Stainless Steel Coiltube for Crude Oil Floating Roof Tank Heating Systems
Product Overview
The stainless steel coiltube (盘管, Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 826) is a specialized heat transfer component designed for integration into crude oil floating roof tank (Floating Roof Tank, FRT) heating systems. Unlike conventional straight-pipe heat exchange configurations, coiltubes leverage the inherent advantages of a coiled geometry to maximize the surface-area-to-volume ratio, thereby enhancing thermal exchange efficiency within confined spatial environments typical of large-scale petroleum storage facilities.
Based on extensive numerical simulation research and effective utilization rate analysis of the coiltube heating process in crude oil floating roof tanks, this product line represents a scientifically optimized solution for maintaining the fluidity and processability of heavy crude oils and viscous petroleum products under ambient and sub-ambient storage conditions. The coiltube serves as the primary heat carrier, circulating thermal fluid (typically hot water, steam, or thermal oil) through its serpentine channels to deliver uniform and controlled heating to the stored crude oil inventory.
Material & Properties
The coiltube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical integrity under prolonged exposure to aggressive petroleum environments. The primary material grades employed include:
- SUS304 / AISI 304 / 06Cr19Ni10 — General-purpose austenitic stainless steel with excellent resistance to atmospheric and mild chemical corrosion. Suitable for standard crude oil storage applications where chloride content is moderate.
- SUS316L / AISI 316L / 022Cr17Ni12Mo2 — Low-carbon variant with added molybdenum (Mo), providing superior resistance to pitting and crevice corrosion in high-chloride environments such as sour crude oils or marine atmospheric conditions.
- SUS321 / AISI 321 / 06Cr18Ni11Ti — Titanium-stabilized austenitic grade offering enhanced resistance to intergranular corrosion at elevated operating temperatures, making it ideal for continuous heating applications where thermal cycling is a concern.
| Property | Specification | Standard Reference |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa (≥ 74.7 ksi) | ASTM A213 / GB/T 12771 |
| Yield Strength (屈服强度) | ≥ 205 MPa (≥ 29.7 ksi) | ASTM A213 / GB/T 12771 |
| Elongation (延伸率) | ≥ 40% (at break) | ASTM A213 |
| Thermal Conductivity (导热系数) | 16.3 W/(m·K) at 100°C | ASTM A213 |
| Operating Temperature Range (使用温度范围) | −196°C to +600°C | ASTM A213 |
| Corrosion Resistance (耐蚀性) | Excellent against H₂S, CO₂, chlorides, and organic acids | NACE MR0175 / ISO 15156 |
| Carbon Content (含碳量) | ≤ 0.03% (low-carbon) | AISI 316L designation |
| Surface Finish (表面光洁度) | Ra ≤ 0.8 μm (polished) or Ra ≤ 1.6 μm (pickled) | ASTM A269 |
Specifications
The coiltube product range is available in a wide spectrum of dimensional configurations to accommodate varying tank geometries, heating capacity requirements, and process design parameters. The following table summarizes the standard specification envelope:
| Parameter (参数) | Range / Value (范围/数值) | Notes |
|---|---|---|
| Outer Diameter (外径, OD) | Φ19 mm – Φ57 mm | Common sizes: Φ25, Φ32, Φ38, Φ45, Φ51 |
| Wall Thickness (壁厚) | 0.8 mm – 3.0 mm | Custom thickness available upon request |
| Coil Diameter (盘管直径) | Φ300 mm – Φ2,000 mm | Adaptable to tank diameter constraints |
| Coil Length (盘管长度) | Up to 500 m per coil | Continuous coil or segmented assemblies |
| Number of Turns (圈数) | 10 – 200+ turns | Configured per thermal load calculation |
| Pressure Rating (压力等级) | PN6 – PN40 (0.6 – 4.0 MPa) | Hydrostatic test at 1.5× working pressure |
| Heat Transfer Fluid (传热介质) | Hot water, saturated/pressurized steam, thermal oil | Maximum fluid temperature ≤ 250°C |
| Heat Transfer Coefficient (传热系数) | 300 – 800 W/(m²·K) | Dependent on fluid velocity and fouling factor |
| Effective Utilization Rate (有效利用率) | ≥ 85% (optimized coil design) | Based on numerical simulation validation |
| End Connections (端部连接) | Flanged, threaded, or welded (butt weld / socket weld) | Per ASME B16.5 or GB/T 9119 |
| Coating (涂层) | Bare (passivated) or epoxy/polyurethane coated | Coating thickness ≥ 200 μm if specified |
| Standards Compliance (标准符合) | ASTM A213, GB/T 12771, GB/T 13296, EN 10216-5 | Multi-standard certification available |
Manufacturing Process
The production of high-quality stainless steel coiltubes follows a rigorously controlled multi-stage manufacturing process, each step governed by strict quality assurance protocols to ensure dimensional accuracy, metallurgical integrity, and consistent performance:
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Raw Material Selection & Inspection (原材料选择与检验)
Stainless steel seamless tubes are sourced from certified mill suppliers, accompanied by full material test certificates (MTC) in accordance with EN 10204 Type 3.1. Incoming material undergoes spectrographic analysis (OES) to verify chemical composition, hardness testing, and visual inspection for surface defects.
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Heat Treatment & Solution Annealing (热处理与固溶退火)
Tubes are solution-annealed at 1,050°C – 1,150°C followed by rapid water quenching to achieve a fully austenitic microstructure with maximum corrosion resistance and ductility. Subsequent pickling and passivation (酸洗钝化) removes scale and oxide layers, forming a protective chromium oxide film (Cr₂O₃) on the surface.
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Coiling / Bending Process (盘绕成型)
Using CNC-controlled coiling machinery with precision mandrels, the straight tubes are formed into the required coil geometry. The coiling process is carefully parameterized to prevent wall thinning, ovality distortion, or residual stress concentrations. Coil diameter, pitch, and turn count are controlled to within ±2% tolerance. Post-forming stress relief annealing (去应力退火) is performed at 350°C – 450°C to minimize residual stresses.
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Welding & Assembly (焊接与组装)
Multi-coil assemblies or coil-to-header connections are fabricated using Gas Metal Arc Welding (GMAW) or Gas Tungsten Arc Welding (GTAW) with matching filler metal (e.g., ER316L or E316L). All welds undergo 100% visual inspection (VT) and are subject to radiographic testing (RT) or dye penetrant testing (PT) as specified by the project requirements, in compliance with ASME Section IX or ISO 3834.
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Hydrostatic Pressure Testing (水压试验)
Each completed coil assembly is subjected to a hydrostatic pressure test at 1.5 times the maximum working pressure for a minimum hold time of 30 minutes, with zero leakage permitted. Test records are documented and archived for traceability.
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Final Inspection & Packaging (最终检验与包装)
Final dimensional verification, surface quality inspection, and chemical composition confirmation are performed. Coiltubes are packaged in moisture-proof packaging with desiccants and protected with end caps to prevent mechanical damage and atmospheric exposure during transit.
Applications
The coiltube product line is purpose-engineered for demanding thermal management applications in the petroleum, petrochemical, and energy sectors. Key application areas include:
- Crude Oil Floating Roof Tank Heating (原油浮顶罐加热) — The primary design application. Coiltubes are installed beneath or within the floating roof structure of large crude oil storage tanks (typically 5,000 – 100,000 m³ capacity) to maintain the temperature of heavy crude oils above their pour point, ensuring continuous flowability and pumpability. Numerical simulation studies have validated that optimized coiltube configurations achieve an effective utilization rate (有效利用率) exceeding 85%, significantly outperforming unoptimized designs.
- Heavy Oil & Bitumen Storage (重油与沥青储存) — Heating of high-viscosity petroleum products in storage tanks and transfer pipelines to reduce viscosity to within acceptable pumping parameters.
- Petrochemical Reactor Cooling/Heating (石化反应器冷却/加热) — Coiltubes serve as internal heat transfer surfaces within fixed-bed or fluidized-bed reactors, where compact geometry and high thermal efficiency are critical.
- Refinery Process Heat Exchangers (炼油厂工艺换热器) — Used as coil-and-shell heat exchangers in distillation units, hydrotreating units, and catalytic cracking units.
- Marine & Offshore Platforms (海洋与海上平台) — Heating systems for oil and chemical storage tanks on offshore platforms, where space constraints and corrosion resistance are paramount.
- Chemical Processing & Pharmaceutical Industry (化工与制药行业) — Sanitary-grade coiltubes for process vessels requiring high cleanliness and corrosion resistance.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework aligned with international standards. The coiltube product line is certified and compliant with the following:
- ISO 9001:2015 — Quality Management Systems (质量管理体系)
- ISO 14001:2015 — Environmental Management Systems (环境管理体系)
- ISO 45001:2018 — Occupational Health and Safety Management Systems (职业健康安全管理体系)
- API Monogram License — American Petroleum Institute certification for oil and gas industry components
- NACE MR0175 / ISO 15156 — Resistance to sulfide stress cracking in sour service environments
- EN 10204 3.1 — Full material test certificates with independent inspection
- ASME Section IX / Section VIII — Welding and pressure vessel compliance
- CE Marking — European conformity for pressure equipment (PED 2014/68/EU)
Unique Selling Points
Simulation-Validated Thermal Efficiency: The coiltube design is informed by rigorous numerical simulation (数值模拟) of the crude oil floating roof tank heating process. Computational Fluid Dynamics (CFD) and finite element thermal analysis (有限元热分析) have been employed to optimize coil geometry, pitch spacing, and turn configuration, achieving an effective utilization rate (有效利用率) of ≥ 85%. This data-driven approach distinguishes the product from empirically designed alternatives.
- Maximized Heat Transfer Surface Area: The coiled geometry provides up to 3–5× more heat transfer surface area per unit of tank floor space compared to straight-pipe configurations, enabling compact installation in space-constrained tank environments.
- Superior Corrosion Resistance: The use of low-carbon austenitic stainless steels (316L, 321) ensures long service life in aggressive crude oil environments containing H₂S, CO₂, chlorides, and organic acids, with design life exceeding 20 years under normal operating conditions.
- Customizable Engineering: Full customization of coil diameter, tube dimensions, turn count, and end connections to match specific tank geometry and process requirements, supported by dedicated engineering design services.
- Full Traceability & Documentation: Each coil assembly is delivered with complete documentation including material test certificates, heat treatment records, welding logs, hydrostatic test reports, and dimensional inspection records, ensuring full supply chain traceability.
- Cost-Effective Lifecycle Performance: Reduced heat transfer losses and higher utilization rates translate into lower energy consumption and operating costs over the asset lifecycle, providing a compelling total cost of ownership (TCO) advantage.
Conclusion
The Wenzhou Jixing Coiltube (Product No. 826) represents a scientifically engineered, standards-compliant solution for crude oil floating