316L BA Coil Tube for Fermentation Tank Jacket — Biopharmaceutical Grade
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 145) presents a precision-engineered stainless steel coil tube (Coil Tube) specifically designed for the jacket and internal heat-exchange coil systems of biopharmaceutical fermentation tanks. This product is engineered to meet the rigorous demands of modern biological process engineering, where culture medium is maintained at controlled temperatures of 30–37 °C and subjected to frequent CIP (Clean-in-Place) and SIP (Sterilize-in-Place) cycles.
Product Overview
The fermentation tank jacket/coil tube is a critical component in upstream bioprocessing. It serves as the primary heat-transfer medium within or around the vessel, enabling precise thermal regulation of culture media during cell cultivation. In biopharmaceutical manufacturing, the coil tube must endure:
- Continuous thermal cycling between ambient conditions and sterilization temperatures (typically 121 °C for SIP at 0.1–0.2 MPa)
- Repeated chemical exposure from aggressive CIP agents including caustic soda (NaOH 1–2%), nitric acid (HNO₃ 1–3%), and sanitizing solutions
- Strict sanitary requirements to prevent microbial contamination of the culture medium
- Long-term fatigue resistance under hundreds of thermal shock cycles per production campaign
Material & Properties
Base Material: ASTM A269 TP316L / EN 1.4404 (00Cr17Ni14Mo2)
The coil tube is fabricated from 316L stainless steel — the industry-standard grade for biopharmaceutical and food-grade applications. The "L" designation denotes a low-carbon variant (C ≤ 0.03%), which significantly reduces the risk of intergranular corrosion during welding and thermal exposure. The addition of 2% molybdenum provides superior resistance to pitting and crevice corrosion, particularly in chloride-containing environments encountered during CIP operations.
Bright Annealed (BA) Surface Finish
The tube receives a Bright Annealed (BA) finish, achieved through controlled atmosphere annealing in a reducing or neutral atmosphere. This process produces a clean, oxide-free surface with excellent passivation characteristics, essential for:
- Minimizing bacterial adhesion and biofilm formation
- Ensuring uniform passivation layer development
- Providing a smooth surface that facilitates effective CIP cleaning
- Meeting FDA 21 CFR Part 210/211 and EU GMP Annex 1 requirements
Key Mechanical & Physical Properties
| Property | Specification |
|---|---|
| Material Grade | 316L (ASTM A269 / EN 1.4404) |
| Surface Finish | Bright Annealed (BA), Ra ≤ 0.8 μm |
| Tensile Strength | ≥ 515 MPa |
| Yield Strength (0.2% offset) | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Thermal Conductivity | 16.3 W/(m·K) at 300 K |
| Maximum Service Temperature | 870 °C (continuous) |
| Corrosion Resistance | Excellent — resistant to pitting, crevice, and intergranular corrosion |
| Thermal Shock Resistance | Withstands repeated cycling between 20 °C and 121 °C without cracking or deformation |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Coil Tube (盘管) for Fermentation Tank Jacket |
| Product No. | 145 |
| Application Category | Biopharmaceutical — Process Materials |
| Sub-Application | Fermentation Tank Jacket / Internal Coil |
| Process Temperature Range | 30–37 °C (culture medium maintenance) |
| SIP Temperature | Up to 121 °C @ 0.1–0.2 MPa |
| CIP Frequency | Multiple cycles per batch (frequent) |
| Material | 316L Stainless Steel, Bright Annealed |
| Surface Roughness (Ra) | ≤ 0.8 μm |
| Welding | Orbital TIG (Tungsten Inert Gas), argon back-purged |
| Weld Surface Finish | Polished to match tube body Ra ≤ 0.8 μm |
| Coil Diameter | Customizable (typically 15–60 mm tube OD, coil pitch 50–300 mm) |
| Tube OD × Wall Thickness | Customizable (common: 12×1.0 mm, 19×1.5 mm, 25×1.5 mm, 32×2.0 mm) |
| Heat-Transfer Medium | Hot water / steam / chilled glycol solution |
| Design Pressure | Up to 0.6 MPa (typical) |
| Design Life | ≥ 15 years under normal operating conditions |
Manufacturing Process
1. Material Selection & Incoming Inspection
Only certified 316L seamless tubes conforming to ASTM A269/A269M are accepted. Each batch undergoes chemical composition analysis (spectrographic verification), mechanical property testing, and surface condition inspection prior to processing.
2. Coil Forming
The straight tube is cold-formed into the required coil geometry using precision CNC-controlled coiling machinery. The forming process is designed to avoid excessive cold work that could compromise the material's corrosion resistance or induce residual stresses detrimental to thermal cycling performance.
3. Bright Annealing (BA) Treatment
After forming, the coil tube undergoes a bright annealing cycle in a controlled atmosphere furnace (hydrogen or argon atmosphere) at 1050–1100 °C followed by controlled cooling. This process:
- Relieves cold-work stresses introduced during forming
- Restores full austenitic microstructure and corrosion resistance
- Produces a clean, bright surface free of heavy oxide scale
- Enables subsequent polishing to achieve Ra ≤ 0.8 μm
4. Precision Polishing
The coil tube surface is polished using multi-stage mechanical and/or electropolishing techniques to achieve the required surface roughness of Ra ≤ 0.8 μm. This ultra-smooth finish is critical for:
- Preventing microbial harborage and biofilm development
- Ensuring complete removal of product residues during CIP
- Meeting sanitary design principles for pharmaceutical applications
5. Orbital TIG Welding
All welds are performed using orbital automatic TIG welding with continuous argon back-purging (minimum 5 L/min) to prevent internal oxidation. Post-weld polishing ensures the weld zone matches the parent tube surface finish (Ra ≤ 0.8 μm), eliminating potential contamination points.
6. Passivation & Cleaning
The completed coil tube undergoes a final electrochemical or chemical passivation treatment (typically nitric acid or citric acid passivation) to establish a uniform chromium oxide passive film. This is followed by thorough rinsing with deionized water (conductivity ≤ 1 μS/cm) and final inspection.
7. Final Inspection & Testing
Each coil tube undergoes comprehensive final testing including:
- Surface roughness verification (Ra ≤ 0.8 μm) using a profilometer
- Visual and borescope inspection of all welds and internal surfaces
- Pressure testing at 1.5× design pressure for 30 minutes minimum
- Dimensional verification (coil diameter, pitch, tube OD, wall thickness)
- Material certification (MTC — Material Test Certificate) per EN 10204 Type 3.1
Applications
Primary Application: Biopharmaceutical Fermentation Systems
This coil tube is purpose-designed for the following bioprocess applications:
- Fermentation Tank Jackets — External helical coil jackets providing uniform heating/cooling of the vessel wall
- Internal Coiled Heat Exchangers — Immersed coil tubes for direct heat exchange with culture medium
- Seed Tank Thermal Control — Precise temperature management during inoculum preparation
- Bioreactor Jacket Systems — Integrated heat transfer in stirred-tank bioreactors for E. coli, CHO cells, yeast, and bacterial fermentation
- Downstream Processing — Thermal conditioning of buffers and process fluids
Process Conditions
The coil tube is engineered for the specific thermal and chemical environment of biopharmaceutical manufacturing:
- Culture medium temperature: 30–37 °C (optimal for most microbial and mammalian cell culture)
- CIP cycles: Frequent — typically 1–2 cycles per batch, involving caustic and acid cleaning at 60–80 °C
- SIP cycles: Frequent — 121 °C saturated steam sterilization at 0.1–0.2 MPa, holding for 30–45 minutes
- Thermal cycling: Hundreds of rapid temperature transitions between 20 °C (ambient), 37 °C (process), and 121 °C (SIP)
Quality Certifications & Compliance
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| EN 10204 Type 3.1 | Material Test Certificate — Inspection Report |
| ASTM A269/A269M | Austenitic Stainless Steel Tubing Specification |
| ASME BPE (Bioprocessing Equipment) | Design and manufacturing for bioprocess equipment |
| 3-A Sanitary Standards | Sanitary design for food and pharmaceutical processing |
| FDA 21 CFR Part 210/211 | Current Good Manufacturing Practice (cGMP) |
| EU GMP Annex 1 | Manufacture of Sterile Medicinal Products |
| PED (Pressure Equipment Directive 2014/68/EU) | Pressure equipment compliance (where applicable) |
Unique Selling Points
- Ultra-Smooth BA Surface (Ra ≤ 0.8 μm): Exceeds standard sanitary requirements, minimizing microbial adhesion and ensuring complete CIP cleaning efficacy
- Proven Thermal Shock Resistance: 316L BA material with full annealing treatment withstands hundreds of rapid temperature transitions without cracking, deformation, or loss of mechanical integrity
- Biopharmaceutical-Grade Design: Engineered from the ground up for the demanding CIP/SIP cycle requirements of modern bioprocessing facilities
- Full Traceability: Every coil tube is accompanied by a complete material traceability dossier including mill certificates, heat treatment records, and weld maps
- Custom Engineering: Coil geometry, tube dimensions, and connection configurations are tailored to specific vessel designs and process requirements
- Corrosion-Resistant Construction: 316L with molybdenum alloying provides exceptional resistance to the aggressive CIP chemistries used in pharmaceutical cleaning protocols
Technical Notes
Design Consideration: When integrating this coil tube into a fermentation system, ensure that the coil geometry provides sufficient surface area for the required heat duty at the specified flow rates. The coil pitch and number of passes should be optimized to achieve uniform temperature distribution across the vessel volume while maintaining acceptable pressure drop (< 0.05 MPa typical).
Thermal Fatigue Note: Although 316L BA possesses excellent thermal shock resistance, proper mechanical support and expansion accommodation must be designed into the system to prevent fatigue cracking at support points during repeated thermal cycling.
For detailed engineering support, custom specifications, or material certification documentation, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly.