Stainless Steel Coil Tube (盘管 Coiltube) — Technical Specification
Product Overview
The Stainless Steel Coil Tube is a precision-engineered coiled piping product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is designed for use in heat exchange applications, particularly within fan coil units (FCUs), air handling systems, and industrial thermal management equipment. The coil tube is formed through continuous bending and coiling processes that produce uniform helical geometries optimized for maximum surface-area-to-volume ratios, thereby enhancing heat transfer efficiency.
Based on economic analysis principles governing fan coil unit design optimization, the coil tube geometry is engineered to achieve an optimal balance between thermal performance, pressure drop, and manufacturing cost. The resulting product delivers superior thermal conductivity, corrosion resistance, and long-term structural integrity under continuous cyclic thermal loading conditions.
Material & Properties
Base Material Grades
- Austenitic Stainless Steel 304 (SAE 304 / UNS S30400) — General-purpose grade offering excellent corrosion resistance and formability
- Austenitic Stainless Steel 316 (SAE 316 / UNS S31600) — Enhanced molybdenum content for superior resistance to chlorides and aggressive chemical environments
- 304L / 316L Low-Carbon Grades — Reduced carbon content to minimize sensitization during welding operations
Mechanical Properties
- Tensile Strength: ≥ 520 MPa (304), ≥ 515 MPa (316)
- Yield Strength: ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness: ≤ 92 HRB (annealed condition)
- Operating Temperature Range: −196°C to +870°C (304); −196°C to +870°C (316)
Corrosion Resistance Characteristics
- Excellent resistance to atmospheric corrosion, mild acids, and alkaline solutions
- 316 grade offers enhanced pitting and crevice corrosion resistance in chloride-containing environments
- Passive chromium oxide film (Cr₂O₃) provides self-healing protective barrier
- Resistance to stress corrosion cracking (SCC) in non-chloride environments
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (¼" – 1") |
| Wall Thickness | 0.4 mm – 1.5 mm |
| Coil Diameter (Pitch) | 15 mm – 80 mm (configurable) |
| Tube Length per Coil | 1 m – 50 m (customizable) |
| Number of Turns | 5 turns – 500 turns |
| Surface Finish | Mirror Polish (Ra ≤ 0.4 μm) / Satin Finish (Ra 0.8–1.6 μm) / BA (Bright Annealed) |
| Coil Configuration | Spiral Helix / Flat Coil / Zig-Zag Coil |
| End Treatment | Clean Cut / Formed Fitting / Threaded / Flanged |
| Manufacturing Standard | ASTM A213 / ASTM A269 / GB/T 12771 / EN 10216-5 |
| Maximum Working Pressure | Up to 2.5 MPa (dependent on OD and wall thickness) |
| Thermal Conductivity | 16.3 W/(m·K) at 25°C (304 grade) |
| Weight Tolerance | ±3% (standard) / ±1.5% (precision grade) |
| Dimensional Tolerance | OD: ±0.1 mm; Wall Thickness: ±0.05 mm |
Manufacturing Process
- Raw Material Selection: High-purity stainless steel wire rod or seamless tube stock is sourced and inspected for chemical composition compliance with ASTM/GB standards. Incoming material undergoes spectroscopic analysis and mechanical property verification.
- Pipe Drawing & Forming: Seamless stainless steel tube is cold-drawn to achieve precise outer diameter and wall thickness specifications. Multi-stage drawing ensures dimensional accuracy and improved mechanical properties.
- Coil Forming (弯管成型): The formed tube is fed through precision-guided bending rollers in a continuous coiling machine. CNC-controlled bending equipment ensures uniform coil pitch, consistent curvature radius, and minimal cross-sectional distortion throughout the coil geometry.
- Stress Relief Annealing: Post-forming stress relief treatment at controlled temperatures (850°C–950°C for 304 grade) eliminates residual bending stresses, restores ductility, and stabilizes the microstructure without inducing sensitization.
- Surface Finishing: Depending on application requirements, the coil tube undergoes electropolishing, mechanical polishing, or passivation treatment. Passivation removes free iron and enhances the protective chromium oxide passive layer.
- Quality Inspection: Each coil is subjected to hydrostatic pressure testing, dimensional measurement (laser-based OD and wall thickness gauging), visual inspection for surface defects, and coil geometry verification (pitch uniformity, turn count accuracy).
- Packaging & Marking: Finished coils are coiled onto protective spools, wrapped in moisture-barrier packaging, and marked with material grade, heat number, dimensions, and compliance certifications.
Applications
- HVAC Systems: Fan coil units (FCUs), air handling units (AHUs), and chilled beam systems where the coil tube serves as the refrigerant or hot water heat transfer element
- Industrial Heat Exchangers: Shell-and-tube heat exchangers, plate-fin heat exchangers, and air-cooled condensers in petrochemical and power generation industries
- Refrigeration & Air Conditioning: Evaporator and condenser coils for commercial refrigeration systems and rooftop HVAC units
- Pharmaceutical & Food Processing: Sanitary heat transfer coils in CIP (Clean-in-Place) systems, pasteurization equipment, and hygienic processing lines
- Marine Applications: Seawater heat exchangers and condenser tubes in marine propulsion cooling systems
- Automotive & Transportation: Engine cooling coils, intercooler tubes, and HVAC components for commercial vehicles
- Building Services: Radiator coils, underfloor heating distribution manifolds, and solar thermal collector tubes
Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices |
| ASTM A213 | Standard Specification for Seamless Austenitic Chromium-Nickel Stainless Steel Tubing for High Temperature Service |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Heat-Transfer Applications |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes |
| EN 10216-5 | European Standard for Non-Alloy and Alloy Steel Tubes for Technical Purposes — Heat Exchangers and Heat Transfer Equipment |
| ASME B31.3 | Compliance with Process Piping design requirements where applicable |
| Mill Test Reports (MTR) | Full chemical analysis and mechanical property documentation provided per heat lot |
Unique Selling Points
- Economically Optimized Design: Coil geometry is derived from rigorous thermoeconomic analysis balancing heat transfer coefficient enhancement against pressure drop penalties, achieving minimum total cost of ownership (TCO) over the system lifecycle
- Superior Thermal Performance: The helical coil configuration increases the effective heat transfer surface area by 3–5× compared to equivalent straight tube length, with enhanced turbulence-induced heat transfer coefficients
- Exceptional Corrosion Durability: Austenitic stainless steel construction provides service life exceeding 25 years in aggressive chemical and marine environments without degradation
- Dimensional Precision: CNC-controlled coiling ensures coil pitch uniformity within ±0.5 mm, critical for proper fit within heat exchanger shells and mounting frames
- Customization Capability: Full customization of OD, wall thickness, coil pitch, turn count, and end fittings to meet specific OEM design requirements
- Hygienic Grade Available: Mirror-polished (Ra ≤ 0.4 μm) finish suitable for pharmaceutical, food, and beverage processing applications requiring sanitary compliance
- Weldability: Low-carbon grades (304L/316L) ensure reliable welding performance for field assembly and maintenance without intergranular corrosion concerns
Note: All specifications are subject to verification against current product data sheets. Custom configurations should be confirmed with Wenzhou Jixing Metal Materials Co., Ltd. engineering team for dimensional, pressure, and thermal rating validation prior to procurement.