Stainless Steel Coil Tube for Organic Heat Carrier Furnace Systems
1. Product Overview
The Stainless Steel Coil Tube (盘管) is a precision-engineered continuous tube product formed into helical or serpentine configurations, specifically designed for use in Organic Heat Carrier Furnace (OHCF) systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube serves as the primary heat exchange medium in thermal fluid heating systems, where it transfers heat energy from combustion gases to organic heat transfer fluids (such as thermal oils) under controlled temperature and pressure conditions.
Unlike conventional straight pipe sections, coil tubes offer superior heat transfer efficiency due to their compact geometry, enhanced fluid turbulence, and reduced pressure drop across the heat exchanger circuit. The coiled configuration maximizes the surface-area-to-volume ratio, enabling rapid and uniform heat absorption within confined furnace chambers.
2. Material & Properties
Coil tubes for organic heat carrier applications are typically fabricated from austenitic stainless steel grades selected for their exceptional resistance to oxidation, thermal fatigue, and chemical degradation under sustained high-temperature service conditions.
Common Material Grades:
- 304 (UNS S30408) — General-purpose austenitic stainless steel with 18% Chromium (Cr) and 8% Nickel (Ni); suitable for moderate-temperature organic heat carrier service up to 600°C.
- 321 (UNS S32108) — Titanium-stabilized austenitic grade; provides superior resistance to intergranular corrosion (IGC) and thermal cycling fatigue; recommended for sustained service above 500°C.
- 310S (UNS S31008) — High-temperature austenitic grade with 25% Cr and 20% Ni; designed for extreme thermal environments up to 1100°C in air atmosphere.
- 316L (UNS S31603) — Low-carbon, molybdenum-bearing austenitic grade; offers enhanced resistance to pitting and crevice corrosion in aggressive chemical environments.
Key Mechanical & Physical Properties (Typical for Grade 321):
- Tensile Strength: 515–700 MPa (at 20°C); 240–350 MPa (at 600°C)
- Yield Strength: 205 MPa minimum (at 20°C)
- Elongation: ≥40% (at 20°C)
- Thermal Conductivity: 14–23 W/(m·K) (20–600°C)
- Linear Thermal Expansion: 17.2 µm/(m·K) (average, 20–600°C)
- Maximum Service Temperature: 900°C (oxidizing atmosphere)
- Corrosion Resistance: Excellent resistance to oxidation, scaling, and hot salt attack
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 19.05 mm – 50.80 mm (¾" – 2") | ASTM A213 / ASME SA213 |
| Wall Thickness | 1.20 mm – 3.96 mm | ASTM A213 / EN 10216-5 |
| Coil Diameter (Bundling) | 150 mm – 800 mm (variable per design) | Custom / OEM Specification |
| Tube Length per Coil | 3.0 m – 12.0 m (continuous) | ASME BPVC Section IV |
| Material Grade | 304 / 321 / 310S / 316L | ASTM A269 / ASTM A213 |
| Surface Finish | Pickled & Passivated (Ra ≤ 0.8 µm) | ASTM A380 / GB/T 4237 |
| Maximum Operating Pressure | ≤ 1.6 MPa (typical OHCF service) | GB/T 17410 / ASME VIII |
| Operating Temperature Range | 200°C – 400°C (organic heat carrier fluid) | GB/T 17410 / EN 12829 |
| Tolerance on OD | ±0.05 mm (precision rolled) | ASTM A213 / ISO 4287 |
| End Preparation | Plain end / Beveled / Threaded (per customer spec) | ASME B1.20.1 |
4. Manufacturing Process
The production of high-quality stainless steel coil tubes for organic heat carrier furnace applications involves a multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and long-term operational reliability.
- Raw Material Selection & Verification: Seamless stainless steel tubes conforming to ASTM A213 or ASTM A269 specifications are procured from certified mills. Incoming material undergoes positive material identification (PMI) via X-ray fluorescence (XRF) spectrometry and chemical composition analysis via optical emission spectrometry (OES).
- Cold Drawing / Cold Rolling: Tubes are cold-worked to achieve precise outer diameter and wall thickness tolerances. This process enhances mechanical properties through strain hardening and improves surface finish quality.
- Solution Annealing: Cold-worked tubes undergo solution annealing at 1050°C – 1150°C followed by rapid water quenching to restore full austenitic microstructure, eliminate residual stresses, and maximize corrosion resistance.
- Pickling & Passivation: Surface treatment using a combination of nitric acid and hydrofluoric acid removes scale and oxide layers, followed by passivation to establish a protective chromium oxide film (Cr₂O₃).
- Coiling / Forming: Annealed tubes are formed into the required helical or serpentine coil geometry using CNC-controlled coiling machines. The bending radius is carefully controlled to avoid excessive thinning or ovality at bend locations.
- Welding & Assembly: Where continuous coil sections require connection, TIG (Tungsten Inert Gas) welding with argon shielding is employed. Weld joints are inspected via radiographic testing (RT) or ultrasonic testing (UT) to ensure full penetration and absence of defects.
- Non-Destructive Testing (NDT): Comprehensive inspection protocols include:
- Visual inspection (VT) for surface defects
- Magnetic particle testing (MT) or eddy current testing (ET) for surface/subsurface flaws
- Acoustic Emission (AE) testing for structural integrity assessment under operational simulation
- Hydrostatic pressure testing at 1.5× maximum operating pressure
5. Applications
Stainless steel coil tubes manufactured to these specifications find primary application in the following industrial sectors:
- Organic Heat Carrier Furnace Systems (OHCF): Primary heat exchange surfaces in thermal oil heating furnaces operating at temperatures between 200°C and 400°C, used in chemical, petrochemical, and polymer manufacturing processes.
- Chemical Processing Plants: Heat transfer coils in reactors, distillation columns, and process heaters requiring corrosion-resistant heat exchange surfaces.
- Textile & Synthetic Fiber Industries: Thermal fluid heating systems for polyester chip melting, filament spinning, and hot drawing processes.
- Food Processing & Pharmaceutical Manufacturing: Sanitary-grade heating coils for pasteurization, sterilization, and controlled temperature processing.
- Plastics & Rubber Industries: Heat carrier systems for extrusion, molding, and vulcanization processes.
- Wood & Paper Industries: Thermal oil heating systems for drying, pressing, and calendaring operations.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications and standards compliance:
- ISO 9001:2015 — Quality Management System certification
- ISO 3834-2 — Quality requirements for welding of metallic materials
- ASME "S" Stamp — Boiler and Pressure Vessel Code compliance
- EN 10204 3.1 — Material test certificates with independent inspection
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU)
- TÜV / SGS Inspection — Third-party quality verification
- GB/T 17410 — Chinese national standard for organic heat carrier systems
7. Unique Selling Points & Technical Advantages
7.1 Acoustic Emission (AE) Detection Technology Integration
A distinctive feature of this coil tube product line is the incorporation of Acoustic Emission (AE) testing technology as a supplementary non-destructive evaluation method. AE testing detects transient elastic waves generated by micro-crack propagation, delamination, or stress concentration within the tube wall. This technology enables:
- Early detection of fatigue-initiated micro-cracks before they reach critical dimensions
- Real-time structural health monitoring during operational service
- Quantitative assessment of remaining useful life (RUL) for in-service coils
- Identification of stress-corrosion cracking (SCC) susceptibility zones
7.2 Additional Technical Advantages:
- Superior Thermal Fatigue Resistance: Titanium-stabilized grades (321) provide excellent resistance to thermal cycling fatigue, extending service life in environments with frequent start-up and shutdown cycles.
- Compact Design Efficiency: The coiled geometry achieves 30–50% higher heat transfer coefficient compared to equivalent straight-tube bundles due to induced fluid turbulence.
- Reduced Installation Footprint: Compact coil configurations minimize the required furnace chamber volume and piping complexity.
- Low Maintenance Requirements: High corrosion resistance eliminates the need for internal protective coatings and reduces inspection frequency.
- Customization Capability: Full flexibility in coil diameter, pitch, tube OD, wall thickness, and end configurations to match specific furnace designs.
- Traceability & Documentation: Complete batch traceability from raw material mill certificate through final inspection, ensuring full supply chain accountability.
8. Service Life & Maintenance Recommendations
Under normal operating conditions within the specified temperature and pressure parameters, stainless steel coil tubes for organic heat carrier furnace systems exhibit a design service life of 10–15 years. Recommended maintenance practices include:
- Annual visual inspection of external surfaces for signs of oxidation, scaling, or mechanical damage
- Biennial ultrasonic thickness measurement (UT) at critical locations (bend radii, weld joints)
- Periodic Acoustic Emission testing during scheduled maintenance shutdowns
- Hydrostatic pressure testing at 5-year intervals or after any repair activity
- Monitoring of thermal oil quality to prevent accelerated corrosion from degraded fluid contaminants