316L EP Coil Tube for Chromatography & Ultrafiltration System Piping
Product Overview
The 316L EP Coil Tube is a precision-engineered stainless steel tubing product specifically designed for process material transfer within chromatography and ultrafiltration (UF) systems in the biopharmaceutical industry. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube is engineered to meet the stringent demands of biologics processing, where chemical compatibility across a wide pH range (pH 2–12), minimal protein adsorption, and electrical conductivity compatibility are critical performance parameters.
Unlike conventional stainless steel tubing, this product is manufactured to Electropolished (EP) surface finish standards, providing a smooth, chemically inert interior that minimizes protein adsorption and biofilm formation. The coil configuration facilitates flexible routing and installation within complex bioprocessing skids, CIP (Clean-In-Place) systems, and skid-mounted chromatography units.
Material & Properties
The coil tube is fabricated from ASTM A270 / AMS 5511 Grade 316L (UNS S31603) austenitic stainless steel. The low-carbon designation ("L") ensures resistance to sensitization during welding and heat treatment processes, preventing chromium carbide precipitation at grain boundaries that could compromise corrosion resistance in aggressive buffer environments.
Key Material Characteristics:
- Low Protein Adsorption Surface: The electropolished surface achieves a Ra (Surface Roughness) of ≤0.25 μm, significantly reducing the surface area available for protein adhesion. This is critical in chromatography and ultrafiltration applications where protein loss to tubing walls directly impacts yield and purity.
- pH Compatibility (2–12): Fully compatible with acidic and alkaline buffer solutions used in protein purification workflows, including glycine-HCl (pH 2–3), sodium phosphate (pH 7), and NaOH (pH 12) for CIP cycles.
- Electrical Conductivity Compatibility: The material and surface finish do not introduce measurable ionic contamination, maintaining buffer conductivity within specification for conductivity-based monitoring and control systems.
- Chloride Ion Resistance: The 2–3% molybdenum content provides superior resistance to pitting and crevice corrosion in chloride-containing solutions (e.g., NaCl buffers, sanitizing solutions).
- Non-leaching: No trace metal contamination (Fe, Cr, Ni, Mo) above USP <641> limits, ensuring product safety for injectable biologics.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Material Grade | 316L (UNS S31603) / ASTM A270 TP316L | ASTM A270 / EN 10216-5 |
| Surface Finish (Internal) | Electropolished (EP), Ra ≤ 0.25 μm | ASTM A967 / ISO 14283 |
| Surface Finish (External) | Mechanically polished, Ra ≤ 0.4 μm | — |
| Available OD Sizes | 6 mm, 8 mm, 12 mm, 19 mm, 22 mm, 25 mm, 32 mm, 38 mm | ASME BPE / DIN 11850 |
| Wall Thickness | 1.0 mm – 3.0 mm (standard); custom available | — |
| Coil Diameter | 300 mm – 1,500 mm (configurable) | — |
| Coil Length | 5 m – 50 m per coil (standard); custom available | — |
| pH Compatibility | 2.0 – 12.0 (continuous exposure) | — |
| Maximum Operating Temperature | –40 °C to +200 °C | — |
| Maximum Operating Pressure | Up to 40 bar (depending on size/thickness) | ASME B31.3 |
| Sanitary Connection | Tri-Clamp (TC) / DIN 11850 / ISO 2852 | 3-A Sanitary Standards |
| Welding Standard | Orbital TIG (Tungsten Inert Gas) welding, 100% radiographic inspection | ASME BPE / ISO 15530 |
| Certification | Mill Test Certificate (MTC), EN 10204 3.1 | — |
Manufacturing Process
The production of this 316L EP Coil Tube follows a multi-stage process designed to ensure surface integrity, dimensional accuracy, and biocompatibility:
- Material Selection & Verification: Virgin 316L stainless steel seamless tubing is sourced from certified mills with full chemical and mechanical traceability (EN 10204 3.1 MTC). Incoming material is verified for chemical composition via XRF (X-Ray Fluorescence) and mechanical properties via tensile testing.
- Coil Forming: The straight tube is precision-formed into coil configuration using CNC-controlled coiling equipment to maintain dimensional tolerances and prevent surface damage or work hardening.
- Passivation: All coils undergo chemical passivation per ASTM A967 using nitric or citric acid solutions to form a uniform chromium oxide passive film, enhancing corrosion resistance and reducing metal ion release.
- Electropolishing (EP): The interior surface is electropolished using a phosphoric-acid-based electrolyte at controlled temperature and current density. This process removes micro-roughness, eliminates dead legs, and produces a surface Ra ≤ 0.25 μm — critical for minimizing protein adsorption in chromatography and ultrafiltration applications.
- Post-EP Cleaning & Passivation: Following electropolishing, coils are rinsed with deionized water and re-passivated to ensure the final surface is chemically stable and free of electrolyte residues.
- End Preparation & Fitting Installation: Tube ends are prepared for Tri-Clamp or DIN 11850 sanitary fittings via orbital TIG welding or compression fitting installation, ensuring leak-tight, cleanable joints.
- Final Inspection & Testing: Each coil undergoes visual inspection, dimensional verification, hydrostatic pressure testing, and optional endoscopic surface inspection to confirm EP quality throughout the entire length.
Applications
This coil tube is purpose-built for process material transfer in biopharmaceutical chromatography and ultrafiltration systems. Key application areas include:
- Chromatography System Piping: Buffer delivery lines, mobile phase transfer, and product elution lines in ion-exchange chromatography (IEX), affinity chromatography, and hydrophobic interaction chromatography (HIC) systems. The low protein adsorption surface ensures maximum recovery of therapeutic proteins, antibodies, and biologics.
- Ultrafiltration/Diafiltration (UF/DF) Systems: Feed and retentate lines in tangential flow filtration (TFF) processes for virus removal, buffer exchange, and concentration steps in bioprocessing.
- Buffer Preparation & Storage Lines: Transfer of acidic and alkaline buffer solutions (pH 2–12) used in column equilibration, washing, and elution steps without material degradation or contamination.
- CIP/COP Systems: Integration with Clean-In-Place (CIP) and Clean-Outside-Place (COP) systems, withstanding repeated cycles of NaOH (pH 12) and acidic sanitizing solutions.
- Conductivity Monitoring Loops: Compatible with inline conductivity sensors used for buffer concentration verification and process control, without introducing measurement interference.
- Downstream Processing (DSP) Skids: Modular installation in skid-mounted purification systems for monoclonal antibody (mAb), recombinant protein, and vaccine manufacturing.
Quality Certifications & Compliance
The 316L EP Coil Tube is manufactured and certified in compliance with the following international standards and regulatory requirements:
- ASME BPE (Bioprocessing Equipment): Design and construction in accordance with ASME BPE Section 5, covering surface finish, welding, and system design for bioprocessing.
- 3-A Sanitary Standards: Compliant with ANSI/3-A Sanitary Standards for materials of construction and design of sanitary equipment.
- EU GMP Annex 1: Suitable for use in cleanroom environments and aseptic processing areas per EU GMP Annex 1 (2022 revision) requirements for sterile manufacturing.
- USP <641>: Non-leachable trace metals, meeting United States Pharmacopeia limits for elemental impurities in pharmaceutical products.
- ISO 14283: Surface roughness and finish verification for electropolished tubing.
- EN 10204 3.1: Mill Test Certificate providing full chemical analysis, mechanical test results, and heat number traceability.
- GMP Compliance: Suitable for use in GMP-regulated manufacturing environments (FDA 21 CFR Part 210/211, EU GMP, PIC/S).
- REACH / RoHS: Compliant with EU regulations regarding restriction of hazardous substances.
Unique Selling Points
1. Ultra-Low Protein Adsorption: Electropolished Ra ≤ 0.25 μm surface finish minimizes protein binding losses, directly translating to higher yield in chromatography and ultrafiltration processes — a critical economic driver in biologics manufacturing.
2. Full pH Range Compatibility (2–12): Unlike standard 304 or 316 (non-L) tubing, the 316L EP grade withstands the full spectrum of buffer pH values encountered in multi-step purification workflows, including aggressive NaOH CIP cycles.
3. Conductivity-Neutral: Zero measurable contribution to solution conductivity, ensuring accurate inline process analytical technology (PAT) monitoring without sensor fouling or baseline drift.
4. Coil Configuration for Compact Installation: Pre-formed coil design reduces installation footprint, minimizes dead volume, and eliminates the need for multiple straight sections with additional fittings — reducing potential contamination points.
5. Full Traceability: Every coil ships with EN 10204 3.1 MTC, providing complete material provenance documentation essential for regulatory audits and quality system compliance.