Stainless Steel Coil Tube — Mixed Gas Preheating Furnace Application (Coiltube)

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd

Product Category: Coil Tube / Furnace Tube for Mixed Gas Preheating Systems

Reference No.: 633

1. Product Overview

The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product specifically designed for Mixed Gas Preheating Furnace applications. These coil tubes serve as critical heat exchange elements within industrial furnace systems where mixed combustion gases must be preheated to optimize thermal efficiency and reduce fuel consumption. The product is supplied in continuous coil form, enabling seamless integration into furnace designs that require complex routing, bending, and heat-transfer geometries without the need for welded joints at critical stress points.

Based on extensive field experience in furnace tube repair and maintenance (炉管修复), Wenzhou Jixing Metal Materials has developed coil tubes with enhanced mechanical properties, superior corrosion resistance, and extended service life under cyclic thermal loading conditions. The coil configuration allows for maximum heat-transfer surface area within compact furnace volumes, making it an ideal solution for energy-intensive industrial processes.

2. Material & Properties

2.1 Commonly Used Grades

• 310S (UNS S31008): High-temperature austenitic stainless steel with excellent oxidation resistance up to 1150°C (2094°F). Ideal for furnace tube applications involving sustained high-temperature exposure.
• 309S (UNS S30908): Austenitic stainless steel offering superior resistance to thermal cracking and scaling at elevated temperatures (up to 982°C / 1800°F). Suitable for cyclic thermal environments.
• 321 (UNS S32100): Titanium-stabilized austenitic stainless steel providing enhanced resistance to intergranular corrosion and stress corrosion cracking in mixed gas environments.
• 347 (UNS S34700): Niobium-stabilized austenitic stainless steel offering improved creep strength and resistance to carburization at high temperatures.

2.2 Key Physical & Mechanical Properties

• Maximum Service Temperature: 1150°C (2094°F) for 310S grade
• Oxidation Resistance: Excellent; forms a stable Cr₂O₃ protective scale in oxidizing atmospheres
• Thermal Conductivity: 25–30 W/(m·K) at operating temperature
• Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C (100–1100°C)
• Yield Strength (at 1000°C): ≥ 100 MPa (310S grade)
• Tensile Strength (room temperature): ≥ 520 MPa
• Corrosion Resistance: Resistant to sulfur, carbon monoxide, and carbon dioxide attack in mixed gas atmospheres

3. Specifications

Parameter	Specification	Standard / Tolerance
Outer Diameter (OD)	25 mm – 159 mm (custom available)	ASTM A213 / GB/T 12771
Wall Thickness	1.0 mm – 6.0 mm	±10% of nominal
Coil Length	Up to 200 m per coil (standard); custom lengths available	—
Minimum Bend Radius	3D (three times outer diameter)	ASTM A999
Surface Finish	Mill finish, polished (Ra ≤ 0.8 μm), or passivated	ASTM A473
End Condition	Cut square, beveled, threaded, or with flange/socket end fittings	Customer specification
Material Grades	310S, 309S, 321, 347, 316L, duplex 2205 (custom)	ASTM A213 / A269
Delivery Form	Coiled (盘管), straight lengths, or pre-formed assemblies	—
Maximum Operating Temperature	1150°C (2094°F)	Grade-dependent
Maximum Operating Pressure	Up to 1.6 MPa (design dependent)	ASME B31.3
Atmosphere Compatibility	Non-oxidizing, oxidizing, mixed combustion gases	—
Coil Inner Diameter	500 mm – 1500 mm (custom available)	—

4. Manufacturing Process

4.1 Seamless Tube Production

1. Raw Material Selection: High-purity stainless steel billets sourced from certified producers with full traceability and mill test reports.
2. Hot Piercing: Billets are heated to 1200–1250°C and pierced on a Mannesmann-type piercing mill to produce seamless hollow blanks.
3. Hot Rolling / Elongation: The pierced blanks undergo multi-pass hot rolling to achieve desired outer diameter and wall thickness dimensions.
4. Intermediate Annealing: Stress-relief annealing at 1050–1100°C in a protective atmosphere to restore ductility and refine grain structure.
5. Cold Drawing / Cold Sizing: Precision cold working to achieve final dimensions within tight tolerances and improve surface finish.
6. Final Solution Annealing: Full solution treatment at 1050–1150°C followed by controlled cooling to achieve optimal austenitic microstructure and corrosion resistance.
7. Pickling and Passivation: Acid pickling to remove surface scale followed by passivation treatment to form a protective chromium oxide layer.

4.2 Coil Forming Process

1. Coil Winding: The annealed tube is wound into a continuous coil using precision coil-winding equipment with controlled tension to prevent deformation or ovality.
2. Bend Radius Control: The winding process maintains a minimum bend radius of 3D to prevent work hardening or cracking in the tube wall.
3. End Sealing: Coil ends are sealed with protective caps to prevent contamination and moisture ingress during storage and transportation.
4. Protective Packaging: Coils are wrapped with moisture-barrier film, wrapped in steel strapping, and secured on wooden pallets or steel skids.

4.3 Furnace Tube Repair & Restoration (Field Service)

Wenzhou Jixing Metal Materials provides specialized furnace tube repair services based on extensive operational experience in mixed gas preheating systems. Repair procedures include:

• Inspection and assessment of tube degradation (wall thinning, scaling, oxidation)
• Identification of failure modes (thermal fatigue cracking, carburization, stress corrosion cracking)
• Replacement of damaged tube sections with matching-grade coil tube
• Application of protective coatings or refractory linings to extend service life
• Post-repair pressure testing and leak detection verification

5. Applications

5.1 Primary Applications

• Mixed Gas Preheating Furnaces: Primary application — coil tubes serve as heating elements for preheating mixed combustion gases (natural gas, blast furnace gas, coke oven gas) to improve thermal efficiency in industrial furnaces.
• Heat Treatment Furnaces: Annealing, normalizing, and hardening furnaces requiring uniform temperature distribution.
• Reheat Furnaces: Steel mill reheating furnaces for hot rolling preparation.
• Incineration Systems: Waste-to-energy and industrial waste incineration systems requiring high-temperature resistant tubing.
• Chemical Process Heaters: Process gas preheating and heat recovery systems in petrochemical and chemical manufacturing.

5.2 Industry Sectors

• Iron and Steel Manufacturing
• Petrochemical and Refining
• Power Generation
• Cement and Ceramics
• Non-Ferrous Metal Smelting
• Environmental Protection (waste incineration)

6. Quality Certifications & Standards Compliance

Certification / Standard	Description
ISO 9001:2015	Quality Management System certification for manufacturing processes
ASTM A213	Standard Specification for Seamless Austenitic Stainless Steel Tubing for High-Temperature Service
ASTM A269	Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
GB/T 12771	Chinese National Standard for Stainless Steel Seamless Tubes for General Application
GB/T 5310	Chinese National Standard for Seamless Steel Tubes for High-Pressure Boilers
EN 10216-5	European Standard for Heat-Resistant Seamless Stainless Steel Tubes
JIS G3459	Japanese Industrial Standard for Heat-Resistant Stainless Steel Tubes
ASME SA-213	ASME Boiler and Pressure Vessel Code — Stainless Steel Tubing
CE / PED 2014/68/EU	Pressure Equipment Directive compliance (where applicable)

7. Unique Selling Points

• Field-Proven Repair Expertise: Direct experience in mixed gas preheating furnace tube failure analysis and restoration ensures products are engineered with real-world degradation mechanisms in mind.
• Custom Coil Configuration: Flexible coil inner diameter, length, and end-condition options to match specific furnace geometry requirements without field welding.
• Extended Service Life: Material selection and heat treatment optimized for cyclic thermal loading, reducing unplanned shutdowns and maintenance costs.
• Full Traceability: Complete material traceability from mill certificate through final delivery, enabling compliance with regulatory and insurance requirements.
• Technical Support: Engineering consultation for furnace tube design, material selection, and failure analysis based on accumulated operational knowledge.
• Competitive Lead Times: Established supply chain and manufacturing capacity enabling rapid delivery of standard and custom coil tube configurations.

8. Inspection & Testing

All coil tube products undergo rigorous quality control at multiple stages:

1. Raw Material Verification: Spectroscopic analysis (PMI) of incoming billets to confirm chemical composition.
2. In-Process Dimensional Checks: Ultrasonic thickness measurement and OD/wall-thickness verification at each production stage.
3. Final Dimensional Inspection: 100% dimensional verification against drawing specifications.
4. Chemical Analysis: Full chemical composition testing per ASTM E415 (spark OES) or wet chemical methods.
5. Mechanical Testing: Tensile testing, hardness testing, and impact testing per ASTM E8/E8M.
6. Hydrostatic / Pneumatic Testing: Pressure testing to verify weld integrity (for welded products) or seam integrity.
7. Non-Destructive Testing (NDT): Eddy current testing (ECT) or magnetic particle inspection (MPI) for surface and near-surface defect detection.
8. Surface Quality Inspection: Visual and magnetic flux leakage (MFL) inspection for surface defects.

Note: All specifications are subject to confirmation based on specific application requirements. Wenzhou Jixing Metal Materials Co., Ltd provides customized engineering solutions for specialized furnace tube applications. Please contact our technical team for detailed quotations and project-specific recommendations.