Stainless Steel Heating Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Heating Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for radiant heating systems, central heating distribution networks, and industrial thermal transfer applications. The product is supplied in coiled form to facilitate on-site installation, minimize joint points, and reduce the risk of leakage in closed-loop heating circuits.
This Coiltube integrates the inherent corrosion resistance and hygienic properties of austenitic stainless steel with the geometric flexibility of continuous coil configuration, making it a superior alternative to traditional carbon steel, copper, or PEX (Polyethylene Pipe, cross-linked) heating tubes in demanding environments.
2. Material & Properties
2.1 Base Material
- Primary Alloy Grades: AISI 304 (UNS S30400) and AISI 316L (UNS S31603), conforming to ASTM A213 / ASTM A269 standards.
- Composition (AISI 304): Carbon (C) ≤ 0.08%, Chromium (Cr) 18.0–20.0%, Nickel (Ni) 8.0–10.5%, Manganese (Mn) ≤ 2.0%, Silicon (Si) ≤ 1.0%, Phosphorus (P) ≤ 0.045%, Sulfur (S) ≤ 0.030%.
- Composition (AISI 316L): Carbon (C) ≤ 0.03%, Chromium (Cr) 16.0–18.0%, Nickel (Ni) 10.0–14.0%, Molybdenum (Mo) 2.0–3.0%, remaining balance Iron (Fe).
2.2 Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (AISI 304); ≥ 485 MPa (AISI 316L).
- Yield Strength (0.2% Offset): ≥ 205 MPa (AISI 304); ≥ 170 MPa (AISI 316L).
- Elongation at Break: ≥ 40% (AISI 304); ≥ 35% (AISI 316L).
- Hardness (Rockwell B): ≤ 95 HRB.
2.3 Thermal & Physical Properties
- Thermal Conductivity: 16.3 W/(m·K) at 100°C.
- Thermal Expansion Coefficient: 16–17.5 × 10⁻⁶ /°C (20–100°C range).
- Maximum Operating Temperature: 870°C (AISI 304); 815°C (AISI 316L).
- Corrosion Resistance: Excellent resistance to atmospheric, freshwater, and mild chemical environments; AISI 316L grade provides superior pitting and crevice corrosion resistance due to Molybdenum addition.
3. Specifications
| Parameter | Specification | Standard / Tolerance |
|---|---|---|
| Outer Diameter (OD) | 8 mm – 35 mm | ASTM A213; ±0.1 mm |
| Wall Thickness (WT) | 0.5 mm – 1.5 mm | ASTM A269; ±10% |
| Coil Inner Diameter (CID) | 500 mm – 1200 mm | Customizable per project requirement |
| Coil Length per Spool | 100 m – 500 m | As per customer order |
| Surface Finish | Ba & Le (Pickled & Polished), 2B, or Mirror (Ra ≤ 0.2 μm) | ASTM A403 |
| End Condition | Plain cut, beveled, or threaded | ISO 16029 |
| Pressure Rating (Design) | Up to 1.6 MPa (PN16) at 95°C | GB/T 21952; EN 12828 |
| Design Service Life | ≥ 50 years | EN 12828; ISO 10555 |
| Heat Medium | Water / Water-Glycol mixture (up to 50% ethylene glycol) | EN 442 |
| Operating Temperature Range | -20°C to +120°C | — |
4. Manufacturing Process
- Raw Material Procurement: Cold-rolled stainless steel strip (coil) is sourced from certified mills with full mill test certificates (MTC) conforming to EN 10204 3.1.
- Strip Inspection & Cleaning: Incoming strip undergoes visual inspection, dimensional verification, and ultrasonic flaw detection (UT) to ensure freedom from surface defects and internal laminations.
- Forming (Roll Forming / Cold Bending): The strip is cold-formed into a tubular profile using precision roll-forming machines with calibrated tooling sets. Controlled forming forces ensure uniform wall thickness and ovality within tolerance.
- Seam Welding (if applicable): For welded coil tubes, Gas Metal Arc Welding (GMAW) or Laser Welding is employed with inert gas shielding (Argon, Ar) to achieve a hermetic seam. Weld bead height is controlled to ≤ 0.1 mm.
- Coiling: The formed tube is wound onto precision coiling drums to produce the final coiltube configuration. Tension control systems prevent coil springback and maintain consistent coil geometry.
- Pickling & Passivation (Ba&Le): The coiltube is subjected to acid pickling (HNO₃/HF mixture) to remove oxide scale, followed by passivation treatment to form a stable chromium oxide protective layer.
- End Trimming & Finishing: Tube ends are trimmed to length, deburred, and optionally beveled or threaded for connection compatibility.
- Final Inspection & Packaging: Each coil undergoes dimensional verification, pressure testing (hydrostatic test at 1.5× design pressure), and visual inspection. Coils are packaged with protective wrapping, moisture barriers, and labeled with traceability data.
5. Applications
- Residential & Commercial Radiant Floor Heating: The Coiltube serves as the primary heat distribution medium in under-floor radiant heating systems, where continuous coil runs eliminate unnecessary fittings and reduce thermal bridging.
- Central Heating Circuits: Used in district heating networks and building-level hydronic loops for heat transfer between boilers/heat exchangers and terminal units.
- Industrial Process Heating: Employed in chemical processing, food & beverage, and pharmaceutical industries where corrosion resistance and sanitary-grade surfaces are critical.
- Heat Exchanger Coils: Configured as coil-type heat exchangers in air-source heat pumps, solar thermal collectors, and cooling towers.
- Agricultural & Greenhouse Heating: Deployed in agricultural facilities requiring corrosion-resistant heating circuits exposed to high-humidity and ammonia-rich environments.
- Marine & Offshore Heating Systems: AISI 316L grade coiltubes are suitable for marine heating applications where chloride-induced pitting corrosion is a concern.
6. Quality Certifications & Standards Compliance
- ISO 9001:2015 — Quality Management System certification covering manufacturing and supply chain processes.
- ISO 14001:2015 — Environmental Management System, ensuring sustainable production practices.
- EN 10204 3.1 — Material Test Certificate (MTC) provided with each batch for full traceability.
- CE Marking — Compliance with EU Construction Products Regulation (CPR) for heating system components.
- GB/T 21952 — Chinese national standard for plastic and metal pipes used in central heating systems.
- EN 12828 — European standard for radiant heating systems in buildings.
- ASME B31.3 — Compliance for process piping applications (where applicable).
- Third-Party Inspection: Available upon request — SGS, TÜV, or Bureau Veritas inspection for dimensional, mechanical, and corrosion testing.
7. Unique Selling Points (USP)
- Zero-Fitting Continuous Runs: The coiltube configuration enables long, uninterrupted pipe runs with minimal or no mechanical joints, significantly reducing the probability of leakage points over the 50-year design life.
- Superior Corrosion Resistance: Unlike carbon steel alternatives, the stainless steel alloy composition provides inherent resistance to oxidation, rust, and chemical degradation — even in aggressive water chemistry (pH 6.5–9.5, chloride content up to 200 ppm).
- Hygienic Surface Integrity: The pickled & passivated surface achieves a roughness of Ra ≤ 0.5 μm, preventing biofilm formation and ensuring sanitary operation in food-grade and pharmaceutical applications.
- Thermal Efficiency: Stainless steel's thermal conductivity (16.3 W/m·K) is significantly higher than PEX (0.4 W/m·K) and PE-RT (0.35 W/m·K), resulting in faster heat response times and reduced system pumping energy.
- Dimensional Stability: The austenitic crystal structure ensures minimal creep deformation at operating temperatures up to 120°C, maintaining system pressure integrity over decades of service.
- Full Traceability: Each coil is serialized with heat number, batch code, and test data, enabling complete lifecycle traceability from raw material to end-of-life recycling.
- 100% Recyclable: Stainless steel is fully recyclable without degradation of material properties, supporting circular economy and ESG (Environmental, Social, and Governance) sustainability goals.
8. Ordering & Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides customized coiltube solutions tailored to specific project requirements, including non-standard diameters, wall thicknesses, coil configurations, and end-finishing options. Technical support, including system design consultation, installation guidance, and commissioning assistance, is available throughout the project lifecycle. For detailed quotations and engineering data sheets, please contact the manufacturer's technical sales department directly.