Stainless Steel Coil Tube — Nuclear Main Pump High-Pressure Cooler Application Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered, continuously wound tubular product designed for demanding heat-exchange applications, particularly within the nuclear power industry. This product series is specifically developed for use in nuclear main pump high-pressure coolers, where it serves as a critical thermal management component ensuring the safe and efficient operation of reactor coolant systems.
The coil tube is formed by cold-winding stainless steel strip into a helical coil geometry, offering superior surface-area-to-volume ratios compared to conventional straight pipe configurations. This geometry enables enhanced heat transfer efficiency, compact system integration, and improved resistance to flow-induced vibration (FIV) — a critical concern in high-pressure, high-velocity coolant environments. The design philosophy draws upon extensive research into the dynamic behavior of coil-type heat exchangers under turbulent flow conditions, ensuring long-term structural integrity under cyclic loading.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel grades, selected for their exceptional corrosion resistance, mechanical strength, and dimensional stability under extreme thermal and pressure conditions.
Primary Material Grades
- SAE 304 (UNS S30408): General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. Suitable for non-aggressive coolant environments.
- SAE 316 (UNS S31608): Molybdenum-enhanced austenitic stainless steel providing superior resistance to pitting and crevice corrosion. Preferred for nuclear-grade applications involving chloride-containing fluids.
- SAE 316L (UNS S31603): Low-carbon variant of 316 with enhanced resistance to intergranular corrosion. Recommended for welding applications and high-purity nuclear service.
- SAE 321 (UNS S32108): Titanium-stabilized austenitic stainless steel offering excellent resistance to intergranular corrosion at elevated temperatures. Suitable for high-temperature coolant loops.
Mechanical Properties (Typical, Annealed Condition)
| Property | SAE 304 | SAE 316 / 316L | SAE 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 | ≥ 515 |
| Yield Strength (0.2% offset, MPa) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (% at fracture) | ≥ 40 | ≥ 40 | ≥ 40 |
| Density (g/cm³) | 8.00 | 8.03 | 8.00 |
| Thermal Conductivity (W/m·K, at 100°C) | 16.3 | 16.3 | 16.3 |
| Thermal Expansion (10⁻⁶/K, 20–100°C) | 17.3 | 17.3 | 17.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 1090 |
Corrosion Resistance
- Excellent resistance to atmospheric corrosion, dilute acids, organic acids, and alkaline solutions
- Outstanding resistance to pitting and crevice corrosion in chloride-containing environments (316/316L grades)
- Non-magnetic in the annealed condition (relative permeability ≤ 1.05)
- Full compliance with ASTM A269 and ASTM A270 specifications for seamless and welded stainless steel tubing
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Catalog No. | 359 |
| Classification | Technical Reference / Literature Study Series |
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (customizable) |
| Wall Thickness | 0.3 mm – 3.0 mm (customizable) |
| Coil Pitch | 5 mm – 50 mm (adjustable per application) |
| Coil Diameter | 50 mm – 600 mm (adjustable) |
| Coil Length | 1 m – 50 m (customizable) |
| Surface Finish | Mirror polish (Ra ≤ 0.4 μm), satin finish, or as-rolled |
| Winding Method | Continuous cold-winding with controlled spring-back compensation |
| End Form | Open coil, closed coil, or with welded end fittings |
| Operating Pressure | Up to 25 MPa (design-dependent) |
| Operating Temperature Range | −196 °C to +870 °C |
| Applicable Standards | ASTM A269, ASTM A270, EN 10217, GB/T 12771 |
| Packaging | Wooden crate with moisture-proof wrapping; custom packaging available |
Manufacturing Process
The production of high-performance stainless steel coil tubes follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Selection & Inspection: High-purity stainless steel strip is sourced from certified mills and subjected to incoming inspection including chemical composition analysis (OES), mechanical property testing, and visual surface examination.
- Strip Forming (Rolling): The flat stainless steel strip is passed through a series of progressive rollers to form a seamless tube. This cold-rolling process maintains the metallurgical integrity of the material while achieving precise wall thickness tolerances.
- Welding (if applicable): For welded coil tubes, a high-frequency induction welding (HFW) or orbital TIG welding process is employed. Weld seams are subsequently ground, polished, and radiographically inspected to ensure full penetration and absence of defects.
- Coil Winding: The formed tube is cold-wound onto precision mandrels using computer-controlled winding machines. The winding process incorporates real-time tension control and spring-back compensation algorithms to achieve consistent coil pitch, diameter, and helix angle. This is the critical step that defines the product's geometric performance characteristics.
- Heat Treatment (Annealing): Where required, the wound coil is subjected to solution annealing (typically 1050–1150 °C followed by controlled cooling) to relieve residual stresses, restore full austenitic microstructure, and ensure maximum corrosion resistance and ductility.
- Pickling & Passivation: The annealed coil undergoes acid pickling to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide layer on the surface.
- Surface Finishing: Depending on application requirements, the coil may undergo electropolishing, mechanical polishing, or passivation to achieve specified surface roughness values (Ra ≤ 0.4 μm for mirror finish).
- Dimensional Inspection & Quality Control: Final inspection includes OD and wall thickness measurement, coil pitch verification, helix angle measurement, hydrostatic pressure testing, and non-destructive testing (NDT) including eddy current testing and dye penetrant inspection.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is engineered for a broad spectrum of high-performance applications:
Primary Application: Nuclear Industry
- Nuclear Main Pump High-Pressure Coolers: The coil tube serves as the heat transfer element in main coolant pump (MCP) heat exchangers within pressurized water reactors (PWR) and boiling water reactors (BWR). The helical geometry provides efficient heat rejection from high-pressure coolant while maintaining structural resilience against flow-induced vibration (FIV) — a phenomenon extensively studied in the context of coil-type nuclear heat exchangers.
- Reactor Coolant System (RCS) Heat Exchangers: Used in auxiliary cooling loops for decay heat removal systems.
- Steam Generator Tubing (Specialty Coils): Custom coil configurations for specific nuclear heat exchanger designs.
Secondary Applications
- Chemical Processing: Heat exchangers, condensers, evaporators, and reboilers in petrochemical and pharmaceutical plants
- Food & Beverage Industry: Sanitary-grade heat exchangers for pasteurization, sterilization, and thermal processing
- Power Generation: Condensers, economizers, and superheaters in thermal power plants
- Oil & Gas: Subsea heat exchangers and offshore platform cooling systems
- Aerospace: Lightweight thermal management coils for engine cooling and environmental control systems
- Medical & Laboratory: Precision temperature control coils in analytical instruments and medical devices
Flow-Induced Vibration (FIV) Considerations
Technical Note: The design and application of coil tubes in nuclear main pump high-pressure coolers requires careful consideration of flow-induced vibration (FIV). Research documented in "Flow-Induced Vibration Analysis of Nuclear Main Pump High-Pressure Cooler with Coil Tube Configuration" highlights that the helical geometry of coil tubes introduces unique dynamic characteristics — including coupled axial-torsional vibration modes, vortex shedding interactions, and fluidelastic instability thresholds — that differ significantly from straight-tube heat exchangers. Wenzhou Jixing Metal Materials Co., Ltd. incorporates these findings into product design optimization, ensuring that coil tube geometries are engineered to operate below critical FIV thresholds across the full range of expected operating conditions.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- ASME NQA-1 — Nuclear Quality Assurance (for nuclear-grade products)
- ASTM A269 / A270 — Compliance with stainless steel tubing specifications
- EN 10217 — European standard for seamless and welded stainless steel tubes
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes
- Third-Party Inspection: Available upon request (SGS, BV, TUV, Lloyd's Register)
- Mill Test Certificates (MTC): EN 10204 Type 3.1 certificates provided with each shipment
- Nuclear Regulatory Compliance: Products designed in accordance with applicable requirements of 10 CFR Part 50 (U.S. NRC) and equivalent international nuclear regulatory standards
Unique Selling Points
- Nuclear-Grade Design Expertise: Products informed by rigorous FIV analysis research, ensuring dynamic stability in high-pressure coolant applications
- Precision Coil Geometry: Computer-controlled winding with ±0.1 mm pitch accuracy and ±0.5° helix angle tolerance
- Custom Engineering: Full customization of OD, wall thickness, coil pitch, coil diameter, and length to meet specific application requirements
- Material Versatility: Available in multiple austenitic stainless steel grades including 304, 316, 316L, and 321
- Full Traceability: Complete material traceability from mill heat number through final product identification
- Advanced NDT: Comprehensive non-destructive testing including eddy current, ultrasonic, radiographic, and hydrostatic pressure testing
- Compact & Efficient: Helical geometry delivers superior heat transfer surface area in minimal footprint, reducing system weight and installation complexity
- Long Service Life: Engineered for extended operational life under cyclic thermal and mechanical loading conditions
Contact & Ordering Information
For detailed technical inquiries, custom quotations, or sample requests regarding the Stainless Steel Coil Tube (Catalog No. 359) and related products, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Engineering support is available for application-specific design consultation, FIV assessment, and material selection guidance.