Stainless Steel Coil Tube for Freeze Dryer Cold Trap
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd (Product No. 1024) is a precision-engineered tubular heat exchange element specifically designed for freeze dryer cold trap applications. This coil tube serves as the critical heat transfer surface within the cold trap assembly, where water vapor sublimated from the freeze-dried product is captured through condensation and frost formation. The design optimizes the surface area-to-volume ratio to maximize frost capture efficiency while maintaining structural integrity under cryogenic operating conditions.
The coil tube is manufactured from high-grade austenitic stainless steel, exhibiting excellent resistance to corrosion, cryogenic embrittlement, and thermal cycling fatigue. Its helical geometry provides a large effective surface area for vapor condensation, enabling rapid and uniform frost formation essential for efficient freeze-drying processes in pharmaceutical, biotechnology, and food processing industries.
Material & Properties
The coil tube is fabricated from Stainless Steel Grade 304 (UNS S30400) or Grade 316L (UNS S31603), selected for their superior performance in cryogenic and hygienic environments.
- Base Material: Austenitic stainless steel (304/316L)
- Chromium Content: 18–20% (provides passive oxide film for corrosion resistance)
- Nickel Content: 8–12% (stabilizes austenitic structure at cryogenic temperatures)
- Molybdenum Content (316L): 2–3% (enhanced pitting and crevice corrosion resistance)
- Carbon Content: ≤0.03% (316L) — minimizes sensitization and intergranular corrosion risk
- Surface Finish: Electropolished (Ra ≤ 0.4 μm) or passivated (Ra ≤ 0.8 μm) for frost adhesion control and hygienic compliance
- Thermal Conductivity: 14.5–16.3 W/(m·K) at 20°C
- Cryogenic Ductility: Retains full tensile strength and elongation down to −196°C (LN2 temperature)
- Operating Temperature Range: −80°C to +200°C
- Chemical Resistance: Resistant to water, steam, dilute acids, alkalis, and common pharmaceutical solvents
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) for Freeze Dryer Cold Trap |
| Product No. | 1024 |
| Material Grade | SUS 304 / SUS 316L |
| Outer Diameter (OD) | φ6 mm – φ12 mm (standard); custom available |
| Wall Thickness | 0.5 mm – 1.0 mm |
| Coil Pitch | 8 mm – 15 mm (adjustable per application) |
| Coil Diameter | φ100 mm – φ300 mm (spiral diameter) |
| Coil Length / Turns | Custom (typically 20–80 turns) |
| Effective Heat Transfer Area | 0.5 m² – 2.5 m² (per coil unit) |
| Surface Finish | Electropolished (Ra ≤ 0.4 μm) / Passivated / Brushed |
| End Connection | Flanged, threaded (BSP/NPT), or sanitary tri-clamp |
| Maximum Working Pressure | 1.0 MPa (gauge) |
| Hydrostatic Test Pressure | 1.5 MPa |
| Minimum Frost Capture Temperature | −80°C (with refrigerant circulation) |
| Applicable Refrigerants | Water (glycol-water mixture), Liquid Nitrogen (LN2) |
| Compliance Standards | ASTM A270, ASTM A312, EN 10217, GB/T 12771 |
| Hygienic Standards | 3-A Sanitary Standards, EHEDG, FDA 21 CFR |
Manufacturing Process
The production of the freeze dryer cold trap coil tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, material homogeneity, and surface quality:
- Material Selection & Inspection: Stainless steel wire or seamless tube stock (SUS 304/316L) is sourced from certified mills. Incoming materials undergo spectroscopic verification (PMI) to confirm chemical composition compliance with ASTM/EN specifications.
- Hot/Roll Forming: The tube is drawn and formed into the helical coil geometry using precision CNC coil-bending machinery. Forming parameters (bend radius, pitch, and tension) are controlled to prevent thinning, wrinkling, or cracking of the tube wall.
- Welding & Joining: End connections and any repair welds are performed using Argon Arc Welding (TIG/GTAW) with pure argon (Ar) shielding gas. Weld procedures follow ASME Section IX qualification standards. Internal purge with high-purity argon during welding prevents oxidation and ensures clean weld beads.
- Stress Relief Annealing: The formed coil is subjected to a controlled annealing cycle (typically 1050°C – 1150°C, followed by rapid water quench) to relieve residual stresses from cold forming and restore full solution-treated properties.
- Pickling & Passivation: The coil is immersed in a citric acid or nitric acid-based passivation solution to remove scale, restore the passive chromium oxide film, and enhance corrosion resistance.
- Electropolishing (Optional): For pharmaceutical-grade applications, the coil undergoes electropolishing to achieve a surface roughness of Ra ≤ 0.4 μm, removing micro-crevices that could harbor microbial contamination.
- Non-Destructive Testing (NDT): Each coil unit is subjected to helium leak testing (leak rate ≤ 1 × 10⁻⁹ mbar·L/s) and hydrostatic pressure testing at 1.5 MPa to verify weld integrity and structural soundness.
- Final Cleaning & Packaging: The coil is cleaned with deionized water, dried with compressed filtered air, and packaged in protective polyethylene wrapping with desiccant to prevent contamination prior to shipment.
Applications
The stainless steel coil tube is a core component in freeze dryer cold trap systems across multiple industries:
- Pharmaceutical Freeze-Drying: Captures water vapor sublimated during lyophilization of biologics, vaccines, antibiotics, and sterile formulations. The hygienic surface finish prevents product contamination and meets GMP requirements.
- Biotechnology: Used in cold traps for cell culture media, protein solutions, and enzyme preparation freeze-drying processes.
- Food Processing: Applied in freeze-drying of fruits, vegetables, coffee, and instant food products, where large-scale vapor capture is required.
- Chemical & Petrochemical: Employed in vacuum systems to capture condensable vapors and protect vacuum pumps from moisture ingress.
- Spacecraft & Aerospace: Utilized in humidity control systems for spacecraft environmental life support.
- Research & Laboratory: Integrated into laboratory-scale freeze dryers for research and development of novel freeze-drying protocols.
Unique Selling Points
- Optimized Frost Capture Geometry: The helical coil design maximizes the effective condensation surface area, enabling efficient frost formation even at low vapor flow rates. Research on frost characteristics (《冻干机冷阱盘管表面结霜特性的研究》) has informed the coil pitch and diameter selection to promote uniform frost layer growth and prevent premature frost bridging.
- Cryogenic Reliability: The austenitic stainless steel construction ensures no loss of mechanical properties at sub-zero temperatures, eliminating the risk of brittle fracture common in carbon steel alternatives.
- Hygienic & GMP-Compliant: Electropolished surfaces with Ra ≤ 0.4 μm meet the stringent cleanliness requirements of pharmaceutical and food-grade freeze-drying operations.
- Custom Engineering: Wenzhou Jixing Metal Materials Co., Ltd offers fully customizable coil dimensions, materials, and end connections to match specific freeze dryer cold trap configurations.
- Long Service Life: Corrosion-resistant material and passivation treatment ensure extended operational life under repeated thermal cycling and humid conditions.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European Machinery Directive (2006/42/EC) and Pressure Equipment Directive (PED 2014/68/EU)
- Material Certifications: Mill test certificates (MTC) per EN 10204 3.1 for each batch of raw material
- Welding Procedure: Welding Procedure Specification (WPS) and Procedure Qualification Record (PQR) per ASME Section IX
- Hygienic Compliance: 3-A Sanitary Standards, EHEDG guidelines, FDA 21 CFR Part 177/178
- Pharmaceutical Compliance: Suitable for GMP (Good Manufacturing Practice) environments; compatible with EU GMP Annex 1 requirements for aseptic processing
- Material Standards: ASTM A270 (seamless stainless steel tube), ASTM A312 (seamless and welded austenitic stainless steel tubing), GB/T 12771 (Chinese national standard for seamless stainless steel tubes)
Technical Note: The performance of the freeze dryer cold trap coil tube is significantly influenced by frost characteristics on its surface. Studies have demonstrated that factors including coil surface roughness, tube diameter, pitch spacing, and coolant flow rate directly affect frost nucleation density, growth rate, and adherence strength. Wenzhou Jixing Metal Materials Co., Ltd incorporates these research findings into the coil tube design and manufacturing process to deliver optimal frost capture efficiency and reliable long-term operation in freeze-drying applications.