Stainless Steel Coil Tube — HVAC Fan Coil & Radiant Floor Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product designed for use in heating, ventilation, and air conditioning (HVAC) systems. This coil tube is specifically engineered for applications in Fan Coil Units (FCU) and Radiant Floor Heating/Cooling Systems, where it serves as the primary heat exchange medium. The product is supplied in continuous coil form to facilitate efficient installation, bending, and integration into complex piping networks with minimal joint requirements.
Based on extensive comparative testing between fan coil unit systems and radiant floor heating/cooling systems, the coil tube has been validated for superior thermal performance, corrosion resistance, and long-term reliability in both hydronic and air-based temperature regulation applications.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, corrosion resistance, and thermal conductivity in HVAC environments.
- Base Material: Austenitic Stainless Steel (SAE 304 / SAE 316L)
- Grade Designation: AISI 304 (UNS S30408) or AISI 316L (UNS S31603)
- Chromium Content: 18.0% – 20.0%
- Nickel Content: 8.0% – 10.5%
- Molybdenum Content (316L): 2.0% – 3.0%
- Carbon Maximum: 0.08% (304) / 0.03% (316L)
- Surface Finish: Polished / Bright Annealed / Passivated
- Corrosion Resistance: Excellent resistance to condensation water, glycol-based heat transfer fluids, and mildly aggressive hydronic media
- Operating Temperature Range: −40°C to +180°C
- Thermal Conductivity: 16.3 W/(m·K) at 25°C
- Specific Heat Capacity: 500 J/(kg·K)
- Maximum Working Pressure: 1.6 MPa (standard) / 2.5 MPa (reinforced)
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Outer Diameter (OD) | 6 / 8 / 10 / 12 / 15 / 16 / 19 / 20 / 22 / 25 / 28 / 32 / 35 / 38 / 40 | mm |
| Wall Thickness | 0.5 / 0.8 / 1.0 / 1.2 / 1.5 / 2.0 | mm |
| Coil Inner Diameter (CID) | 600 / 800 / 1000 / 1200 | mm |
| Coil Length per Spool | 50 – 500 (customizable) | m |
| Tolerance on OD | ±0.05 – ±0.10 | mm |
| Tolerance on Wall Thickness | ±10% | — |
| Minimum Bend Radius | 1.5 × OD (cold bending) | — |
| Surface Roughness (Ra) | ≤ 0.4 | μm |
| Hydrostatic Test Pressure | 2.0 MPa (30 s hold) | MPa |
| Standard Compliance | GB/T 14976, ASTM A554, EN 10217-7 | — |
| End Condition | Plain end / Beveled end / Threaded connection | — |
| Packaging | Wooden pallet + stretch film + desiccant | — |
Manufacturing Process
The coil tube production at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Inspection: Incoming stainless steel strip or seamless tube blanks undergo spectroscopic analysis to verify chemical composition and mechanical properties conform to the specified grade.
- Forming / Welding: For welded coil tube, precision cold-rolled strip is formed into a tubular shape and joined via TIG (Tungsten Inert Gas) welding or frequency induction welding with internal and external argon shielding to prevent oxidation.
- Heat Treatment: Post-weld annealing at 1050°C – 1100°C followed by controlled cooling to restore austenitic microstructure and relieve residual stresses.
- Coiling: The straight tube is cold-coiled to the specified inner diameter using precision winding equipment with controlled tension to avoid deformation or kinking.
- Surface Treatment: Acid pickling and passivation (HNO₃/HF blend) to remove oxide scale and establish a protective chromium oxide passive layer.
- Quality Control: Each coil undergoes hydrostatic pressure testing, dimensional measurement, visual inspection, and non-destructive testing (EDDY CURRENT / ULTRASONIC TESTING) to detect internal and surface defects.
- Final Inspection & Packaging: Coils are labeled, bundled, and packaged for shipment with full traceability documentation.
Applications
The stainless steel coil tube is designed for a wide range of HVAC and building services applications:
- Fan Coil Units (FCU): Serves as the heat exchanger coil tubing in both air-cooled and water-cooled fan coil units for commercial and residential temperature regulation.
- Radiant Floor Heating/Cooling: Embedded within concrete screed or underfloor structures as the hydronic piping loop for low-temperature heating and chilled-water cooling.
- Chilled Beam Systems: Used in active and passive chilled beam air conditioning configurations.
- Underfloor Air Distribution (UFAD): Integrated into displacement ventilation systems requiring corrosion-resistant piping.
- Commercial Refrigeration: Evaporator and condenser coil tubing in food processing and cold storage facilities.
- Industrial Process Cooling: Heat exchanger tubes in chemical, pharmaceutical, and food-grade process loops.
- Geothermal Heat Pump Systems: Buried piping for ground-source heat exchange loops.
Comparative Performance: Fan Coil vs. Radiant Floor Systems
Based on comparative testing between fan coil unit systems and radiant floor heating/cooling systems, the following key performance indicators were established:
| Performance Parameter | Fan Coil Unit System | Radiant Floor System |
|---|---|---|
| Heat Transfer Efficiency | High (convection-dominated) | Moderate (radiation-dominated) |
| Temperature Uniformity | Moderate (±2.0°C) | Excellent (±0.5°C) |
| Energy Consumption (kWh/m²·a) | 45 – 65 | 30 – 50 |
| Comfort Index | Good | Superior |
| Installation Complexity | Moderate | High |
| Maintenance Frequency | Quarterly (filter cleaning) | Minimal (closed-loop) |
| Coil Tube Service Life | 20 – 25 years | 25 – 50 years |
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and compliance standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- GB/T 14976 — Chinese National Standard for Cold-Drawn Stainless Steel Seamless Tubes
- ASTM A554 — Standard Specification for Welded Austenitic Stainless Steel Tubing
- EN 10217-7 — European Standard for Non-Alloy and Stainless Steel Tubes for Technical Purposes
- GB/T 12771 — Chinese Standard for Stainless Steel Welded Tubes
- Material Test Report (MTR): Provided with each batch, including chemical analysis, mechanical test data, and heat treatment records
- Mill Test Certificate (MTC): Full traceability from raw material to finished product
- Third-Party Inspection: Available upon request (SGS, BV, TUV)
Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel construction ensures immunity to corrosion from condensation water, glycol solutions, and mildly aggressive hydronic media, significantly extending service life beyond carbon steel alternatives.
- Low Surface Roughness (Ra ≤ 0.4 μm): Minimizes hydraulic resistance and fouling tendency, maintaining consistent heat transfer performance over the system's operational lifetime.
- Continuous Coil Supply: Delivered in coil form to eliminate field welding joints, reducing leak risk and installation time by up to 40% compared to straight-length pipe.
- Flexible Bending Capability: Cold-bendable to a minimum radius of 1.5 × OD without special tooling, enabling on-site adaptation to complex floor plans and equipment layouts.
- Validated HVAC Performance: Tested and proven in both fan coil unit and radiant floor heating/cooling applications with documented comparative performance data.
- Food-Grade & Pharmaceutical Compatibility: 316L grade available for applications requiring compliance with FDA and pharmaceutical-grade hygienic standards.
- Full Traceability: Every coil is accompanied by a complete Material Test Report (MTR) and Mill Test Certificate (MTC) for engineering verification and quality audit purposes.
Technical Note: The selection between Fan Coil Unit (FCU) systems and Radiant Floor systems should be determined by a comprehensive analysis of building load characteristics, indoor comfort requirements, installation constraints, and lifecycle cost evaluation. The coil tube from Wenzhou Jixing Metal Materials Co., Ltd is engineered to perform optimally in either configuration, providing a versatile solution for modern building HVAC design.