Stainless Steel Coil Tube — Fan Coil Unit System Component
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coil tube component designed specifically for integration into building internal Fan Coil Unit (FCU) systems. This product serves as a critical heat exchange and fluid circulation element within modern hydronic air conditioning and heating infrastructure. The coil tube is engineered to withstand the rigorous thermal cycling, pressure fluctuations, and continuous fluid flow demands inherent in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) environments.
With the advancement of intelligent building control methodologies — particularly Deep Reinforcement Learning (DRL)-based optimization frameworks — the demand for high-performance coil tube components that respond reliably to variable-speed pumping and dynamic thermal regulation has increased substantially. This product is designed to meet the operational parameters required by next-generation smart building management systems (Building Management Systems, BMS) that employ reinforcement learning agents for real-time thermal load balancing and energy consumption minimization.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and mechanical durability. The material composition ensures long-term performance stability in both water-based and glycol-based heat transfer media environments.
- Base Material: Austenitic Stainless Steel (grades 304 / 316L conforming to ASTM A269 / A270 standards)
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and general atmospheric corrosion, particularly in chloride-containing environments
- Thermal Conductivity: Optimized for efficient heat transfer between the internal fluid medium and the external fin structure of the FCU coil assembly
- Mechanical Strength: High tensile strength and yield strength ensuring structural integrity under operating pressures up to 1.6 MPa (232 psi)
- Weldability: Excellent cold and hot forming properties enabling reliable expansion, bending, and brazing during coil assembly
- Surface Finish: Interior surface with low roughness (Ra ≤ 0.8 μm) to minimize flow resistance and fouling accumulation
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) | — |
| Catalogue No. | 373 | Wenzhou Jixing Internal Classification |
| Material Grade | ASTM 304 / 316L (Austenitic Stainless Steel) | ASTM A269 / A270 |
| Outer Diameter (OD) | Φ 6.35 mm / Φ 8.00 mm / Φ 9.53 mm (configurable) | ANSI B8.18.1 |
| Wall Thickness | 0.5 mm – 1.2 mm (selectable per application) | — |
| Coil Diameter (Coil OD) | 150 mm – 600 mm (configurable) | — |
| Tube Length per Coil | Up to 120 m (continuous coil form) | — |
| Operating Pressure | Up to 1.6 MPa (232 psi) | EN 12745 / ISO 1307 |
| Operating Temperature Range | −20 °C to +150 °C | — |
| Surface Treatment | Pickled and Passivated (Interior & Exterior) | ASTM A967 |
| End Form | Plain end / Flared / Threaded / Brazed (customizable) | — |
| Heat Transfer Medium | Water / Glycol-Water Mixture (up to 50% ethylene glycol) | ASHRAE Standard 90.1 |
| Fin Configuration | Compatible with aluminum louvered / plain fins (24–32 FPI) | — |
| Standards Compliance | ISO 9001:2015, CE Marking, EN 12745 | — |
4. Manufacturing Process
The production of the stainless steel coil tube follows a multi-stage precision manufacturing workflow designed to ensure dimensional accuracy, material homogeneity, and functional reliability:
- Raw Material Selection: Cold-rolled stainless steel strip of certified grade is procured from accredited mills, with full chemical composition analysis (spectrometric verification) and mechanical property testing prior to acceptance.
- Forming & Seaming: The flat strip is passed through a series of progressive roll-forming stations to achieve the target tube diameter. The seam is formed via a high-precision welding process (TIG welding or resistance seam welding) with 100% seam integrity inspection.
- Heat Treatment & Annealing: Post-forming annealing at controlled temperatures relieves residual stresses introduced during cold working, restoring full austenitic microstructure and optimal mechanical properties.
- Pickling & Passivation: Both interior and exterior surfaces undergo chemical pickling to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide layer, ensuring maximum corrosion resistance.
- Coil Winding: The formed tube is wound onto precision mandrels using CNC-controlled coiling machines to achieve uniform coil diameter, consistent pitch, and controlled winding tension — critical for maintaining tube geometry during downstream fin-tube assembly.
- Quality Inspection: Each coil batch undergoes dimensional verification (laser measurement), pressure testing (hydrostatic at 2.4× operating pressure for 30 minutes), and visual/eddy current inspection for seam defects.
- Packaging & Delivery: Coils are wrapped in protective film, secured with strapping, and packaged for transport with appropriate documentation including material test certificates (MTC) and dimensional inspection reports.
5. Applications
The stainless steel coil tube is engineered for deployment in the following application domains:
- Fan Coil Units (FCU): Primary application — serving as the core heat exchange tube in ceiling-mounted, wall-mounted, and ducted FCU systems for commercial buildings, hotels, hospitals, and residential complexes.
- Smart Building Systems: Optimized for integration with DRL-based intelligent control systems that dynamically modulate flow rates, pump speeds, and valve positions for energy-efficient thermal regulation.
- Commercial HVAC Systems: Suitable for constant-volume and variable-air-volume (VAV) air handling units where corrosion resistance and long service life are paramount.
- Hydronic Heating & Cooling Circuits: Compatible with district heating networks, geothermal systems, and heat pump-based cooling plants.
- Process Cooling: Applicable in pharmaceutical, food processing, and laboratory environments requiring hygienic-grade fluid handling components.
- Marine & Coastal Environments: Grade 316L variant provides enhanced resistance to salt-laden atmospheres for coastal and offshore facility HVAC applications.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity to international standards:
- ISO 9001:2015 — Quality Management System certification covering the entire manufacturing and supply chain
- CE Marking — Conformity with European Union directives for construction products (CPR 305/2011)
- EN 12745 — Compliance with European standard for air conditioning equipment and heat pumps (tube assemblies)
- ASTM A269 / A270 — Material specifications for welded austenitic stainless steel tubing
- Material Test Certificates (MTC) — EN 10204 Type 3.1 certificates provided with each shipment
- Pressure Test Reports — Batch-level hydrostatic pressure test documentation included
7. Unique Selling Points
Intelligent System Compatibility: This coil tube product is specifically characterized for seamless integration into Deep Reinforcement Learning–based FCU control architectures. Its uniform geometry, consistent hydraulic characteristics, and predictable thermal response enable accurate system modeling and efficient agent training for real-time energy optimization in smart building environments.
- Enhanced Corrosion Longevity: Superior resistance to scaling and corrosion extends system service life beyond 20 years under normal operating conditions, reducing lifecycle maintenance costs.
- Hydraulic Consistency: Precision winding and dimensional control ensure uniform flow distribution across all coil passes, preventing localized flow maldistribution that degrades heat transfer efficiency.
- Customizable Configuration: Multiple tube diameters, wall thicknesses, coil diameters, and end treatments available to accommodate diverse FCU designs and system design pressures.
- Full Traceability: Each production batch carries complete material provenance documentation, enabling end-to-end supply chain traceability for regulatory and audit compliance.
- Energy Efficiency Contribution: Low-surface-roughness interior finish minimizes pressure drop (ΔP), reducing pumping energy consumption — a critical factor in LEED and Green Star building certification projects.