● Closed-loop calibration: integrate a mass flow meter (MFM) to compare set vs. actual in real time and auto scale for dosing error ≤ 1%.
● Auto-cal routine: every 8 h or at batch switch, run self-check (dry run + flow calibration) and record reports to meet GMP.
● Powder charging/storage: design to ATEX Zone 21; equipment protection level ≥ Ex tD A21 IP65.
● Solvent vapor areas (e.g., viscous liquid charging, solvent recovery): design to ATEX Zone 1; equipment rating ≥ Ex d IIB T4.
● Inerted feeding:
● Combustible powders: nitrogen inerting to O2 ≤ 8% (below MOC); install inline O2 analyzer (±0.1%); auto N2 make-up on exceedance.
● Combustible solvents: use explosion-proof motors, sealed pumps/valves; install flame arrestors; deploy combustible gas alarms + automatic exhaust (face velocity ≥ 0.5 m/s).
● Pressure relief and isolation: dust equipment (dryers, charging stations) with rupture discs (burst pressure 0.15 MPa); solvent lines with check valves to prevent flame propagation.
● Powder charging: fully enclosed charging stations (glovebox type, vacuum loading), enclosure rating ≥ IP65; dust control to ISO 14644-1 Class 6 (shop dust ≤ 10 mg/m³).
● High-viscosity liquid charging: use closed couplings (tri-clamp with PTFE seals) to prevent drips; enclosure rating ≥ IP67; no special dust control (only solvent vapor control).
Negative pressure and LEL:
● Powders (especially combustible powders like PE, PVDF): use negative-pressure charging (−0.02 to −0.05 MPa) to prevent dust dispersion.
● High-viscosity liquids with flammable solvents (e.g., NMP, DMAc): install LEL monitors (≤ 1% LEL accuracy) in charging area; on exceedance, trigger exhaust + alarm.
● Toxic solvents (e.g., DMSO): co-install toxic gas detectors; keep concentrations ≤ OEL.
● Terminal fine filtration: before the spinneret, install high-precision filters (sintered metal or cartridge filters, 10–50 μm or finer).
● Duplex filters in parallel: standard practice. One set runs while the other is standby. When ΔP reaches the setpoint, auto valves switch to the standby set without shutdown.
● Backflushing: configure automatic backwash for sintered elements using clean solvent or compressed gas, regenerating elements and extending life.
Summary:
● Coarse (50–100 μm): basket filter, manual cleaning (upstream).
● Fine (5–20 μm): duplex bag/cartridge filters, switch without stopping.
● Final (0.5–5 μm): high-pressure candle filters or self-cleaning backwash elements (e.g., Pall).
● Alarm and auto switch when filter ΔP > 0.3 MPa.
● Phase 1 (basic automation):
● Investment: replace manual valves with precision metering pumps + VFDs at critical nodes (dope, bore fluid); add sensors for flow, pressure, level.
● Return: enable basic monitoring and remote start/stop; reduce human error; immediately improve product consistency.
● Phase 2 (process automation):
● Investment: build standalone PLCs; implement PID control for key variables (flow, pressure) to automate regulation.
● Return: lower reliance on skilled operators; enhance efficiency and stability.
● Phase 3 (informatization and optimization):
● Investment: introduce MES for batch management/traceability; develop APC (advanced process control), e.g., auto fine-tuning across raw material lots.
● Return: refined production management, reduced raw material loss, higher prime yield.
Principle: prioritize automating tasks that are repetitive, quality-critical, labor-intensive, or hazardous.
● Logic control: configure production recipes in the MES. After feed prep, the system sends a start signal; upon batch completion, the equipment sends a changeover command to the feeding system for fully automatic batch switching.
● Status feedback: install pressure sensors and flow switches in feed lines. On anomalies (low pressure, flow interruption), immediately send a stop signal to prevent dry running or product defects.
● Gelation/crystallization risk: Excessive shear rate or long shear history (dead zones) can over-orient chains, triggering premature crystallization or physical gelation.
● Consequences: Microgels form, accumulating in channels or blocking orifices intermittently or permanently.
● Flow-path optimization: Streamlined, large-orifice, short-land, low-shear design to avoid local high shear.
● Temperature control: Precisely control temperature—key to gelation kinetics.
● Eliminate dead zones: Remove all stagnation regions to minimize shear history.
● Closed-loop control: acquire real-time temperature and viscosity data (via an inline viscometer or IR temperature sensor) and feed back to the pump servo drive to synchronize flow–ΔP–temperature adjustments, reducing flow fluctuation from ±5% to ±0.3%.
● For high-viscosity dope, add a preheating loop (hot water or steam) upstream of the pump to keep the fluid within the set temperature window and reduce feed instability caused by viscosity gradients.
● Gelation/crystallization risk: Excessive shear rate or long shear history (dead zones) can over-orient chains, triggering premature crystallization or physical gelation.
● Consequences: Microgels form, accumulating in channels or blocking orifices intermittently or permanently.
● Flow-path optimization: Streamlined, large-orifice, short-land, low-shear design to avoid local high shear.
● Temperature control: Precisely control temperature—key to gelation kinetics.
● Eliminate dead zones: Remove all stagnation regions to minimize shear history.
● High-T TIPS (200–250°C): Use high temperature alloys (Hastelloy, Ti) to avoid thermal deformation; integrate cooling channels (annular passages) to remove heat and prevent degradation; flow-paths designed to limit thermal aging.
● Practice note: SUS304 and SUS316 have been used long-term for 32-hole TIPS lines without quality issues.
● High-T outlet free span: Extend to 15–20 mm for melt relaxation and to mitigate die swell–induced wall jumps.
● Thermal control: Lower thermal conductivity requires multi-zone heaters to keep axial ΔT < 1.5°C.
● Design allowance: Compute ΔD = ΔT × (α₁ − α₂) × D, and pre-clearance (e.g., ~0.02 mm) so that concentricity is optimal at operating temperature.
● Heat-up/cool-down rate: Recommend ≤30°C/h to keep thermal stresses <50 MPa and avoid micro-slip/scratching at seals.
● For same-material assemblies, effects are smaller.
● Needle damage: Traditional designs are hard to disassemble; bore needles are easily damaged and scrapped.
● Precision loss: Concentricity may shift after reassembly, requiring re-calibration.
● FCT Gen-5 advantage: Independent, pinless modular inserts enable quick change without damaging the body; reduces mechanical damage and precision drift, extending service life.
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