Stainless Steel Coil Tube for Closed Circuit Cooling Tower Systems
Product Overview
The Stainless Steel Coil Tube (Product No. 1033) is a precision-engineered heat exchange coil specifically designed for closed circuit cooling tower (CCCT) applications. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents an optimized design that addresses the critical thermal management requirements of industrial cooling systems. The coil tube serves as the core heat transfer element within closed-loop recirculation systems, where process heat is rejected to the atmosphere through evaporative cooling without direct contact between the cooling medium and the process fluid.
Unlike conventional open-loop cooling tower tubes, the coil tube for closed circuit cooling towers is engineered to withstand prolonged exposure to ambient conditions, humidity variations, and thermal cycling while maintaining structural integrity and thermal efficiency over extended service life.
Material & Properties
Base Material
- Primary Alloy: Austenitic Stainless Steel (奥氏体不锈钢), conforming to ASTM A213 / ASME SA-213 standards
- Common Grades: TP304, TP304L, TP316, TP316L, TP321, TP347, TP904L
- Alternative Grades: Duplex Stainless Steel (双相不锈钢) 2205, Super Duplex (超级双相) 2507
- Specialty Alloys: Alloy 20, Hastelloy C-276, Inconel 625 (for highly corrosive environments)
Key Mechanical Properties
| Property | Specification (304/304L Grade) | Specification (316/316L Grade) |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa (74,700 psi) | ≥ 515 MPa (74,700 psi) |
| Yield Strength (屈服强度) | ≥ 205 MPa (29,700 psi) | ≥ 205 MPa (29,700 psi) |
| Elongation (延伸率) | ≥ 40% | ≥ 40% |
| Thermal Conductivity (热导率, 100°C) | 16.3 W/(m·K) | 16.3 W/(m·K) |
| Specific Heat Capacity (比热容) | 502 J/(kg·K) | 502 J/(kg·K) |
| Operating Temperature Range (工作温度范围) | −196°C to +870°C | −196°C to +870°C |
| Corrosion Resistance (耐蚀性) | Good (atmospheric, mild chemicals) | Excellent (chloride, marine, chemical) |
Chemical Composition (Typical, wt%)
| Element | 304/304L | 316/316L | 321 |
|---|---|---|---|
| Carbon (C) | ≤ 0.08 / ≤ 0.03 | ≤ 0.08 / ≤ 0.03 | ≤ 0.08 |
| Chromium (Cr) | 18.0 – 20.0 | 16.0 – 18.0 | 17.0 – 19.0 |
| Nickel (Ni) | 8.0 – 10.5 | 10.0 – 14.0 | 9.0 – 12.0 |
| Molybdenum (Mo) | — | 2.0 – 3.0 | — |
| Titanium (Ti) | — | — | 5 × (C × 100) – 0.70 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 |
Specifications
| Parameter | Specification |
|---|---|
| Product Category (产品类别) | Closed Circuit Cooling Tower Coil Tube (闭式冷却塔冷却盘管) |
| Outer Diameter (外径) | Φ12.7 mm – Φ38.1 mm (½" – 1½") |
| Wall Thickness (壁厚) | 0.8 mm – 3.0 mm (Schedules 10S – 80S) |
| Coil Length (盘管长度) | 10 m – 120 m (customizable) |
| Bend Radius (弯曲半径) | ≥ 3D (minimum), typically 4D – 6D |
| Surface Finish (表面光洁度) | 2B (mill finish), BA (bright annealed), or No. 4 brushed |
| Surface Roughness (表面粗糙度) | Ra ≤ 0.8 μm (standard), Ra ≤ 0.4 μm (polished) |
| Manufacturing Standard (制造标准) | ASTM A213/A213M, ASME SA-213, EN 10216-5, GB/T 14976 |
| Testing Standard (检测标准) | ASTM E10 (hardness), ASTM A923 (intergranular corrosion) |
| Heat Treatment (热处理) | Solution Annealing (固溶退火), 1010°C – 1150°C, water quench |
| Pressure Rating (压力等级) | Up to 1.6 MPa (standard), up to 4.0 MPa (heavy wall) |
| Design Life (设计寿命) | ≥ 15 years (continuous duty) |
| Maximum Operating Pressure (最大工作压力) | 1.6 – 4.0 MPa (depending on wall thickness) |
| Coil Winding Pattern (盘绕方式) | Spiral (螺旋式), Helical (螺旋形), or Double-Loop (双回路) |
| End Preparation (端部处理) | Flat cut, beveled (坡口), or threaded (螺纹) |
Manufacturing Process
The production of optimized coil tubes for closed circuit cooling towers follows a rigorous multi-stage manufacturing protocol:
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Raw Material Selection (原材料选择):
Hot-rolled stainless steel strip (热轧不锈钢带材) or seamless tube blanks are procured from certified mills with full chemical and mechanical traceability (MTC — Mill Test Certificate).
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Pipe Forming (制管成型):
Continuous pipe rolling (连续制管) or seamless extrusion (无缝挤压) processes produce tubes meeting dimensional tolerances per ASTM A213. Dimensional accuracy is maintained within ±0.1 mm for outer diameter and ±10% for wall thickness.
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Welding (焊接):
Where applicable, longitudinal or spiral welding is performed via Automatic Submerged Arc Welding (SAW, 自动埋弧焊) or Gas Tungsten Arc Welding (GTAW/TIG, 钨极惰性气体保护焊). Weld penetration is verified by 100% Visual Testing (VT, 目视检测) and ≥ 20% Radiographic Testing (RT, 射线检测).
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Coil Forming / Bending (盘管成型/弯曲):
Computer Numerical Control (CNC, 计算机数控) coil forming machines produce precise spiral geometries. The bending process employs mandrel-assisted forming (芯棒辅助成型) to prevent ovalization (椭圆变形) and maintain minimum bend radius compliance. Post-bend dimensional inspection ensures ovality ≤ 2% of nominal OD.
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Heat Treatment (热处理):
Solution annealing (固溶处理) at 1010°C – 1150°C with rapid water quenching restores full austenitic microstructure, eliminates sensitization (敏化) risks, and achieves maximum corrosion resistance. For stabilized grades (321/347), stabilization annealing (稳定化处理) at 870°C – 900°C is performed.
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Surface Treatment (表面处理):
Pickling (酸洗) and passivation (钝化) remove surface contaminants and form a protective chromium oxide layer (Cr₂O₃). For high-purity applications, electropolishing (电解抛光) achieves Ra ≤ 0.4 μm surface finish.
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Quality Inspection (质量检验):
Comprehensive testing includes: Hydrostatic Pressure Testing (水压试验, ASTM A530), Spectrographic Analysis (光谱分析, PMI verification), Ultrasonic Testing (UT, 超声波检测) for internal defects, and Intergranular Corrosion Testing (晶间腐蚀试验, ASTM A923 Practice E).
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Coating & Protection (涂层与保护):
External protective coatings (外部保护涂层) may include: PTFE (聚四氟乙烯) coating for enhanced corrosion resistance, or epoxy powder coating (环氧粉末涂层) for atmospheric protection in aggressive environments.
Applications
The optimized stainless steel coil tube for closed circuit cooling towers finds extensive application across multiple industrial sectors:
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Petrochemical Industry (石油化工行业):
- Refinery process cooling (炼油工艺冷却)
- Chemical reactor temperature control (化学反应器温度控制)
- Distillation column condensate cooling (精馏塔冷凝液冷却)
-
Power Generation (发电行业):
- Nuclear power plant secondary cooling systems (核电站二次冷却系统)
- Combined cycle gas turbine (CCGT) exhaust heat recovery (联合循环燃气轮机余热回收)
- Biomass power plant process cooling (生物质电厂工艺冷却)
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Pharmaceutical & Food Processing (制药与食品加工):
- Clean steam generation (洁净蒸汽产生)
- Process fluid heat rejection (工艺流体热排放)
- Hygienic cooling applications requiring GMP compliance
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Electronics & Semiconductor Manufacturing (电子与半导体制造):
- Lithography equipment cooling (光刻设备冷却)
- High-purity water system heat exchange (高纯水系统换热)
- Plasma etching system thermal management (等离子蚀刻系统热管理)
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Marine & Offshore (海洋与海上工程):
- Offshore platform process cooling (海上平台工艺冷却)
- Shipboard HVAC and process systems (船舶暖通空调及工艺系统)
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Textile & Paper Industry (纺织与造纸行业):
- Dyeing process heat recovery (染色工艺热回收)
- Paper machine drying section cooling (造纸机干燥部冷却)
Optimized Design Features (优化设计特点)
"Optimized Design of Cooling Coils for Closed Circuit Cooling Towers" — Key learnings and design principles:
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Enhanced Heat Transfer Efficiency (增强换热效率):
Internal surface texturing (内表面波纹处理) and optimized tube pitch (管间距优化) increase turbulence intensity (湍流强度) within the coil, improving the overall heat transfer coefficient (总传热系数) by 15–25% compared to smooth-wall designs.
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Corrosion Fatigue Resistance (腐蚀疲劳抗性):
Material selection prioritizes chloride pitting resistance equivalent number (PREN ≥ 24 for 316L, PREN ≥ 35 for 2205 duplex) to withstand long-term exposure to humid, potentially corrosive atmospheric conditions in cooling tower environments.
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Thermal Stress Management (热应力管理):
Strategic placement of expansion loops (膨胀圈) and optimized support spacing (支撑间距优化) accommodate differential thermal expansion (差热膨胀) during temperature cycling, preventing