Stainless Steel Coil Tube for Heat Transfer Oil Boiler Systems
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 591) supplies high-performance Stainless Steel Coil Tubes (盘管 / Coiltube) engineered specifically for demanding industrial thermal systems, including heat transfer oil (HTO) boilers, organic heat transfer fluid circuits, and high-temperature process heating applications. These coil tubes are manufactured to withstand sustained thermal cycling, elevated operating pressures, and aggressive chemical environments, ensuring long service life and operational safety in continuous-duty industrial processes.
Extensive field analysis of heat transfer oil boiler coil tube failures—particularly rupture and oil leakage events—has informed the design criteria, material selection, and manufacturing tolerances adopted by Wenzhou Jixing Metal Materials. This empirical foundation ensures that the product addresses the root causes of premature failure, including thermal fatigue cracking, oxidation-induced wall thinning, stress corrosion cracking (SCC), and mechanical degradation under cyclic loading.
Material & Properties
Material Grades
- Austenitic Stainless Steel: Grade 304 (UNS S30400), Grade 316 (UNS S31600), Grade 321 (UNS S32100), and Grade 347 (UNS S34700) for general to moderate-temperature service.
- Heat-Resistant Austenitic Stainless Steel: Grade 310S (UNS S31008) for sustained operating temperatures exceeding 900 °C.
- Super-Austenitic / Duplex Grades: Available upon request for extreme corrosion and mechanical integrity requirements.
Key Mechanical & Physical Properties
- Maximum Service Temperature: Up to 1150 °C (depending on grade selection)
- Operating Pressure Resistance: Designed for pressures up to 2.5 MPa (362.6 psi) in boiler coil configurations
- Thermal Conductivity: 14.2–16.3 W/(m·K) at 100 °C (Grade 304/316)
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C (20–1000 °C)
- Yield Strength: ≥ 205 MPa (Grade 304, annealed condition)
- Tensile Strength: ≥ 515 MPa (Grade 304, annealed condition)
- Oxidation Resistance: Excellent resistance to scaling and oxidation in oxidizing atmospheres up to 1000 °C
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and intergranular corrosion (particularly Grade 316 with molybdenum addition)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ASTM A213 / ASME SA-213 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A213 / ASME SA-213 |
| Coil Diameter | 500 mm – 3000 mm (configurable) | Customer-specific / GB/T 14976 |
| Tube Length per Coil | 5 m – 200 m (continuous coil) | — |
| Surface Finish | Mill finish, polished (Ra ≤ 0.8 μm), or electropolished | ASTM A269 |
| Temperature Range | −196 °C to +1150 °C | — |
| Pressure Rating | Up to 2.5 MPa (design-dependent) | ASME Section VIII / GB 50041 |
| Tolerance (OD) | ± 0.1 mm (precision grade) | ASTM A213 |
| Tolerance (Wall) | ± 10% of nominal | ASTM A213 |
| Heat Treatment Condition | Solution annealed (SA) or cold-worked (CW) | — |
| Coil Weight | Up to 5,000 kg per coil (maximum) | — |
| Standards Compliance | ASTM A213, ASME SA-213, GB/T 14976, EN 10216-5 | — |
Manufacturing Process
The manufacturing process for Wenzhou Jixing Metal Materials' stainless steel coil tubes follows a rigorous, multi-stage procedure designed to ensure dimensional accuracy, metallurgical integrity, and long-term service reliability:
- Raw Material Selection: Certified stainless steel seamless tube blanks or welded strip are procured from accredited mills with full chemical composition (CE) documentation.
- Hot Rolling / Seamless Forming: Billet material is hot-rolled or hot-extruded into seamless tube stock, ensuring homogeneous microstructure and freedom from inclusion-related defects.
- Piercing and Elongation: The solid billet is pierced and elongated to achieve the required inner diameter and wall thickness.
- Cold Drawing / Cold Rolling: Tubes are cold-drawn or cold-rolled to achieve precise dimensional tolerances (± 0.1 mm OD) and enhanced mechanical properties through work hardening.
- Solution Annealing: Tubes are solution-annealed at 1050–1150 °C followed by controlled cooling (air or water quench) to dissolve carbides, restore full austenitic structure, and maximize corrosion resistance.
- Coiling / Coil Forming: Straight tubes are coiled to the specified coil diameter using precision coiling equipment that maintains uniform bending stress without introducing micro-cracking or residual stress concentrations.
- Pickling and Passivation: Surface oxide scale is removed via acid pickling (nitric/hydrofluoric acid blend), followed by passivation treatment to form a protective chromium oxide layer.
- Quality Inspection: Each coil undergoes ultrasonic testing (UT), eddy current testing (ECT), hydrostatic pressure testing, and visual inspection for surface defects.
- Packaging and Dispatch: Coils are wrapped with moisture-proof protective film, strapped, and palletized for safe transport.
Applications
These stainless steel coil tubes are engineered for a broad spectrum of industrial thermal and process applications, with particular emphasis on heat transfer oil boiler systems where failure analysis has driven enhanced design standards:
- Heat Transfer Oil (HTO) Boilers: Primary and secondary heating coils in organic heat transfer fluid systems, where thermal cycling and oxidation resistance are critical.
- Industrial Process Heating: Polymer extrusion, rubber vulcanization, chemical reaction vessels, and food processing equipment requiring precise temperature control.
- Power Generation: Auxiliary heating systems in combined heat and power (CHP) plants and district heating networks.
- Chemical Processing: Heat exchanger coils in aggressive chemical environments (acid, alkali, halide-containing process streams).
- Pharmaceutical and Food Industries: Sanitary-grade heating coils requiring high-purity, corrosion-resistant materials (316L electropolished).
- Textile and Paper Industries: High-temperature drying and calendering equipment.
- Oil and Gas: Downhole heating elements and subsea process heating systems.
Failure Prevention Design Considerations
Based on documented failure analyses of heat transfer oil boiler coil tube ruptures and oil leakage incidents, Wenzhou Jixing Metal Materials incorporates the following engineering safeguards:
- Thermal Fatigue Mitigation: Material selection prioritizes high-temperature creep resistance and low thermal expansion to reduce cyclic stress accumulation at coil bends and tube-to-header joints.
- Oxidation and Scaling Prevention: Enhanced chromium and silicon content in austenitic grades (e.g., 310S) provide superior resistance to high-temperature oxidation, preventing wall thinning and scale-induced flow restriction.
- Stress Corrosion Cracking (SCC) Resistance: Grade 316 and 316L (low-carbon) variants are recommended for environments containing chloride or halide species, which are common degradation catalysts in heat transfer oil systems.
- Uniform Wall Thickness: Precision manufacturing tolerances prevent local wall thinning that could lead to premature perforation under sustained thermal and pressure loading.
- Residual Stress Elimination: Post-coiling stress-relief annealing reduces residual bending stresses that could initiate fatigue cracks at stress-concentration points.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and holds the following certifications and compliance credentials:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- NADCAP (National Aerospace and Defense Contractors Accreditation Program) — Available for aerospace-grade coil tube production
- ASME "S" Stamp — Authorization for pressure vessel and piping components
- EN 10204 3.1 / 3.2 — Material test certificates per European standard
- API 5CT / API 5L — Compliance for oil and gas industry applications (where applicable)
- CE Marking — Compliance with European Pressure Equipment Directive (PED 2014/68/EU)
- GB/T 14976 — Chinese National Standard for seamless stainless steel tubes
Unique Selling Points
- Failure-Informed Engineering: Product design is directly informed by real-world failure analysis of heat transfer oil boiler coil tube ruptures, ensuring that common degradation mechanisms—thermal fatigue, oxidation, SCC, and mechanical wear—are proactively addressed.
- Custom Coil Configuration: Flexible coil diameter, tube dimensions, and length configurations tailored to specific boiler and heat exchanger designs.
- Full Traceability: Every coil is accompanied by mill test certificates, chemical composition reports, and dimensional inspection records for complete supply-chain traceability.
- Multi-Grade Availability: Comprehensive range of austenitic, heat-resistant, and duplex stainless steel grades to match diverse service conditions and temperature regimes.
- Post-Sales Technical Support: Engineering consultation for material selection, failure analysis, and system optimization to extend service life and prevent catastrophic coil tube failures.
Conclusion
Wenzhou Jixing Metal Materials Co., Ltd. delivers stainless steel coil tubes that combine metallurgical excellence, precision manufacturing, and application-specific engineering intelligence. By integrating lessons learned from documented heat transfer oil boiler failures into the product development lifecycle, the company ensures that its coil tube solutions provide superior reliability, safety, and operational continuity for demanding industrial thermal systems worldwide.