Stainless Steel Coil Tube — HVAC Fan Coil Unit Application
1. Product Overview
The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubing product designed primarily for the HVAC (Heating, Ventilation, and Air Conditioning) industry, particularly for use in fan coil units (FCUs) within commercial and residential building systems. This product is engineered to address persistent challenges in HVAC applications, including water leakage, corrosion resistance, and long-term thermal efficiency, as identified in field studies and maintenance analyses of building heating and cooling systems.
The coil tube is formed from high-grade stainless steel wire through advanced coiling and forming processes, resulting in a compact, durable, and corrosion-resistant heat exchange component that significantly extends service life compared to conventional carbon steel alternatives.
2. Material & Properties
The coil tube is fabricated from premium stainless steel (奥氏体不锈钢), selected for its superior mechanical properties, corrosion resistance, and thermal conductivity suitable for HVAC heat exchange applications.
- Material Grade: SUS304 / SUS316L (Austenitic Stainless Steel)
- Composition: Chromium (Cr) ≥ 18%, Nickel (Ni) ≥ 8%, Carbon (C) ≤ 0.08%
- Corrosion Resistance: Excellent resistance to chloride-induced pitting corrosion (pitting) and general atmospheric corrosion, making it suitable for humid indoor environments
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, providing efficient heat transfer performance
- Mechanical Strength: Yield strength ≥ 205 MPa; tensile strength ≥ 515 MPa
- Operating Temperature Range: −40°C to +250°C, accommodating both heating and cooling cycles
- Surface Finish: BA (Bright Annealed) or 2B finish, ensuring smooth internal and external surfaces to minimize flow resistance
3. Specifications
| Parameter | Specification | Unit | Standard Reference |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 / 8.0 / 10.0 | mm | GB/T 14976 |
| Wall Thickness (WT) | 0.5 – 1.5 | mm | GB/T 14976 |
| Coil Diameter | 150 – 600 (customizable) | mm | — |
| Tube Length per Coil | 5 – 50 (customizable) | m | — |
| Operating Pressure | ≤ 1.6 | MPa | GB/T 12771 |
| Hydrostatic Test Pressure | 2.4 | MPa | GB/T 12771 |
| Coil Pitch (Spacing) | 10 – 25 (adjustable) | mm | — |
| Number of Turns | 4 – 20 (configurable) | turns | — |
| Surface Roughness (Ra) | ≤ 0.8 | μm | GB/T 1041 |
| Dimensional Tolerance | ±0.1 | mm | ISO 1128 |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, material integrity, and long-term performance reliability:
- Raw Material Selection: Hot-rolled stainless steel strip (HRS) is sourced from certified mills, undergoing incoming inspection for chemical composition (via Spectroscopic Analysis) and mechanical properties.
- Slitting & Annealing: The strip is slit to precise width and annealed to relieve residual stresses, ensuring uniform material properties and optimal formability.
- Tube Forming: The flat strip is formed into seamless tubing using a high-precision roll-forming (辊压成型) process, followed by resistance welding of the seam where required.
- Coil Winding: The formed tube is wound into the specified coil geometry using a computer-controlled coiling machine (卷管机), with CNC programming ensuring consistent pitch, turn count, and dimensional accuracy.
- Heat Treatment: Post-forming annealing is performed to restore metallurgical properties, eliminate work-hardening effects, and enhance corrosion resistance through passivation (钝化处理).
- Quality Inspection: Each coil tube undergoes hydrostatic pressure testing, dimensional measurement (using CMM — Coordinate Measuring Machine), and visual inspection for surface defects, weld integrity, and geometric conformity.
- Packaging: Finished products are protected with anti-corrosion wrapping and packaged in export-grade wooden crates or plastic wrapping for safe transportation.
5. Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is widely deployed across multiple sectors, with the following primary applications:
- HVAC Fan Coil Units (风机盘管): The primary application — used as the heat exchange coil within FCUs for commercial buildings, hotels, hospitals, and residential complexes. The stainless steel construction directly addresses the water leakage issues commonly encountered with carbon steel coils due to corrosion degradation.
- Chilled Water Systems (冷冻水系统): Serves as the evaporator coil in air handling units (AHUs) and constant volume boxes (CVBs).
- Heating Systems (采暖系统): Utilized in radiant heating coils and underfloor heating manifold connections.
- Industrial Process Cooling: Applied in pharmaceutical, food processing, and electronics manufacturing facilities requiring hygienic, corrosion-resistant heat exchange.
- Marine & Coastal Environments: SUS316L grade coils provide enhanced resistance to salt spray and chloride corrosion in coastal or marine HVAC installations.
Key Technical Advantage: Field studies documented in HVAC maintenance literature have identified water leakage in fan coil units as a critical failure mode, primarily caused by corrosion of carbon steel coils over time. The adoption of stainless steel coil tubes eliminates this failure mechanism, reducing maintenance costs by an estimated 60–70% over the system lifecycle and improving indoor air quality by preventing microbial growth associated with water leakage.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European health, safety, and environmental protection standards
- GB/T 14976 — Seamless and welded stainless steel tubing for general engineering purposes (Chinese National Standard)
- GB/T 12771 — Seamless and welded austenitic stainless steel tubes for fluid transport
- ASTM A312 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
- EN 10216-5 — European standard for heat exchanger tubes made of stainless steel
Every production batch is accompanied by a Mill Test Certificate (MTC) and Material Certificate (材质证明书) documenting chemical composition, mechanical test results, and traceability information in full compliance with international trade and engineering standards.
7. Unique Selling Points
- Superior Corrosion Resistance: Eliminates the root cause of water leakage in HVAC fan coil units, extending service life beyond 15 years under normal operating conditions.
- Precision Coiling: CNC-controlled coiling ensures uniform geometry, optimal airflow distribution, and maximum heat transfer efficiency.
- Customizable Configurations: Available in multiple diameters, wall thicknesses, coil pitches, and turn counts to meet specific OEM requirements.
- Hygienic Surface: Smooth internal bore (Ra ≤ 0.8 μm) minimizes scale buildup and facilitates cleaning, ideal for food-grade and pharmaceutical applications.
- Full Traceability: Each coil tube is traceable from raw material mill through final inspection, ensuring complete quality accountability.