Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered continuous spiral tube product supplied by Wenzhou Jixing Metal Materials Co., Ltd. (Product Catalog No. 603). Unlike conventional straight-length tubing, the Coiltube is manufactured as a continuous helical coil configuration, which confers unique thermal-hydraulic performance characteristics particularly suited for heat exchanger and condenser applications. The product is available in austenitic stainless steel grades, most commonly SUS304 (AISI 304) and SUS316L (AISI 316L), and is supplied in coiled form to facilitate installation, reduce welding joints, and minimize pressure drop in fluid systems.
Key Comparative Insight: A dedicated experimental study comparing Coil-Type Condensers against Shell-and-Tube Condensers has demonstrated that coil-type configurations achieve superior heat transfer coefficients (up to 20–35% higher), more compact footprint, reduced fouling resistance, and lower pumping power consumption due to the inherent centrifugal and secondary flow effects generated within the curved tube geometry.
Material & Properties
The Coiltube is fabricated from high-quality austenitic stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity. The following material grades are standard offerings:
- SUS304 / AISI 304 (UNS S30400): The most widely used austenitic stainless steel, offering excellent general corrosion resistance, good formability, and weldability. Suitable for non-aggressive aqueous environments, food processing, and general industrial heat exchange applications.
- SUS316L / AISI 316L (UNS S31603): Low-carbon variant with added molybdenum (Mo) content (2.0–2.5%), providing superior resistance to pitting and crevice corrosion in chlorinated environments. Recommended for marine, chemical processing, and pharmaceutical applications.
- SUS321 / AISI 321 (UNS S32100): Titanium-stabilized grade with enhanced resistance to intergranular corrosion, suitable for elevated-temperature applications up to 870°C.
Typical Mechanical and Physical Properties (SUS304, Annealed Condition)
- Tensile Strength (UTS): ≥ 520 MPa
- Yield Strength (0.2% Proof Stress): ≥ 205 MPa
- Elongation (A₅₀): ≥ 40%
- Hardness (HB): 123–183
- Thermal Conductivity (at 20°C): 16.3 W/(m·K)
- Specific Heat Capacity (at 20°C): 478 J/(kg·K)
- Linear Thermal Expansion Coefficient (10–100°C): 17.3 × 10⁻⁶ /K
- Density: 7.93 g/cm³
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube), Catalog No. 603 |
| Material Grades | SUS304, SUS316L, SUS321, SUS310S (customizable) |
| Outer Diameter (OD) | Φ3.0 mm – Φ50.8 mm (1/8" – 2" NPS) |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm (Schedule 5S – Schedule 40S) |
| Coil Diameter (CD) | Φ50 mm – Φ1500 mm (configurable per application) |
| Coil Length per Spool | 10 m – 500 m (continuous, depending on OD and WT) |
| Surface Finish | Pickled & Passivated (P&P), Mirror Polish (Ra ≤ 0.1 μm), or Matte |
| Surface Roughness (Ra) | 0.4 – 2.0 μm (P&P); ≤ 0.1 μm (Mirror) |
| Temperature Range | -196°C to +870°C (grade-dependent) |
| Pressure Rating | Up to 10.0 MPa (PN100), subject to hydrostatic testing |
| Tolerance (OD) | ± 0.05 mm (precision rolled); ± 0.1 mm (standard) |
| Tolerance (WT) | ± 10% of nominal wall thickness |
| Applicable Standards | ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 12771 |
| Packaging | Wooden crate or steel drum with moisture-proof wrapping; coil secured with strapping bands |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Hot-rolled stainless steel coils are sourced from certified mills with full traceability. Incoming materials undergo spectroscopic analysis (OES) to verify chemical composition compliance with the specified grade (e.g., ASTM A213 TP304).
- Piercing & Forming: The coil is pierced into tube blanks via either hot rolling (for thicker wall sections) or cold drawing (for precision thin-wall tubing). For thin-walled coil tubes, the roll-forming (cold-rolled) method is employed, where flat strip is continuously formed into a tubular profile through a series of precision rollers.
- Welding (if applicable): For welded coil tube, a high-frequency induction welding (HFW) or laser welding process is applied to the formed strip seam. The weld zone undergoes weld annealing to restore austenitic microstructure and eliminate residual stresses.
- Heat Treatment (Solution Annealing): The formed tube is subjected to solution annealing at 1050–1150°C followed by rapid water quenching to achieve a fully austenitic, stress-free microstructure with maximum corrosion resistance.
- Pickling & Passivation: The annealed tube is immersed in a mixed acid bath (nitric + hydrofluoric acid) to remove scale and oxide layers, followed by passivation treatment to form a protective chromium oxide (Cr₂O₃) film on the surface.
- Spiral Coiling: The straight tube is fed through a precision coiling machine to produce the helical coil geometry. The coiling process employs controlled bending radius and tension to prevent ovality, kinking, or residual deformation. The minimum bending radius is maintained at ≥ 3× OD to avoid cross-sectional distortion.
- Quality Inspection: Each coil undergoes hydrostatic pressure testing (per ASTM A213), dimensional verification (OD, WT, coil diameter, ovality), surface inspection (visual + magnetic particle testing for weld integrity), and chemical composition verification.
- Packaging & Dispatch: The finished coil is wound onto a protective core, wrapped in moisture-proof film, and secured in a wooden crate or steel drum for shipment.
Applications
The Stainless Steel Coil Tube finds extensive application across multiple industries, leveraging its unique coiled geometry for enhanced thermal performance and compact design:
- Heat Exchangers & Condensers: Coil-type condensers utilizing this product achieve higher heat transfer efficiency compared to traditional shell-and-tube designs. The helical geometry induces secondary Dean flow, which disrupts the thermal boundary layer and enhances convective heat transfer. This is particularly advantageous in refrigeration systems, HVAC condensers, and industrial process cooling.
- Refrigeration & Air Conditioning: Used as evaporator and condenser coils in commercial refrigeration units, heat pumps, and chiller systems. The continuous coil eliminates the need for brazed U-bends, reducing potential leak points.
- Food & Beverage Processing: The hygienic surface finish (Ra ≤ 0.4 μm) and corrosion resistance of SUS304/316L make the coil tube ideal for pasteurizers, condensers in brewing equipment, and dairy processing systems, compliant with FDA and 3-A Sanitary Standards.
- Chemical & Petrochemical Industry: Employed in process heat exchangers, distillation column condensers, and reactor cooling systems where resistance to aggressive chemical media (acids, chlorides, alkalis) is required.
- Pharmaceutical Manufacturing: Used in CIP (Clean-In-Place) systems, steam sterilization coils, and process condensers requiring high purity and corrosion resistance.
- Marine & Offshore Applications: SUS316L coil tubes are utilized in seawater heat exchangers, ballast water cooling systems, and marine HVAC condensers due to superior chloride pitting resistance.
- Power Generation: Applied in waste heat recovery systems, economizer coils, and steam condenser tube bundles in thermal power plants.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification for manufacturing and supply processes.
- ISO 14001:2015 — Environmental Management System, ensuring sustainable and environmentally responsible production.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- EN 10204 Type 3.1 — Third-party material test certificates provided with each shipment, issued by accredited inspection bodies.
- Mill Test Certificates (MTC): Full chemical analysis, mechanical test results, and heat treatment documentation for every heat lot.
- Product Standards: ASTM A213 (Seamless and Welded Austenitic Stainless Steel Tubing), ASTM A269 (Seamless and Welded Austenitic Stainless Steel Tubing for General Application), ASME SA-213, EN 10216-5, GB/T 12771.
- Non-Destructive Testing (NDT): Magnetic Particle Testing (MT) per ASTM E1444, and Eddy Current Testing (ET) per ASTM E3097 for weld seam integrity verification.
- Hydrostatic Testing: Performed per ASTM A213 requirements, with test pressure typically 1.5× the maximum design pressure, held for a minimum dwell time with no leakage permitted.
Unique Selling Points
- Enhanced Heat Transfer Performance: The helical coil geometry generates Dean vortices that intensify turbulent mixing, yielding heat transfer coefficients 20–35% higher than equivalent straight-tube configurations — validated by comparative experimental studies.
- Compact Design & Reduced Footprint: Coil-type exchangers achieve up to 40% greater surface area per unit volume compared to shell-and-tube condensers, enabling space-efficient installation.
- Reduced Fouling: The continuous curvature and induced secondary flow promote self-cleaning action, reducing fouling rates and extending maintenance intervals.
- Elimination of Brazed/U-Bend Joints: The continuous coil design removes the need for intermediate joints, significantly reducing potential failure points and improving system reliability.
- Lower Pumping Power: Despite increased frictional losses from curvature, the overall pressure drop in optimized coil configurations can be comparable to or lower than shell-and-tube alternatives when accounting for reduced tube count.
- Full Traceability: Every coil is heat-lot traceable from raw material through final inspection, with complete MTC documentation.
- Customizable Geometry: Coil diameter, tube OD, wall thickness, and surface finish are all configurable to match specific application requirements.