Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
Product Catalog No.: 957 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Classification: Literature Study — Fan Coil Unit (FCU) Noise Analysis & Performance Optimization
1. Product Overview
Stainless Steel Coil Tubes (Coiltubes) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. represent a high-performance fluid transfer solution engineered for demanding industrial and commercial applications. These continuously wound tubular products are fabricated from austenitic stainless steel grades and are designed to deliver superior corrosion resistance, thermal conductivity, and mechanical durability in HVAC (Heating, Ventilation, and Air Conditioning), heat exchanger, and process engineering systems.
A critical area of study associated with this product category is the noise analysis in Fan Coil Units (FCUs) during operational use. Extensive research has demonstrated that the geometric configuration, wall thickness uniformity, and surface finish quality of coil tubes directly influence aerodynamic and hydrodynamic noise generation. Wenzhou Jixing Metal Materials Co., Ltd. applies rigorous manufacturing tolerances and quality control protocols to minimize vibration-induced noise, ensuring compliance with international acoustic performance standards.
2. Material & Properties
2.1 Base Material Grades
Coiltubes are produced from premium austenitic stainless steel grades conforming to ASTM (American Society for Testing and Materials) and EN (European Norms) specifications. The following grades are available:
- ASTM 304 / EN 1.4301 (X2CrNi18-10): General-purpose grade with excellent corrosion resistance and formability. Suitable for most HVAC and food-grade applications.
- ASTM 316 / EN 1.4401 (X2CrNiMo17-12-2): Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion in chloride-containing environments.
- ASTM 316L / EN 1.4404 (X2CrNiMo17-12-3): Low-carbon variant of 316, ideal for welded applications requiring resistance to intergranular corrosion.
- ASTM 321 / EN 1.4541 (X8CrNiTi18-10): Titanium-stabilized grade for elevated-temperature service up to 870°C.
2.2 Mechanical Properties
- Tensile Strength: 515–720 MPa (ASTM A269 / ASTM A270)
- Yield Strength: 205–310 MPa (0.2% offset)
- Elongation: ≥ 40% (minimum, per ASTM A269)
- Hardness: ≤ 92 HRB (annealed condition)
- Thermal Conductivity: 14.9 W/(m·K) at 100°C (Grade 304)
- Operating Temperature Range: −196°C to +870°C (grade-dependent)
2.3 Corrosion Resistance
The passive chromium oxide layer (Cr₂O₃) formed on the surface provides exceptional resistance to atmospheric corrosion, acidic media, and chlorinated solutions. Grade 316L exhibits a Pitting Resistance Equivalent Number (PREN) of approximately 24–26, making it suitable for marine and chemical processing environments.
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Outer Diameter (OD) | 3.175 mm – 25.4 mm (1/8" – 1") |
| Wall Thickness | 0.50 mm – 2.00 mm (±10% tolerance) |
| Coil Length | 10 m – 500 m (customizable) |
| Coil Diameter | 150 mm – 1,200 mm (packing diameter) |
| Surface Finish | Bright Annealed (BA), Pickled & Passivated (P&P), Brushed, or Custom Ra ≤ 0.4 μm |
| Manufacturing Standard | ASTM A269, ASTM A270, EN 10217-7, GB/T 12771 |
| Welding Method | Continuous TIG (Tungsten Inert Gas) Welding with internal/external argon shielding |
| Hydrostatic Test Pressure | ≥ 2.5 × Working Pressure (100% leak testing) |
| Acoustic Performance | ≤ 45 dB(A) at rated flow velocity (optimized for FCU integration) |
| Packing | Wooden crate / export-grade pallet with moisture barrier wrapping |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel strip is verified for chemical composition (Spectroscopic Analysis, SEM — Scanning Electron Microscopy) and mechanical properties per ASTM A240.
- Slitting & Leveling: Precision slitting to target width with edge quality inspection; tension leveling to eliminate coil set and flatness defects.
- Forming (Rolling): Multi-stand roll forming converts flat strip into the target tube geometry with controlled reduction ratios to maintain uniform wall thickness.
- Continuous TIG Welding: High-frequency tungsten inert gas welding under argon atmosphere ensures clean, defect-free longitudinal seams. Real-time weld monitoring via inline optical sensors.
- Induction Annealing: Controlled heating to 1,050–1,150°C followed by rapid quenching relieves cold-work stresses, restores full austenitic microstructure, and achieves the bright annealed surface finish.
- Pickling & Passivation: Immersion in mixed acid baths (HNO₃ + HF) removes scale and contaminants; subsequent passivation forms a stable chromium oxide protective film.
- Coiling & Packaging: Tubes are wound onto precision mandrels at controlled tension to prevent deformation, then packaged for shipment.
4.2 Noise Optimization in Fan Coil Unit Integration
Based on comprehensive literature study of noise analysis in fan coil units during use, Wenzhou Jixing Metal Materials Co., Ltd. has incorporated the following engineering improvements into their coil tube production:
- Wall Thickness Uniformity: Tight tolerance control (±5%) eliminates thickness variation that causes localized flow turbulence and vibration-induced noise.
- Surface Roughness Reduction: Achieving Ra ≤ 0.4 μm minimizes boundary layer separation, reducing aerodynamic noise by 3–5 dB(A).
- Geometric Precision: Consistent bend radii and straightness (≤ 1 mm/m) prevent fluid instabilities that generate broadband noise.
- Material Grade Selection: Higher-grade stainless steels (316L) exhibit superior damping characteristics compared to carbon steel alternatives, reducing structure-borne noise transmission.
5. Applications
5.1 HVAC & Fan Coil Units
Primary application for coil tubes in commercial and residential HVAC systems, including FCUs, air handling units (AHUs), and rooftop units. The corrosion resistance and thermal conductivity of stainless steel coil tubes ensure long service life and efficient heat transfer.
5.2 Heat Exchangers
Used in shell-and-tube heat exchangers, plate-fin heat exchangers, and radiators for industrial process cooling, refrigeration systems, and district heating networks.
5.3 Food & Pharmaceutical Processing
Compliant with FDA (U.S. Food and Drug Administration) and EU 1935/2004 regulations for food-contact surfaces. Employed in pasteurization systems, CIP (Clean-In-Place) loops, and sanitary process lines.
5.4 Chemical & Marine Industries
Grade 316L coil tubes are specified for chemical dosing systems, seawater cooling circuits, and desalination plant components due to exceptional chloride resistance.
5.5 Medical & Laboratory Equipment
Used in medical gas delivery systems, sterilizer chambers, and laboratory fluid handling apparatus requiring hygienic, non-toxic, and autoclavable materials.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — certified manufacturing processes |
| ISO 14001:2015 | Environmental Management System — sustainable production practices |
| CE Marking (EU) | Conformity with European Machinery and Pressure Equipment Directives |
| EN 10204 3.1 | Material Test Reports — third-party certified chemical and mechanical analysis |
| ASTM A269 / A270 | American material specifications for seamless and welded austenitic stainless steel tubing |
| GB/T 12771 | Chinese National Standard for stainless steel welded tubing (general industrial use) |
| PED 2014/68/EU | Pressure Equipment Directive compliance for pressure-containing applications |
| NSF/ANSI 61 | Drinking Water System Components — health effects certification (food & beverage grade) |
7. Unique Selling Points
- Acoustic Engineering Integration: Industry-leading noise optimization derived from extensive FCU noise analysis research, delivering ≤ 45 dB(A) operational performance.
- Multi-Grade Availability: Full range from 304 to 316L and 321, allowing precise material matching to application-specific corrosion and temperature requirements.
- Custom Coiling Solutions: Flexible coil length, diameter, and packaging configurations to suit OEM (Original Equipment Manufacturer) integration needs.
- 100% Leak Testing: Every coil undergoes hydrostatic pressure testing, ensuring zero-defect delivery and eliminating field failure risk.
- Traceability & Documentation: Complete mill-to-finish traceability with EN 10204 3.1 test certificates for every batch, supporting audit and regulatory compliance.
- Export-Grade Packaging: Robust, moisture-protected packaging suitable for international logistics and long-term storage without surface degradation.
Note: All specifications are subject to verification against the latest product data sheets issued by Wenzhou Jixing Metal Materials Co., Ltd. Custom specifications and non-standard configurations are available upon request. For detailed material test reports (MTR — Material Test Report) and dimensional tolerances, contact the manufacturer's technical sales department.