Stainless Steel Coil Tube for Cryogenic Heat Exchangers

Product Overview

The Stainless Steel Coil Tube (Model No. 554) is a precision-engineered helical tube product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for use in large-scale helium cryogenic systems. These coil tubes serve as critical heat transfer elements in cryogenic heat exchangers, where they facilitate efficient thermal exchange between superfluid helium (He-II) and warm fluids at temperatures as low as 1.8 K. The product is engineered to meet the demanding requirements of superconducting magnet applications, particle accelerators, and advanced scientific research facilities.

Based on extensive research into the heat exchange characteristics and structural optimization of coil tube heat exchangers in large-scale helium cryogenic systems, this product line incorporates advanced design principles that maximize thermal performance while minimizing thermal contraction stresses and flow resistance. The coil geometry is optimized to achieve superior heat transfer coefficients under cryogenic conditions, ensuring reliable operation in extreme low-temperature environments.

Unique Selling Points

• Optimized Helical Geometry: Coil pitch and diameter are precisely calculated to enhance turbulence and heat transfer efficiency at cryogenic temperatures, achieving heat transfer coefficients significantly higher than straight-tube configurations.
• Thermal Stress Mitigation: The helical coil structure inherently accommodates differential thermal contraction between the tube material and surrounding components, reducing mechanical failure risk during cooldown cycles.
• Compact Heat Exchange Area: The coiled configuration provides maximum heat transfer surface area within a minimum volumetric envelope, essential for space-constrained cryogenic installations.
• Proven Cryogenic Performance: Validated through rigorous testing in large-scale helium cryogenic systems, demonstrating reliable operation across the full temperature range from 1.8 K to ambient temperature.
• Superfluid Compatibility: Manufactured to ultra-low roughness tolerances suitable for superfluid helium (He-II) flow, minimizing pressure drop and maintaining laminar flow characteristics required for superfluid transport.

Material & Properties

The coil tubes are manufactured from high-purity austenitic stainless steel grades, selected for their exceptional cryogenic mechanical properties, corrosion resistance, and thermal conductivity characteristics at ultra-low temperatures.

Primary Material Grades

• AISI 316L (UNS S31603): Low-carbon variant with superior cryogenic toughness and enhanced resistance to intergranular corrosion. Carbon content ≤ 0.03% ensures excellent weldability and resistance to sensitization during manufacturing.
• AISI 304L (UNS S30403): General-purpose austenitic stainless steel offering excellent ductility and thermal conductivity at cryogenic temperatures. Suitable for applications where molybdenum resistance is not required.
• Custom Alloy Grades: Available upon request for specialized applications requiring specific thermal or mechanical property profiles.

Key Physical Properties at Cryogenic Temperatures (1.8 K)

• Thermal Conductivity: 12–18 W/(m·K) (316L at 1.8 K), providing efficient radial heat transfer through the tube wall.
• Yield Strength: ≥ 310 MPa, maintaining structural integrity under cryogenic pressure differentials.
• Tensile Strength: ≥ 520 MPa, ensuring resistance to mechanical deformation during thermal cycling.
• Linear Thermal Expansion: 1.2–1.8 × 10⁻⁶ /K, enabling predictable dimensional behavior during cooldown.
• Surface Roughness (Ra): ≤ 0.4 μm (internal), minimizing flow resistance for superfluid helium transport.

Specifications

Parameter	Specification	Standard / Reference
Product Category	Coil Tube (Helical Heat Exchanger Tube)	—
Material Grade	AISI 316L / AISI 304L (Custom available)	ASTM A270 / ASTM A269
Outer Diameter (OD)	3.0 mm – 16.0 mm (customizable)	± 0.05 mm tolerance
Wall Thickness	0.3 mm – 1.0 mm (customizable)	± 0.02 mm tolerance
Coil Diameter	15 mm – 200 mm	± 0.5 mm tolerance
Coil Pitch	5 mm – 30 mm	± 0.2 mm tolerance
Tube Length (Uncoiled)	1 m – 50 m (continuous)	Custom lengths available
Surface Finish (Internal)	Ra ≤ 0.4 μm (electropolished)	ASTM A967
Surface Finish (External)	Ra ≤ 0.8 μm (brushed/polished)	—
Operating Temperature Range	1.8 K – 600 K	—
Maximum Operating Pressure	≤ 2.5 MPa (design-dependent)	ASME VIII Div. 1
Heat Treatment	Solution annealed (1050–1150 °C), water quenched	ASTM A270
Welding Method	TIG (GTAW) / Orbital welding	ASME IX
Helium Leak Test	≤ 1 × 10⁻⁹ atm·cm³/s	ASTM E2337
Hydrostatic Pressure Test	1.5 × design pressure, 30 min hold	ASME B31.3
End Preparation	Beveled, ground, or threaded per specification	ASME B16.11 / B16.12
Coating / Passivation	Acid pickling and passivation (citric or nitric acid)	ASTM A967

Manufacturing Process

The production of cryogenic-grade stainless steel coil tubes involves a meticulously controlled multi-stage manufacturing process to ensure dimensional accuracy, material integrity, and surface quality suitable for superfluid helium applications.

Process Flow

1. Raw Material Procurement: Certified austenitic stainless steel seamless tubes are sourced from approved mills, accompanied by full mill test certificates (MTC) in accordance with EN 10204 Type 3.1.
2. Incoming Inspection: Dimensional verification, chemical composition analysis (spectrometric), mechanical property testing, and visual surface inspection of incoming tube stock.
3. Dimensional Preparation: Precision cutting and end preparation of tube stock to required lengths with controlled tolerances. Internal and external surfaces are inspected for defects.
4. Coil Forming: The straight tube is helically wound using CNC-controlled coil forming machinery to achieve precise coil diameter, pitch, and turn uniformity. The forming process is optimized to avoid work hardening and residual stress concentrations.
5. Solution Annealing: Coiled tubes undergo solution annealing at 1050–1150 °C followed by rapid water quenching to restore full austenitic structure, eliminate residual stresses, and achieve maximum cryogenic toughness.
6. Internal Surface Treatment: Electropolishing of the internal bore to achieve Ra ≤ 0.4 μm surface finish, critical for minimizing superfluid helium flow resistance and ensuring uniform heat transfer.
7. Acid Pickling and Passivation: Chemical cleaning using citric or nitric acid solution to remove oxide scale and form a stable chromium oxide passive layer on all exposed surfaces.
8. Welding and Assembly: TIG welding of end fittings, manifolds, and structural supports using inert gas shielding. Weld parameters are qualified per ASME IX welding procedure specifications.
9. Non-Destructive Testing (NDT): Radiographic testing (RT), eddy current testing (ET), and dye penetrant testing (PT) of all welds and critical surfaces.
10. Pressure and Leak Testing: Hydrostatic pressure testing at 1.5× design pressure with subsequent helium leak detection to verify weld integrity and system tightness.
11. Final Inspection and Documentation: Complete dimensional verification, surface finish measurement, and compilation of full traceability documentation including heat numbers, test results, and certification packages.

Applications

Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd are employed in a wide range of high-performance cryogenic and process applications:

Cryogenic Systems

• Superconducting Magnet Systems: Heat exchangers for superconducting accelerator magnets, MRI/NMR systems, and fusion reactor magnets requiring operation at 4.2 K (superfluid helium) or 1.8 K.
• Large Helium Cryogenic Systems: Primary and secondary heat exchangers in helium liquefaction plants, helium distribution systems, and cryogenic temperature stabilization systems.
• Particle Accelerators: Coil tube heat exchangers for RF cavity cooling, beam dump cooling, and magnet cooling circuits in CERN-type and domestic accelerator facilities.
• Space Simulation Facilities: Cryogenic thermal management systems for spacecraft thermal vacuum testing and satellite component qualification.

Process Industries

• LNG (Liquefied Natural Gas) Systems: Heat exchangers for gas liquefaction, vaporization, and temperature equalization in LNG production and storage facilities.
• Hydrogen Production: Cryogenic heat exchangers in hydrogen liquefaction plants and hydrogen storage systems operating at 20–30 K.
• Food and Beverage Processing: Rapid cooling and freezing heat exchangers requiring hygienic stainless steel construction and efficient heat transfer.
• Chemical Processing: Low-temperature reaction heat exchangers, condensers, and evaporators in petrochemical and pharmaceutical applications.

Scientific Research

• Quantum Computing Systems: Cryogenic heat exchangers for dilution refrigerator cold stages and quantum processor cooling systems.
• Low-Temperature Physics: Heat exchangers for laboratory-scale cryogenic systems, cryotrons, and superfluid helium experiments.
• Biomedical Research: Cryopreservation systems, ultra-low temperature storage, and cryogenic sample handling equipment.

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management and certification programs to ensure product compliance with international standards and customer requirements:

Quality Management Systems

• ISO 9001:2015: Quality Management System certification covering all manufacturing, inspection, and documentation processes.
• ISO 14001:2015: Environmental Management System certification for environmentally responsible manufacturing practices.
• ISO 45001:2018: Occupational Health and Safety Management System certification.

Product Standards Compliance

• ASTM A270: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service.
• ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Fossil Fuel Process Applications.
• ASME B31.3: Process Piping Code compliance for pressure-containing cryogenic service.
• ASME VIII Division 1: Boiler and Pressure Vessel Code compliance for pressure vessel components.
• EN 10216-5: European standard for welded and seamless steel tubes for mechanical and thermal uses.
• GB/T 12771: Chinese national standard for welded austenitic stainless steel tubes for general use.

Testing and Inspection Certifications

• ASME IX: Welding procedure qualification and welder certification for all joining operations.
• ASNT NDT Level III: Non-destructive testing personnel certification for radiographic, ultrasonic, and eddy current testing.
• Third-Party Inspection: Available upon customer request (e.g., SGS, Bureau Veritas, TÜV Rheinland, DNV).
• Mill Test Certificates (MTC): EN 10204 Type 3.1 material certificates with full chemical and mechanical property data.

Special Certifications for Cryogenic Service

• Cryogenic Impact Testing: Charpy V-notch impact testing at 4.2 K and 1.8 K to verify material toughness under operating conditions.
• Thermal Cycling Testing: Multi-cycle cooldown and warmup testing to verify dimensional stability and structural integrity.
• Helium Leak Testing: Full-system helium leak rate verification to ≤ 1 × 10⁻⁹ atm·cm³/s per ASTM E2337.

Technical Support & Customization

Wenzhou Jixing Metal Materials Co., Ltd provides comprehensive technical support for coil tube heat exchanger design and optimization, including:

• Thermal Performance Simulation: CFD and thermal analysis modeling of coil tube heat exchanger performance under specific operating conditions.
• Structural Optimization: Finite element analysis (FEA) for thermal stress, vibration, and mechanical integrity verification.
• Custom Engineering: Tailored coil geometry, material selection, and fabrication specifications for unique application requirements.
• Application Engineering: On-site technical consultation and integration support for cryogenic system installations.

Note: All specifications listed herein are representative values based on standard configurations. Custom specifications are available upon request and subject to mutual agreement between the supplier and the customer. Final product dimensions, tolerances, and performance characteristics shall be governed by the applicable purchase order and technical agreement.