainless Steel Coil Tube (Product No. 1212) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous coil pipe specifically designed for underfloor radiant heating (UFH) systems. This product addresses the critical engineering challenges encountered when integrating heating coil infrastructure within moisture-exposed environments such as kitchens and bathrooms. Unlike conventional underfloor heating piping, this coil tube incorporates design features and material selections that ensure long-term structural integrity, thermal efficiency, and resistance to water ingress when embedded within waterproofing assemblies.
The coil tube is supplied in a continuous coiled configuration, enabling rapid and seamless installation without the need for field welding or soldering, thereby minimizing potential leak points in waterproof-sensitive zones. This product represents an intersection of heating technology, materials science, and civil engineering waterproofing principles.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and mechanical strength under cyclic thermal loading conditions.
Base Material Specification
- Primary Alloy Grade: AISI 304 / EN 1.4301 (18% Cr, 8% Ni austenitic stainless steel)
- Alternative Grade (for aggressive environments): AISI 316L / EN 1.4404 (16–18% Cr, 10–14% Ni, 2–3% Mo)
- Surface Finish: 2B cold-rolled or BA (Bright Annealed) finish with passivation treatment
- Wall Thickness Tolerance: ±0.05 mm per EN 10216-5
Mechanical & Thermal Properties
- Tensile Strength: ≥ 520 MPa (AISI 304), ≥ 485 MPa (AISI 316L)
- Yield Strength: ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Operating Temperature Range: −40°C to +250°C
- Maximum Working Pressure: 1.6 MPa (16 bar)
- Corrosion Resistance: Equivalent to ASTM A269/A270 standard
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Coil Tube — Product No. 1212 |
| Outer Diameter (OD) | 16 mm, 20 mm, 25 mm (custom sizes available) |
| Wall Thickness | 1.5 mm, 2.0 mm, 2.5 mm |
| Coil Inner Diameter | 500 mm – 1,200 mm |
| Coil Length | 50 m – 300 m (continuous, adjustable per project requirements) |
| Material Standard | AISI 304 / AISI 316L conforming to ASTM A269, EN 10216-5, GB/T 14976 |
| Surface Treatment | Acid pickling and passivation (ASTM A967) |
| Bending Radius | ≥ 5 × OD (cold-formed, no work-hardening) |
| Hydrostatic Test Pressure | 2.5 MPa for 30 seconds, no leakage |
| Service Life | ≥ 50 years (design life under normal operating conditions) |
| Applicable Standards | EN 12156 (UFH systems), GB 50494, JGJ 142 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
Manufacturing Process
The production of this stainless steel coil tube follows a rigorous, multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical homogeneity, and surface quality:
- Raw Material Selection & Incoming Inspection: Stainless steel strip is sourced from certified mills and subjected to spectroscopic analysis (OES) to verify alloy composition within specification tolerances.
- Cold Rolling & Annealing: The strip undergoes precision cold rolling to achieve target thickness, followed by controlled annealing in a protective atmosphere to restore ductility and eliminate residual stresses.
- Seam Welding: Continuous seam welding is performed using TIG (Tungsten Inert Gas) or automatic orbital welding techniques. The weld seam is ground flush and subjected to 100% eddy current testing (ECT) for defect detection.
- Pipe Forming & Coiling: The welded tube is formed to precise outer diameter and wall thickness using calibrated rollers, then coiled at controlled tension to prevent deformation or kinking.
- Acid Pickling & Passivation: The tube undergoes chemical cleaning to remove oxide scale and surface contaminants, followed by passivation treatment to form a stable chromium oxide layer, enhancing corrosion resistance.
- Hydrostatic Pressure Testing: Each coil is subjected to 100% hydrostatic testing at 2.5 MPa to verify structural integrity and weld seam quality.
- Dimensional & Visual Inspection: Final quality control includes verification of outer diameter, wall thickness, coil length, and surface finish against applicable standards.
Applications
This stainless steel coil tube is engineered for demanding underfloor heating applications where conventional polymer piping may be insufficient:
- Underfloor Radiant Heating in Wet Areas: Ideal for kitchens, bathrooms, and laundry rooms where the heating coil must coexist with waterproofing membranes and moisture-prone environments.
- Commercial & Institutional Buildings: Hotels, hospitals, and public facilities requiring durable, long-life heating systems with minimal maintenance.
- High-Temperature Radiant Systems: Suitable for applications requiring sustained operating temperatures up to 250°C, including industrial drying floors.
- Waterproofing-Integrated Floor Systems: The coil tube's corrosion-resistant properties ensure compatibility with cementitious waterproofing compounds, bituminous membranes, and chemical grouts without degradation.
- Marine & Coastal Environments: AISI 316L grade is recommended for coastal buildings where chloride-induced corrosion is a concern.
Waterproofing Integration Guidelines
When embedding this coil tube within waterproofing assemblies for kitchens and bathrooms, the following engineering considerations are critical:
- A minimum concrete or screed cover of 30 mm above the coil tube is required to protect against mechanical damage and ensure uniform heat distribution.
- Compatible waterproofing membranes (e.g., cementitious flexible coatings, liquid-applied membranes) should be applied over the screed layer, not in direct contact with the coil tube.
- Expansion joints should be provided at intervals not exceeding 6 m to accommodate differential thermal expansion between the stainless steel coil and surrounding concrete.
- The thermal expansion coefficient of AISI 304 (17.3 × 10⁻⁶ /°C) should be factored into structural design calculations.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework to ensure product conformity:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Conformity with European Construction Products Regulation (CPR)
- GB/T 19001 — Chinese national standard for quality management
- Material Traceability: Full mill certificates (EN 10204 Type 3.1) available for each batch
- Third-Party Testing: Products available for independent verification by SGS, Bureau Veritas, or TÜV
Unique Selling Points
- Zero-Joint Continuous Coiling: Eliminates field welding entirely, removing the primary failure point in underfloor heating systems installed in waterproof-sensitive zones.
- Superior Corrosion Resistance: Austenitic stainless steel construction provides immunity to chloride pitting, acid attack, and galvanic corrosion — critical advantages over copper and polymer alternatives in wet-area applications.
- Thermal Stability: Maintains dimensional accuracy and mechanical strength across extreme thermal cycling, preventing fatigue failure over decades of service.
- Hygienic Surface: Passivated stainless steel surface resists bacterial colonization, making it suitable for food-processing facilities and healthcare environments.
- Design Flexibility: Continuous coil configuration allows custom layout planning for complex floor geometries without material waste.
- Sustainability: Stainless steel is 100% recyclable, contributing to green building certifications (LEED, BREEAM, Green Star).