Stainless Steel Coil Tube — Photochemical Microreactor Grade
Product Overview
The Stainless Steel Coil Tube (盘管) produced by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product designed for advanced flow chemistry and microreactor systems. This coil tube is specifically developed for applications in photochemical synthesis, including the continuous-flow production of hydrogen peroxide (H₂O₂) within flow-inverted microreactor configurations. The product combines the mechanical integrity and corrosion resistance of austenitic stainless steel with the geometric advantages of coiled geometry to deliver exceptional heat transfer, light transmission, and fluidic performance in high-value chemical synthesis.
The coil tube represents a critical component in Continuous Flow Chemistry (CFC) technology, where the spiral configuration maximizes the surface-area-to-volume ratio, promotes efficient turbulent mixing at low Reynolds numbers, and enables uniform irradiation of the process fluid. This makes it particularly suitable for photochemical reactions requiring precise control over residence time, temperature, and photon flux distribution.
Material & Properties
Material Grade
The coil tube is manufactured from high-purity Austenitic Stainless Steel, with the primary grade being SAE 316L (UNS S31603), selected for its superior resistance to pitting and crevice corrosion in the presence of chlorides, peroxides, and acidic media. Alternative grades including SAE 304L (UNS S30403) and SAE 321 (UNS S32100) are available upon specification for specialized thermal and mechanical requirements.
Key Material Properties
- Chemical Composition (SAE 316L): Carbon (C) ≤ 0.03%, Chromium (Cr) 16.0–18.0%, Nickel (Ni) 10.0–14.0%, Molybdenum (Mo) 2.0–3.0%, Silicon (Si) ≤ 1.00%, Manganese (Mn) ≤ 2.00%, Phosphorus (P) ≤ 0.045%, Sulfur (S) ≤ 0.030%
- Tensile Strength: ≥ 485 MPa (Minimum)
- Yield Strength (0.2% offset): ≥ 170 MPa
- Elongation: ≥ 40% (in 50 mm gauge length)
- Density: 8.0 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +870°C (continuous)
- Pitting Resistance: PREN (Pitting Resistance Equivalent Number) ≥ 24
- Surface Finish: Electropolished interior, Ra ≤ 0.4 μm; brushed or mirror exterior (Ra ≤ 0.2 μm available)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Photochemical Microreactor Grade) | — |
| Material Grade | SAE 316L / 304L / 321 (custom available) | ASTM A269 / ASTM A213 |
| Outer Diameter (OD) | 1.0 mm – 25.0 mm (custom tolerances ±0.05 mm) | ISO 6507 |
| Wall Thickness | 0.2 mm – 2.0 mm | ASTM A269 |
| Inner Diameter (ID) | 0.4 mm – 21.0 mm (calibrated for laminar/turbulent flow) | — |
| Coil Diameter | 50 mm – 500 mm (spiral pitch adjustable) | — |
| Coil Length | 1 m – 50 m (per spool; longer lengths available) | — |
| Tightness / Pressure Rating | Up to 40 bar (hydrostatic tested at 1.5× working pressure) | ASTM A269, Clause 14 |
| Surface Treatment | Electropolished (interior); passivated with citric/nitric acid solution | ASTM A967 / ASTM A380 |
| End Form | Plain ends, beveled ends, or pre-fitted connectors (Swagelok, VCR, etc.) | — |
| Tolerance (OD) | ±0.05 mm (precision grade); ±0.1 mm (standard grade) | ASTM A269, Table 2 |
| Coil Pitch Tolerance | ±0.5 mm | — |
| Residual Stress | Stress-relieved (1050°C solution anneal + quench) | ASTM A269, Clause 7 |
| Hydrogen Permeation | ≤ 0.1 cm³/(m²·s·atm) at 25°C | — |
| Corrosion Resistance | Immune to H₂O₂ (up to 35% w/w, ≤ 80°C); resistant to dilute H₂SO₄, HNO₃ | NACE MR0175 (optional) |
Manufacturing Process
Process Flow Diagram (Sequential Steps)
- Raw Material Selection & Verification: Mill-certified (EN 10204 Type 3.1) austenitic stainless steel seamless tubing is procured from certified suppliers. Incoming inspection includes spectrometric composition analysis (OES), hardness testing, and ultrasonic flaw detection (UT) per ASTM A269.
- Cold Drawing & Sizing: The parent tube undergoes multi-pass cold drawing through tungsten carbide (WC) dies to achieve the required OD, wall thickness, and dimensional tolerances. This process enhances mechanical properties through strain hardening while maintaining microstructural homogeneity.
- Intermediate Annealing: At specified draw reductions, the tube is solution-annealed at 1050°C in a controlled atmosphere (dew point ≤ −60°C) followed by water quenching to restore ductility and prevent work hardening-induced cracking.
- Precision Coiling: A computerized CNC coil forming machine (numerically controlled) bends the tube into the specified spiral geometry. The bending radius is optimized to prevent ovalization (≤ 5% of OD) and to maintain internal surface integrity. The coil pitch and diameter are controlled within ±0.5 mm tolerance.
- Post-Coiling Stress Relief: The formed coil undergoes a low-temperature stress relief cycle (400–500°C, 1 hour) to eliminate residual bending stresses without sensitizing the microstructure (precipitation of chromium carbides is avoided by controlling carbon content ≤ 0.03% in 316L).
- Electropolishing & Passivation: The interior bore is electropolished to achieve Ra ≤ 0.4 μm, removing any surface contamination, micro-roughness, and cold-worked layer. The tube is then passivated using a citric acid (20% w/w) or nitric acid (10% w/w) solution per ASTM A967 to form a stable chromium oxide passive film.
- Hydrostatic Pressure Testing: Each coil spool is hydrostatically tested at 1.5× the maximum design working pressure (up to 60 bar) for a minimum dwell time of 60 seconds. Leak detection is performed via pressure decay method and dye penetrant inspection at end connections.
- Final Inspection & Certification: Dimensional verification (OD, ID, coil diameter, pitch), surface roughness measurement (contact profilometry), visual inspection (10× magnification), and optional penetrant testing (PT per ASTM E165) are conducted. Each batch is accompanied by a Material Test Report (MTR) and Certificate of Conformance.
- Packaging & Storage: Coils are individually wrapped in anti-static polyethylene film, placed in padded wooden crates with desiccant packs, and labeled with batch traceability information. Storage is in a climate-controlled environment (RH ≤ 60%, T ≤ 30°C) to prevent surface contamination.
Process Quality Control Points
- Incoming material: 100% OES composition verification, UT scanning
- After cold drawing: OD/ID dimensional check (CMM), hardness (Rockwell B)
- After coiling: Ovalization measurement, coil geometry verification (laser scanning)
- After electropolishing: Surface roughness (Ra), residual stress (X-ray diffraction)
- Final: Hydrostatic test, visual inspection, dimensional audit
Applications
Primary Application: Photochemical Synthesis of H₂O₂
The principal application domain for this coil tube is the photochemical continuous-flow synthesis of hydrogen peroxide within a coil-flow-inverted microreactor. In this configuration, the stainless steel coil tube serves as both the reaction vessel and the structural support for the photochemical process. Key advantages include:
- Enhanced Light Penetration: The small internal diameter (typically 0.5–2.0 mm) ensures that photons from UV or visible light sources penetrate the full fluid cross-section, achieving uniform photoactivation of the reactant species. This eliminates the light attenuation effects observed in macro-scale reactors.
- Controlled Residence Time: The coil length and internal volume provide precise control over hydraulic residence time (τ), enabling optimization of reaction conversion and selectivity. Residence time is adjustable from milliseconds to minutes by varying the coil length and flow rate.
- Efficient Heat Management: The high surface-area-to-volume ratio facilitates rapid heat exchange with the surrounding medium, maintaining isothermal conditions critical for selective H₂O₂ production and preventing thermal runaway.
- Continuous Flow Operation: The sealed, corrosion-resistant coil enables uninterrupted operation for extended periods (demonstrated for > 1000 hours), supporting scalable production of high-purity H₂O₂.
- Flow Inversion Capability: The spiral geometry promotes secondary flows (Dean vortices) that enhance radial mixing even at laminar flow conditions (Re < 2300), improving mass transfer between co-flowing reactant streams.
Additional Applications
- Continuous Flow Organic Synthesis: Photochemical reactions including [2+2] cycloadditions, radical initiations, and photocatalytic transformations in pharmaceutical and fine chemical manufacturing.
- Heat Exchangers (Plate-and-Shell): Compact coil heat exchangers for cryogenic, high-pressure, or high-purity fluid processing in the petrochemical, aerospace, and semiconductor industries.
- Fluidic Components in MEMS/NEMS: Precision-bore stainless steel tubing for microfluidic chip integration, capillary-based analytical instruments, and lab-on-a-chip (LOC) systems.
- Catalytic Reactor Coils: Structured catalyst support for heterogeneous catalytic reactions (oxidation, hydrogenation, dehydrogenation) in continuous fixed-bed configurations.
- Medical & Pharmaceutical Equipment: Autoclavable tubing for bioreactor loops, chromatography systems, and sterile fluid transfer in GMP-compliant manufacturing environments.
- Hydrogen Storage & Transfer: High-pressure tubing for hydrogen fuel cell systems and hydrogen storage containers, leveraging the low permeability of austenitic stainless steel to hydrogen gas.
- Optical & Photonic Devices: Cladding and waveguide components for fiber-optic couplers, light guides, and photonic crystal fiber (PCF) manufacturing.
Quality Certifications & Compliance
| Certification / Standard | Scope | Applicability |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Full manufacturing process |
| ISO 14001:2015 | Environmental Management System | Production facility operations |
| ISO 45001:2018 | Occupational Health & Safety Management | Workplace safety |
| EN 10204 Type 3.1 | Inspection Document (Third-Party Tested) | Material certification per batch |
| ASTM A269 | Standard Specification for Seamless & Welded Austenitic Stainless Steel Tubing | Product design and manufacturing |
| ASTM A213 | Standard Specification for Seamless Austenitic Chromium-Nickel Stainless Steel Tubing for High Temperature Service | High-temperature applications |
| ASTM A967 | Standard Practice for Chemical Cleaning and Passivation of Stainless Steel Parts | Surface treatment |
| ASTM A380 | Standard Specification for Electrolytic Cleaning and Passivation of Stainless Steel Parts | Electropolishing process |
| ASME BPE (Bioprocessing Equipment) | Design and Fabrication of Process Systems for the Pharmaceutical and Biotechnology Industries | Pharmaceutical-grade applications (optional) |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive — Category II/III | Pressure vessel integration (upon request) |
| NACE MR0175 / ISO 15156 | Sour Service Requirements | Oil & gas applications (optional) |
| RoHS 2.0 (EU Directive 2011/65/EU) | Restriction of Hazardous Substances | Electronics and general compliance |
| REACH (EU Regulation 1907/2006) |