Stainless Steel Coil Tube for Packed Closed-Circuit Cooling Towers
Product Overview
The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange component specifically designed for packed coil tube type closed cooling towers (Packed Coil Tube Closed Cooling Towers, PCTCCTs). These coil tubes serve as the primary heat transfer surfaces within closed-circuit cooling systems, enabling efficient thermal dissipation through indirect contact between the process fluid and the ambient air. The product is engineered to meet the rigorous demands of industrial cooling applications where contamination prevention, corrosion resistance, and thermal efficiency are critical performance parameters.
The coil tube assembly integrates seamlessly with structured packing (填料) elements within the cooling tower shell, forming a hybrid heat exchange configuration that maximizes the surface area-to-volume ratio. This design facilitates both sensible and latent heat transfer mechanisms, significantly enhancing the overall cooling capacity of the system.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for superior mechanical properties, corrosion resistance, and thermal stability across a wide operating temperature range.
- Base Material: Stainless steel conforming to ASTM A269 / ASTM A312 specifications, with typical grades including 304 (UNS S30408), 304L (UNS S30403), 316 (UNS S31608), and 316L (UNS S31603).
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, chloride-induced pitting, and stress corrosion cracking (SCC), particularly in 316L grade.
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, ensuring efficient heat transfer performance.
- Mechanical Strength: Minimum tensile strength of 515 MPa (304) and 485 MPa (316L); elongation ≥ 40%.
- Operating Temperature Range: -196°C to +870°C (304 grade); -196°C to +870°C (316L grade).
- Surface Finish: Electropolished or passivated finish with surface roughness Ra ≤ 0.4 μm, minimizing fouling and biofilm adhesion.
Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | 12.7 mm (1/2"), 19.05 mm (3/4"), 25.4 mm (1"), 31.75 mm (1-1/4"), customizable |
| Tube Wall Thickness | 0.5 mm – 2.0 mm, standard 1.0 mm |
| Coil Pitch (螺旋间距) | 10 mm – 50 mm, optimized per thermal load |
| Coil Diameter | 500 mm – 3000 mm, configurable per tower geometry |
| Coil Length | Up to 12,000 mm continuous coil |
| Heat Transfer Coefficient (U-value) | 2,500 – 4,500 W/(m²·K) depending on flow regime |
| Maximum Operating Pressure | 1.6 MPa (standard); 2.5 MPa (high-pressure variant) |
| Flow Velocity | 1.0 – 3.0 m/s (optimal range for heat transfer) |
| Welding Method | Automatic TIG (Gas Tungsten Arc Welding) per AWS D10.9 |
| End Connection Types | Flanged (ANSI B16.5), threaded (NPT/BSP), or welded socket |
| Applicable Standards | GB/T 14976, GB/T 12771, ASTM A269, EN 10217-7 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, structural integrity, and thermal performance:
- Material Selection and Inspection: Raw stainless steel tubes are procured from certified suppliers and subjected to spectroscopic analysis, ultrasonic testing (UT), and visual inspection to verify grade compliance and absence of internal defects.
- Cold Drawing and Dimensional Precision: Tubes undergo cold drawing to achieve precise outer diameter and wall thickness tolerances within ±0.05 mm, ensuring uniform heat transfer characteristics along the entire coil length.
- Coil Forming (螺旋成型): Precision coil forming machinery bends the straight tube into the specified helical geometry with controlled pitch and diameter. The forming process is executed at room temperature to avoid work-hardening-induced residual stresses, or followed by controlled stress relief annealing at 850–950°C in inert atmosphere.
- Welding and Assembly: Inlet and outlet headers are welded to the coil ends using automatic TIG welding (per AWS D10.9 / ASME B31.3). All welds are 100% radiographic or penetrant tested (PT) for quality assurance.
- Surface Treatment: Electropolishing or chemical passivation is applied to remove surface contamination, create a chromium oxide passive layer, and reduce surface roughness, thereby enhancing corrosion resistance and minimizing scaling.
- Pressure Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5× the maximum operating pressure, with a minimum hold time of 30 minutes to verify leak-tightness and structural integrity.
- Final Inspection and Packaging: Dimensional verification, material traceability documentation, and protective packaging are completed prior to shipment.
Applications
The stainless steel coil tube is integral to the following industrial and commercial applications:
- Packed Coil Tube Closed Cooling Towers (PCTCCTs): Primary heat exchange element in closed-circuit cooling towers combined with structured packing media, providing high-efficiency cooling for process fluids including glycol solutions, brines, and specialty chemicals.
- Industrial Process Cooling: Cooling of lubricants, hydraulic fluids, and process streams in manufacturing facilities where water quality and contamination control are critical.
- Power Generation: Condenser cooling and auxiliary cooling systems in power plants, particularly where corrosion-resistant materials are mandated.
- Food and Pharmaceutical Industry: Closed-loop cooling systems requiring hygienic-grade stainless steel (316L) with electropolished surfaces to meet FDA and GMP standards.
- Chemical Processing: Heat recovery and cooling in chemical reactors, distillation columns, and process loops involving corrosive media.
- Marine and Offshore Applications: Cooling systems in marine vessels and offshore platforms where chloride resistance is essential.
- HVAC Systems: Closed-circuit chiller condensers and heat rejection units in commercial and industrial HVAC installations.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework and holds the following certifications to ensure product excellence and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering the entire manufacturing and supply chain process.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking (EN 10217-7) — Conformity with European standards for welded stainless steel tubes.
- PED 2014/68/EU — Pressure Equipment Directive compliance for components used in pressurized systems.
- ASME Stamp — Authorized for components designed per ASME Boiler and Pressure Vessel Code, Section VIII.
- NACE MR0175 / ISO 15156 — Material compliance for sour service environments (for applicable grades).
- Mill Test Certificates (MTC) — Full traceability documentation (EN 10204 3.1/3.2) provided with every shipment, including chemical composition analysis, mechanical test results, and heat treatment records.
Unique Selling Points
The stainless steel coil tube products from Wenzhou Jixing Metal Materials Co., Ltd. offer several distinguishing advantages:
- Thermally Optimized Geometry: Coil pitch and diameter are engineered based on theoretical analysis and experimental validation of cooling tower heat transfer performance, maximizing the overall heat transfer coefficient while minimizing pressure drop.
- Customization Capability: Flexible manufacturing capacity allows for tailored coil dimensions, material grades, and end connections to match specific cooling tower designs and thermal load requirements.
- Extended Service Life: The combination of high-grade stainless steel, precision manufacturing, and surface passivation ensures a design life exceeding 20 years with minimal maintenance.
- Hygienic and Corrosion-Resistant Design: Electropolished surfaces eliminate dead legs and reduce biofilm formation, making the product suitable for sanitary and chemical processing applications.
- Integrated System Compatibility: Designed for seamless integration with structured packing elements in packed coil tube cooling towers, providing a synergistic heat exchange configuration that outperforms conventional tube-and-shell alternatives in compact installations.
- Full Traceability and Documentation: Every coil tube is accompanied by comprehensive material certification, dimensional inspection reports, and pressure test records, ensuring full regulatory and audit compliance.