Stainless Steel Coil Tube for Ultra-High Temperature Sterilization Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component designed specifically for fully automatic coil-type ultra-high temperature sterilization (UHT) machines. This product represents a critical heat-exchange element within industrial sterilization systems, where continuous, reliable thermal transfer is essential for achieving microbiological safety in liquid food products, pharmaceuticals, and medical solutions. The coil tube configuration maximizes surface-area-to-volume ratio, enabling efficient heat exchange between the process medium and the sterilizing agent under extreme thermal conditions.
Unlike conventional straight-tube heat exchangers, the coiled geometry provides superior turbulent flow characteristics, reduced fouling tendency, and compact footprint, making it the preferred solution for high-throughput sterilization lines operating at temperatures exceeding 135 °C (275 °F).
Material and Properties
The coil tube is fabricated from austenitic stainless steel grades, primarily SUS316L (UNS S31603) and SUS304 (UNS S30408), selected for their exceptional resistance to corrosion, pitting, and crevice attack under aggressive sterilization conditions. The 316L grade, with its added molybdenum (Mo) content of 2.0–2.5 wt%, provides superior resistance to chloride-induced stress corrosion cracking (SCC), making it ideal for applications involving acidic or saline process fluids.
- Alloying Elements: Chromium (Cr) 16.0–18.0%, Nickel (Ni) 10.0–14.0%, Molybdenum (Mo) 2.0–2.5% (for 316L)
- Carbon Content: ≤ 0.03% (L-grade, low carbon) to prevent intergranular corrosion during high-temperature exposure
- Operating Temperature Range: −196 °C to 870 °C (continuous); intermittent exposure up to 135 °C (275 °F) at pressures up to 6.0 MPa
- Surface Finish: Electropolished or mechanically polished to Ra ≤ 0.4 μm for hygienic and sanitary applications
- Mechanical Properties: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40%
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Outer Diameter (OD) | Φ6 – Φ38 (customizable) | mm |
| Wall Thickness | 0.5 – 2.0 | mm |
| Coil Diameter | 100 – 800 | mm |
| Tube Length (developed) | 5 – 100 (customizable) | m |
| Coil Pitch | 10 – 50 | mm |
| Number of Turns | 5 – 200 | — |
| Maximum Operating Pressure | 6.0 (design); 8.0 (test) | MPa |
| Maximum Operating Temperature | 150 | °C |
| Material Grade | SUS316L / SUS304 / SUS321 / SUS310S | — |
| End Connections | Tri-Clamp, Weld-end, Flanged, Threaded | — |
| Surface Treatment | Electropolished / Passivated | — |
| Manufacturing Standard | ASTM A269 / ASTM A270 / GB/T 12771 | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage process to ensure dimensional accuracy, mechanical integrity, and hygienic surface quality:
- Material Selection and Inspection: Virgin stainless steel strip or seamless tubing is sourced from certified mills, accompanied by mill test certificates (MTC) verifying chemical composition and mechanical properties per ASTM E415 (spark OES) and ASTM A923 (spectrographic analysis).
- Coiling/Forming: Precision CNC coiling machines wind the straight tube into the specified helical geometry with controlled coil diameter, pitch, and turn count. The coiling process maintains cold-worked properties without inducing residual stress concentrations.
- Welding (if applicable): Butt-welded joints are performed using orbital TIG (Tungsten Inert Gas) welding per ASME BPVC Section VIII, with 100% radiographic inspection (RT) or ultrasonic testing (UT) of weld seams.
- Heat Treatment and Stress Relief: Solution annealing at 1050–1100 °C followed by rapid quenching to restore full austenitic structure and relieve cold-work hardening.
- Surface Finishing: Electropolishing removes the top 25–50 μm of material, eliminating surface contamination and achieving a mirror-like finish (Ra ≤ 0.4 μm). Chemical passivation with nitric acid or citric acid solutions forms a stable chromium oxide layer.
- Hydrostatic Testing: Each coil assembly undergoes 100% hydrostatic pressure testing at 1.5× the design pressure to verify leak-tightness and structural soundness.
- Final Inspection and Packaging: Dimensional verification via CMM (Coordinate Measuring Machine), visual inspection, and protective packaging with desiccant for shipment.
Applications
The stainless steel coil tube for UHT sterilization systems finds extensive application across multiple industries:
- Food and Beverage Industry: UHT processing of dairy products (milk, cream, yogurt), fruit juices, plant-based beverages, and soups, where the coil tube serves as the heating/cooling section of the sterilization heat exchanger.
- Pharmaceutical Industry: Sterilization of injectable solutions, oral liquids, and parenteral preparations requiring validated thermal processing at 121–135 °C.
- Medical Devices: Heat treatment and sterilization of medical fluids, reagents, and diagnostic solutions.
- Chemical Processing: High-temperature heat exchange in corrosion-resistant process lines involving aggressive chemical media.
- Biotechnology: Bioreactor ancillary systems, enzyme solution sterilization, and media preparation equipment.
Unique Selling Points
- Optimized Helical Geometry: Engineered coil pitch and diameter ratios maximize turbulence and heat-transfer coefficient (U-value), achieving energy efficiency gains of 15–25% over straight-tube configurations.
- Low Carbon L-Grade Construction: The use of SUS316L ensures resistance to sensitization and intergranular corrosion during prolonged high-temperature exposure, extending service life beyond 10 years under continuous operation.
- Hygienic Design Compliance: Electropolished surfaces meet EHEDG (European Hygienic Engineering Design Group) and 3-A (Three-A Sanitary Standards) requirements for food-grade applications.
- Customizable Configurations: Flexible design parameters (OD, wall thickness, coil diameter, number of turns) allow tailoring to specific process requirements and equipment integration needs.
- Full Traceability: Each coil tube batch is accompanied by comprehensive documentation including material certificates, process records, and test reports ensuring full quality traceability.
Quality Certifications and Standards
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system aligned with international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Design and manufacture of pressure-containing equipment |
| ISO 14001:2015 | Environmental Management System |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance for Category II/III pressure vessels |
| ASME Section VIII Div. 1 | American Society of Mechanical Engineers — Boiler and Pressure Vessel Code |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects certification |
| 3-A Sanitary Standards | Dairy and Food Equipment — Hygienic design verification |
| ASTM A269 / A270 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing |
| GB/T 12771 | Chinese National Standard — Stainless Steel Seamless Tubes for General Purposes |
Note: All products are manufactured under a documented Quality Assurance (QA) and Quality Control (QC) program with in-process inspections at critical stages. Non-conforming products are segregated, documented, and dispositioned per the established corrective and preventive action (CAPA) procedure. Customers may request witness testing or third-party inspection (e.g., SGS, BV, TÜV) at any production stage.