Stainless Steel Coiltube (Coil Tube) for Thermal Tracing Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Designation: Coiltube — Stainless Steel Heat Tracing Coil
Catalog No.: 370
1. Product Overview
The Stainless Steel Coiltube is a precision-engineered spiral-wound tubing product designed for thermal tracing (heat tracing) applications in industrial process vessels, particularly in sewage sedimentation tanks and similar containment systems exposed to environmental thermal loads. The coiltube is fabricated by winding continuous stainless steel tube into a consistent spiral geometry, providing uniform heat distribution along the vessel wall or internal surface.
Based on rigorous academic research into temperature distribution characteristics inside sewage sedimentation tanks under solar radiation, the structural configuration of the coiltube has been optimized to ensure efficient heat transfer, minimize thermal gradients, and maintain process fluid temperature within specified operational limits even under extreme external thermal loading conditions.
2. Material & Properties
2.1 Base Material
- Primary Alloy: Austenitic Stainless Steel (奥氏体不锈钢)
- Common Grades: SUS304 (UNS S30408), SUS316L (UNS S31603), SUS321 (UNS S32100)
- Chromium Content: ≥ 18.0% (SUS304) / ≥ 25.0% (SUS316L)
- Nickel Content: ≥ 8.0% (SUS304) / ≥ 12.0% (SUS316L)
- Molybdenum Content: ≤ 0.08% (SUS304) / 2.0–3.0% (SUS316L)
2.2 Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (SUS304), ≥ 485 MPa (SUS316L)
- Yield Strength (0.2% Proof Stress): ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness: ≤ 217 HB (SUS304), ≤ 210 HB (SUS316L)
- Operating Temperature Range: −196 °C to +870 °C (SUS304), −196 °C to +870 °C (SUS316L)
2.3 Thermal Properties
- Thermal Conductivity (at 20 °C): 14.9 W/(m·K) (SUS304), 13.5 W/(m·K) (SUS316L)
- Thermal Expansion Coefficient (20–100 °C): 17.3 × 10⁻⁶ /°C (SUS304), 16.0 × 10⁻⁶ /°C (SUS316L)
- Specific Heat Capacity: ~500 J/(kg·K)
2.4 Corrosion Resistance
- Excellent resistance to pitting and crevice corrosion in chloride-containing environments (particularly SUS316L)
- High resistance to intergranular corrosion after sensitization treatment (SUS321 with Ti stabilization)
- Suitable for prolonged exposure to sewage media, industrial wastewater, and chemical process fluids
3. Specifications
| Parameter | Specification | Unit | Standard Reference |
|---|---|---|---|
| Outer Diameter (OD) | Φ6.0 – Φ25.4 | mm | ASTM A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.5 – 2.0 | mm | ASTM A269 / GB/T 14976 |
| Coil Pitch (Spiral Spacing) | 25 – 100 (customizable) | mm | Per project requirement |
| Coil Diameter (Bundle OD) | Φ100 – Φ2000 | mm | Per vessel design |
| Length per Spool | 3 – 30 | m | Per installation requirement |
| Surface Finish | Mirror polished / Pickle & passivated / Matte | — | ASTM A473 |
| Surface Roughness (Ra) | ≤ 0.8 (mirror) / ≤ 1.6 (polished) / ≤ 3.2 (standard) | μm | ISO 1302 |
| End Preparation | Plain end / Threaded / Flanged / Welded socket | — | ASME B1.20.1 / B16.5 |
| Winding Tolerance | ±0.5 mm pitch deviation | mm | Internal standard |
| Pressure Rating | Up to PN40 (4.0 MPa) depending on WT | MPa | ASME B31.3 |
| Heat Medium | Hot water / Steam / Thermal oil / Electric resistance | — | Per system design |
| Maximum Heat Flux | Up to 25,000 W/m² | W/m² | Engineering design |
4. Manufacturing Process
- Material Procurement & Inspection: Raw stainless steel seamless tube or welded tube is procured from certified mills. Each batch undergoes spectroscopic analysis (OES), mechanical testing, and chemical composition verification per ASTM A270 or GB/T 12771.
- Tube Straightening & Cutting: Tubes are cold-straightened to eliminate residual curvature and cut to precise spool lengths using CNC sawing equipment.
- End Preparation: Tube ends are deburred, chamfered, and prepared for welding or mechanical connection. Surface passivation treatment is applied to remove scale and contaminants.
- Spiral Winding (Coiling): Using CNC-controlled spiral winding machinery, the straight tube is wound around a mandrel or form at a precisely controlled pitch and diameter. The winding process maintains constant tension to prevent tube deformation or ovality exceeding 2% of nominal OD.
- Welding & Joining: Inlet/outlet connections and inter-spool joints are fabricated using orbital TIG (Tungsten Inert Gas) welding or automated laser welding, ensuring full-penetration welds with minimum heat-affected zone.
- Heat Treatment (if required): Solution annealing at 1050–1150 °C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Pickle & Passivate: Chemical pickling removes weld scale and oxidation; passivation forms a protective chromium oxide film on the surface.
- Non-Destructive Testing (NDT): Radiographic testing (RT) or ultrasonic testing (UT) of welds; hydrostatic pressure testing at 1.5× design pressure for leak-tightness verification.
- Final Inspection & Packaging: Dimensional verification, surface finish assessment, and protective packaging with desiccant for shipment.
5. Applications
5.1 Primary Applications
- Sewage Sedimentation Tanks: Thermal tracing to prevent freezing in cold climates and maintain optimal settling temperatures under solar radiation thermal loading. Research demonstrates that optimized coiltube configuration reduces maximum internal temperature differential by up to 35% compared to conventional heating methods.
- Process Vessels & Reactors: Temperature maintenance in chemical processing, pharmaceutical manufacturing, and food industry equipment.
- Heat Exchangers: Internal coil configurations for shell-and-coil heat exchangers providing high surface-area-to-volume ratios.
- Pipe Tracing Systems: Spiral-wound coil assemblies for maintaining flow temperature in long-distance process piping.
- Solar Thermal Systems: Heat collection coils for concentrated solar energy (CSP) applications.
5.2 Environmental & Industrial Sectors
- Municipal wastewater treatment plants (WWTP)
- Petrochemical and refinery process units
- Pharmaceutical clean-room processing
- Food and beverage thermal processing
- Power generation (auxiliary heating systems)
- Marine and offshore platforms
6. Quality Certifications & Standards Compliance
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 3834-2 | Quality requirements for welding of metallic materials |
| EN 10204 3.1 | Inspection certificates — material test reports |
| ASME BPV Code Section I | Power boiler and pressure vessel construction |
| ASTM A213 | Seamless austenitic stainless steel tubing |
| ASTM A269 | Welded austenitic stainless steel tubing |
| GB/T 12771 | Chinese national standard for stainless steel tubing |
| GB/T 14976 | Chinese national standard for welded steel tubes |
| PED 2014/68/EU | European Pressure Equipment Directive (if applicable) |
| NSF/ANSI 61 | Water system components — public health standards (optional) |
7. Unique Selling Points
- Research-Optimized Configuration: Coiltube geometry is derived from published academic research on temperature distribution characteristics in sewage sedimentation tanks under solar radiation, ensuring empirically validated thermal performance.
- Uniform Heat Distribution: The spiral winding geometry provides consistent heat flux along the entire vessel surface, minimizing hot spots and thermal stratification.
- Superior Corrosion Durability: Full austenitic stainless steel construction ensures decades of service life in aggressive sewage and chemical environments without degradation.
- Customizable Geometry: Pitch, diameter, and spool length are tailored to specific vessel dimensions and thermal load requirements.
- Low Maintenance Design: Sealed, leak-free construction eliminates the need for periodic inspection and replacement in normal operating conditions.
- Energy Efficiency: Optimized coiltube structure achieves target process temperatures with minimum thermal energy input, reducing operational costs.
- Full Traceability: Every coil is manufactured with complete material traceability from mill heat number through final inspection, ensuring compliance with international quality standards.
8. Technical Notes
Design Consideration: In applications involving solar radiation exposure (e.g., open-top sedimentation tanks), the coiltube thermal output must be designed to compensate for peak solar gain while also maintaining minimum process temperature during ambient low-temperature events. The coil pitch and heat medium temperature should be selected based on a thermal balance analysis considering both solar irradiance intensity (up to 1000 W/m²) and ambient temperature variation.
Company: Wenzhou Jixing Metal Materials Co., Ltd. — Specialized manufacturer of stainless steel coil tubes, spiral wound assemblies, and custom thermal tracing solutions for industrial applications across Asia and international markets.