Stainless Steel Coil Tube (Coiltube) — Cooling Water Pipe
Product Code: 414 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd | Category: Literature Study & Technical Reference
This technical specification is derived from the research study titled "Coil-type Cooling Water Pipe Manufacturing Process Research" (盘管型冷却水管制造工艺研究), providing a comprehensive overview of the product's design philosophy, material science foundation, manufacturing methodology, and industrial applications.
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuous-length, cold-formed tubular product manufactured in a coiled configuration, specifically engineered for use in cooling water piping systems. Unlike straight-length seamless or welded tubes, coil tubes are produced through a cold-drawing or cold-rolling process that forms the tube into a continuous spiral or helical coil, enabling high-volume deployment with minimal joint connections.
The coiled geometry offers significant advantages in thermal management applications, including reduced installation labor, lower risk of leakage at weld joints, and superior heat transfer performance due to the inherent turbulence generated within the coiled geometry. This product represents a convergence of metallurgical precision engineering and process optimization research, as documented in the referenced manufacturing process study.
2. Material & Properties
2.1 Base Material Composition
Stainless steel coil tubes for cooling water applications are typically fabricated from austenitic stainless steel grades, selected for their outstanding corrosion resistance, thermal stability, and mechanical integrity under cyclic thermal loading.
- Grade 304 (UNS S30400 / 06Cr19Ni10): The most widely specified grade for general cooling water service, offering excellent resistance to atmospheric and mild chemical corrosion.
- Grade 316 (UNS S31600 / 022Cr17Ni12Mo2): Enhanced molybdenum content provides superior resistance to chloride-induced pitting and crevice corrosion, making it ideal for coastal or chemically aggressive environments.
- Grade 321 (UNS S32100 / 06Cr18Ni11Ti): Titanium-stabilized variant suitable for elevated temperature cooling circuits where sensitization resistance is critical.
2.2 Mechanical Properties (Typical Values for Annealed Condition)
| Property | Grade 304 | Grade 316 | Test Standard |
|---|---|---|---|
| Tensile Strength (Rm) | 515–730 MPa | 515–730 MPa | ASTM A270 / GB/T 12771 |
| Yield Strength (Rp0.2) | ≥205 MPa | ≥205 MPa | ASTM A270 / GB/T 12771 |
| Elongation (A50mm) | ≥40% | ≥40% | ASTM A270 / GB/T 12771 |
| Hardness (HV) | ≤200 HV | ≤200 HV | ISO 6507 |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | ASTM E153 |
| Corrosion Resistance (Pitting, ASTM G48) | Moderate | Excellent | ASTM G48 |
2.3 Surface Finish
- Standard: 2B cold-rolled and annealed finish (Ra ≤ 0.8 μm)
- Optional: Electropolished interior surface (Ra ≤ 0.2 μm) for hygienic or high-flow applications
- Optional: Mirror finish (8K) for aesthetic or specialty installations
3. Specifications
| Parameter | Specification | Applicable Standard |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ108.0 mm | ASTM A270 / GB/T 12771 |
| Wall Thickness | 0.3 mm – 6.0 mm | ASTM A270 / GB/T 12771 |
| Coil Diameter (Major) | Φ150 mm – Φ600 mm (customizable) | Manufacturer specification |
| Coil Pitch | 15 mm – 100 mm (adjustable per application) | Manufacturer specification |
| Coil Length per Package | 50 m – 200 m (continuous) | — |
| Temperature Range (Operating) | −196°C to +870°C (Grade 304); −196°C to +800°C (Grade 316) | ASME BPVC Section VIII |
| Pressure Rating | Up to 16 MPa (design dependent) | ASME B31.3 |
| Welding Process | Automatic Laser Welding / TIG (GTAW) | ASME BPVC Section IX |
| Dimensional Tolerance | ±0.05 mm (OD); ±0.1 mm (wall thickness) | ASTM A270 |
| End Form | Plain end / Beveled end (customizable) | — |
| Packaging | Coiled on protective wooden or steel core, wrapped in moisture-proof film | ISO 4180 |
4. Manufacturing Process
The manufacturing process for stainless steel coil tubes, as detailed in the referenced research study, follows a rigorous multi-stage production sequence designed to ensure metallurgical integrity, dimensional accuracy, and surface quality:
- Raw Material Preparation: Cold-rolled stainless steel strip of specified grade and thickness is received and inspected for chemical composition (via spectroscopic analysis per ASTM E415) and mechanical properties.
- Slitting & Leveling: The master coil is slit to the required tube blank width using precision slitting lines, followed by leveling to eliminate coil set and ensure flatness within 0.05 mm/m.
- Forming (Cold Roll Forming): The flat strip is passed through a series of progressive forming rollers that gradually shape the strip into a tubular cross-section. This cold-forming process induces beneficial work hardening while maintaining the austenitic microstructure.
- Welding: The formed tube blank is longitudinally welded using either:
- Laser Welding: For thin-wall applications (≤2.0 mm), providing a narrow heat-affected zone (HAZ) and superior weld quality with minimal distortion.
- High-Frequency Induction Welding (HFW): For thicker walls, offering high production rates with controlled fusion characteristics.
- Coil Winding: The continuous welded tube is wound onto a mandrel or forming jig to create the desired coil geometry. The winding parameters (pitch, diameter, tension) are precisely controlled to ensure uniform curvature and prevent permanent deformation.
- Solution Annealing: The coiled tube undergoes solution annealing at 1050–1150°C followed by rapid quenching (air or water) to restore full austenitic structure, eliminate residual stresses from cold working and welding, and achieve the required mechanical properties.
- Surface Treatment & Passivation: Post-annealing pickling and acid passivation remove scale and form a protective chromium oxide layer (Cr2O3) on the surface, ensuring optimal corrosion resistance.
- Quality Inspection: Comprehensive non-destructive testing (NDT) including eddy current testing (per ASTM E709), hydrostatic pressure testing (per ASTM A270), and visual inspection of weld seams.
- Packaging & Dispatch: Finished coil tubes are protected against moisture and mechanical damage during transportation.
5. Applications
5.1 Primary Applications
- Industrial Cooling Water Systems: Heat exchanger coil assemblies in chemical processing plants, power generation facilities, and petrochemical refineries where corrosion-resistant cooling loops are essential.
- HVAC (Heating, Ventilation, and Air Conditioning) Systems: Chilled water coil tubes for commercial and industrial air handling units.
- Process Cooling in Food & Beverage Industry: Sanitary-grade cooling circuits requiring hygienic surfaces and resistance to acidic process fluids.
- Pharmaceutical & Biotechnology: Closed-loop cooling systems for bioreactors and purification equipment.
- Marine & Offshore Applications: Seawater cooling circuits where chloride resistance (Grade 316) is critical.
- Automotive & Aerospace Thermal Management: Lightweight cooling coil assemblies for engine cooling and air conditioning systems.
5.2 Secondary Applications
- Oil & gas industry — process cooling circuits
- Semiconductor manufacturing — ultra-pure water (UPW) cooling loops
- Waste heat recovery systems
- Condenser and evaporator coil assemblies
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity with international standards:
| Standard / Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing operations |
| ASTM A270 / A269 | American standards for seamless, welded, and heavily cold-worked austenitic stainless steel tubing |
| GB/T 12771 | Chinese national standard for welded austenitic stainless steel tubing |
| ASME BPVC Section VIII | Pressure vessel and piping code compliance |
| EN 10216-5 | European standard for austenitic stainless steel seamless and welded tubes |
| Mill Test Certificates (MTC) | EN 10204 Type 3.1 material certificates provided with each shipment |
| NDT Reports | Eddy current and hydrostatic test reports available upon request |
7. Unique Selling Points
- Reduced Installation Complexity: The continuous coil form eliminates the need for numerous butt welds or flanged joints, reducing installation time by up to 60% compared to straight-length tube installations.
- Superior Leak Resistance: Fewer connection points directly translate to a significantly reduced probability of system leakage, enhancing operational safety and reliability.
- Process-Optimized Manufacturing: The manufacturing methodology documented in the referenced research study incorporates advanced process control parameters, ensuring consistent product quality across batch variations.
- Customizable Coil Geometry: Coil diameter, pitch, and length can be tailored to specific heat exchanger or piping layout requirements, offering design flexibility not available with standard straight tubes.
- Enhanced Heat Transfer Efficiency: The coiled configuration promotes internal turbulence, improving convective heat transfer coefficients (h) by 15–30% compared to straight tube geometries of equivalent cross-section.
- Material Versatility: Available in multiple austenitic grades (304, 316, 321, and others) to address diverse corrosion and temperature requirements.
- Cost-Effectiveness: Continuous production from coil stock minimizes material waste and reduces per-meter cost compared to discrete-length tube fabrication.
8. Technical Reference
This product specification is informed by the academic research publication "Coil-type Cooling Water Pipe Manufacturing Process Research" (盘管型冷却水管制造工艺研究), which systematically investigates the interplay between forming parameters, welding conditions, post-weld heat treatment, and final product performance characteristics for stainless steel coil tubes used in cooling water applications. The study provides the theoretical and empirical foundation for the manufacturing tolerances and quality criteria specified herein.
Document Classification: Literature Study (文献学习) — Technical Reference | Reference Index: 414