Stainless Steel Coil Tube — Fan Coil Unit Grade (Item No. 1062)
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous coil of austenitic stainless steel tubing, designed specifically for use in fan coil unit (FCU) air conditioning systems, heat exchanger assemblies, and thermal-fluid transfer applications. This product is supplied in continuous coil form, enabling high-speed automated coil-to-coil processing, finning, and brazing operations downstream in HVAC manufacturing lines.
Coil tubes serve as the primary heat-transfer medium in fan coil units, where chilled or hot water circulates through the coiled stainless steel tubing to provide space conditioning. The coil geometry maximizes surface area within a compact footprint, making it an essential component in commercial and residential HVAC systems. Wenzhou Jixing Metal Materials produces these coil tubes to meet the demanding requirements of thermal efficiency, corrosion resistance, and long-term structural integrity.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel grades, most commonly SUS304 (UNS S30408) and SUS316L (UNS S31603), selected for their superior combination of mechanical strength, corrosion resistance, and weldability.
Key Material Characteristics
- Grade SUS304 / 304L: Contains a minimum of 18% chromium and 8% nickel (18/8 stainless), offering excellent general corrosion resistance, formability, and oxidation resistance at temperatures up to 870°C. The 304L variant features reduced carbon content (≤0.03%) for enhanced resistance to intergranular corrosion during welding.
- Grade SUS316L: Incorporates 2–3% molybdenum in addition to the base austenitic composition, providing superior resistance to pitting and crevice corrosion in chlorinated or marine environments.
- Crystal Structure: Face-Centered Cubic (FCC) austenitic structure, ensuring non-magnetic behavior, excellent ductility, and resistance to stress corrosion cracking (SCC).
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C for SUS304, providing efficient heat transfer in chilled water and hot water applications.
- Thermal Expansion Coefficient: ~17.3 × 10⁻⁶ /°C (20–100°C), compatible with aluminum fin materials used in coil-to-fin heat exchanger assemblies.
Mechanical Properties (Annealed Condition)
| Property | Grade SUS304 / 304L | Grade SUS316L |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 515 MPa |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (A50) | ≥ 40% | ≥ 40% |
| Hardness (HV) | ≤ 210 | ≤ 210 |
| Density | 7.93 g/cm³ | 8.00 g/cm³ |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管, Coiltube) |
| Item Number | 1062 |
| Material Grades | SUS304, SUS304L, SUS316L, SUS321, SUS310S (upon request) |
| Outer Diameter (OD) | 6.0 mm – 12.7 mm (standard range); custom sizes available |
| Wall Thickness (WT) | 0.30 mm – 0.80 mm |
| Coil Inner Diameter (CID) | 300 mm – 600 mm |
| Coil Length per Spool | 100 m – 500 m (continuous coil) |
| Surface Finish | BA (Bright Annealed), No. 1, 2B, or Mirror Polish (custom) |
| OD Tolerance | ±0.05 mm (standard); ±0.02 mm (precision grade) |
| Wall Thickness Tolerance | ±10% of nominal |
| Roundness | ≤ 2% of nominal OD |
| Coil Tolerance | ±2 mm on coil diameter |
| End Condition | Plain cut, deburred; optional crimped or capped ends |
| Packing | Wooden pallet with moisture-proof wrapping; export-grade packaging available |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorously controlled multi-stage process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Incoming Inspection: Stainless steel strip or bar stock is procured from certified mills and subjected to spectroscopic analysis (OES) to verify chemical composition against ASTM/EN standards. Mechanical property certification is reviewed prior to processing.
- Piercing & Drawing: Solid stainless steel billets are pierced to form seamless tube blanks, which are then cold-drawn through a series of tungsten carbide (WC) dies to achieve the target OD and wall thickness. This seamless process eliminates weld seams, ensuring uniform corrosion resistance and pressure integrity.
- Pipe Milling & Sizing: The drawn tube is passed through sizing rollers to correct minor dimensional deviations and ensure consistent roundness and wall thickness throughout the length.
- Intermediate Annealing: Where multiple drawing passes are required, intermediate solution annealing at 1050–1150°C followed by controlled cooling (water quench or air cool) relieves accumulated work hardening and restores ductility.
- Pickling & Passivation: The tube surface is treated with a mixed acid solution (nitric + hydrofluoric acid) to remove oxide scale, followed by passivation to form a protective chromium oxide layer, ensuring a clean, corrosion-resistant surface.
- Coiling: The continuous tube is wound onto precision-controlled coil reels using a tension-controlled pay-off system, producing uniform coil geometry with consistent pitch and layer alignment.
- Final Quality Inspection: Each coil undergoes 100% visual inspection, dimensional measurement (OD, WT, roundness), hydrostatic pressure testing (typically at 1.5–2.0× working pressure), and optional eddy current or ultrasonic flaw detection.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials is engineered for demanding thermal and fluid-handling applications. Key application domains include:
- Fan Coil Units (FCUs) & Air Handling Units (AHUs): The primary application, where coil tubes are finned and brazed into serpentine heat exchanger bundles for chilled water cooling and hot water heating in commercial buildings, hotels, hospitals, and residential HVAC systems. Research studies on fan coil air conditioning system summer energy-saving simulation and control (《风机盘管空调系统夏季节能模拟与控制研究》) have demonstrated that the selection of tube material and coil geometry significantly impacts system COP (Coefficient of Performance) and seasonal energy efficiency.
- Chilled Water & Hot Water Heat Exchangers: Used in plate-and-tube, shell-and-tube, and finned-tube heat exchanger configurations for industrial process cooling and heating.
- Refrigeration & Air Conditioning Systems: Serves as refrigerant-side tubing in evaporators and condensers for commercial refrigeration equipment.
- Food & Beverage Processing: Hygienic-grade coil tubing for pasteurization, CIP (Clean-In-Place) systems, and sanitary heat exchangers in food-grade environments (FDA-compliant, 3A standards).
- Pharmaceutical & Bioprocessing: High-purity SUS316L coil tubes for pharmaceutical manufacturing equipment requiring strict sanitary and corrosion resistance requirements.
- Marine & Offshore Applications: SUS316L coil tubes for marine HVAC systems, bilge water heat exchangers, and offshore platform utility systems where chloride-induced corrosion is a concern.
- Solar Thermal & Geothermal Systems: Coil tubing for solar water heaters, geothermal heat pump systems, and renewable energy thermal collection circuits.
- Automotive HVAC: Compact coil assemblies for vehicle heating, ventilation, and air conditioning (HVAC) systems.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with international standards:
- ISO 9001:2015 — Quality Management Systems certification, ensuring consistent product quality and process control.
- ISO 14001 — Environmental Management Systems certification, demonstrating commitment to sustainable manufacturing practices.
- ISO 45001 — Occupational Health and Safety Management Systems certification.
- EN 10204-3.1 — Third-party inspection certificates available for each batch, confirming conformance to declared specifications.
- Material Standards Compliance: ASTM A269/A269M (Seamless and Welded Austenitic Stainless Steel Tubing), EN 10217-7, GB/T 12771 (Chinese National Standard for stainless steel tubes).
- HACCP & FDA Compliance: Available for food-grade applications (SUS316L grades).
- Pressure Vessel & PED Compliance: Product data supports compliance with the EU Pressure Equipment Directive (PED 2014/68/EU) for heat exchanger applications.
- Mill Test Certificates (MTC): Provided with every shipment, including chemical composition analysis, mechanical test results, and heat traceability.
Unique Selling Points
- Seamless Construction: All coil tubes are produced via seamless piercing and drawing processes, eliminating longitudinal weld seams and ensuring uniform corrosion resistance and pressure integrity throughout the tube length.
- Precision Dimensional Control: Tight tolerances on OD (±0.05 mm) and wall thickness (±10%) ensure reliable compatibility with downstream finning, brazing, and assembly operations in HVAC coil manufacturing.
- Continuous Coil Supply: Delivered in continuous coils of up to 500 meters, enabling uninterrupted automated processing and minimizing splice joints that could compromise heat exchanger performance.
- Multi-Grade Availability: A broad range of stainless steel grades (SUS304, 304L, 316L, 321, 310S) allows customers to select the optimal material for specific service conditions, from general HVAC to marine and high-temperature applications.
- Energy-Efficient Design Support: Coil tube geometry and material selection are optimized to support high-efficiency fan coil unit designs, contributing to improved seasonal energy efficiency ratios (SEER) and reduced operational energy consumption in commercial HVAC systems.
- Export-Grade Quality: Full traceability from raw material to finished coil, with comprehensive documentation supporting international regulatory compliance and customer audit requirements.
Note: The selection of stainless steel coil tube grade and specification should be based on the specific service environment, fluid medium, operating temperature and pressure, and applicable regulatory requirements. Wenzhou Jixing Metal Materials Co., Ltd. provides technical consultation and material selection guidance to assist customers in optimizing their product specifications for maximum performance and cost-effectiveness.