Stainless Steel Coil Tube for Ultra-High Temperature (UHT) Sterilization Systems — Coiltube
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular component designed for integration into Ultra-High Temperature (UHT) sterilization systems, including both coil-type and scraper-type UHT sterilizers manufactured by industry-leading equipment providers such as Tetra Pak. This product serves as the primary heat exchange element within UHT processing lines, where rapid and uniform heat transfer is critical to achieving microbial inactivation while preserving the nutritional and sensory qualities of liquid food products.
Coil tubes leverage their inherently high surface-area-to-volume ratio to deliver superior thermal efficiency compared to conventional straight-tube heat exchangers. The continuous helical geometry promotes turbulent flow of the product stream, thereby enhancing the heat transfer coefficient and ensuring consistent sterilization performance across the entire processing volume. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube product is engineered to meet the rigorous demands of the dairy, beverage, and liquid food processing industries.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, mechanical integrity, and compliance with international food-grade hygiene standards. The primary material specifications are as follows:
- Material Grade: AISI 316L / 316L (UNS S31603) — preferred for high-purity food processing applications; AISI 304 (UNS S30403) available for less aggressive media.
- Chromium (Cr) Content: 16.5–18.5% — provides superior resistance to chloride-induced pitting and crevice corrosion.
- Nickel (Ni) Content: 10.0–14.0% — enhances structural stability and corrosion resistance in high-temperature environments.
- Molybdenum (Mo) Content: 2.0–3.0% — critical for resistance to UHT sterilization media and acidic food products.
- Carbon (C) Content: ≤ 0.03% (for 316L) — minimizes intergranular corrosion risk during welding and high-temperature exposure.
- Surface Finish: Electropolished or mechanically polished to a surface roughness (Ra) of ≤ 0.4 μm, meeting 3-A Sanitary Standards and EHEDG (European Hygienic Engineering Design Group) requirements.
- Operating Temperature Range: −40 °C to +150 °C (continuous); transient exposure up to 180 °C.
- Operating Pressure: Up to 0.6 MPa (6 bar) for standard configurations; custom ratings available upon request.
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | Φ 12 mm – Φ 50 mm (customizable) | ASME B36.19M |
| Tube Wall Thickness | 0.8 mm – 2.0 mm | ASTM A269 / ASTM A213 |
| Coil Mean Diameter (CMD) | Φ 200 mm – Φ 800 mm (customizable) | — |
| Coil Pitch (Helix Spacing) | 15 mm – 40 mm | — |
| Coil Length (Developed) | Up to 120 m per single coil assembly | — |
| Dimensional Tolerance (OD) | ± 0.05 mm | ISO 4783 |
| Dimensional Tolerance (Wall Thickness) | ± 5% | ASTM A269 |
| Helical Roundness Tolerance | ± 0.5 mm | — |
| End Connection Type | Sanitary Tri-Clamp, Socket Weld, or Flanged (ASME B16.11) | 3-A / ASME |
| Welding Process | Orbital TIG (Tungsten Inert Gas) welding with internal purge | ASME Section IX |
| Heat Transfer Coefficient | Enhanced by turbulent flow (Re > 10,000); up to 4,000 W/m²·K | — |
| Residence Time Control | Adjustable via coil geometry; typical range 4–30 seconds at 135–150 °C | — |
4. Manufacturing Process
The production of stainless steel coil tubes for UHT sterilization applications follows a multi-stage precision manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and hygienic surface quality:
- Raw Material Selection & Verification: Certified stainless steel seamless tubing (ASTM A269) is procured with full material traceability documentation, including mill test certificates (MTC) and positive material identification (PMI) verification via X-ray fluorescence (XRF) spectroscopy.
- Tube Straightening & Annealing: Raw tubing is mechanically straightened and solution-annealed at 1050–1100 °C followed by rapid water quenching to achieve a uniform austenitic microstructure free of residual stresses.
- Coil Forming (Cold or Hot): The tube is helically coiled using precision CNC-controlled forming equipment. Cold forming is employed for smaller diameters (≤ Φ 32 mm), while hot forming is utilized for larger diameters to prevent work-hardening and cracking. The helical geometry is maintained within tight tolerances to ensure consistent flow dynamics.
- Post-Forming Annealing: The formed coil undergoes stress-relief annealing at 850–900 °C to eliminate residual stresses introduced during the coiling process, ensuring dimensional stability during subsequent welding and operation.
- Hygienic Welding: All joints are fabricated using automated orbital TIG welding with internal inert gas (argon) purge to prevent oxidation of the weld root. Weld parameters are validated in accordance with ASME Section IX qualification procedures.
- Surface Finishing: The interior and exterior surfaces are subjected to mechanical polishing followed by electropolishing to achieve a surface roughness of Ra ≤ 0.4 μm. This process removes surface contaminants, eliminates micro-crevices, and enhances passive film stability.
- Pickling & Passivation: The finished coil tube is immersed in a nitric acid-based pickling and passivation solution to dissolve any residual heat-affected zone discoloration and to establish a stable, protective chromium oxide passive layer.
- Hygienic Cleaning & Inspection: Final cleaning is performed using food-grade detergents and potable water. Each coil tube undergoes 100% visual inspection, dimensional verification, and hydrostatic pressure testing at 1.5× the maximum operating pressure.
- Protective Packaging: Qualified coil tubes are wrapped in food-grade protective film and packaged in moisture-resistant containers to prevent contamination prior to shipment.
5. Applications
The Stainless Steel Coil Tube for UHT Sterilization Systems is engineered for deployment in the following critical applications:
- Coil-Type UHT Sterilizers: Serves as the primary heat exchange coil where the product is rapidly heated to sterilization temperatures (135–150 °C) and subsequently cooled. The helical geometry maximizes heat transfer area while minimizing residence time, ensuring effective sterilization with minimal product degradation.
- Scraper-Type UHT Sterilizers: Functions as the heated jacket or internal coil within scraper-type sterilizers, where mechanical agitation ensures uniform heat distribution for viscous or particulate-laden products such as condensed milk, fruit purees, and dairy creams.
- Dairy Processing: UHT treatment of milk, cream, yogurt base, and whey products for extended shelf-life distribution (6–12 months ambient storage).
- Plant-Based Beverage Processing: Sterilization of soy milk, oat milk, almond milk, and other plant-based beverages requiring UHT treatment for long shelf life.
- Infant Formula & Nutritional Products: Critical sterilization component in processing lines for infant formula, where the highest hygiene standards and precise thermal control are mandated.
- Condensed & Evaporated Milk Production: Integrated into evaporator and sterilizer systems for concentrated dairy products with high viscosity and solids content.
- Whey Protein & Dairy Ingredient Processing: UHT treatment of whey protein concentrate and isolate streams to ensure microbiological safety while preserving protein functionality.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring that every coil tube product meets or exceeds international standards for food-grade stainless steel components:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing processes and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification for sustainable production practices.
- 3-A Sanitary Standards (International Dairy Foods Association) — Certification for design and construction of dairy processing equipment components meeting the highest sanitary requirements.
- EHEDG Compliance (European Hygienic Engineering Design Group) — Design validation for hygienic equipment ensuring cleanability, drainage, and absence of dead legs.
- CE Marking — Conformity with European machinery and food-contact material directives.
- NSF/ANSI 61 — Certification for materials in contact with potable water and food products.
- ASTM A269 / ASTM A213 — Material compliance for seamless and welded austenitic stainless steel tubing.
- ASME BPE (Bioprocessing Equipment) — Applicable to pharmaceutical-grade and ultra-high-purity applications requiring enhanced surface quality and weld integrity.
- EU Regulation EC 1935/2004 & EC 1937/2004 — Compliance with European Union regulations on materials and articles intended to come into contact with food.
- GB 4806.9-2016 (China National Standard) — Compliance with Chinese national standards for food contact stainless steel materials.
7. Unique Selling Points
- Superior Heat Transfer Efficiency: The helical coil geometry generates inherently turbulent flow, achieving heat transfer coefficients up to 4,000 W/m²·K — significantly outperforming conventional straight-tube heat exchangers in UHT applications.
- Precision Dimensional Control: CNC-controlled coiling with ± 0.05 mm outer diameter tolerance ensures uniform flow distribution, predictable residence time, and consistent sterilization performance across the entire coil length.
- Full Hygienic Design: Electropolished surfaces (Ra ≤ 0.4 μm) with sanitary Tri-Clamp or flanged connections eliminate dead legs, minimize biofilm formation risk, and facilitate rapid Clean-in-Place (CIP) and Sterilize-in-Place (SIP) operations.
- Complete Traceability: Every coil tube is accompanied by a full material traceability package including mill test certificates, PMI verification reports, welding procedure qualifications (WPQ), welder performance qualifications (WPQ), and final inspection certificates.
- Custom Engineering Capability: Flexible customization of coil diameter, pitch, length, tube size, wall thickness, and connection type to integrate seamlessly with existing Tetra Pak and other OEM UHT sterilizer platforms.
- Proven UHT Application Heritage: Product development informed by in-depth study of Tetra Pak coil-type and scraper-type UHT sterilizer systems, ensuring application-specific performance optimization for the demanding requirements of UHT sterilization technology.
Note: All specifications listed in this document are representative values based on standard configurations. Custom engineering solutions are available upon submission of detailed application requirements. Wenzhou Jixing Metal Materials Co., Ltd reserves the right to refine manufacturing processes and specifications to enhance product performance without prior notice, provided that all applicable standards and certifications are maintained.