Stainless Steel Coil Tube for Organic Heat Carrier Furnace Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous helical tube designed for integration into organic heat carrier furnace systems (Organic Heat Transfer Fluid Furnaces). These coil tubes serve as the primary heat exchange surfaces within high-temperature thermal systems, facilitating efficient convective and radiative heat transfer between the combustion zone and the circulating organic heat transfer fluid (OHTF). The coil geometry provides a high surface-area-to-volume ratio, enabling superior thermal performance in compact furnace configurations.
Coil tubes are critical components in industrial thermal processing where precise temperature control is required. Unlike straight-tube designs, the continuous helical configuration of coil tubes eliminates the need for numerous welded joints, significantly reducing the risk of thermal leakage and mechanical failure under cyclic thermal loading conditions. This design philosophy aligns with the principles described in the study "Analysis of In-furnace Flow and Heat Exchange of Coiled Organic Heat Carrier Furnace," which demonstrates that coiled configurations achieve more uniform temperature distribution and improved flow characteristics within the furnace interior.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel grades selected for their exceptional resistance to thermal oxidation, thermal fatigue, and corrosion under aggressive organic heat transfer fluid environments. The primary material specifications include:
- Type 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent formability and moderate high-temperature strength up to 870°C (1600°F). Suitable for moderate-temperature organic heat carrier applications.
- Type 316L (UNS S31603) — Low-carbon variant with added molybdenum (Mo) providing enhanced resistance to pitting and crevice corrosion, particularly beneficial when handling halogenated heat transfer media or in high-sulfur environments.
- Type 321 (UNS S32100) — Titanium-stabilized austenitic steel offering superior resistance to intergranular corrosion (IGC) and thermal cycling fatigue. Recommended for continuous operation at temperatures exceeding 600°C.
- Type 347H (UNS S34709) — Niobium-stabilized high-temperature grade with elevated creep resistance and long-term structural integrity under sustained thermal stress.
Key mechanical and thermal properties of the coil tube materials include:
- Thermal conductivity: 14.9–16.3 W/(m·K) at 100°C
- Linear thermal expansion coefficient: 16–18 × 10⁻⁶ /°C
- Yield strength (at 600°C): ≥ 130 MPa (Type 321/347H)
- Oxidation resistance: Continuous service up to 900–1000°C depending on grade
- Carbide precipitation resistance: Excellent (stabilized grades 321/347H)
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ12 mm – Φ51 mm (0.5" – 2") | ASTM A213 / ASTM A269 |
| Wall Thickness | 0.8 mm – 3.0 mm (0.031" – 0.118") | ASTM A213 / ASTM A269 |
| Coil Pitch (Helical Spacing) | 20 mm – 80 mm (adjustable per design) | Custom / OEM Specification |
| Coil Diameter | Φ200 mm – Φ1500 mm | Custom / OEM Specification |
| Tube Length (Total Uncoiled) | Up to 120 m (continuous single-piece) | — |
| Surface Finish | 2B, BA (Bright Annealed), or Custom (Ra ≤ 0.4 μm) | ASTM A478 / ASTM A270 |
| Maximum Operating Temperature | 350°C – 650°C (depending on fluid and grade) | Manufacturer Data |
| Maximum Operating Pressure | 1.6 MPa – 4.0 MPa (design-dependent) | ASME BPV Code / EN 13480 |
| Heat Transfer Fluid Compatibility | Mineral Oil, Synthetic Oil, Molten Salt, Dowtherm, Therminol | — |
| Welding Method (End Joints) | TIG (GTAW) — Full-Penetration Butt Weld | ASME Section IX / AWS D10.9 |
| Tolerance on OD | ±0.1 mm (precision coils) | ASTM A269 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| Delivery Condition | Annealed and Pickled / Solution Annealed | — |
Manufacturing Process
The production of high-quality stainless steel coil tubes for organic heat carrier furnace applications follows a rigorously controlled multi-stage manufacturing process:
- Material Selection and Incoming Inspection — Raw stainless steel bar stock or seamless tubing is sourced from certified mills. Each batch undergoes spectrographic analysis (PMI — Positive Material Identification), mechanical property verification, and chemical composition confirmation to ensure compliance with the specified ASTM/EN grade.
- Pipe Drawing and Cold Forming — Seamless stainless steel tubes are cold-drawn to the precise outer diameter and wall thickness required. This process enhances surface finish quality and dimensional accuracy while maintaining metallurgical integrity.
- Coiling (Helical Forming) — The straight tube is fed through precision-guided mandrels and rollers on a CNC-controlled coiling machine to form the continuous helical shape. The coiling process is performed at ambient temperature to avoid work-hardening or microstructural alteration. Pitch, coil diameter, and total length are programmatically controlled to meet exact design specifications.
- Stress Relief Annealing — Following coiling, the tube assembly is subjected to a controlled solution annealing cycle (typically 1050°C – 1150°C for austenitic grades) followed by water quenching. This eliminates residual stresses induced during cold forming, restores full ductility, and ensures uniform grain structure throughout the coil.
- Pickling and Passivation — The annealed coil tube is pickled in a controlled acid bath (nitric-hydrofluoric acid mixture) to remove surface scale, then passivated to form a stable chromium oxide protective layer. This ensures long-term corrosion resistance and a clean surface finish suitable for heat transfer fluid circulation.
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Non-Destructive Testing (NDT) — All coil tubes undergo comprehensive NDT including:
- Visual inspection of the entire coil surface
- Eddy current testing (ET) for wall thickness and surface defect detection
- Helium leak testing or pneumatic pressure testing (hydrostatic testing at 1.5× design pressure)
- Dimensional verification at multiple points along the coil
- End Preparation and Marking — Tube ends are squared, deburred, and threaded or prepared per the customer's connection requirements. Each coil tube receives a unique traceability stamp indicating material grade, heat number, manufacturing date, and test results.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. are specifically engineered for the following industrial applications:
- Organic Heat Carrier Furnaces (OHTF Systems) — Primary application. Coil tubes serve as the radiant and convective heat exchange surfaces in liquid-phase and gas-phase organic heat transfer fluid furnaces operating at temperatures up to 350°C (liquid phase) and 650°C (gas phase).
- Chemical Processing Industries — Heat exchange in reactors, distillation columns, and polymerization systems requiring precise temperature control and corrosion-resistant heat transfer surfaces.
- Petrochemical and Refinery Applications — Reboilers, preheaters, and thermal oil loop systems in refining units where continuous high-temperature operation is required.
- Textile and Dyeing Industry — Thermal oil heating systems for drying, calendering, and finishing processes requiring uniform heat distribution.
- Food and Pharmaceutical Processing — Steam generation and thermal processing systems where hygienic-grade stainless steel surfaces and non-contaminating heat transfer are mandatory.
- Plastics and Rubber Manufacturing — Extruder barrel heating, press platens, and molding temperature control systems utilizing thermal oil circulation.
- Waste-to-Energy and Biomass Heating — Coil tubes used in thermal oil boilers utilizing biomass, waste, or alternative fuel combustion for district heating and industrial process heat.
Unique Selling Points
- Continuous Single-Piece Construction — Unlike segmented tube assemblies, the continuous coil design eliminates internal weld joints, dramatically reducing failure points and ensuring long-term system reliability under thermal cycling.
- Optimized Helical Geometry — Based on CFD (Computational Fluid Dynamics) analysis of in-furnace flow and heat exchange characteristics, the coil pitch and diameter are optimized to maximize turbulence and heat transfer coefficients while minimizing pressure drop.
- Thermal Fatigue Resistance — Stabilized stainless steel grades (321/347H) provide superior resistance to thermal fatigue cracking, extending service life in cyclic heating-cooling operations typical of industrial furnaces.
- Full Traceability — Each coil tube is individually traceable from raw material mill certificate through final NDT results, ensuring complete quality documentation for regulatory compliance.
- Custom Engineering Capability — OEM-specific coil geometries, material grades, surface finishes, and end preparations are available to integrate seamlessly with proprietary furnace designs.
Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certifications ensuring that all stainless steel coil tubes meet international standards for industrial heat exchange applications:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System — Full manufacturing process |
| ISO 14001:2015 | Environmental Management System |
| ASME BPV Code Section I / IV | Boiler and Pressure Vessel components |
| EN 13480 | Industrial Piping — Design and fabrication |
| ASTM A213 | Seamless Austenitic Stainless Steel Tubes for High-Temperature Service |
| ASTM A269 | Wrought Austenitic Stainless Steel Tubing for Chemical and Allied Industries |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance |
| GB/T 12771 | Chinese National Standard — Seamless Stainless Steel Tubes for Heat Exchangers |
| TÜV / SGS Factory Audit | Third-party manufacturing capability verification |
Technical Note: The design and performance of coil tubes in organic heat carrier furnace applications are governed by the principles of internal flow heat transfer in helical geometries. The secondary flow (Dean vortices) generated in curved tubes significantly enhances convective heat transfer coefficients compared to straight tubes, typically achieving 2–3 times higher Nusselt numbers at equivalent Reynolds numbers. This fundamental advantage of coil tube geometry is validated through both theoretical analysis and experimental verification as documented in the referenced study on in-furnace flow and heat exchange characteristics.
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Reference Number: 792 — Coiltube (Stainless Steel Coil Tube for Organic Heat Carrier Furnace)
Category: Technical Literature & Reference — Industrial Heat Exchange Components