Stainless Steel Coil Tube (Coiltube) — Industrial Heat Transfer Coiled Tubing
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous coiled tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for high-efficiency heat exchange applications, particularly in Organic Heat Transfer Fluid (OHTF) furnace systems. Unlike conventional straight-pipe assemblies, coil tubes are supplied in continuous helical coil configurations, which inherently enhance turbulent flow characteristics and improve convective heat transfer coefficients through the centripetal acceleration effect induced by the curved geometry.
Based on numerical simulation research into the internal flow heat transfer characteristics of coiled tubes in organic heat transfer fluid furnaces, the helical curvature of the coil tube generates secondary Dean vortices within the fluid stream. These secondary flow structures significantly augment the mixing intensity, reduce the thermal boundary layer thickness, and thereby increase the overall heat transfer coefficient by 20–40% compared to equivalent straight tubes. This fundamental hydrodynamic advantage makes coil tubes the preferred geometry for compact, high-performance thermal systems.
Material & Properties
Coil tubes are fabricated from high-purity austenitic and duplex stainless steel grades, selected to ensure superior corrosion resistance, high-temperature strength, and long-term thermal stability in demanding industrial environments.
Available Material Grades
- 304 / 304L (UNS S30400 / S30403) — General-purpose austenitic grade with excellent weldability and moderate corrosion resistance; suitable for temperatures up to 870 °C (1600 °F).
- 316 / 316L (UNS S31600 / S31603) — Molybdenum-enhanced austenitic grade offering superior resistance to pitting and crevice corrosion in chlorinated or acidic environments.
- 321 (UNS S32100) — Titanium-stabilized austenitic grade providing outstanding resistance to intergranular corrosion and thermal cycling, ideal for high-temperature furnace applications.
- 310S (UNS S31008) — High-nickel, high-chromium austenitic grade with exceptional oxidation resistance, suitable for sustained service temperatures up to 1150 °C (2100 °F).
- 316Ti (UNS S31635) — Titanium-stabilized variant of 316L combining superior corrosion resistance with enhanced high-temperature creep strength.
- 2205 Duplex (UNS S32205) — Duplex austenitic-ferritic stainless steel offering roughly double the yield strength of standard austenitic grades, with excellent resistance to chloride stress corrosion cracking.
Key Mechanical & Physical Properties (Typical for Grade 316L)
| Property | Value | Unit |
|---|---|---|
| Yield Strength (0.2% Offset) | ≥ 170 | MPa |
| Tensile Strength (Rm) | ≥ 485 | MPa |
| Elongation (A5) | ≥ 40 | % |
| Thermal Conductivity (at 20 °C) | 16.3 | W/(m·K) |
| Specific Heat Capacity (at 20 °C) | 500 | J/(kg·K) |
| Linear Thermal Expansion (20–100 °C) | 17.3 × 10⁻⁶ | K⁻¹ |
| Maximum Continuous Service Temperature | 870 | °C |
| Density | 8.0 | g/cm³ |
| Surface Roughness (Ra, as-delivered) | 0.8 – 1.6 | μm |
Specifications
| Parameter | Specification Range |
|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ114.3 mm (¼" – 4½") |
| Wall Thickness | 0.3 mm – 8.0 mm (SWS 00S – 160S equivalent) |
| Coil Winding Diameter | 200 mm – 2,000 mm (adjustable per customer requirement) |
| Coil Length (per coil) | Up to 300 m (continuous coil) |
| Tolerance on OD | ±0.05 mm (precision grade); ±0.10 mm (standard grade) |
| Tolerance on Wall Thickness | ±10% (standard); ±5% (precision grade) |
| End Condition | Plain cut, chamfered, beveled, or threaded (per ASME B1.20.1) |
| Surface Finish | Pickled & Passivated (P&P), Electropolished (Ra ≤ 0.4 μm), Brushed, or Mirror Polished (Ra ≤ 0.1 μm) |
| Heat Treatment Condition | Annealed (Solution Annealed at 1050–1100 °C with water quench) |
| Standard References | ASTM A213 / A269, ASME SB167, EN 10216-5, GB/T 14976 |
| Packaging | Export-grade wooden crates with desiccant; protective end caps; coil wrapped in stretch film |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous, multi-stage manufacturing sequence designed to ensure dimensional precision, metallurgical integrity, and surface quality:
- Raw Material Procurement & Inspection: Cold-rolled stainless steel strip or seamless tube blanks are sourced from certified mills and subjected to incoming quality control, including Chemical Composition Analysis (CCA) via Optical Emission Spectroscopy (OES) and Positive Material Identification (PMI).
- Coiling / Pipe Forming: For welded coil tubes, the stainless steel strip is precisely formed into a helical coil through a high-precision coiling machine, followed by longitudinal seam welding using Automatic Submerged Arc Welding (SAW) or Gas Tungsten Arc Welding (GTAW) with inert gas shielding.
- Heat Treatment (Solution Annealing): The formed coil tube is solution annealed at 1050–1100 °C followed by rapid water quenching to dissolve carbide precipitates, restore full austenitic microstructure, and achieve maximum corrosion resistance and ductility.
- Pickling & Passivation: The annealed coil is immersed in a mixed acid bath (HNO₃/HF or H₂SO₄/HNO₃) to remove surface scale and discoloration, followed by nitric acid passivation to form a stable chromium oxide passive film (Cr₂O₃), ensuring corrosion resistance in the delivered condition.
- Precision Sizing & Straightening (if applicable): Cold drawing or roll-sizing operations may be applied to achieve tight dimensional tolerances on OD and wall thickness.
- Surface Finishing: Optional electropolishing (EP) or mechanical polishing to achieve specified surface roughness levels for sanitary, pharmaceutical, or high-efficiency heat transfer applications.
- Final Quality Inspection: Each coil undergoes 100% visual inspection, dimensional verification (OD and wall thickness via ultrasonic thickness gauging), and helical eddy current testing (ECT) to detect seam weld defects and wall thickness variations. Hydrostatic testing is performed per ASTM A213 at 5× the maximum allowable working pressure.
- Packaging & Dispatch: Coils are wound onto protective wooden or steel spools, wrapped in moisture-proof packaging, and secured with metal banding for safe transit.
Applications
The enhanced heat transfer performance inherent to the helical coil geometry makes these stainless steel coil tubes indispensable across a wide spectrum of industrial thermal systems:
- Organic Heat Transfer Fluid (OHTF) Furnaces: As the primary heating element in liquid-phase organic heat transfer systems, where coil tubes circulate heat carrier fluids (e.g., Dowtherm A, Therminol VP-1) to deliver precise, uniform thermal energy to process loads. Numerical simulation studies confirm that the Dean number (De = Re·√(d/D)) governs the intensity of secondary flow and directly correlates with the enhancement of the Nusselt number (Nu) in coiled tube configurations.
- Heat Exchangers & Condensers: Compact spiral-wound heat exchangers for petrochemical, oil & gas, and power generation applications requiring high heat transfer efficiency in limited footprint.
- Boilers & Steam Generators: Water tube boilers, waste heat recovery boilers, and superheaters utilizing coil tubes as evaporator or superheater elements.
- Chemical Processing: Reactor coil tubes, jacketed vessel internals, and heat tracing systems in corrosive chemical environments where austenitic or duplex stainless steel provides essential corrosion protection.
- Food & Pharmaceutical Industry: Electropolished coil tubes for pasteurization, sterilization (CIP/SIP systems), and process heating in sanitary-grade environments compliant with 3-A and EHEDG standards.
- Solar Thermal Systems: Concentrated solar power (CSP) receiver tubes and solar water heating collectors where high-temperature oxidation resistance is critical.
- Automotive & HVAC: Condenser coils, evaporator coils, and refrigerant circuit tubing in automotive air conditioning and industrial HVAC systems.
- Marine & Offshore: Seawater heat exchanger coils and cooling systems for marine propulsion and offshore platform utilities, leveraging the corrosion resistance of 316L and duplex grades.
Unique Selling Points
- Superior Heat Transfer Efficiency: The helical coil geometry generates Dean secondary vortices that enhance turbulent mixing, increasing the convective heat transfer coefficient by 20–40% over straight tubes of equivalent diameter, as validated by CFD numerical simulation research.
- Continuous Coil Supply: Delivered in continuous coil lengths up to 300 m, minimizing field welding joints and reducing potential failure points in high-pressure thermal systems.
- Custom Coil Configuration: Winding diameter, pitch, and coil length are fully customizable to match specific furnace geometry, heat exchanger design, or process requirements.
- Multi-Grade Material Portfolio: Six stainless steel grades available, spanning standard austenitic (304L, 316L) through high-temperature (321, 310S) to high-strength duplex (2205), ensuring optimal material selection for every service condition.
- Sanitary-Grade Surface Finishing: Electropolished surfaces with Ra ≤ 0.4 μm available, meeting the stringent hygiene and cleanliness requirements of food, pharmaceutical, and biotechnology industries.
- Comprehensive Quality Assurance: Full traceability from mill certificate to final inspection, with PMI verification, ultrasonic thickness testing, and helical eddy current flaw detection on every coil.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that all stainless steel coil tube products meet or exceed international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering design, manufacturing, and service processes. |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices. |
| ISO 45001:2018 | Occupational Health & Safety Management System certification. |
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-temperature Service. |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severe Service. |
| ASME SB167 | Boiler & Pressure Vessel Code — Specification for Seamless and Welded Austenitic Chromium-Nickel Stainless Steel Tubing. |
| EN 10216-5 | European Standard for Heat-resistant, Pressure-resistant, and Mechanical non-alloy and alloy steel tubes — Part 5: Non-alloy and alloy steel tubes for heat transfer. |
| GB/T 14976 | Chinese National Standard for Fluid Transport Stainless Steel Seamless Tubes. |
| 3-A Sanitary Standards | Compliance with 3-A Dairy, Food & Beverage Sanitary Equipment Standards (for electropolished grades). |
| Mill Test Certificate (MTC) | EN 10204 3.1 type certification provided with each shipment, including chemical composition, mechanical properties, and heat treatment records. |
Technical Notes on Heat Transfer Performance
Numerical simulation research on the internal flow heat transfer characteristics of coiled tubes in Organic Heat Transfer Fluid (OHTF) furnaces demonstrates that the helical geometry fundamentally alters the flow regime within the tube. The centripetal force acting on the fluid in the curved path generates Dean vortices — pairs of counter-rotating secondary flow structures that intensify radial mixing and thin the thermal boundary layer. The dimensionless Dean number (De = Re·√(d/D), where d is the tube inner diameter and D is the coil helix diameter) serves as the primary governing parameter for quantifying this enhancement. CFD simulations reveal that for De numbers in the range of 100–1,500, the Nusselt number (Nu) in coiled tubes exceeds the Dittus-Boelter correlation for straight tubes by a factor of 1.2 to 1.4, translating to a 20–40% improvement in heat transfer efficiency. This inherent performance advantage, combined with the space-saving compact geometry, makes the coil tube configuration the optimal choice for high-efficiency thermal systems where both heat transfer performance and spatial constraints are critical design parameters.
Ordering Information
To place an order or request a technical quotation, please provide the following specifications:
- Material grade (e.g., 304L, 316L, 321, 310S, 316Ti, 2205)
- Outer diameter (OD) and wall thickness
- Coil winding diameter and coil length
- Surface finish requirement (P&P, Electropolished, Brushed, Mirror)
- Applicable standard (ASTM, ASME, EN, GB)
- Quantity and required delivery schedule
Wenzhou Jixing Metal Materials Co., Ltd. — Precision stainless steel coil tube solutions engineered for superior thermal performance and reliable industrial service.