316L Electropolished Stainless Steel Coil Tube for WFI Distribution Loops
Product Overview
The 316L Electropolished Stainless Steel Coil Tube is a precision-engineered piping solution purpose-built for Water for Injection (WFI) distribution loops in the biopharmaceutical industry. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube is designed to maintain the highest levels of water purity, sterility, and process integrity throughout complex WFI recirculation systems. The product meets the stringent requirements of ASME BPE (Bioprocessing Equipment) standards and is fully qualified for use in sterile pharmaceutical water distribution networks where microbial control, endotoxin elimination, and total organic carbon (TOC) management are critical to patient safety and regulatory compliance.
Unlike conventional tubing solutions, this coil tube is engineered from the outset to address the unique challenges of WFI loop applications, including continuous recirculation flow dynamics, thermal cycling, and the need for complete drainage to prevent stagnant zones where biofilm formation could compromise water quality.
Material & Properties
The coil tube is fabricated from ASTM A270 316L (UNS S31603) austenitic stainless steel, the gold standard material for pharmaceutical and bioprocessing applications. The addition of molybdenum (2.0–2.5%) to the 316L alloy provides exceptional resistance to pitting and crevice corrosion in the presence of chlorides and other aggressive ions that may be encountered in WFI systems.
- Base Material: 316L (Low Carbon) Austenitic Stainless Steel — ASTM A270 / ASME SA-270
- Carbon Content: ≤ 0.03% (reduces carbide precipitation and sensitization risk during welding)
- Chromium Content: 17.0–18.5% — provides robust passive film formation and general corrosion resistance
- Nickel Content: 10.0–14.0% — ensures excellent ductility and oxidation resistance
- Molybdenum Content: 2.0–2.5% — enhances pitting and crevice corrosion resistance
- Surface Finish: Electropolished (EP) to ASME BPE SF4 grade — Ra ≤ 0.38 μm
- Operating Temperature Range: Ambient to 120°C (continuous); up to 150°C (intermittent)
- Pressure Rating: Designed for typical WFI loop operating pressures up to 6 bar (g)
Specifications
| Parameter | Specification |
|---|---|
| Material Grade | 316L (ASTM A270 / ASME SA-270), EP finish |
| Product Form | Coil Tube (Continuous Coil) |
| Surface Roughness (Ra) | ≤ 0.38 μm (ASME BPE SF4) |
| Design Standard | ASME BPE (Bioprocessing Equipment) |
| Endotoxin Level | < 0.25 EU/mL |
| Total Organic Carbon (TOC) | < 500 ppb |
| Sterility | Sterile (validated by pyrogen-free sterilization) |
| Recommended Installation Slope | ≥ 1:100 (for complete drainage and no dead legs) |
| Welding Compatibility | Orbital TIG (GTAW) welding — BPE-compliant welds |
| Typical Outer Diameter Range | DN15 – DN100 (per customer requirement) |
| Coil Length | Customizable per project requirement |
| End Treatment | Beveled ends per ASME BPE (60° included angle) |
| Traceability | Full heat number traceability and material certification |
Manufacturing Process
The manufacturing process for this coil tube follows a tightly controlled, multi-stage procedure designed to ensure the final product meets the exacting standards required for WFI applications:
- Material Selection & Inbound Inspection: Only certified 316L stainless steel seamless tubing from qualified mills is accepted. Each incoming lot undergoes full chemical composition analysis and mechanical property verification against ASTM A270 specifications.
- Coil Forming: The straight seamless tube is cold-formed into precise coil geometry using high-precision roll-forming equipment. The forming process is carefully controlled to prevent work hardening, surface deformation, or residual stress that could compromise the final surface finish or mechanical integrity.
- Internal Cleaning & Passivation: The coil tube undergoes thorough internal chemical cleaning to remove all mill scale, oils, and contaminants. An acid pickling and passivation treatment establishes a uniform chromium oxide passive film on the internal surface, critical for corrosion resistance and low endotoxin release.
- Electropolishing (EP): The tubing is subjected to precision electropolishing to achieve the ASME BPE SF4 surface finish of Ra ≤ 0.38 μm. This process removes up to 25–50 μm of surface material, eliminating micro-pores, inclusion sites, and surface irregularities that could harbor microorganisms or leach organic compounds into the WFI stream.
- End Beveling: Tube ends are precision-beveled to a 60° included angle with a burr-free, polished finish to ensure clean, leak-tight orbital weld joints compliant with ASME BPE welding requirements.
- Final Cleaning & Packaging: The finished coil tube undergoes a final clean using pharmaceutical-grade reagents, followed by inspection, protective capping of tube ends, and packaging in clean, moisture-protected materials to maintain surface integrity until installation.
Applications
This 316L EP coil tube is specifically engineered for the following critical biopharmaceutical and pharmaceutical water system applications:
- WFI Distribution Loops: Primary recirculation loops for Water for Injection systems in pharmaceutical manufacturing facilities, ensuring continuous water quality through dynamic recirculation at slopes ≥ 1:100.
- WFI Storage Tanks & Loop Interconnections: Tubing connecting WFI storage vessels, heat exchangers, and purification units within the WFI system architecture.
- Purified Water (PW) Systems: Upstream distribution loops for Purified Water systems feeding WFI generators.
- Steam Systems: High-purity steam distribution for sterilization and clean steam applications in pharmaceutical cleanrooms.
- Bioprocessing Piping: Process piping for bioreactor loops, fermentation systems, and downstream purification train interconnections.
- Injectable Drug Manufacturing: Direct-contact piping for sterile injectable drug product processing where endotoxin and TOC control are paramount.
- Biotechnology & Cell Therapy: Distribution systems in advanced cell and gene therapy manufacturing facilities.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring full regulatory and industry-standard compliance:
- ASME BPE Compliance: Full compliance with ASME BPE (Bioprocessing Equipment) standards for material, surface finish, welding, and fabrication practices.
- ISO 9001: Certified quality management system ensuring consistent product quality and process control.
- ISO 13485: Quality management system for medical devices applicable to pharmaceutical equipment components.
- EHEDG Guidelines: Design and construction in accordance with European Hygienic Engineering and Design Group guidelines for food and pharmaceutical equipment.
- 3-A Sanitary Standards: Compliance with 3-A sanitary standards for dairy, food, and pharmaceutical processing equipment.
- Material Certifications: Full EN 10204 3.1 mill certificates provided for every batch, including chemical composition, mechanical properties, and heat number traceability.
- Pyrogen-Free: All product batches are validated as pyrogen-free (endotoxin < 0.25 EU/mL) through validated analytical testing.
- TOC Compliance: Verified Total Organic Carbon levels < 500 ppb through validated headspace GC or combustion TOC analysis.
- CE Marking: Available for products intended for the European market under applicable directives.
- Full Traceability: Each coil tube is serialized with a unique batch identifier, enabling complete traceability from raw material mill certificate through to final delivery and installation documentation.
Key Selling Points
- Ultra-Low Surface Roughness: Ra ≤ 0.38 μm electropolished finish minimizes microbial adhesion, biofilm formation, and particulate leaching — critical for maintaining WFI water quality.
- Validated Purity Performance: Endotoxin levels < 0.25 EU/mL and TOC < 500 ppb ensure the tubing does not introduce contaminants into the WFI stream, meeting USP <1231> and EP 2.2.44 requirements.
- ASME BPE SF4 Certified: Full compliance with the internationally recognized bioprocessing equipment standard, reducing qualification burden during facility validation.
- Optimized Drainage Design: Coil geometry supports installation at slopes ≥ 1:100, eliminating dead legs and stagnant zones that could compromise water quality through microbial growth.
- Superior Corrosion Resistance: 316L low-carbon grade with molybdenum alloying provides long-term reliability in chloride-containing and thermally cycling WFI environments.
- Welding-Ready End Preparation: Precision 60° beveled ends ensure BPE-compliant orbital weld joints with minimal heat-affected zone and preserved surface finish at weld seams.
- Full Documentation Package: Comprehensive delivery documentation including material certificates, surface finish reports, endotoxin and TOC test results, and installation recommendations to streamline regulatory audits.