Stainless Steel Coil Tube for Reforming Furnace Feed Preheaters
Product Overview
The Coil Tube (盘管) is a specialized tubular heat transfer component designed for use in reforming furnace feed preheaters within petrochemical and chemical processing facilities. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product is engineered to withstand extreme thermal cycling, high-temperature oxidation, and aggressive chemical environments encountered during catalytic reforming and steam reforming operations. The coil tube configuration provides an optimal surface-area-to-volume ratio, enabling efficient heat transfer between combustion gases and process feedstocks prior to their introduction into the reformer reactor.
Two primary coil tube configurations are employed in reforming furnace feed preheaters: the vertical serpentine coil and the horizontal helical coil. Each configuration presents distinct advantages in terms of thermal efficiency, mechanical stress distribution, and operational reliability. The comparative study of these configurations informs optimal design selection based on specific process parameters, including feedstock composition, operating pressure, and furnace thermal load.
Material & Properties
Coil tubes for reforming furnace applications are fabricated from high-temperature austenitic stainless steels and nickel-based alloys, selected to ensure long-term structural integrity and resistance to degradation mechanisms including oxidation, carburization, and thermal fatigue.
Primary Material Grades
- TP310H (UNS S31008) – Chromium-Nickel austenitic stainless steel with enhanced carbon content, suitable for continuous service up to 1200°C (2192°F). Offers superior resistance to thermal cycling and carburization in hydrocarbon environments.
- TP347H (UNS S34709) – Niobium-stabilized austenitic stainless steel, resistant to intergranular corrosion, suitable for temperatures up to 1150°C (2092°F).
- HP-Nb (Haynes 230) – Nickel-Chromium-Silicon superalloy, providing exceptional resistance to oxidation and carburization at temperatures exceeding 1200°C (2192°F).
- TP304H / TP309H – General-purpose austenitic grades for lower-temperature preheat sections (up to 950°C / 1742°F).
Key Mechanical and Physical Properties
- Thermal conductivity: 22–30 W/(m·K) at operating temperature
- Coefficient of thermal expansion: 16–18 × 10⁻⁶ /°C (20–800°C)
- Creep strength at 1100°C: ≥ 50 MPa (for TP310H)
- Oxidation rate at 1100°C: < 0.1 mg/(dm²·h) in air atmosphere
- Carburization resistance: Excellent in reducing hydrocarbon atmospheres
- Weldability: Excellent; supports automatic orbital welding and TIG (Tungsten Inert Gas) welding
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 21.3 mm – 114.3 mm (¾" – 4½") |
| Wall Thickness | 1.65 mm – 6.35 mm (0.065" – 0.250") |
| Coil Diameter | 150 mm – 1200 mm (adjustable per furnace design) |
| Coil Length | Up to 200 m per continuous coil |
| Operating Temperature Range | 200°C – 1200°C (392°F – 2192°F) |
| Operating Pressure | Up to 40 MPa (5800 psi) |
| Bending Radius | ≥ 4D (minimum, to prevent wall thinning) |
| Tolerance – OD | ±0.05 mm (ASME B36.19M / ASTM A213) |
| Tolerance – Wall Thickness | ±10% nominal |
| Surface Finish | Mirror polished or mill finish (Ra ≤ 0.8 μm for high-efficiency heat transfer) |
| Coil Configuration | Vertical Serpentine / Horizontal Helical / Hybrid |
| End Preparation | Beveled per ASME B1.20.1,坡口角度 37.5° ± 3.75° |
| Heat Treatment | Solution annealed at 1050–1150°C, followed by water quench |
Manufacturing Process
1. Material Selection and Incoming Inspection
Raw materials are sourced from certified mills with full traceability documentation (Mill Test Reports per EN 10204 Type 3.1). Each heat is verified for chemical composition (by spectral analysis), mechanical properties, and grain structure. Non-conforming material is rejected prior to processing.
2. Cold Drawing and Sizing
Hot-rolled seamless tube blanks are cold-drawn through precision dies to achieve exact dimensional tolerances. This process enhances mechanical strength, improves surface finish, and ensures uniform wall thickness critical for consistent heat transfer performance.
3. Heat Treatment
Tubes are solution-annealed in a protective atmosphere (argon or nitrogen) at temperatures between 1050°C and 1150°C, followed by rapid quenching. This eliminates residual stresses from cold working and restores full austenitic microstructure, ensuring optimal creep resistance and thermal fatigue life.
4. Cold Coiling and Forming
Continuous tube lengths are coiled using CNC-controlled coiling equipment with precision-bore rollers. The coiling process maintains dimensional accuracy while avoiding localized wall thinning, cracking, or flattening. Minimum bend radii are enforced to prevent plastic deformation exceeding the material's elongation limit.
5. Welding and Fabrication
Orbital TIG welding (Gas Tungsten Arc Welding, GTAW) is employed for all circumferential and butt welds, utilizing inert gas shielding (argon) to prevent oxidation of the weld zone. Weld procedures are qualified per ASME Section IX and AWS D17.9 (Specification for Welding of Stainless Steel). Post-weld heat treatment (PWHT) is performed when required by design codes.
6. Non-Destructive Testing (NDT)
- Visual Inspection – 100% of external surfaces
- Eddy Current Testing (ECT) – 100% of tube length for wall thickness verification and surface defect detection
- Hydrostatic Pressure Testing – 100% at 1.5× design pressure, per ASTM A213
- Penetrant Testing (PT) – All welds, per ASTM E165
- Ultrasonic Testing (UT) – Where specified for internal defect detection
7. Final Inspection and Packaging
Completed coil tubes undergo dimensional verification, surface quality assessment, and certification documentation compilation. Tubes are protected with anti-corrosion coatings, end caps, and wrapped in protective packaging to prevent damage during shipping and storage.
Applications
Primary Applications
- Catalytic Reforming Feed Preheaters – Preheating of naphtha and kerosene feedstocks prior to entry into reformer reactors in petroleum refining units
- Steam Methane Reforming (SMR) – Tubes in pre-reformers and primary reformers for hydrogen production
- Autothermal Reformers (ATR) – Heat exchanger coil sections for syngas production
- Partial Oxidation (POX) Systems – Preheat coils for natural gas or hydrocarbon feed
- Ammonia Synthesis Plants – Feed preheating in shift converters and reforming sections
- Methanol Synthesis – Preheat exchangers for syngas conditioning
Comparison of Coil Configurations
Based on comparative analysis of two coil tube configurations for reforming furnace feed preheaters:
| Criteria | Vertical Serpentine Coil | Horizontal Helical Coil |
|---|---|---|
| Heat Transfer Efficiency | High – natural convection enhancement | Moderate – requires forced circulation |
| Thermal Stress Distribution | Non-uniform; higher stress at U-bends | More uniform along coil length |
| Footprint | Compact (vertical arrangement) | Larger (horizontal arrangement) |
| Mechanical Support Complexity | Requires spring-loaded supports | Requires expansion loops |
| Flow Distribution | Potential for maldistribution in multi-pass | More uniform single-pass flow |
| Inspection Accessibility | Limited (vertical access difficult) | Better (horizontal access easier) |
| Recommended Application | High-temperature, compact furnace designs | Lower-temperature, high-flow preheat sections |
Quality Certifications and Standards Compliance
Applicable Standards
- ASTM A213 / A213M – Standard Specification for Seamless Austenitic Stainless Steel Tube for High-Temperature Service
- ASTM A312 – Standard Specification for Seamless and Welded Austenitic Stainless Steel Tube
- ASME B31.3 – Process Piping Code (for installed systems)
- ASME Section IX – Welding Qualifications
- EN 10216-5 – Seamless Steel Tubes for Heat Exchangers and Heat Transfer Equipment
- EN 10217-7 – Heat Exchanger and Heat Transfer Equipment Tubes – Stainless Steel
- ISO 9001:2015 – Quality Management Systems
- API 5CT – Where applicable for energy industry applications
Certifications Held by Wenzhou Jixing Metal Materials Co., Ltd.
- ISO 9001:2015 Quality Management System Certification
- ISO 14001:2015 Environmental Management System Certification
- ISO 45001:2018 Occupational Health and Safety Management System
- ASME "U" Stamp Certification (Pressure Vessel and Piping)
- PED (Pressure Equipment Directive) 2014/68/EU Conformity Assessment
- API Monogram License (where applicable)
- TÜV / DNV / Lloyd's Register Third-Party Inspection Available
Unique Selling Points
- Engineered for Extreme Duty – Materials and fabrication processes specifically optimized for reforming furnace environments with temperatures exceeding 1000°C and aggressive reducing atmospheres.
- Configuration Flexibility – Capability to manufacture both vertical serpentine and horizontal helical coil configurations, enabling optimal thermal-hydraulic performance tailored to specific furnace designs.
- Full Traceability – Complete material traceability from mill certification through final inspection, supporting asset integrity management and regulatory compliance.
- Advanced NDT Capability – 100% eddy current and hydrostatic testing ensures defect-free delivery with zero tolerance for wall thinning or internal imperfections.
- Engineering Support – Technical team provides comparative analysis of coil configurations, thermal stress calculations, and fatigue life predictions to support optimal design selection.
- Global Compliance – Products certified to meet international codes and standards, enabling seamless integration into projects worldwide.
- Custom Fabrication – Ability to manufacture to customer-specific drawings with dimensional tolerances as tight as ±0.05 mm on OD, ensuring plug-and-fit installation.
Conclusion
The stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. represents a critical component in the reliable operation of reforming furnace feed preheaters. Through rigorous material selection, precision manufacturing, comprehensive testing, and adherence to international standards, these coil tubes deliver the thermal efficiency, mechanical durability, and operational reliability demanded by modern petrochemical and hydrogen production facilities. The availability of multiple coil configurations allows engineers to optimize furnace performance for specific process requirements, ensuring maximum energy efficiency and minimum maintenance intervals.