Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (commonly referred to as Coiltube) is a precision-engineered continuous-length tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for thermal-fluid distribution systems, including underfloor radiant heating, hydronic heating loops, and compact branch-unit heating circuits. The coil tube is supplied in continuous coiled form, enabling seamless installation over extended distances without the need for field welding or mechanical fittings at intermediate points.
Based on thermal performance research into light and thin water underfloor heating systems combined with branch coil tube joint heating configurations, the Coiltube product line demonstrates superior heat transfer efficiency, hydraulic stability, and long-term durability when deployed in integrated hydronic heating networks. The continuous coil geometry minimizes pressure drop and eliminates potential leak points, making it an ideal choice for high-reliability heating infrastructure.
2. Material & Properties
The Coiltube product is fabricated from high-purity austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical integrity under sustained thermal cycling.
- Primary Grades: AISI 304 (UNS S30408) and AISI 316 (UNS S31608), with 316L (UNS S31603) available for aggressive chemical environments.
- Surface Finish: Electro-polished or mechanical-polished interior surface (Ra ≤ 0.4 μm) to minimize fouling and reduce flow resistance.
- Corrosion Resistance: Excellent resistance to oxidation, scaling, and pitting in potable water, glycol-based heat transfer fluids, and condensate environments.
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 25°C (grade-dependent), ensuring efficient radiant heat transfer to the surrounding medium.
- Operating Temperature Range: −196°C to +870°C (AISI 304); −196°C to +870°C (AISI 316), with sustained cyclic performance without embrittlement.
- Pressure Rating: Designed to withstand internal pressures up to 1.6 MPa (PN16) for standard wall thicknesses; custom high-pressure variants available upon request.
- Mechanical Properties: Tensile strength ≥ 515 MPa (AISI 304, annealed); elongation ≥ 40%; yield strength ≥ 205 MPa.
- Non-Magnetic (Annealed): After full solution annealing, magnetic permeability is negligible, suitable for MRI-adjacent installations.
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm, 8.0 mm, 10.0 mm, 12.0 mm, 15.0 mm, 16.0 mm, 20.0 mm (custom sizes available) | EN 10217, ASTM A213 |
| Wall Thickness | 0.5 mm – 1.5 mm (standard); up to 3.0 mm (special order) | ISO 3506 |
| Coil Diameter (Bundle) | 500 mm – 3,000 mm (configurable based on application) | — |
| Coil Length per Spool | 50 m – 300 m (continuous, seam-free) | — |
| Material Grade | AISI 304 / 304L / 316 / 316L | ASTM A213 / EN 10217-7 |
| Manufacturing Method | Continuous cold drawing (cold-drawn seamless) | ISO 10449 |
| Surface Roughness (Interior) | Ra ≤ 0.4 μm (electro-polished); Ra ≤ 0.8 μm (mechanical-polished) | ISO 1302 |
| Dimensional Tolerance | OD: ±0.05 mm; Wall thickness: ±0.02 mm | EN 10217-3 |
| Hydrostatic Test Pressure | ≥ 2.5 × working pressure (100% inspection) | ISO 449 |
| Coating / Protection | Passivated; optional PTFE inner coating for enhanced anti-fouling | — |
| End Condition | Plain cut, chamfered, or pre-threaded (upon request) | — |
| Maximum Operating Pressure | 1.6 MPa (standard); 4.0 MPa (reinforced variant) | ASME B31.3 |
| Minimum Bend Radius | ≥ 3 × OD (cold bending without deformation) | — |
| Delivery Condition | Annealed (soft), Solution Annealed, or Work-Hardened | ASTM A240 |
4. Manufacturing Process
The Coiltube product undergoes a rigorous multi-stage manufacturing process to ensure dimensional precision, metallurgical homogeneity, and surface integrity:
- Raw Material Procurement & Verification: Ingot or strip stock is sourced from certified mills with full chemical composition analysis (spectrometric verification of Cr, Ni, Mo, C, Si, Mn content per ASTM/EN specifications).
- Continuous Cold Drawing (Cold-Drawn Seamless): Strip or pre-formed blanks are drawn through precision tungsten carbide dies to produce seamless tubing with tight dimensional tolerances. This process eliminates weld seams, ensuring uniform wall thickness and leak-free integrity throughout the entire coil length.
- Intermediate Annealing: Periodic solution annealing (1050–1150°C, followed by rapid water quench) relieves cold-work hardening, restores ductility, and ensures consistent mechanical properties along the coil length.
- Precision Sizing & Coiling: The drawn tubing passes through a series of calibrating dies to achieve final OD and wall thickness tolerances, then is coiled onto precision mandrels at controlled tension to prevent ovality and distortion.
- Surface Treatment & Passivation: Interior surfaces are electro-polished or mechanically polished to achieve specified roughness values. Exterior surfaces receive chemical passivation (nitric acid or citric acid treatment) to establish a stable chromium oxide protective layer.
- Hydrostatic Testing: 100% of production coils are subjected to hydrostatic pressure testing at 2.5× the rated working pressure for a minimum dwell time of 10 seconds per joint length, with automated leak detection systems.
- Non-Destructive Testing (NDT): Eddy current testing (per ASTM E309) and ultrasonic testing (per ASTM E1650) are performed to detect internal defects, wall thickness variations, and surface discontinuities.
- Final Inspection & Packaging: Each coil is tagged with a unique batch identification number, accompanied by a Mill Test Certificate (MTC) per EN 10204 Type 3.1. Coils are wrapped in protective film and secured on wooden or steel pallets for shipment.
5. Applications
The Stainless Steel Coiltube is engineered for demanding thermal-fluid applications where reliability, hygiene, and longevity are paramount:
- Underfloor Radiant Heating Systems: Continuous coil tubes are embedded in lightweight, thin-profile underfloor heating assemblies. Research into light and thin water underfloor heating with branch coil tube joint heating has demonstrated that stainless steel coil configurations achieve superior heat distribution uniformity (temperature deviation ≤ ±2°C across the heated zone) compared to conventional PEX or copper alternatives, with significantly reduced thermal mass and faster response times.
- Branch-Unit Heating Circuits: Coiltube is deployed in compact, modular branch heating units for commercial and industrial facilities, where space-constrained installations require high-density heat exchange loops with minimal footprint.
- HVAC Chilled Water Distribution: Used in chilled water supply and return lines for air conditioning systems, leveraging corrosion resistance and long service life in glycol-water mixtures.
- Food & Beverage Processing: Sanitary-grade 316L Coiltube is employed in CIP (Clean-In-Place) systems, pasteurization loops, and hygienic fluid transfer where FDA-compliant surfaces are mandated.
- Pharmaceutical & Bioprocessing: GMP-compliant tubing for clean steam distribution, condensate return, and process water circuits in pharmaceutical manufacturing environments.
- Geothermal & Solar Thermal Systems: Resistant to mineral-laden geothermal brines and solar thermal heat transfer fluids (HTF), providing 25+ year service life without degradation.
- Marine & Desalination Systems: 316L grade Coiltube resists chloride-induced pitting and crevice corrosion in seawater and brackish water applications.
- Industrial Process Heating: Deployed in heat exchanger tube bundles, steam tracing systems, and process heater circuits in chemical, petrochemical, and pulp/paper industries.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification frameworks to ensure traceability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing operations.
- ISO 14001:2015 — Environmental Management System, ensuring sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- EN 10204 Type 3.1 — Mill Test Certificates (MTC) issued with every batch, documenting chemical composition, mechanical properties, and test results.
- Product Standards Compliance:
- ASTM A213 / A269 — Specification for seamless austenitic stainless steel tubing.
- EN 10217-3 — Heat-resistant, creep-resistant, and high-strength steels (tubular products).
- ISO 3506 — Specifications for stainless steel tubes and pipes for general purposes.
- GB/T 12771 — Chinese national standard for welded stainless steel tubes (applicable where relevant).
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes.
- Third-Party Testing: Products are periodically verified by accredited laboratories (SGS, TÜV, Intertek) for dimensional accuracy, chemical composition, mechanical properties, and corrosion resistance.
- Traceability: Each coil is laser-marked with a unique batch code enabling full traceability from raw material mill to end installation.
7. Unique Selling Points
- Seamless Continuous Construction: Elimination of weld joints across the entire coil length ensures zero leak risk points, dramatically improving system reliability and reducing maintenance costs over the service life.
- Proven Thermal Performance: Validated through research on integrated light/thin underfloor heating with branch coil tube configurations, demonstrating superior heat transfer efficiency and temperature uniformity in real-world hydronic heating systems.
- Exceptional Corrosion Resistance: Austenitic stainless steel composition provides decades of service life in aggressive aqueous environments, including glycol heat transfer fluids, geothermal brines, and chlorinated water systems.
- Precision Dimensional Tolerances: Cold-drawing process achieves ±0.05 mm OD and ±0.02 mm wall thickness tolerances, ensuring consistent hydraulic performance and compatibility with precision fittings.
- Hygienic Surface Quality: Electro-polished interior surfaces (Ra ≤ 0.4 μm) prevent biofilm formation and facilitate CIP cleaning, meeting the most stringent food-grade and pharmaceutical hygiene standards.
- Design Flexibility: Available in a wide range of ODs, wall thicknesses, coil diameters, and material grades, with custom configurations available for specialized applications.
- Full Traceability & Certification: Every batch is accompanied by EN 10204 Type 3.1 MTC and full traceability documentation, ensuring compliance with international regulatory frameworks.
8. Ordering Information & Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support for Coiltube selection, system design consultation, and installation guidance. Customers are encouraged to provide application-specific parameters (operating temperature, pressure, fluid type, coil layout requirements) to receive optimized product recommendations and engineering drawings. Custom manufacturing lead times range from 15 to 30 calendar days depending on specification complexity and order volume.