Stainless Steel Spiral Coil Tube (Coiltube) — Technical Specification
Product Code: 547 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular component characterized by a helically wound geometry within a cylindrical envelope. This product is specifically designed for high-efficiency heat exchange applications, where maximizing the surface-area-to-volume ratio is critical. The spiral coiling architecture facilitates enhanced convective heat transfer and thermal fluid dynamics, making it particularly suitable for solar thermal energy systems, industrial heat exchangers, and process heating applications.
Based on advanced research into solar-thermal conversion characteristics and convective heat loss mechanisms within cylindrical receivers, this Coiltube product integrates optimized coil pitch, tube diameter, and material selection to achieve superior thermal performance while minimizing parasitic heat losses. The product represents a convergence of metallurgical science and thermal engineering principles, delivering a robust solution for demanding industrial environments.
2. Material & Properties
2.1 Base Material
The Coiltube is fabricated from high-grade austenitic stainless steel, primarily conforming to the following specifications:
- Grade 304 (UNS S30400): General-purpose corrosion resistance with excellent formability; chromium content ≥18%, nickel content ≥8%.
- Grade 316L (UNS S316L3): Enhanced resistance to pitting and crevice corrosion due to the addition of molybdenum (2–3%); low carbon grade for improved weldability and intergranular corrosion resistance.
- Grade 321 (UNS S32100): Titanium-stabilized austenitic stainless steel for superior resistance to intergranular corrosion at elevated temperatures (up to 870°C).
2.2 Key Mechanical Properties
- Tensile Strength: ≥515 MPa (Grade 304); ≥485 MPa (Grade 316L)
- Yield Strength: ≥205 MPa (Grade 304); ≥170 MPa (Grade 316L)
- Elongation: ≥40% (Grade 304); ≥35% (Grade 316L)
- Operating Temperature Range: −196°C to +870°C (Grade 321); −196°C to +595°C (Grade 304/316L)
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical environments including acidic and alkaline solutions
2.3 Thermal Properties
- Thermal Conductivity: 14–16 W/(m·K) at 20°C
- Specific Heat Capacity: 478–502 J/(kg·K) at 20°C
- Thermal Expansion Coefficient: 16–17 × 10⁻⁶ /°C (20–100°C)
- Oxidation Resistance: Maintains structural integrity and surface stability under prolonged high-temperature exposure
3. Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Tube Outer Diameter (OD) | 6.0 mm – 25.4 mm | ±0.05 mm |
| Wall Thickness | 0.5 mm – 2.0 mm | ±10% |
| Coil Pitch (Helical Spacing) | 5 mm – 50 mm (customizable) | ±0.5 mm |
| Coil Diameter (Mean) | 50 mm – 300 mm | ±1.0 mm |
| Coil Length | Up to 2000 mm (continuous) | ±2.0 mm |
| Surface Finish | Ra ≤ 0.8 μm (polished); Ra ≤ 1.6 μm (brushed) | — |
| End Preparation | Plain, threaded (G/BSP), flanged, or welded | Per drawing |
| Material Grade | 304, 304L, 316, 316L, 321 | — |
| Heat Treatment | Solution annealing (1050–1150°C) + water quench | — |
| Coil Turns | 10 – 200 turns (standard); custom available | ±1 turn |
4. Manufacturing Process
4.1 Material Selection & Incoming Inspection
Raw stainless steel tube stock is sourced from certified mills with full material traceability. Each batch undergoes spectrographic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with ASTM, EN, or JIS standards. Incoming inspection includes dimensional verification, visual examination, and surface quality assessment.
4.2 Cold Forming & Coil Winding
The Coiltube is manufactured using a precision cold-coiling process, which preserves the metallurgical integrity of the stainless steel while achieving the required helical geometry. The process involves:
- Tube Straightening: Initial straightening of the raw tube to eliminate residual curvature and ensure uniform feed geometry.
- Coil Winding: The tube is wound around a precision mandrel using a CNC-controlled coil winding machine. The pitch, coil diameter, and number of turns are programmatically controlled to achieve dimensional accuracy within ±0.5 mm.
- Welded Joint Formation (if applicable): For continuous coil configurations, the tube ends are joined via orbital TIG (Tungsten Inert Gas) welding to ensure leak-tight integrity and minimal heat-affected zone (HAZ).
- Spring Relaxation Compensation: Post-winding dimensional drift due to elastic recovery is compensated through controlled over-winding followed by heat stabilization.
4.3 Surface Treatment & Finishing
- Pickling & Passivation: Removal of oxide scale and formation of a protective chromium oxide passive layer using citric or nitric acid-based solutions.
- Polishing (optional): Mechanical or electrochemical polishing to achieve Ra ≤ 0.8 μm surface roughness for enhanced heat transfer and reduced fouling.
- Internal Cleaning: High-pressure water or steam flushing to remove all particulate matter and ensure internal cleanliness for hygienic or high-purity applications.
4.4 Quality Control & Testing
- Dimensional Inspection: Coordinate Measuring Machine (CMM) or laser scanning for coil geometry verification.
- Pressure Testing: Hydrostatic pressure test at 1.5× working pressure, held for minimum 30 seconds to verify leak-tightness.
- Visual & Dye Penetrant Inspection (DPI): Surface and weld inspection for cracks, porosity, or defects.
- Material Certification: Full EN 10204 3.1 material certificates provided with each shipment.
5. Applications
5.1 Solar Thermal Energy Systems
The primary application domain for this Coiltube product is solar thermal energy conversion. As demonstrated in research on solar-thermal conversion characteristics within cylindrical receivers, spiral coil tubes exhibit superior heat absorption efficiency compared to straight tubes due to the enhanced turbulence and extended residence time of the working fluid within the coil. The helical geometry promotes secondary flow patterns (Dean vortices) that significantly improve the convective heat transfer coefficient, resulting in higher overall system efficiency.
5.2 Industrial Heat Exchangers
- Shell-and-coil heat exchangers for process heating and cooling
- Oil coolers and hydraulic fluid temperature control systems
- Refrigeration evaporators and condensers
5.3 Process Industries
- Chemical processing: reaction vessel heating coils, distillation column reboilers
- Pharmaceutical manufacturing: sanitary-grade heating elements for fluid processing
- Food & beverage industry: pasteurization systems, thermal sterilization units
- Petrochemical: heat transfer coils for distillation and refining processes
5.4 Specialized Applications
- Concentrated Solar Power (CSP) receiver tubes
- Geothermal heat extraction systems
- Automotive thermal management components
- Power generation: exhaust heat recovery systems
6. Unique Selling Points
Enhanced Thermal Performance: The helical coil geometry generates Dean vortices within the flowing fluid, increasing the convective heat transfer coefficient by 30–60% compared to equivalent straight tubes, as validated by research on cylindrical receiver thermal conversion characteristics.
- Compact Design: High heat transfer surface area per unit volume enables space-efficient system integration.
- Minimized Convective Heat Loss: Optimized coil pitch and spacing reduce parasitic convective heat losses from the receiver surface, improving net thermal efficiency.
- Full Material Traceability: Every production batch is accompanied by certified material documentation with full chemical and mechanical property data.
- Customization Capability: Flexible manufacturing capacity allows customization of coil diameter, pitch, tube dimensions, and end preparations to meet specific application requirements.
- Durability & Longevity: Austenitic stainless steel construction ensures resistance to thermal cycling fatigue, oxidation, and corrosion over extended service life.
7. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Ensures consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System — Sustainable manufacturing practices |
| EN 10204 3.1 | Material Test Certificate — Full traceability with chemical and mechanical test data |
| ASTM A213 / A269 | Standard Specification for Seamless Austenitic Stainless Steel Tubing |
| GB/T 12771 | Chinese National Standard for Welded Stainless Steel Tubes |
| DIN EN 10216-5 | European Standard for Welded Seamless Stainless Steel Tubes |
| CE Marking | Conformity with European CE directives for industrial equipment |
| PED (2014/68/EU) | Pressure Equipment Directive compliance for pressure-containing applications |
8. Packaging & Delivery
Each Coiltube assembly is individually protected with anti-corrosion wrapping and secured within custom-fitted wooden or steel crates to prevent deformation during transit. For bulk shipments, containers are equipped with moisture-absorbing desiccants and shock indicators. Delivery lead time is typically 15–30 working days for standard configurations and 30–45 working days for custom specifications, subject to order volume and complexity.
9. Technical Support & After-Sales Service
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including:
- Pre-sales engineering consultation and application-specific design optimization
- Custom CAD/3D modeling for system integration verification
- Thermal performance simulation and validation support
- On-site installation guidance and commissioning assistance
- Warranty coverage of 24 months from date of delivery against manufacturing defects
This technical specification is intended for engineering reference and procurement purposes. All dimensions and specifications are subject to final confirmation through formal quotation and drawing approval. Wenzhou Jixing Metal Materials Co., Ltd. reserves the right to modify product specifications with prior notification to customers.