Stainless Steel Convective Coil Tube — Tubular Furnace Application
1. Product Overview
The Stainless Steel Convective Coil Tube (product reference: Coiltube, Catalog No. 327) is a precision-engineered tubular component designed for use in the convective sections of tubular heating furnaces. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product is engineered to maximize heat transfer efficiency while extending service life under demanding thermal cycling conditions. The coil tube is formed from continuous stainless steel strip or seamless pipe, cold-bent into a serpentine or helical configuration to achieve optimal surface-area-to-volume ratios within the furnace convective zone.
This product addresses a critical engineering challenge in petroleum refining, chemical processing, and petrochemical industries: improving the utilization rate of convective coil tube material while maintaining structural integrity and thermal performance over extended operating cycles.
2. Material & Properties
The convective coil tube is available in a range of high-grade stainless steel alloys selected for exceptional resistance to oxidation, scaling, and thermal fatigue at elevated operating temperatures:
- 304 / 304L (UNS S30400 / S30403): General-purpose austenitic stainless steel; excellent corrosion resistance and formability; suitable for moderate temperature applications up to approximately 870 °C (1598 °F).
- 310 / 310S (UNS S31000 / S31008): High-temperature austenitic alloy with superior resistance to scaling and oxidation; recommended for service temperatures up to 1150 °C (2094 °F).
- 321 / 321H (UNS S32100 / S32109): Ti-stabilized austenitic grade; excellent resistance to intergranular corrosion and thermal cracking; ideal for cyclic thermal environments.
- 347H (UNS S34709): Nb-stabilized austenitic grade; enhanced high-temperature strength and resistance to sensitization; suitable for prolonged service above 800 °C (1472 °F).
- Custom Alloy Grades: Specialized compositions (e.g., 310H, 310J, 601, 601HA) available upon request for extreme thermal or chemical exposure conditions.
Key Mechanical & Thermal Properties (Typical)
| Property | 304 / 304L | 310 / 310S | 321 / 321H | 347H |
|---|---|---|---|---|
| Tensile Strength (≥ MPa) | 520 | 520 | 520 | 520 |
| Yield Strength (≥ MPa) | 205 | 205 | 205 | 205 |
| Elongation (≥ %) | 40 | 40 | 40 | 40 |
| Maximum Service Temperature (°C) | 870 | 1150 | 900 | 900 |
| Thermal Expansion Coefficient (×10⁻⁶/K, 20–800 °C) | 17.3 | 18.0 | 17.3 | 17.3 |
| Density (g/cm³) | 8.00 | 8.00 | 8.00 | 8.00 |
| Thermal Conductivity (W/m·K, at 100 °C) | 16.3 | 31.4 | 16.3 | 16.3 |
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Convective Coil Tube (Coiltube) |
| Catalog Reference | No. 327 |
| Product Classification | Literature Study / Technical Application Series |
| Outer Diameter (OD) | 19.0 mm – 168.3 mm (custom dimensions available) |
| Wall Thickness | 1.5 mm – 12.0 mm (tailored to thermal flux requirements) |
| Bend Radius (Minimum) | 3D (3 × outer diameter); cold bending capability |
| Coil Configuration | Serpentine (U-bend), Helical, or Custom Geometry |
| Surface Finish | Mill finish, Pickled & Passivated, or Polished |
| Applicable Standards | ASTM A213, ASTM A312, ASME SA-213, ASME SA-312, GB/T 12770, GB/T 13296 |
| Length per Coil | Customized per furnace design; typically 2,000 mm – 15,000 mm developed length |
| Delivery Condition | Annealed & Pickled (A&P), Solution Treated |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
4. Manufacturing Process
The production of high-quality convective coil tubes follows a rigorously controlled multi-stage process to ensure dimensional accuracy, metallurgical integrity, and resistance to thermal degradation:
- Raw Material Selection & Inspection: Certified stainless steel strip or seamless pipe stock is procured from accredited mills. Incoming materials undergo full spectrographic analysis (OES — Optical Emission Spectroscopy) and mechanical property verification to confirm compliance with specified alloy chemistry and tensile/yield requirements.
- Heat Treatment & Solution Annealing: Raw stock is solution annealed at temperatures between 1050 °C and 1150 °C (depending on grade) followed by controlled cooling to achieve a fully austenitic microstructure, maximize ductility, and dissolve any carbide precipitates.
- Pickling & Passivation: Post-annealing acid pickling (using a mixed HNO₃/HF or HNO₃/HCl bath) removes oxide scale, followed by passivation treatment to establish a chromium-rich passive film that enhances corrosion resistance.
- Cold Bending & Coil Forming: Precision CNC-controlled bending equipment forms the tube into the required serpentine or helical geometry. Bend parameters — including radius, angle, and spacing — are calculated based on furnace design specifications to optimize heat transfer area while minimizing material waste.
- Post-Form Heat Treatment (as required): Bends that experience work hardening during cold forming may undergo a localized stress-relief anneal to restore ductility and prevent cracking under thermal cycling.
- Dimensional Inspection & NDT: Each coil tube assembly undergoes dimensional verification (OD, wall thickness, bend radius, overall developed length) and non-destructive testing — including eddy current testing (ECT) and/or ultrasonic testing (UT) — to detect subsurface defects, wall thinning, or bend-induced imperfections.
- Final Cleaning, Marking & Packaging: Tubes are cleaned, marked with traceability identifiers (heat number, alloy grade, dimensions, batch ID), and packaged with protective end caps and moisture-absorbing desiccants for shipment.
5. Applications
The stainless steel convective coil tube is a critical heat-exchange component in a wide range of industrial processes where efficient convective heat transfer from flue gases to process fluids is required:
- Petrochemical Refining: Convective sections of tubular reformers, cracker furnaces, and hydrotreater heaters in petroleum refineries.
- Chemical Processing: Vaporizers, superheaters, and waste-heat boilers in ethylene plants, propylene plants, and ammonia synthesis facilities.
- Petrochemical Aromatics Production: Toluene dehydrogenation furnaces, BTX (benzene-toluene-xylene) separation units.
- Power Generation: Waste-heat recovery systems and superheater coils in combined-cycle power plants.
- Pharmaceutical & Food Processing: Sanitary-grade heat exchangers and pasteurization systems requiring high-purity stainless steel construction.
- Metal Heat Treatment: Annealing furnaces and tempering ovens in steel and alloy production facilities.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications to ensure product reliability and traceability:
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health & Safety Management
- ASME "S" Stamp / "R" Stamp — Authorization for pressure-retaining components (where applicable)
- EN 10204 3.1 / 3.2 — Material test certificates (third-party inspection available upon request)
- NACE MR0175 / ISO 15156 — Compliance for sour service environments (where applicable)
All products are accompanied by a full Mill Test Certificate (MTC) detailing chemical composition, mechanical test results, and heat treatment records. Third-party inspection (TPI) by entities such as SGS, Bureau Veritas, or TÜV is available for critical applications.
7. Unique Selling Points
Maximized Material Utilization: The coil tube design philosophy emphasizes optimized material utilization rates in convective furnace sections — reducing scrap and off-cut waste while maintaining full thermal performance. This directly translates to lower capital expenditure (CAPEX) and reduced lifecycle costs for end-users.
- Customized Geometry Engineering: Each coil tube assembly is designed to match the specific furnace architecture, maximizing convective heat transfer surface area within spatial constraints.
- Enhanced Thermal Fatigue Resistance: Selection of Ti- or Nb-stabilized grades (321H, 347H) and high-temperature austenitics (310S) ensures resistance to thermal cracking during repeated heating and cooling cycles.
- Full Traceability: From raw material heat number through to finished coil assembly, every component is traceable via unique identification markings and digital records.
- Engineering Support: Wenzhou Jixing provides pre-sales thermal performance modeling and post-sales technical consultation to optimize coil tube performance in specific furnace applications.
- Competitive Lead Times: Leveraging integrated manufacturing capabilities in the Wenzhou industrial cluster, the company offers rapid turnaround for standard configurations and flexible scheduling for custom orders.
8. Technical Reference
This product specification is informed by the technical study "Discussion on Improving the Utilization Rate of Convective Coil Tube Material in Tubular Heating Furnaces" (《关于提高管式加热炉对流盘管管材利用率的探讨》), which provides the engineering basis for the design optimization principles incorporated into this product line. The study emphasizes that material utilization in convective coil sections can be improved by up to 15–25% through strategic geometry optimization, appropriate alloy selection, and refined manufacturing tolerances — all of which are integrated into the production methodology of this product.
9. Ordering Information
| Item | Details |
|---|---|
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Product Code | No. 327 — Coiltube |
| Minimum Order Quantity (MOQ) | Varies by configuration; contact sales for details |
| Lead Time | Standard: 15–30 days; Custom: 30–60 days |
| Warranty | 12 months from delivery date against manufacturing defects |
| Technical Consultation | Available — provide furnace operating parameters, fluid properties, and thermal flux requirements for tailored recommendations |