Pasteurizer Heat Exchanger Coil Tube — 316L Sanitary-Grade Stainless Steel
Product Overview
The Pasteurizer Heat Exchanger Coil Tube is a precision-engineered stainless steel coil tube specifically designed for direct-contact and indirect-contact heat exchange systems in dairy pasteurization processes. This product addresses the critical thermal processing requirements of liquid milk, where temperatures of 72–85 °C are maintained for a minimum holding time of 15 seconds to achieve effective microbial inactivation while preserving the organoleptic and nutritional quality of the product.
Developed and manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube is engineered to overcome the persistent challenge of proteolytic fouling (protein scaling) that occurs during pasteurization. Whey proteins — particularly β-lactoglobulin and α-lactalbumin — denature and deposit on heated surfaces, progressively reducing heat transfer efficiency and posing food safety risks. The turbulent flow design integrated into this coil tube geometry actively mitigates boundary-layer accumulation, ensuring sustained thermal performance throughout extended production cycles.
Material & Properties
The coil tube is fabricated from AISI 316L (UNS S31603) sanitary-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, hygienic surface characteristics, and mechanical integrity under repeated thermal cycling.
- Chemical Composition: Maximum carbon content of 0.03% (L-grade), 2–3% molybdenum (Mo), 16–18% chromium (Cr), and 10–14% nickel (Ni), providing superior resistance to pitting and crevice corrosion in chloride-containing dairy environments.
- Surface Roughness: Electropolished to a surface roughness of Ra ≤ 0.8 μm (Arithmetic Mean Surface Roughness), meeting and exceeding the requirements of 3-A Sanitary Standards and EU Directive 1935/2004/EC for food-contact surfaces.
- Weld Integrity: Fully welded construction with internal mirror-polished weld seams, eliminating dead zones and crevices where microbial biofilm can develop.
- Temperature Range: Suitable for continuous operation at temperatures from −40 °C to +400 °C, with optimal performance in the pasteurization window of 72–85 °C.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name | Pasteurizer Heat Exchanger Coil Tube |
| Material Grade | AISI 316L (UNS S31603) — Sanitary-Grade Welded Pipe |
| Surface Finish | Electropolished, Ra ≤ 0.8 μm (internal and external) |
| Operating Temperature | 72–85 °C (pasteurization range) |
| Minimum Holding Time | 15 seconds (HTST — High Temperature Short Time) |
| Flow Design | Turbulent flow configuration (Reynolds number Re > 4000) for anti-fouling performance |
| Welding Method | Orbital TIG (GTAW) with back-purging (Argon/Nitrogen) |
| Applicable Standards | ASTM A270, EN 10216-5, 3-A Sanitary Standards, ASME BPE |
| Anti-Fouling Feature | Geometric coil configuration promoting secondary flow and vortex generation |
| End Connections | Tri-Clamp (TC), Sanitary Threaded, or Weld End (customizable) |
Manufacturing Process
The production of this sanitary coil tube follows a rigorous, multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical quality, and hygienic surface integrity:
- Material Selection & Inspection: Certified 316L stainless steel seamless or welded pipe stock is received with full mill test certificates (MTC) per EN 10204 Type 3.1. Incoming material undergoes spectroscopic verification (PMI — Positive Material Identification) to confirm alloy composition.
- Pipe Forming & Coil Winding: Precision cold-forming equipment shapes the pipe into the specified coil geometry. The winding process is controlled to maintain consistent coil diameter, pitch, and number of turns, ensuring uniform flow distribution and optimal turbulent flow characteristics.
- Orbital TIG Welding: All weld joints are executed using automated orbital Gas Tungsten Arc Welding (GTAW) with continuous inert gas back-purging. This eliminates internal oxidation and ensures a smooth, crevice-free weld bead.
- Acid Pickling & Passivation: Welded assemblies undergo hydrofluoric/nitric acid pickling to remove heat-affected zone discoloration and chromium-depleted layers, followed by passivation treatment to restore the protective chromium oxide film.
- Electropolishing: Internal and external surfaces are electropolished to achieve Ra ≤ 0.8 μm. This process removes microscopic surface irregularities, eliminates dead zones, and enhances the passive film stability of the 316L surface.
- Final Cleaning & Inspection: Coils are cleaned using potable-grade water and food-safe detergents. Non-destructive testing (NDT) — including dye penetrant inspection (DPI) and borescope examination — verifies weld integrity and surface quality.
Applications
This coil tube is purpose-engineered for the following applications within the dairy processing industry:
- HTST Pasteurization Systems: Serving as the core heat exchange element in plate-and-frame or tubular pasteurizers operating at 72–85 °C with a 15-second minimum hold time, ensuring compliance with FDA 21 CFR 1240 and EU Regulation 853/2004.
- Regenerative Heat Recovery: Utilized in the regeneration section of pasteurizers to pre-heat incoming raw milk against outgoing pasteurized product, improving energy efficiency by up to 90%.
- Cooling Sections: Deployed in the cooling stage to rapidly bring pasteurized milk below 4 °C, inhibiting post-pasteurization microbial growth.
- Ultra-High Temperature (UHT) Pre-Heating: Applicable in pre-heating circuits for UHT processing lines where temperatures approach 135–150 °C.
Key Design Advantage: The turbulent flow configuration — achieved through the coil geometry and internal surface finish — generates secondary Dean vortices that continuously disrupt the thermal boundary layer. This prevents the deposition of denatured whey proteins on the tube wall, reducing fouling rates by up to 60% compared to conventional straight-tube designs and significantly extending clean-in-place (CIP) intervals.
Quality Certifications & Compliance
The Pasteurizer Heat Exchanger Coil Tube is manufactured under a certified quality management system and complies with the following international standards and regulations:
- ISO 9001:2015 — Quality Management Systems certification for manufacturing processes.
- ISO 14001:2015 — Environmental Management Systems compliance.
- 3-A Sanitary Standards (American Dairy Association) — Design and construction standards for dairy equipment.
- ASME BPE (Bioprocessing Equipment) — Guidelines for process equipment in the pharmaceutical and food industries.
- EU Regulation 1935/2004/EC — Framework regulation on materials and articles intended to come into contact with food.
- EU Regulation 10/2011 — Specific migration limits and material requirements for stainless steel food-contact articles.
- FDA 21 CFR 184 & 178.3010 — U.S. Food and Drug Administration requirements for food-contact materials.
- NSF/ANSI 61 — Drinking water system components certification (where applicable for CIP water circuits).
Each production batch is accompanied by a comprehensive documentation package including Mill Test Certificates (MTC), weld traceability records, surface roughness measurement reports, and dimensional inspection certificates, ensuring full traceability and regulatory compliance throughout the product lifecycle.