Stainless Steel Coil Tube for Reforming Reaction Feed Preheater
Product Code: JX-CT-269 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (盘管, Coil Tube) is a precision-engineered tubular product designed specifically for use in Reforming Reaction Feed Preheaters (重整反应进料加热炉) within petrochemical and chemical processing industries. These coil tubes serve as critical heat-transfer elements, facilitating the controlled heating of hydrocarbon feedstocks prior to catalytic reforming reactions.
Based on comparative studies of two distinct coil configurations for reforming reaction feed preheaters, this product line incorporates advanced design principles that optimize thermal efficiency, mechanical integrity, and operational longevity under extreme process conditions. The coil tubes are manufactured to meet the rigorous demands of continuous operation in high-temperature, high-pressure environments typical of refinery and petrochemical processing units.
The two primary coil configurations compared in the referenced technical study include:
- Vertical Coil Configuration — characterized by vertically oriented helical winding, offering superior natural convection and reduced thermal stratification
- Horizontal Coil Configuration — characterized by horizontally wound helical geometry, providing compact footprint and enhanced mechanical support stability
Wenzhou Jixing Metal Materials Co., Ltd. manufactures both configurations to accommodate diverse furnace design requirements and process specifications.
2. Material & Properties
2.1 Base Materials
The coil tubes are fabricated from high-performance stainless steel alloys selected for their exceptional resistance to oxidation, corrosion, and thermal fatigue under sustained high-temperature service. Commonly specified grades include:
| Material Grade | UNS Designation | Key Alloying Elements | Maximum Service Temperature (°C) | Primary Application |
|---|---|---|---|---|
| 310S | S31008 | Cr 25%, Ni 19%, Si ≤2% | 1150 | Primary heat-exchange coil tubes in reforming preheaters |
| 309 | S30900 | Cr 22–24%, Ni 12–15% | 900 | Moderate-temperature preheater sections |
| 316L | S31603 | Cr 16–18%, Ni 10–14%, Mo 2–3% | 600 | Low-temperature feed preheating zones |
| TP347H | S34701 | Cr 17–19%, Ni 9–13%, Nb stabilized | 870 | High-temperature, high-pressure process piping |
2.2 Mechanical Properties
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa (at room temperature) | ASTM A213 / ASTM A312 |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ASTM A213 |
| Elongation (in 50 mm) | ≥ 35% | ASTM A213 |
| Hardness (Rockwell B) | ≤ 95 HRB | ASTM A262 |
| Creep Strength (870°C, 1000 h) | ≥ 35 MPa | ASTM E139 |
2.3 Physical & Thermal Properties
| Property | Value (Typical for 310S) |
|---|---|
| Density | 8.0 g/cm³ |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) |
| Thermal Conductivity (800°C) | 32.5 W/(m·K) |
| Specific Heat Capacity | 0.50 J/(g·K) |
| Coefficient of Thermal Expansion (20–800°C) | 18.1 × 10⁻⁶ /K |
| Oxidation Resistance | Continuous service up to 1150°C in oxidizing atmosphere |
2.4 Corrosion Resistance
The stainless steel coil tubes exhibit outstanding resistance to:
- High-temperature oxidation (氧化) — formation of a stable, self-healing chromium oxide (Cr₂O₃) protective layer
- Intergranular corrosion (晶间腐蚀) — enhanced by stabilization through niobium (Nb) or titanium (Ti) addition
- Scaling (结垢) — minimal scale adhesion under reducing and neutral atmospheres
- Sulfidation (硫化) — resistance to sulfur-containing process gases at elevated temperatures
3. Specifications
3.1 Geometric Dimensions
| Parameter | Range / Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 19.05 mm – 168.3 mm (3/4" – 6") | ASTM A213 / ASME B36.19M |
| Wall Thickness (WT) | 1.50 mm – 12.70 mm (5/8" – 1/2") | ASTM A213 |
| Coil Mean Diameter (CMD) | 200 mm – 2000 mm (adjustable per furnace design) | Customer specification |
| Coil Length (Developed) | 10 m – 120 m (per continuous coil section) | Customer specification |
| Helix Pitch | 150 mm – 600 mm | Customer specification |
| Number of Turns | 2 – 80 turns per coil assembly | Customer specification |
| End Condition | Beveled, flat-ended, or with forged/fitted connectors | ASME B1.20.1 |
| Surface Finish | Mill finish, polished (Ra ≤ 0.8 μm), or electropolished | ASTM A967 |
3.2 Coil Configuration Comparison
| Characteristic | Vertical Coil Configuration | Horizontal Coil Configuration |
|---|---|---|
| Winding Orientation | Vertical helical arrangement | Horizontal helical arrangement |
| Thermal Efficiency | Higher — enhanced natural convection | Moderate — requires supplementary flow design |
| Footprint | Larger — requires vertical furnace space | Compact — suitable for space-constrained installations |
| Thermal Stress Distribution | Uniform — gravity-assisted thermal expansion | Requires careful support design to manage differential expansion |
| Maintenance Accessibility | Moderate — access from top/bottom | Excellent — easy lateral access for inspection |
| Recommended Application | High-temperature reforming zones (> 800°C) | Preheating zones and moderate-temperature sections |
| Typical Feed Flow Rate | High — 5000 – 50000 kg/h | Moderate — 2000 – 20000 kg/h |
3.3 Process Design Parameters
| Parameter | Specification |
|---|---|
| Design Pressure | 1.0 – 15.0 MPa (145 – 2175 psi) |
| Operating Pressure | 0.5 – 12.0 MPa |
| Operating Temperature Range | 200°C – 1100°C (depending on alloy grade) |
| Heat Flux (Maximum) | 80 kW/m² (38,000 BTU/hr·ft²) |
| Process Medium | Hydrocarbon feedstocks, hydrogen-rich gases, syngas |
| Service Life (Design) | ≥ 10 years continuous operation |
| Design Code | ASME Section VIII, Div. 1 / GB 150 |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Procurement & Inspection — Mill certificates (MTC) verified per ASTM A213/A312; incoming material subjected to chemical composition analysis (光谱分析), dimensional inspection, and visual examination.
- Cutting & Straightening — Seamless tubes cut to required lengths using precision plasma or abrasive cutting; straightened on hydraulic mandrel straighteners to achieve ≤ 1 mm/m straightness tolerance.
- End Preparation — Tube ends beveled per ASME B1.20.1 specifications; deburred and chamfered for welding compatibility.
- Coil Forming (盘管成型) — Tubes bent into helical coil geometry using CNC-controlled coil forming machinery with adjustable mandrel systems. Forming is performed at room temperature or with controlled induction heating to prevent work-hardening and microstructural degradation.
- Welding & Joining — Butt welds executed using Gas Tungsten Arc Welding (GTAW) or Shielded Metal Arc Welding (SMAW) with matching filler metals. Weld procedures qualified per ASME Section IX / AWS D1.6.
- Heat Treatment — Solution annealing (固溶处理) at 1050°C – 1150°C followed by controlled air cooling to restore full austenitic microstructure and maximize corrosion resistance. Stress relief (去应力退火) applied where required per furnace design specifications.
- Pickling & Passivation (酸洗钝化) — Surface treatment using citric acid or nitric-hydrofluoric acid solutions to remove oxide scale and form a passive chromium oxide film per ASTM A967.
- Non-Destructive Testing (NDT) — 100% visual inspection; magnetic particle inspection (MPI) for surface defects; ultrasonic thickness testing (UT) for wall integrity; radiographic testing (RT) on all weld joints per ASME Section V.
- Dimensional & Geometric Verification — Coil diameter, pitch, turn count, and overall dimensions verified against engineering drawings using laser scanning or coordinate measurement systems.
- Hydrostatic Pressure Testing (水压试验) — Each coil assembly tested at 1.5× design pressure for a minimum of 30 minutes with zero leakage tolerance.
- Final Inspection & Documentation — Compilation of complete quality documentation including MTC, NDT reports, heat treatment records, and dimensional certificates.
- Packaging & Shipping — Coils wrapped in protective VCI (Vapor Corrosion Inhibitor) paper, secured on wooden pallets or cradles, and labeled with product identification and handling instructions.
4.2 Key Manufacturing Technologies
- CNC Coil Forming — Computer-numerically controlled bending ensures repeatable geometry with tolerance of ±2 mm on coil diameter and ±3 mm on pitch
- Induction Heating — Localized controlled heating during forming prevents cold-work cracking in high-temperature alloys
- Orbital GTAW Welding — Automated orbital welding for consistent, high-quality circumferential welds on coil-to-header connections
- Laser Scanning Inspection — 3D laser scanning for full geometric verification of coil assemblies against CAD models
5. Applications
The Stainless Steel Coil Tubes manufactured by Wenzhou Jixing Metal Materials Co., Ltd. are deployed across a wide spectrum of industrial applications:
5.1 Petrochemical & Refining Industry
- Catalytic Reforming Units (加氢重整装置) — Feed preheaters for naphtha reforming processes
- Hydrocracking Units (加氢裂化装置) — High-pressure feed preheating systems
- Fluid Catalytic Cracking (FCC, 流化催化裂化) — Regenerator coil systems
- Steam Methane Reforming (SMR, 蒸汽甲烷重整) — Primary reformer tube bundles
5.2 Chemical Processing
- Olefin Cracking Furnaces (乙烯裂解炉) — High-temperature process coils for ethylene production
- Propylene Oxidation Furnaces — Coils for acrolein and propylene oxide synthesis
- Ammonia Synthesis Plants (氨合成装置) — Syngas preheating systems
- Phthalic Anhydride Production — Process coils in oxidation furnaces
5.3 Power Generation & Energy
- Cogen Heat Recovery Systems — High-temperature exhaust gas heat exchange coils