Stainless Steel Coiltube for Ethylene Cracking Furnace Radiation Section — Inlet/Outlet Insulated Design
Product Overview
The stainless steel coiltube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a critical heat-transfer component designed specifically for the radiation section of ethylene cracking furnaces (乙烯裂解炉辐射盘管). These coils serve as the primary heat exchange medium within the radiant zone, where hydrocarbon feedstock undergoes thermal decomposition at extreme temperatures to produce ethylene and other olefinic products. The inlet and outlet sections of these coils are particularly subject to thermal stress, mechanical fatigue, and thermal shock, necessitating specialized insulation design (保温设计) to ensure operational integrity and extended service life.
This product line addresses the unique engineering challenges associated with the transition zones between the radiation section and the convection section of cracking furnaces, where rapid temperature gradients and cyclic thermal loading impose severe demands on material performance and structural reliability.
Material & Properties
Primary Alloy Grades
- 310S / 310H (UNS S31008 / S31009): Austenitic stainless steel with elevated carbon content (H-grade) offering superior high-temperature strength and resistance to thermal cycling. Chromium content of 24–26% and Nickel content of 19–22% provide exceptional oxidation resistance at temperatures up to 1150°C (2094°F).
- 304H (UNS S30409): Enhanced carbon version of 304 stainless steel, suitable for moderate radiation zone applications with temperatures up to 900°C (1652°F).
- 316H (UNS S31609): Molybdenum-enhanced austenitic grade for applications requiring additional resistance to sulfidation and chloridation.
- HP-Nb (UNS S31050): Niobium-stabilized high-performance austenitic grade for severe thermal cycling duty, offering superior creep resistance and reduced sensitization tendency.
- Alloy 600 (UNS N06600): Nickel-chromium alloy for extreme temperature applications exceeding 1000°C with outstanding resistance to oxidation and carburization.
Key Mechanical Properties (at Elevated Temperature)
- Creep Strength: Maintains ≥25 MPa (3.6 ksi) at 1000°C for 310H grade over 10,000-hour exposure
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C (20–800°C range)
- Thermal Conductivity: 25–30 W/(m·K) at operating temperatures
- Yield Strength: ≥205 MPa at 20°C; ≥100 MPa at 900°C (310H)
- Tensile Strength: ≥520 MPa at 20°C; ≥250 MPa at 900°C (310H)
Corrosion & Oxidation Resistance
- Scale growth rate ≤1.0 mg/(dm²·h) at 1100°C in air atmosphere (310H)
- Resistance to sulfidation attack in H₂S-containing environments up to 950°C
- Excellent resistance to carburization in hydrocarbon-rich atmospheres
- Resistance to thermal shock with temperature differentials exceeding 200°C/minute
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Ethylene Cracking Furnace Radiation Coiltube (乙烯裂解炉辐射盘管) |
| Product Code | No. 377 — Coiltube |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Material Grade | 310S/310H, 304H, 316H, HP-Nb, Alloy 600 (customizable) |
| Outer Diameter (OD) | Φ25 mm – Φ60 mm (typical: Φ32 mm, Φ38 mm, Φ48 mm) |
| Wall Thickness | 2.5 mm – 6.0 mm (typical: 3.0 mm, 3.5 mm, 4.0 mm) |
| Inside Diameter (ID) | Φ20 mm – Φ54 mm (calculated per OD and wall thickness) |
| Coil Diameter | 2.0 m – 6.0 m (customized per furnace design) |
| Coil Length (Uncoiled) | 15 m – 120 m per coil unit |
| Surface Finish | Pickled & Passivated (P&P), Ra ≤ 0.8 μm |
| Maximum Operating Temperature | 1150°C (2094°F) continuous; 1250°C short-term |
| Operating Pressure | Up to 1.5 MPa (217 psi) gauge |
| Design Pressure | Up to 2.5 MPa (363 psi) gauge |
| Heat Treatment | Solution Annealed (1050–1150°C) + Air Cooled |
| Insulation Design (Inlet/Outlet) | Specialized thermal insulation (保温设计) for transition zones |
| Applicable Standards | ASTM A213, ASTM A269, ASME B36.19M, GB/T 14976, EN 10216-5 |
| Delivery Condition | Coiled, Annealed, Pickled & Passivated |
Manufacturing Process
1. Raw Material Selection & Inspection
High-purity vacuum-induction-melted (VIM) or argon-oxygen-decARBONIZATION (AOD) ingots are selected to ensure low sulfur, phosphorus, and nitrogen content. Incoming material undergoes 100% spectroscopic analysis (OES) and ultrasonic testing (UT) to verify chemical composition and internal soundness per ASTM E1246 and ASTM A388.
2. Hot Rolling & Piercing
Ingots are reheated to 1150–1200°C and hot-rolled through multi-stand mills to produce seamless tube blanks. The piercing process (Mannesmann or plug-type) establishes the initial bore geometry. Rolling schedules are optimized to achieve controlled grain size (ASTM 4–8) and uniform wall thickness.
3. Cold Drawing & Sizing
Tubes undergo multi-pass cold drawing through tungsten carbide dies to achieve precise dimensional tolerances (±0.05 mm for OD, ±5% for wall thickness). This process enhances mechanical properties through work hardening and produces a superior surface finish.
4. Solution Annealing & Stress Relief
Drawn tubes are solution-annealed at 1050–1150°C in a protective atmosphere (endothermic gas or vacuum) to dissolve carbide precipitates, restore full austenitic microstructure, and relieve residual stresses. Controlled cooling rates prevent sensitization and chromium carbide precipitation at grain boundaries.
5. Pickling & Passivation
The annealing scale is removed via citric acid or nitric-hydrofluoric acid pickling. Subsequent passivation treatment establishes a stable chromium oxide film (Cr₂O₃) with a minimum thickness of 2–5 nm, providing immediate corrosion protection. Surface roughness is verified to Ra ≤ 0.8 μm.
6. Coil Forming & Mandrel Design
Precision mandrel-based coil forming is employed to create uniform spiral geometries. Mandrel diameters are selected to ensure minimum bend radius ≥5× OD, preventing wall thinning and ovality beyond acceptable limits (ovality ≤3% of OD). The coiling process incorporates controlled tension to maintain dimensional stability.
7. Inlet/Outlet Insulation Design (保温设计)
The transition zones at the coil inlet and outlet are designed with specialized thermal insulation systems to manage the steep temperature gradients between the radiation and convection sections. Key design features include:
- Multi-layer ceramic fiber wrap with thermal conductivity ≤0.035 W/(m·K) at 800°C
- Expansion joint provisions to accommodate thermal growth (up to 12% linear expansion at 1100°C)
- Thermal barrier coatings (TBC) on transition-zone tube segments
- Instrumentation ports for thermocouple insertion to monitor wall temperature
- Anchor supports with thermal break design to prevent heat conduction to refractory structure
8. Non-Destructive Testing (NDT)
- Eddy Current Testing (ECT): 100% inline inspection for wall thickness verification and surface defect detection per ASTM E309
- Hydrostatic Testing: 100% at 1.5× design pressure, held for minimum 30 seconds per ASTM A530
- Ultrasonic Testing (UT): 100% for internal flaw detection per ASTM E213
- Visual Inspection: 100% for surface quality, passivation effectiveness, and dimensional verification
Applications
Primary Applications
- Ethylene Cracking Furnaces: Radiation zone coil tubes in steam cracking furnaces for ethylene, propylene, and butadiene production (乙烯裂解炉辐射盘管)
- Pyrolysis Gas Heater (PGH) Tubes: Heat exchange tubes in process gas heating systems
- Quench Heat Exchanger (QHX) Tubes: Rapid heat recovery tubes downstream of cracking coils
- Steam Superheater Tubes: High-temperature steam generation in petrochemical and power generation facilities
Industry Sectors
- Petrochemical processing (olefins and aromatics production)
- Chemical manufacturing (ethylene oxide, acetaldehyde, and methanol synthesis)
- Oil refining (catalytic reforming and visbreaking units)
- Power generation (supercritical and ultra-supercritical steam systems)
- Cement and glass manufacturing (high-temperature process heating)
Inlet/Outlet Insulation Design — Critical Application Context
The insulation design for coil inlet and outlet sections is particularly critical in the following scenarios:
- Quench transitions: Where process gas temperature drops from ~850°C in the radiation zone to ~400°C entering the convection section
- Steam injection points: Where superheated steam is introduced, creating localized thermal gradients
- Furnace wall proximity: Where radiant heat flux from refractory walls creates asymmetric heating of coil segments
- Start-up and shutdown cycles: Where rapid temperature changes impose cyclic thermal fatigue on transition zone materials
Quality Certifications & Compliance
International Standards & Certifications
- ISO 9001:2015: Quality Management System certification for manufacturing processes
- ISO 14001:2015: Environmental Management System certification
- ASME Section IX: Welding procedure qualification for coil fabrication and field installation
- ASTM A213: Standard specification for austenitic stainless steel seamless, cold-drawn or cold-rolled tubing for high-temperature service
- ASTM A269: Standard specification for austenitic stainless steel seamless, welded, and heavily cold-worked welded tubing
- EN 10216-5: European standard for non-ferrous metallic tubes for heat exchangers and heat transfer
- API 5CT: Compliance for casing and tubing applications where applicable
Chinese National Standards (GB)
- GB/T 14976: Cold-rolled or cold-drawn seamless steel tubes for fluid transport
- GB/T 12771: Stainless steel seamless tubes for general engineering and construction
- GB/T 20878: Technical delivery conditions for austenitic stainless steels
- SH/T 3057: Petrochemical industry standard for heat exchanger tubes
Third-Party Inspection & Verification
- Mill Test Reports (MTR) issued per ASTM A751 for each heat lot
- Third-party inspection (TPI) by Lloyd's Register, Bureau Veritas, or DNV available upon request
- Material traceability maintained from ingot heat number through final coil identification
- Positive Material Identification (PMI) verification per ASTM E1476 available
Unique Selling Points
- Specialized Inlet/Outlet Insulation Engineering: Proprietary thermal insulation design (保温设计) for transition zones, reducing thermal fatigue life-limiting cycles by up to 40% compared to conventional designs
- Extended Service Life: Optimized material selection and heat treatment protocols delivering 2–3× longer service intervals than industry baseline, reducing unplanned shutdown frequency
- Full Traceability: Complete material pedigree from VIM/AOD ingot through final coil, enabling root-cause analysis and quality assurance throughout the supply chain
- Customization Capability: Flexible manufacturing parameters accommodating non-standard coil geometries, material grades, and insulation configurations tailored to specific furnace designs
- Integrated Design Support: Engineering team provides thermal stress analysis (FEA), fatigue life prediction, and insulation system optimization for inlet/outlet transition zones
- Cost-Effective Lifecycle: While premium material grades command higher initial cost, the extended service life and reduced maintenance frequency deliver superior total cost of ownership (TCO)
Technical Consultation & Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including material selection guidance, coil geometry optimization, insulation system design review,