316L Sanitary Stainless Steel Coil Tube for Dairy CIP Cleaning Loops
Product Overview
The 316L sanitary stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is purpose-engineered for Clean-In-Place (CIP) cleaning circuits within the dairy processing industry. These coil tubes are designed to withstand the rigorous and repetitive exposure to alternating alkaline and acidic cleaning solutions at elevated temperatures, ensuring long-term structural integrity and hygienic performance in critical dairy processing environments.
CIP systems are the backbone of dairy sanitation, requiring piping components that can endure aggressive chemical cycling without degradation. This coil tube product is specifically formulated to handle the standard dairy CIP protocol—alternating between sodium hydroxide (NaOH) at 1–2% concentration and nitric acid (HNO₃) at 0.5–1% concentration, operating at temperatures ranging from 70°C to 80°C (158°F–176°F).
Unique Selling Points
- Exceptional Chemical Resistance: 316L grade with low carbon content provides superior resistance to pitting and crevice corrosion under alternating acid-alkali attack, outperforming standard 304L in chlorinated and nitric acid environments.
- Hygienic Weld Finish: All welds are ground and polished to a smooth, crevice-free surface (Ra ≤ 0.5 μm), eliminating bacterial harborage points and facilitating complete CIP drainage.
- Coil Form Efficiency: Delivered in coil configuration to minimize installation labor, reduce weld joints, and accelerate system assembly for large-scale dairy processing lines.
- Temperature Resilience: Maintains mechanical and corrosion resistance properties at sustained operating temperatures of 70–80°C, avoiding sensitization or intergranular corrosion risks.
- Low Carbon Stabilization: The "L" (low carbon) designation limits carbon content to ≤ 0.03%, preventing chromium carbide precipitation during thermal cycling and preserving the passive film integrity.
Material & Properties
Base Material: ASTM A270 / ASTM A312 — Type 316L
Type 316L austenitic stainless steel is the industry-preferred alloy for dairy and pharmaceutical applications due to its enhanced molybdenum content (2.0–2.5%), which provides critical resistance to chloride-induced pitting and acid corrosion encountered during CIP cycling.
- Chemical Composition (wt%):
- Carbon (C): ≤ 0.03%
- Chromium (Cr): 17.0–18.5%
- Nickel (Ni): 12.0–14.0%
- Molybdenum (Mo): 2.0–2.5%
- Nitrogen (N): ≤ 0.10%
- Iron (Fe): Balance
- Mechanical Properties:
- Tensile Strength: ≥ 485 MPa (≥ 70 ksi)
- Yield Strength (0.2% offset): ≥ 170 MPa (≥ 25 ksi)
- Elongation: ≥ 40%
- Hardness: ≤ 217 HB
- Corrosion Performance:
- Pitting Resistance Equivalent Number (PREN): 24–26
- Resistance to 1–2% NaOH at 80°C: Excellent
- Resistance to 0.5–1% HNO₃ at 80°C: Excellent
- Resistance to 3% NaCl solution: Superior
- Surface Finish:
- Internal Surface: Electropolished or mechanical polished, Ra ≤ 0.5 μm (≤ 0.00002 in)
- External Surface: 2B or No. 4 finish, Ra ≤ 1.0 μm
- Weld Finish: Ground smooth, Ra ≤ 0.5 μm, no crevices
Specifications
| Parameter | Specification |
|---|---|
| Material Grade | 316L (UNS S31603 / 1.4404) |
| Product Form | Coil Tube (continuous coil) |
| Manufacturing Method | Seamless or welded (per ASTM A270 / ASME BPE) |
| Outer Diameter Range | 6.35 mm – 101.6 mm (¼ in – 4 in) |
| Wall Thickness Range | 0.5 mm – 3.0 mm (0.020 in – 0.118 in) |
| Coil Length | Up to 200 m (656 ft) per coil |
| Surface Finish (Internal) | Electropolished, Ra ≤ 0.5 μm (0.00002 in) |
| Surface Finish (External) | 2B / No. 4 brushed, Ra ≤ 1.0 μm |
| Weld Surface Treatment | Ground and polished smooth, Ra ≤ 0.5 μm |
| Operating Temperature | −196°C to +450°C (−321°F to +842°F) |
| CIP Operating Conditions | 70–80°C (158–176°F), NaOH 1–2% / HNO₃ 0.5–1% |
| Pressure Rating | Up to 1.6 MPa (232 psi) typical (per EN 10217-7) |
| End Treatment | Plain, beveled, or threaded per customer specification |
| Standards Compliance | ASTM A269, ASTM A270, ASME BPE, EN 10217-7, 3-A |
Manufacturing Process
- Raw Material Selection: Virgin 316L austenitic stainless steel billets or strip are sourced from certified mills, verified through mill test reports (MTR) for full chemical and mechanical compliance.
- Hot Rolling / Cold Drawing: Seamless tubes are produced via piercing and hot rolling, followed by cold drawing to achieve precise dimensional tolerances. Welded alternatives utilize precision TIG welding on cold-rolled strip.
- Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1050–1100°C (1922–2012°F) followed by controlled quenching to restore full austenitic structure, eliminate residual stresses, and maximize corrosion resistance.
- Pickling and Passivation: Pickled in a mixed acid solution (nitric + hydrofluoric acid) to remove oxide scale, followed by passivation with dilute nitric acid to establish a stable chromium oxide passive film.
- Internal Surface Polishing: Electropolishing or mechanical rotary polishing is applied to achieve a mirror-like internal surface with Ra ≤ 0.5 μm, critical for preventing product retention and bacterial adhesion.
- Weld Finishing: All longitudinal and circumferential welds are ground flush and polished to eliminate crevices, ensuring smooth flow and complete CIP drainage. Weld quality is verified by visual inspection and, where applicable, dye penetrant testing.
- Coiling: Finished tubes are carefully coiled using precision winding equipment to prevent mechanical damage, surface scratches, or dimensional distortion. Coils are wrapped in protective film and secured for shipment.
- Final Inspection: Each coil undergoes dimensional verification, surface finish measurement (profilometer), chemical composition analysis (spectrometer), and hydrostatic pressure testing before release.
Applications
Primary Application: Dairy CIP Cleaning Systems
This coil tube is specifically designed for integration into CIP (Clean-In-Place) circuits in dairy processing facilities, where it serves as the primary conduit for circulating cleaning solutions through milk processing equipment, holding tanks, pasteurizers, and distribution lines.
- CIP Concentrate Circulation: Transporting NaOH (1–2%) alkaline solution for organic matter removal and HNO₃ (0.5–1%) acid solution for mineral deposit elimination at 70–80°C.
- Hot Water Rinse Loops: High-temperature rinse circuits operating at 70–80°C between chemical cleaning stages.
- Sanitizer Distribution: Delivery of final sanitizing agents (e.g., peracetic acid, chlorine dioxide) to processing equipment.
Additional Applications
- Dairy pasteurization and UHT processing piping
- Milk storage tank circulation and drain systems
- Cheese and yogurt production equipment
- Beverage processing (juice, soft drink) CIP systems
- Pharmaceutical and bioprocessing clean loops
- Food-grade heat exchanger tubing
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications and compliance credentials:
- ISO 9001:2015 — Quality Management System
- ISO 14001 — Environmental Management System
- ISO 22000 / HACCP — Food Safety Management (for food-grade products)
- 3-A Sanitary Standards — Compliant with 3-A International Food Industry Sanitation Standards
- ASME BPE — Bioprocessing Equipment guidelines compliance
- CE Marking — European conformity for pressure equipment
- Mill Test Reports (MTR) — Provided with every shipment per EN 10204 Type 3.1
- NADCAP / PED Compliance — Available upon request for regulated applications
All products are traceable through batch/heat numbers from raw material through final delivery, ensuring complete supply chain accountability and facilitating customer quality audits.
Technical Notes
Important: For optimal CIP performance, ensure all tube joints and fittings maintain equivalent surface finish (Ra ≤ 0.5 μm internal). Any surface roughness discontinuity can create dead legs that compromise cleaning efficacy. Recommend regular inspection of weld areas for early signs of crevice corrosion, particularly at weld-to-base metal transitions. Maintain passivation integrity by avoiding contact with carbon steel tools during installation.
Order Reference: Product No. 149 — Coil Tube for Dairy CIP Cleaning Loops | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.