Stainless Steel Coil Tube (Coiltube) — HVAC & Heat Exchange Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed primarily for use in Fan Coil Unit (FCU) systems, heat exchangers, and industrial thermal management applications. The coil tube is formed through a continuous cold-bending process that transforms straight stainless steel tubing into a compact helical or serpentine coil configuration, maximizing heat transfer surface area within a minimal footprint.
This product addresses critical engineering challenges in HVAC (Heating, Ventilation, and Air Conditioning) systems, particularly the issue of ceiling water leakage associated with fan coil unit installations. By employing high-grade stainless steel materials with superior corrosion resistance and dimensional precision, the coil tube ensures long-term structural integrity and watertight performance under continuous thermal cycling conditions.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades selected for their exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity. The primary material specifications are as follows:
- Grade 304 (AISI 304 / SUS304 / 06Cr19Ni10): The standard grade offering excellent general corrosion resistance, weldability, and formability. Contains a minimum of 18% Chromium (Cr) and 8% Nickel (Ni).
- Grade 316 (AISI 316 / SUS316 / 06Cr17Ni12Mo2): Enhanced grade with 2–3% Molybdenum (Mo) addition, providing superior resistance to chloride-induced pitting and crevice corrosion, suitable for aggressive environments.
- Grade 316L (AISI 316L / SUS316L / 022Cr17Ni12Mo2): Low-carbon variant of 316 grade, ideal for welded coil tube assemblies where intergranular corrosion resistance is critical.
| Property | Grade 304 | Grade 316 | Grade 316L |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 485 |
| Yield Strength (MPa) | ≥ 205 | ≥ 205 | ≥ 170 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Thermal Conductivity (W/m·K, at 20°C) | 16.3 | 14.6 | 14.6 |
| Maximum Service Temperature (°C) | 870 | 870 | 870 |
| Chromium (Cr) Content (%) | 18–20 | 16–18 | 16–18 |
| Nickel (Ni) Content (%) | 8–10.5 | 10–14 | 10–14 |
| Molybdenum (Mo) Content (%) | — | 2–3 | 2–3 |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code / Catalog No. | 1445 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Coil Tube Outer Diameter (OD) | 6 mm / 8 mm / 10 mm / 12 mm / 15 mm / 19 mm / Custom |
| Wall Thickness | 0.5 mm – 2.0 mm (selectable) |
| Coil Pitch (Center-to-Center Spacing) | 15 mm – 50 mm (configurable per heat exchanger design) |
| Coil Length / Development Length | Up to 3,000 mm (continuous coil) |
| Surface Finish | Bright Annealed (BA) / No. 4 Brushed / Mirror Polish (Ra ≤ 0.4 μm) |
| Tolerance on OD | ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ±10% of nominal |
| End Treatment | Deburred, Square-Cut, or Threaded (per customer specification) |
| Coil Configuration | Single Helix / Double Helix / Serpentine / Custom Geometry |
| Packaging | Wooden Pallet with Moisture-Proof Film Wrapping |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Selection & Incoming Inspection: Stainless steel seamless or welded tubing conforming to ASTM A213 / EN 10216-5 standards undergoes spectral analysis (PMI — Portable Metal Identifier) verification and dimensional inspection prior to acceptance.
- Tube Straightening & Cutting: Coils of straight tubing are fed through a high-precision straightening line to eliminate residual curvature, then cut to the required development length with a tolerance of ±1 mm.
- Coil Forming (Cold Bending): The straightened tubes are fed into a CNC-controlled coil bending machine that applies controlled bending forces to form the helical or serpentine coil geometry. The bending process is performed at room temperature to avoid work-hardening-induced cracking, with a minimum bend radius of 3× the tube OD to prevent ovalization and wall thinning.
- Heat Treatment (if required): For larger coil diameters or thicker wall sections, a solution annealing cycle at 1,050°C followed by rapid water quenching may be applied to restore full austenitic microstructure and eliminate residual bending stresses.
- Surface Finishing: The coil tube surface is polished using multi-stage belt grinding and buffing to achieve the specified finish grade (BA, No. 4, or Mirror). This process removes scale, improves corrosion resistance, and enhances aesthetic appearance.
- Final Inspection & Testing: Each coil tube batch undergoes hydrostatic pressure testing (typically at 1.5× working pressure), dimensional verification using laser scanners, and visual inspection for surface defects, weld quality, and geometric accuracy.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. finds extensive application across multiple industries:
- Commercial HVAC Systems: Primary application in Fan Coil Units (FCUs) for air conditioning in commercial buildings, hotels, hospitals, and office complexes. The coil tube serves as the core heat exchange element, transferring thermal energy between refrigerant/water and ambient air.
- Industrial Heat Exchangers: Used in shell-and-tube heat exchangers, condensers, evaporators, and air preheaters in petrochemical, pharmaceutical, and food processing industries.
- Process Cooling & Heating: Integrated into process piping systems requiring corrosion-resistant heat transfer surfaces, particularly in environments with acidic or alkaline media.
- Boiler & Steam Systems: Employed in low-pressure boiler tubes, steam coils, and thermal fluid heating loops where stainless steel's oxidation resistance extends service life.
- Domestic Appliances: Used in water heaters, air conditioners, refrigerators, and heat pump systems where compact, efficient heat exchange coils are required.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and adheres to internationally recognized standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ASTM A213 — Specification for Seamless Ferritic, Austenitic, and Carbon Steel Alloy Tubing for High-Temperature Service.
- EN 10216-5 — European standard for non-ferrous metallic tubular products for heat exchangers and heat sinks.
- GB/T 14976 — Chinese national standard for cold-rolled stainless steel seamless tubes.
- GB/T 12771 — Chinese national standard for welded stainless steel tubes for general service.
Each production batch is accompanied by a Mill Test Certificate (MTC) conforming to EN 10204 3.1, documenting chemical composition, mechanical properties, and dimensional conformity. Third-party inspection services (e.g., SGS, BV — Bureau Veritas) are available upon customer request.
Unique Selling Points
1. Precision Coil Geometry: CNC-controlled bending ensures uniform coil pitch and consistent bend radii, eliminating the irregularities common in manually formed coils and ensuring optimal heat transfer efficiency.
2. Superior Corrosion Resistance: The use of high-purity 304/316/316L stainless steel with controlled impurity levels provides exceptional resistance to corrosion in humid HVAC environments, directly addressing the root cause of ceiling water leakage in fan coil unit systems.
3. Leak-Proof Integrity: Hydrostatic pressure testing and full-length visual inspection guarantee zero-defect delivery, minimizing the risk of water leakage that plagues poorly manufactured coil tube assemblies.
4. Customization Capability: Flexible manufacturing parameters allow customization of coil diameter, pitch, tube length, wall thickness, and surface finish to match specific heat exchanger designs and OEM requirements.
5. Proven Track Record: With product catalog designation No. 1445 reflecting extensive product development experience, Wenzhou Jixing Metal Materials Co., Ltd. delivers reliable, repeatable quality backed by decades of industry expertise.