Primary Reformer Cold-End Coil Tube (Coiltube) — High-Temperature Stainless Steel Alloy
1. Product Overview
The Primary Reformer Cold-End Coil Tube is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for deployment in the cold-end section of primary reformer furnaces used in natural gas conversion and hydrogen production processes. These coil tubes operate under extreme thermal cycling conditions and are subjected to continuous exposure to reducing atmospheres containing hydrogen, hydrocarbons, and trace sulfur compounds. The product is engineered to deliver exceptional resistance to thermal fatigue, carburization, and intergranular oxidation (IGO), ensuring extended service life and operational reliability in critical petrochemical and gas processing applications.
2. Material & Properties
The coil tube is fabricated from advanced heat-resistant austenitic stainless steel alloys, typically conforming to UNS N08810 (Incoloy 800H) or UNS S31008 (310H) grade specifications. These materials exhibit superior creep strength, oxidation resistance, and dimensional stability at elevated operating temperatures ranging from 800°C to 1,100°C.
2.1 Key Material Properties
- Chemical Composition: High chromium (Cr ≥ 24–26 wt%) and nickel (Ni ≥ 19–22 wt%) content, with controlled carbon (C ≤ 0.08 wt%) and sulfur (S ≤ 0.015 wt%) levels to minimize sulfidation and carbide precipitation.
- Operating Temperature Range: Continuous service up to 1,100°C; short-term peak tolerance up to 1,200°C.
- Thermal Expansion Coefficient: Approximately 17–18 × 10⁻⁶ /°C (20–1,000°C), ensuring compatibility with furnace structural components.
- Creep Strength: Minimum 10 MPa at 1,000°C over 100,000 hours, meeting API 530 and ASME B31.3 requirements.
- Oxidation Resistance: Formulates a stable, self-healing Cr₂O₃ and Al₂O₃ protective oxide scale under reducing and oxidizing atmospheres.
- Carburization Resistance: Enhanced through low-carbon chemistry and optimized grain boundary engineering.
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Material Grade | UNS N08810 (Incoloy 800H) / UNS S31008 (310H) | ASTM B407 / ASTM B336 |
| Outer Diameter (OD) | 19.05 mm – 25.40 mm (¾" – 1") | ASME B36.19M |
| Wall Thickness | 1.65 mm – 3.18 mm (Schedule 10S – 40S) | ASME B36.19M |
| Coil Diameter | 1,200 mm – 3,000 mm (customizable) | Manufacturer Specification |
| Tube Length per Coil | 100 m – 500 m (configurable) | Project-Specific Requirement |
| Surface Finish | Pickled and passivated; Ra ≤ 0.8 μm | ASTM A380 / AMS 2700 |
| Heat Treatment | Solution annealed at 1,120–1,150°C, water quenched | ASTM B407 |
| Tensile Strength (RT) | ≥ 517 MPa (75 ksi) | ASTM B407 |
| Yield Strength (RT) | ≥ 205 MPa (30 ksi) | ASTM B407 |
| Elongation at Break | ≥ 40% | ASTM B407 |
| Maximum Operating Pressure | Up to 3.0 MPa (design dependent) | ASME B31.3 |
| Compressive Stress Atmosphere | H₂, CH₄, CO, CO₂, H₂O, trace H₂S | API 530 / NACE MR0175 |
4. Manufacturing Process
4.1 Raw Material Selection & Verification
Only certified vacuum induction melted (VIM) or vacuum arc remelted (VAR) ingots are used to ensure ultra-low impurity levels and homogeneous microstructure. Each heat lot undergoes spectroscopic analysis (OES), gas analysis (C, N, O), and inclusion rating per ASTM E542 to confirm conformance with specified chemical composition.
4.2 Hot Rolling & Annealing
Ingot billets are reheated to 1,250–1,300°C and hot-rolled into seamless tube blanks. Intermediate annealing cycles are performed to relieve residual stresses and restore ductility for subsequent forming operations.
4.3 Seamless Tube Forming
Tubes are produced via the Mannesmann plug piercing method or Autoclave process, followed by cold reduction and stretching to achieve precise dimensional tolerances (±0.1 mm on OD, ±0.1 mm on wall thickness) in accordance with ASTM A213/A312 standards.
4.4 Coil Winding
Finished straight tubes are precisely wound into coils using CNC-controlled winding equipment with integrated tension control and alignment systems. Coil diameter and pitch are optimized to minimize bending-induced microstructural damage and ensure uniform stress distribution along the coil length.
4.5 Final Heat Treatment
Coils undergo a final solution annealing treatment at 1,120–1,150°C in a protective atmosphere (argon or dissociated ammonia), followed by controlled cooling. This treatment dissolves carbides, refines grain structure, and maximizes high-temperature mechanical properties.
4.6 Surface Treatment & Passivation
The coil surface is pickled using a controlled nitric/hydrofluoric acid mixture and passivated to form a uniform chromium oxide film, ensuring corrosion resistance and surface cleanliness suitable for direct installation.
5. Applications
The Primary Reformer Cold-End Coil Tube is deployed in the following critical industrial sectors:
- Natural Gas Steam Methane Reforming (SMR): Primary reformer cold-end sections where hydrocarbon feedstock is preheated and partially converted to hydrogen and carbon monoxide at temperatures of 750–900°C.
- Ammonia Production: Synthesis gas generation units in large-scale ammonia plants (Haber-Bosch process).
- Hydrogen Production Facilities: Dedicated hydrogen plants utilizing steam reforming technology for electrolyzer feedstock or fuel cell applications.
- Methanol Synthesis: Syngas preparation sections in methanol synthesis complexes.
- Petrochemical Cracking: Preheat coils in ethylene crackers and steam crackers where thermal cracking of hydrocarbons occurs.
- Gas-to-Liquids (GTL): Fischer-Tropsch synthesis gas generation units.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications and compliances:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification.
- API Q1 / API Q2 — Quality Management System for Oil and Gas Industry.
- ASME "U" Stamp — Authorization for manufacturing pressure vessels and piping components.
- EN 10204 3.1 / 3.2 — Material certification per European standard.
- ASTM A380 — Compliance for stainless steel pipe and tube inspection.
- NACE MR0175 / ISO 15156 — Compliance for materials in H₂S-containing environments.
- API 530 — Recommended practices for materials selection in hydrogen service.
All products are accompanied by full mill test certificates (MTC) including chemical composition, mechanical properties, heat treatment records, dimensional inspection reports, and non-destructive testing (NDT) results including ultrasonic testing (UT) per ASTM E309 and eddy current testing (ECT) per ASTM E309.
7. Unique Selling Points
7.1 Advanced Thermal Fatigue Resistance
Through optimized grain boundary engineering and controlled carbon chemistry, the coil tube exhibits significantly enhanced resistance to thermal fatigue cracking during repeated startup and shutdown cycles — a critical failure mode identified in primary reformer cold-end sections. This directly addresses the over-temperature incidents documented during cold-end coil startup operations, where rapid temperature transients can exceed design limits.
7.2 Precision Dimensional Control
State-of-the-art CNC winding technology ensures coil geometry accuracy within ±0.5 mm tolerance on coil diameter and ±1° on pitch angle, minimizing installation difficulties and reducing residual stress concentrations at tube bends and supports.
7.3 Extended Service Life
Field-proven performance data demonstrates service life exceeding 50,000 hours in primary reformer cold-end applications, outperforming conventional 304/310 grade alternatives by a factor of 2–3× under equivalent operating conditions.
7.4 Comprehensive Technical Support
Wenzhou Jixing provides full lifecycle technical support including startup guidance, thermal management protocols, and post-installation monitoring recommendations. Their engineering team offers customized coil configurations tailored to specific furnace geometry and process conditions.
7.5 Rigorous Quality Assurance
Each coil undergoes 100% ultrasonic internal inspection, hydrostatic pressure testing at 1.5× design pressure, and dimensional verification at multiple intervals along the coil length. All materials are traceable to individual heat lots with complete documentation.
8. Operational Guidance — Cold-End Startup Considerations
Important: Based on documented operational experience with primary reformer cold-end coil tubes, the following startup protocols are recommended to prevent over-temperature incidents:
- Controlled Ramp Rate: Limit furnace temperature increase to ≤ 50°C/hour during initial startup to prevent thermal shock and differential expansion between coil tube and furnace structure.
- Pre-Heating of Coil Section: Ensure gas flow through the coil tube is established before applying full furnace heat to prevent localized hot spots and stagnant zone overheating.
- Thermocouple Monitoring: Deploy redundant thermocouples at critical points along the cold-end coil, with automated high-temperature alarm thresholds set at 95% of maximum design temperature.
- Hydrogen Break-In: Gradually introduce hydrogen-containing atmosphere to prevent carburization during the initial heating cycle.
- Post-Startup Inspection: Conduct visual and ultrasonic inspection of coil tube surface and supports after the first 100 operating hours to detect any early-stage degradation.
9. Conclusion
The Primary Reformer Cold-End Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. represents a premium-grade solution for the most demanding high-temperature tubular applications in the petrochemical and hydrogen production industries. Combining advanced materials science, precision manufacturing, and comprehensive quality assurance, this product delivers the reliability, durability, and performance required for continuous operation in extreme thermal and chemical environments. The company's deep understanding of coil tube failure modes — particularly over-temperature events during startup — is reflected in both the product design and the accompanying operational guidance, ensuring optimal performance throughout the service life of the component.