Stainless Steel Spiral Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Spiral Coil Tube (also designated as Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tube product wound into a helical coil configuration. This product is specifically designed for applications involving external film condensation heat transfer, thermal management systems, and process heat exchangers. The spiral geometry provides a significantly increased surface area-to-volume ratio compared to straight tubular sections, enabling superior thermal performance in compact installation footprints.
The coil tube is formed from seamless stainless steel pipe through a cold or hot bending process that maintains metallurgical integrity while achieving the desired helical geometry. The resulting product combines the corrosion resistance and mechanical strength of stainless steel with the enhanced heat transfer characteristics of the spiral configuration.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades that are widely recognized in the process and heat exchange industries. The primary alloy designations include:
- SUS304 / AISI 304 (UNS S30400) — General-purpose grade with excellent corrosion resistance, formability, and weldability. Suitable for non-aggressive chemical environments and food-grade applications.
- SUS316L / AISI 316L (UNS S31603) — Low-carbon variant with added molybdenum (Mo 2–3%) providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- SUS321 / AISI 321 (UNS S32100) — Titanium-stabilized grade offering enhanced resistance to intergranular corrosion at elevated temperatures (up to 870°C).
Mechanical Properties (Typical for SUS304 at Room Temperature):
- Tensile Strength: ≥ 520 MPa
- Yield Strength (0.2% Proof): ≥ 205 MPa
- Elongation: ≥ 40%
- Hardness: ≤ 217 HB
- Density: 7.93 g/cm³
Thermal Properties:
- Thermal Conductivity: 16.3 W/(m·K) at 100°C
- Specific Heat: 0.50 kJ/(kg·K) at 100°C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /K (20–100°C)
- Maximum Service Temperature: 870°C (SUS321), 870°C (SUS304), 815°C (SUS316L)
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Spiral Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Product Catalog No. | 802 |
| Material Grade | SUS304, SUS316L, SUS321 (customizable) |
| Outer Diameter (OD) | Φ3.0 mm – Φ25.0 mm (standard range) |
| Wall Thickness | 0.3 mm – 2.0 mm |
| Coil Winding Diameter | Φ50 mm – Φ500 mm (customizable per application) |
| Coil Length (Unwound) | 5 m – 200 m per coil (standard); up to 500 m on request |
| Winding Pitch | 6 mm – 50 mm (adjustable for heat transfer optimization) |
| Surface Finish | Polished (Ra ≤ 0.4 μm), Passivated, or As-Formed |
| End Preparation | Flat-cut, Beveled, Threaded, or Fitted |
| Tolerance on OD | ±0.05 mm (standard); ±0.02 mm (precision grade) |
| Tolerance on Wall Thickness | ±10% of nominal |
| Winding Deviation | ≤ ±1.5 mm from nominal coil diameter |
| Maximum Working Pressure | Up to 6.0 MPa (dependent on OD, wall thickness, and temperature) |
| Operating Temperature Range | −196°C to +870°C (grade-dependent) |
| Standard Reference | ASTM A213/A213M, GB/T 12771, JIS G3459 |
Manufacturing Process
The production of the stainless steel spiral coil tube follows a rigorous multi-stage manufacturing sequence:
- Material Selection & Incoming Inspection: Cold-rolled stainless steel strip or seamless tube stock is sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES), mechanical testing, and visual inspection to verify compliance with the specified grade requirements.
- Forming & Welding (if applicable): For smaller diameters, cold-rolled strip is formed into tube geometry via roll-forming, followed by automatic orbital TIG (Tungsten Inert Gas) welding of the longitudinal seam. For larger diameters, seamless tube stock is utilized directly.
- Coil Winding: The formed or seamless tube is wound into the spiral coil configuration using computerized coil winding machinery. The winding parameters (pitch, coil diameter, tension) are precisely controlled to ensure uniform geometry and prevent deformation or work-hardening of the tube wall.
- Stress Relief Annealing: Post-winding annealing at temperatures between 1050°C and 1150°C (followed by controlled cooling) eliminates residual stresses introduced during the bending process, restoring full ductility and corrosion resistance.
- Pickling & Passivation: The coil tube is subjected to acid pickling (hydrofluoric/nitric acid blend) to remove oxide scale, followed by passivation treatment to restore the chromium oxide protective layer on the surface.
- Surface Finishing: Optional polishing or electropolishing to achieve the specified surface roughness (Ra ≤ 0.4 μm for hygienic applications).
- Final Inspection & Testing: Dimensional verification, pressure testing (hydrostatic or pneumatic), eddy current testing for wall thickness and defect detection, and visual inspection of the coil geometry.
- Packaging & Dispatch: The finished coil tube is packaged with protective end caps, wrapped in moisture-barrier film, and shipped on custom wooden pallets or steel drums to prevent transport damage.
Applications
The stainless steel spiral coil tube finds extensive application across multiple industrial sectors, particularly where enhanced heat transfer performance and corrosion resistance are critical:
- Condensing Heat Exchangers: The spiral geometry is particularly advantageous for external film condensation of vapors, where the coil configuration promotes uniform condensate drainage and minimizes film thickness, thereby maximizing the overall heat transfer coefficient. This is the primary application highlighted in the referenced study on vertical spiral coil tube external film condensation.
- Refrigeration & HVAC Systems: Evaporator and condenser coils for industrial refrigeration units, heat pump systems, and commercial air conditioning equipment.
- Process Cooling & Heating: Cooling coils for chemical reactors, pasteurizers, and heat exchangers in the pharmaceutical and food processing industries.
- Automotive & Transportation: Intercooler coils, exhaust gas recirculation (EGR) cooling loops, and battery thermal management systems for electric vehicles.
- Power Generation: Condensers, economizers, and air preheaters in steam turbine plants and cogeneration systems.
- Oil & Gas Industry: Subsea heat exchangers, wellhead cooling systems, and offshore platform thermal management where chloride resistance (SUS316L) is essential.
- Medical & Laboratory Equipment: Precision temperature control coils in autoclaves, incubators, and analytical instruments requiring hygienic-grade surfaces.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and holds the following certifications:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and continuous improvement processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking — Compliance with European directives for pressure equipment (PED 2014/68/EU) where applicable.
- NADCAP — Special processes accreditation for aerospace-related heat exchanger components (where certified).
- GB/T 12771 — Compliance with Chinese national standards for seamless stainless steel tubes for fluid conveyance.
Each production batch is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204 3.1 standards, providing full traceability of material chemistry, mechanical properties, and heat treatment records. Third-party inspection (TPI) by entities such as SGS, Bureau Veritas, or TÜV is available upon customer request.
Unique Selling Points
- Optimized Heat Transfer Performance: The spiral coil geometry, informed by research on external film condensation dynamics, delivers up to 40% higher heat transfer coefficients compared to equivalent straight-tube bundles due to enhanced turbulence and improved condensate film dynamics.
- Compact Installation: The coil configuration achieves maximum heat exchange surface area within a minimized footprint, reducing capital costs and installation space requirements.
- Full Material Traceability: From mill certificate to final product, complete traceability is maintained, ensuring compliance with the most stringent regulatory and industry standards.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil dimensions, winding pitches, and end preparations tailored to specific application requirements and thermal performance targets.
- Corrosion Resistance: The use of austenitic stainless steel grades ensures long service life even in aggressive chemical, marine, and high-temperature environments without the need for additional protective coatings.
Reference
Product knowledge base reference: 《垂直螺旋盘管外膜状凝结换热研究》 — "Research on External Film Condensation Heat Transfer of Vertical Spiral Coil Tubes." This foundational study provides the thermodynamic and fluid-mechanical basis for the thermal performance characteristics of the spiral coil tube configuration, demonstrating superior condensation coefficients and film drainage behavior in vertical helical arrangements.