Stainless Steel Coil Tube — Industrial Fan Coil Unit Application Series
Wenzhou Jixing Metal Materials Co., Ltd. presents its premium-grade stainless steel coil tube product line, engineered for integration into fan coil unit (FCU) wireless IoT control system applications. This product series represents the convergence of advanced metallurgical engineering and modern building automation technology, delivering superior thermal performance, corrosion resistance, and long-term structural integrity for HVAC (Heating, Ventilation, and Air Conditioning) systems.
Product Overview
The stainless steel coil tube is a precision-formed tubular product manufactured in continuous coil form, specifically designed for use as heat exchange elements within fan coil units. These units serve as terminal devices in hydronic air conditioning systems, transferring thermal energy between circulating fluid and ambient air. The coil tube forms the core heat transfer surface, making its material properties and dimensional accuracy critical to system efficiency.
Wenzhou Jixing Metal Materials Co., Ltd. produces stainless steel coil tubes that comply with international standards for tubing dimensions, mechanical properties, and chemical composition. The products are manufactured to meet the rigorous requirements of modern IoT-enabled HVAC systems, where reliable heat exchange performance is essential for maintaining precise temperature and humidity control.
Material & Properties
Base Material Grades
- Grade 304 (AISI 304 / 06Cr19Ni10): The most widely used austenitic stainless steel, offering excellent general corrosion resistance, formability, and weldability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- Grade 316 (AISI 316 / 022Cr17Ni12Mo2): Enhanced corrosion resistance due to the addition of 2-3% Molybdenum (Mo), making it suitable for aggressive chemical environments and high-moisture applications.
- Grade 321 (AISI 321 / 06Cr18Ni11Ti): Stabilized with Titanium (Ti) to prevent intergranular corrosion during welding, ideal for high-temperature heat exchange applications.
Key Mechanical Properties
| Property | Grade 304 | Grade 316 | Grade 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Thermal Conductivity (W/m·K at 20°C) | 16.3 | 14.6 | 16.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
| Density (g/cm³) | 8.0 | 8.0 | 8.0 |
Corrosion Resistance Characteristics
- Excellent resistance to atmospheric corrosion, acid solutions, and industrial chemicals
- Non-magnetic in the annealed condition (austenitic structure)
- Low carbon content (≤ 0.08%) minimizes sensitization during welding
- Surface finish options: 2B (cold rolled and annealed), BA (Bright Annealed), No. 4 (brushed), and No. 8 (mirror polished)
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Fan Coil Unit Series) |
| Item No. | 505 |
| Tube Outer Diameter (mm) | 6.35 / 8.0 / 9.52 / 12.7 (custom sizes available) |
| Tube Wall Thickness (mm) | 0.40 – 0.80 |
| Coil Width (mm) | 100 – 500 (configurable per application) |
| Coil Inner Diameter (mm) | 508 / 610 |
| Coil Length (m) | 30 – 100 (standard); custom upon request |
| Material Grade | SUS 304 / SUS 316 / SUS 321 |
| Surface Finish | 2B / BA / No. 4 / No. 8 |
| Tolerance (OD) | ± 0.05 mm |
| Tolerance (Wall Thickness) | ± 10% |
| Applicable Standards | ASTM A269 / ASTM A213 / GB/T 12771 / EN 10216-5 |
| Operating Pressure | Up to 1.6 MPa (standard); up to 4.0 MPa (reinforced) |
| Operating Temperature Range | -50°C to +250°C |
| Coating Options | Uncoated / Anti-corrosion inner coating / Fluoropolymer coating |
Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing process to ensure consistent quality and dimensional accuracy:
- Raw Material Selection: Certified stainless steel strip (cold-rolled coil) is sourced from approved mills and subjected to incoming quality inspection, including spectroscopic analysis for chemical composition verification.
- Slitting: The master coil is slit to the required width using high-precision slitting lines, ensuring clean edges with minimal burr formation.
- Forming (Roll Forming): The slitted strip is passed through a series of progressive rolls that incrementally form the flat strip into a tubular shape. This cold-forming process maintains the material's mechanical properties while achieving the target outer diameter.
- Welding: The formed tube is welded using high-frequency induction welding (HF welding) or TIG (Tungsten Inert Gas) welding. The weld seam is subsequently dressed and ground to achieve a smooth internal surface, minimizing flow resistance.
- Heat Treatment: Where required, the tube undergoes solution annealing at temperatures between 1050°C and 1150°C followed by rapid quenching to restore full austenitic microstructure and maximum corrosion resistance.
- Pickling and Passivation: The surface is treated with acid pickling to remove oxide scale, followed by passivation to form a protective chromium oxide layer.
- Surface Finishing: The tube is polished or brushed to the specified surface finish grade, achieving the desired aesthetic and functional properties.
- Quality Inspection: Each coil undergoes dimensional measurement, hydrostatic pressure testing, and visual inspection of weld seams. Non-destructive testing (NDT) methods including ultrasonic testing (UT) and eddy current testing (ECT) are applied as required.
- Coiling and Packaging: Finished coils are wound onto standard cores, protected with moisture-absorbent packaging, and labeled with traceability information.
Applications
Primary Application: Fan Coil Unit Heat Exchangers
The principal application of this stainless steel coil tube is as the heat exchange element in fan coil units. In a typical FCU system, chilled or heated water circulates through the coil tubes while a fan blows ambient air across the tube fins. The stainless steel material provides:
- Superior corrosion resistance: Eliminates the risk of tube deterioration from humid air, condensate, or chemical cleaning agents commonly used in HVAC maintenance.
- Long service life: Expected operational lifespan exceeding 25 years under normal conditions, significantly outperforming carbon steel alternatives.
- Hygienic performance: Smooth internal surfaces prevent biofilm accumulation, making the product suitable for cleanroom and pharmaceutical applications.
- IoT integration compatibility: The dimensional stability and thermal properties of stainless steel coil tubes ensure reliable performance when integrated with wireless IoT control systems for real-time monitoring of flow rate, temperature differential, and heat transfer efficiency.
Secondary Applications
- Chilled beam systems and radiant cooling panels
- Industrial process cooling and heating circuits
- Food and beverage industry heat exchangers (hygienic grade)
- Pharmaceutical cleanroom HVAC systems
- Marine HVAC applications (Grade 316)
- Refrigeration evaporator coils
- Geothermal heat pump systems
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliances:
- ISO 9001:2015 — Quality Management System certification, demonstrating systematic control of manufacturing processes
- ISO 14001:2015 — Environmental Management System certification, ensuring environmentally responsible production practices
- ISO 45001:2018 — Occupational Health and Safety Management System certification
- CE Marking — Conformity with European standards for safety and performance
- ASTM Compliance — Products meet ASTM A269 and ASTM A213 specifications for seamless and welded stainless steel tubing
- GB/T Standards — Compliance with Chinese national standards including GB/T 12771 (stainless steel welded tubes) and GB/T 13296 (heat exchanger tubes)
- Mill Test Reports (MTR) — Each production batch is accompanied by a full chemical and mechanical test report with traceable heat number
- Third-Party Inspection — Products are available for third-party inspection by SGS, BV (Bureau Veritas), or TÜV upon customer request
Unique Selling Points
1. IoT-Ready Thermal Performance: The dimensional precision and consistent wall thickness of these coil tubes ensure uniform heat transfer coefficients, enabling accurate sensor readings and reliable IoT-based control algorithms for energy optimization.
2. Zero-Corrosion Guarantee: Unlike carbon steel alternatives, these stainless steel coil tubes require no internal epoxy coating or cathodic protection, reducing lifecycle maintenance costs by up to 60%.
3. Custom Engineering Capability: Wenzhou Jixing offers fully customized coil tube specifications including non-standard diameters, wall thicknesses, and coil configurations tailored to specific FCU designs and IoT system integration requirements.
4. Traceability and Compliance: Every coil is produced with complete material traceability from mill to end-user, supporting compliance with stringent building codes and energy efficiency regulations.
5. Sustainable Manufacturing: The production process incorporates recycled stainless steel content (minimum 40% recycled material in standard grades) and minimizes waste through optimized nesting and forming processes.
Technical Notes for IoT System Integration
When deploying these stainless steel coil tubes within fan coil unit wireless IoT control systems, the following technical considerations should be observed:
- Temperature sensors (RTD or thermistor type) should be mounted on the tube surface at designated positions to measure inlet and outlet fluid temperatures accurately
- The thermal conductivity of the stainless steel material (14.6–16.3 W/m·K) permits reliable surface-mounted temperature measurement with minimal thermal lag
- Flow rate sensors should be installed upstream of the coil to enable real-time calculation of heat transfer rate (Q = ṁ × cp × ΔT)
- Wireless sensor modules should be mounted in locations that avoid electromagnetic interference with the coil tube assembly
- Communication protocols (Zigbee, LoRaWAN, or Wi-Fi) should be selected based on the installation environment and required data transmission frequency
Wenzhou Jixing Metal Materials Co., Ltd. is committed to providing stainless steel coil tube solutions that meet the highest standards of quality, reliability, and technical performance for the global HVAC and building automation industries.