Stainless Steel Coil Tube for Organic Heat Carrier Furnace Systems
Product Overview
The Stainless Steel Coil Tube is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for use in Organic Heat Carrier Furnace (有机热载体炉) systems. Coil tubes are helically wound tubular components that serve as critical heat transfer elements in industrial thermal processing applications. Unlike straight pipe sections, coil tubes offer significantly greater heat exchange surface area per unit volume, making them indispensable in high-efficiency thermal systems where compactness and thermal performance are paramount.
This product line addresses a well-documented engineering challenge: the deformation of coil tubes under prolonged thermal cycling and operational stress. Through rigorous material selection, advanced manufacturing techniques, and comprehensive quality control protocols, Wenzhou Jixing Metal Materials Co., Ltd delivers coil tubes that maintain dimensional integrity and structural reliability under demanding service conditions.
Material & Properties
Coil tubes for organic heat carrier furnace applications are fabricated from high-grade austenitic stainless steels, selected for their superior combination of oxidation resistance, thermal stability, and mechanical properties at elevated temperatures.
- Primary Alloy Grades: 304 (UNS S30408), 316L (UNS S31603), 321 (UNS S32108), and 347H (UNS S34701)
- Corrosion Resistance: Excellent resistance to organic heat transfer fluids including mineral oils, synthetic fluids, and thermal oils operating at temperatures up to 400°C
- Thermal Stability: Maintains mechanical strength and dimensional stability under continuous thermal cycling between ambient and 350°C operating temperatures
- Creep Resistance: Enhanced creep strength at sustained high temperatures, critical for preventing gradual deformation over extended service life
- Weldability: Full weldability with standard filler metals, enabling seamless splicing and field repair capabilities
- Surface Finish: Available in pickled-and-passivated (2B), bright annealed (BA), or custom polished finishes
Key Mechanical Properties (Typical Values for Grade 321)
| Property | Specification |
|---|---|
| Tensile Strength (Room Temperature) | ≥ 515 MPa |
| Yield Strength (0.2% Offset) | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) |
| Thermal Conductivity (300°C) | 23.0 W/(m·K) |
| Linear Thermal Expansion (20–300°C) | 17.4 × 10⁻⁶ /K |
| Maximum Service Temperature | 870°C (continuous) |
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 19 mm – 51 mm | ASTM A269 / ASTM A312 |
| Wall Thickness | 0.8 mm – 3.0 mm | ASTM A269 |
| Coil Mean Diameter (CMD) | 150 mm – 1200 mm | Custom per application |
| Coil Length | Up to 30,000 mm per spool | Customer requirement |
| Number of Turns | 15 – 500 turns | Custom per application |
| Manufacturing Method | Induction Heating Coil Forming / Cold Bending | — |
| Surface Condition | Pickled & Passivated / Bright Annealed | ASTM A478 |
| Pressure Rating | Up to 2.5 MPa (design dependent) | ASME VIII Div.1 |
| Applicable Fluid | Organic Heat Transfer Oil (mineral / synthetic) | ASTM D6580 |
| Operating Temperature Range | -40°C to +350°C | — |
| Delivery Condition | Coiled spool / Straightened sections | — |
Manufacturing Process
The manufacturing of high-quality stainless steel coil tubes for organic heat carrier furnace applications involves a multi-stage process designed to minimize residual stresses and prevent post-installation deformation.
- Raw Material Selection & Inspection: Stainless steel seamless tubing or welded tubing is sourced from certified mills. Each batch undergoes spectrographic analysis (OES) to verify chemical composition, and ultrasonic testing (UT) for internal defect detection per ASTM A213 or ASTM A269 requirements.
- Pre-Forming Heat Treatment: Tubes undergo solution annealing at 1050–1150°C followed by controlled cooling to relieve prior processing stresses and achieve optimal grain structure. Stabilization annealing is performed for Ti-stabilized grades (321/347H) at 850–880°C to bind carbon to titanium, preventing sensitization.
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Coil Forming: Two primary forming methods are employed:
- Induction Heating Coil Forming: The tube is locally heated by induction to 800–950°C, reducing yield strength and allowing controlled bending around a forming mandrel. This method produces uniform coil geometry with minimal residual stress.
- Cold Bending with Intermediate Annealing: For tighter tolerances, cold bending is performed with periodic solution annealing to prevent work hardening and springback. This method is preferred for smaller diameter tubes (OD ≤ 32 mm).
- Stress Relief Annealing: Post-forming stress relief at 850–900°C (for 321/347H grades) or 1050–1100°C (for 304/316L grades) eliminates residual stresses introduced during forming, which is critical for preventing operational deformation.
- Surface Treatment: Final pickling and passivation removes oxide scale and forms a protective chromium oxide film per ASTM A478. This ensures corrosion resistance and dimensional accuracy.
- Dimensional & Quality Verification: Each coil spool is inspected for diameter accuracy (±1 mm), turn-to-turn spacing uniformity, straightness of ends, and surface integrity. Hydrostatic testing is performed at 1.5× design pressure to verify weld and tube integrity.
Deformation Prevention Engineering Measures
Based on extensive field experience and failure analysis of coil tube deformation in organic heat carrier furnace service, Wenzhou Jixing Metal Materials Co., Ltd incorporates the following engineering controls to prevent premature failure:
- Thermal Expansion Accommodation: Coil tube supports and expansion joints are designed to accommodate linear thermal expansion of up to 60 mm/m at 350°C operating temperature, preventing thermal buckling.
- Support Spacing Optimization: Maximum unsupported span is calculated based on fluid velocity, pressure, and weight loading per ASME B31.3 guidelines, typically not exceeding 2.5× the coil mean diameter.
- Creep-Resistant Grade Selection: For applications exceeding 300°C, 321H or 347H grades are recommended over standard 304 to provide superior creep rupture strength at elevated temperatures.
- Uniform Heat Distribution: Coil tube geometry is optimized to ensure uniform heat flux distribution, preventing localized overheating that accelerates creep deformation and thermal fatigue.
- Flow Velocity Control: Minimum fluid velocity of 1.0 m/s is maintained to ensure adequate convective heat transfer and prevent local hot spots on the tube outer surface.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd are deployed across a wide range of industrial thermal processing applications:
- Organic Heat Carrier Furnace Systems: Primary heat transfer coils in indirect-fired and direct-fired thermal oil heaters for continuous temperature control up to 350°C
- Chemical Processing: Reactor heating coils, distillation column reboilers, and heat exchange loops in petrochemical and fine chemical plants
- Food & Pharmaceutical Industry: Sanitary-grade heating coils for pasteurization, sterilization, and process heating systems requiring food-contact compliance
- Textile Manufacturing: Heat transfer coils for dyeing machines, calendering units, and drying systems
- Paper & Pulp Industry: Heating coils for paper drying cylinders and pulp preparation systems
- Wood Processing: Heat transfer elements in wood drying kilns and veneer pressing systems
- Plastics & Rubber Processing: Temperature control coils for injection molding machines and extruder heating zones
- Heating Systems: Floor heating coils and radiant heating systems in commercial and industrial buildings
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 — 3.1 Type Material Test Reports available for all shipments
- ASME — Manufacturer's Data Report (MDR) available for pressure-containing applications
- CE Marking — Compliance with European Pressure Equipment Directive (PED 2014/68/EU)
Testing & Inspection Protocols
| Test Method | Standard | Purpose |
|---|---|---|
| Hydrostatic Testing | ASTM A269 / ASME B31.3 | Verify pressure integrity |
| Ultrasonic Testing (UT) | ASTM E127 | Detect internal defects |
| Positive Material Identification (PMI) | ASTM E1683 | Verify alloy composition |
| Intergranular Corrosion Test | ASTM A262 Practice E | Confirm sensitization resistance |
| Dimensional Inspection | ASTM A213 / A269 | Verify OD, wall thickness, and coil geometry |
| Hardness Testing | ASTM E18 (Rockwell B) | Confirm heat treatment condition |
Unique Selling Points
- Expertise in Deformation Prevention: Leveraging documented field experience in organic heat carrier furnace coil tube failure analysis, Wenzhou Jixing provides engineering solutions that directly address the root causes of coil deformation — thermal stress concentration, inadequate support, and creep under sustained high temperature — resulting in significantly extended service life.
- Custom Coil Geometry: Fully customizable coil mean diameter, turn spacing, and spool configuration to match specific furnace designs and thermal load requirements, with engineering support for finite element analysis (FEA) of thermal and mechanical performance.
- Integrated Solution Capability: From material selection through coil forming, heat treatment, and surface finishing, all processes are managed under a single quality system, ensuring traceability and consistency.
- Grade Selection Advisory: Technical team provides expert guidance on optimal stainless steel grade selection based on operating temperature, fluid type, pressure, and environmental conditions, ensuring cost-effective yet reliable performance.
Ordering Information
When specifying coil tube orders, customers should provide the following parameters to ensure optimal product configuration:
- Required tube outer diameter and wall thickness
- Coil mean diameter and number of turns (or total coil length)
- Operating temperature and maximum fluid temperature
- Operating pressure and design pressure
- Heat transfer fluid type (mineral oil, synthetic fluid, etc.)
- Preferred alloy grade (if not specified, our engineering team will recommend)
- Applicable standards and required certifications
- End preparation requirements (beveled, capped, or field-welded)