Stainless Steel Spiral Coil Tube for Organic Heat Carrier Furnace Systems
Product Overview
The Stainless Steel Spiral Coil Tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component designed specifically for organic heat carrier (OHC) furnace systems and high-temperature thermal transfer applications. This product is engineered to provide superior thermal conductivity, mechanical integrity, and long-term corrosion resistance under demanding operating conditions.
Unlike conventional straight heat exchanger tubes, spiral coil tubes offer a significantly increased heat transfer surface area per unit volume, enhanced turbulence within the fluid flow path, and improved convective heat transfer coefficients. Numerical simulation studies on the flow performance of spiral coil tubes in organic heat carrier furnaces have confirmed that the helical geometry induces secondary flow patterns (Dean vortices), which effectively disrupt the thermal boundary layer and promote uniform heat distribution throughout the working medium.
This coil tube product represents a critical component in industrial thermal management systems where precise temperature control, energy efficiency, and operational reliability are paramount.
Material Composition and Properties
Base Material
The coil tubes are fabricated from high-grade austenitic stainless steel, with the primary material grade being AISI 321 (UNS S32100) or AISI 310S (UNS S31008), selected for their exceptional resistance to thermal cycling, oxidation, and carburization at elevated temperatures.
Chemical Composition (Typical)
| Element | 321 Grade (%) | 310S Grade (%) |
|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.08 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 |
| Chromium (Cr) | 17.00 – 19.00 | 24.00 – 26.00 |
| Nickel (Ni) | 9.00 – 13.00 | 19.00 – 22.00 |
| Titanium (Ti) | ≥ 5 × C, min 0.40 | — |
| Nitrogen (N) | — | ≤ 0.15 |
| Iron (Fe) | Balance | Balance |
Mechanical and Thermal Properties
| Property | 321 Grade | 310S Grade |
|---|---|---|
| Tensile Strength (MPa, min) | 515 | 515 |
| Yield Strength (0.2% offset, MPa) | 205 | 205 |
| Elongation (% at rupture, min) | 40 | 40 |
| Thermal Conductivity (W/m·K, at 100°C) | 16.3 | 16.3 |
| Maximum Service Temperature (°C) | 870 (continuous) | 1150 (continuous) |
| Thermal Expansion Coefficient (μm/m·°C, 20–100°C) | 17.2 | 18.0 |
| Density (kg/m³) | 7900 | 8000 |
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Type | Spiral Coil Tube (Helical Coil) |
| Tube Outer Diameter (OD) | 19 mm – 114.3 mm (customizable) |
| Tube Wall Thickness | 1.0 mm – 6.0 mm |
| Coil Diameter (Pitch Diameter) | 200 mm – 2000 mm |
| Coil Pitch (Center-to-Center Spacing) | 15 mm – 150 mm |
| Helix Angle | 5° – 30° (configurable) |
| Coil Length (Effective Heating Length) | Up to 50 m (continuous winding) |
| End Connection Type | Threaded (NPT/BSP), Flanged, or Butt-Welded |
| Surface Finish | Mirror Polish (Ra ≤ 0.4 μm) or Standard Pickled & Passivated |
| Operating Pressure | Up to 2.5 MPa (design dependent) |
| Design Temperature Range | −50°C to +900°C (material dependent) |
| Standards Compliance | ASTM A213 / ASTM A269 / ASME B36.19M / EN 10216-5 |
Manufacturing Process
Step 1: Raw Material Selection and Inspection
High-purity stainless steel seamless tubes conforming to ASTM A213 standards are sourced from certified mill suppliers. Incoming material undergoes 100% chemical composition verification via Optical Emission Spectroscopy (OES) and mechanical property testing including tensile and hardness evaluations.
Step 2: Straightening and Dimensional Preparation
Seamless tubes are precision-straightened using hydraulic draw benches to achieve straightness tolerances of ≤ 1 mm/m. Cut lengths are prepared according to the calculated coil development length with ±2 mm tolerance.
Step 3: Coil Forming (Cold Bending)
Specialized CNC-controlled coil forming machines are employed to wind the straight tubes into precise helical geometries. The forming process is executed at ambient temperature (cold forming) to maintain the metallurgical integrity of the material while achieving dimensional accuracy within ±0.5 mm for coil diameter and ±1 mm for pitch. The helix angle is precisely controlled through synchronized feed and rotation mechanisms.
Step 4: Stress Relief Annealing
Following coil formation, the product undergoes stress relief annealing at 870°C – 950°C for austenitic grades, followed by controlled air cooling. This process eliminates residual stresses introduced during cold forming, restoring ductility and ensuring dimensional stability during subsequent service.
Step 5: Surface Treatment and Passivation
The coil tubes are subjected to pickling and passivation treatment using a citric acid or nitric acid-based solution to remove oxide scales and restore the protective chromium oxide layer. For applications requiring enhanced cleanliness, electropolishing is available to achieve a surface roughness of Ra ≤ 0.4 μm.
Step 6: Hydrostatic Pressure Testing
Each coil tube assembly undergoes hydrostatic pressure testing at 1.5 times the maximum design pressure for a minimum hold time of 10 minutes to verify weld integrity and structural soundness. No leakage or permanent deformation is permissible.
Step 7: Final Inspection and Certification
Completed products undergo comprehensive dimensional verification, visual inspection, and (where applicable) Non-Destructive Testing (NDT) including dye penetrant testing (DPT) on end connections. Each batch is accompanied by a full material test certificate (MTC) per EN 10204 Type 3.1.
Applications
Primary Applications
- Organic Heat Carrier (OHC) Furnace Systems: Spiral coil tubes serve as the primary heat exchange elements in organic heat transfer fluid systems, where thermal oils or synthetic heat transfer media are circulated to achieve precise temperature control in industrial processes.
- Chemical Processing Plants: Used in reactor heating, distillation column reboilers, and process heat exchangers handling corrosive media including acids, alkalis, and organic solvents.
- Petrochemical Industry: Applied in crude oil fractionation, catalytic cracking units, and polymerization reactors requiring high-temperature heat transfer under aggressive chemical environments.
- Food and Pharmaceutical Processing: Employed in pasteurization systems, sterilization equipment, and thermal processing lines where hygiene and corrosion resistance are critical.
- Textile and Paper Manufacturing: Integrated into drying cylinders, calendering systems, and heat recovery units operating with organic heat transfer fluids.
- Synthetic Rubber and Resin Production: Used as heating coils in polymerization reactors and devolatilization systems.
Performance Advantages in OHC Systems
Numerical simulation studies of spiral coil tube flow performance in organic heat carrier furnaces have demonstrated several key advantages:
- Enhanced Heat Transfer Coefficient: The helical geometry generates Dean vortices that increase the convective heat transfer coefficient by 20% – 50% compared to equivalent straight tubes, resulting in more compact and efficient heat exchanger designs.
- Uniform Temperature Distribution: The secondary flow patterns promote radial mixing, minimizing hot spots and thermal stratification within the heat transfer fluid.
- Reduced Fouling: Increased turbulence near the tube wall reduces deposition of thermal decomposition products from organic heat transfer fluids, extending maintenance intervals.
- Compact Footprint: The coiled configuration maximizes heat exchange area within a limited furnace volume, optimizing space utilization.
- Thermal Shock Resistance: The continuous helical geometry accommodates differential thermal expansion without inducing excessive stress concentrations, enhancing fatigue life during start-up and shutdown cycles.
Quality Certifications and Standards Compliance
Manufacturing Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management
- NACE SP0169 — Corrosion Prevention Compliance (where applicable)
- PED 2014/68/EU — Pressure Equipment Directive Compliance
Product Standards
- 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 Chromium-Chromium-Nickel Stainless Steel Tube for Chemical and Similar Severe Service
- ASME B36.19M — Dimensional Requirements for Stainless Steel Pipe
- EN 10216-5 — Non-alloy and Alloy Steel Tubes for Pressure Purposes — Technical Delivery Conditions — Part 5: Austenitic Steels
- GB/T 12771 — Chinese National Standard for Stainless Steel Tubes for General Fluid Conveyance
Testing and Documentation
- Mill Test Certificate (MTC) per EN 10204 Type 3.1 — Inspection Report
- Hydrostatic Test Report for each individual coil assembly
- Dimensional Inspection Report with certified measuring instruments
- Chemical Analysis Report (OES-verified)
- Mechanical Property Test Report (Tensile, Hardness)
- Third-Party Inspection available upon request (e.g., SGS, Bureau Veritas, TÜV)
Unique Selling Points
1. Precision Helical Geometry: CNC-controlled coil forming ensures dimensional accuracy of ±0.5 mm, guaranteeing optimal fit within furnace assemblies and consistent flow characteristics throughout the coil length.
2. Enhanced Thermal Performance: Leveraging validated numerical simulation data, the coil geometry is optimized to maximize heat transfer efficiency while minimizing pressure drop, achieving the best possible balance between thermal performance and pumping power requirements.
3. Extended Service Life: Superior resistance to thermal cycling, oxidation, and organic heat transfer fluid degradation ensures service life exceeding 10 years under normal operating conditions, significantly reducing total cost of ownership.
4. Customization Capability: Full customization of coil diameter, pitch, helix angle, tube dimensions, and end connections to match specific furnace designs and process requirements.
5. Complete Traceability: From raw material mill certificates to final product testing, every coil tube is fully traceable, meeting the rigorous quality documentation requirements of the chemical, pharmaceutical, and food processing industries.
Ordering Information
When specifying this product, the following information should be provided to ensure correct manufacturing:
- Material Grade (e.g., 321, 310S, 304, 316L)
- Tube Outer Diameter and Wall Thickness
- Coil Diameter (Pitch Diameter) and Pitch Spacing
- Total Effective Heating Length
- End Connection Type and Dimensions
- Surface Finish Requirement
- Maximum Operating Pressure and Temperature
- Applicable Standards and Certification Requirements
Wenzhou Jixing Metal Materials Co., Ltd. offers comprehensive technical support and engineering consultation to assist customers in selecting the optimal coil tube configuration for their specific thermal system requirements.