DESIGN QUALIFICATION (DQ) WFI STORAGE & DISTRIBUTION SYSTEM
1. INTRODUCTION
The Water for Injection (WFI) Storage and Distribution System is designed to store and distribute WFI for manufacturing and cleaning applications.
WFI is generated from the Multi Column Distillation Plant (MCDP) and stored in a 1500 L jacketed storage tank, followed by distribution through a recirculating loop to user points.
The system is designed in compliance with USP (United States Pharmacopoeia) requirements.
WFI Quality Requirements (USP 40):
| Parameter | Limit |
|---|---|
| pH | 5.0 – 7.0 |
| Conductivity | ≤ 1.3 µS/cm @ 25°C |
| TOC | ≤ 500 ppb |
| Microbial Count | ≤ 10 CFU/100 ml |
| Endotoxin | < 0.25 EU/ml |
The system includes defined Design, Alert, and Action limits to ensure compliance at point of use (POU).
DESIGN QUALIFICATION (DQ) OF PURIFIED WATER GENERATION SYSTEM
1.1 SYSTEM INFORMATION
- Equipment: WFI Storage & Distribution System
2. SCOPE
This Design Qualification document:
- Defines system design and engineering principles
- Verifies compliance with URS and technical specifications
- Serves as a base document for validation (IQ/OQ/PQ)
- Covers complete WFI storage and distribution system
3. RESPONSIBILITIES
Vendor
- Design system as per standards, URS, and specifications
- Provide drawings (P&ID, GA, layout)
- Supply compliant equipment and documentation
- Conduct training for operating personnel
Client
- Review and approve documents
- Provide site readiness and utilities
- Ensure inspection requirements
- Provide work permits and EHS compliance
- Manage unloading and storage at site
4. BASIS OF DESIGN
4.1 Output Quality Parameters
System designed to meet:
| Parameter | Design Limit |
|---|---|
| Conductivity | < 1.3 µS/cm |
| TOC | < 500 ppb |
| Microbial Count | < 10 CFU/100 ml |
| pH | 5 – 7 |
4.2 Operational Limits
| Parameter | Design | Alert | Action |
|---|---|---|---|
| Conductivity | <1.3 | >1.1 | >1.2 |
| TOC | <500 | >350 | >450 |
| Microbial | <100 | >80 | >90 |
| pH | 5–7 | <5.5/>6.5 | <5/>7 |
4.3 User Points
| Valve | POU | Area |
|---|---|---|
| POU-1 | Sterilization | |
| POU-2 | Unit Preparation | |
| POU-3 | Vial Washing |
4.4 Pump Sizing
- Peak Consumption: 0.9 m³/hr
- Total Flow Required: 2.56 m³/hr
- Pump Capacity: 2.6 m³/hr @ 63 MWC
- Pump Make: Fristam (Model FP 742)
5. SYSTEM DESCRIPTION
- WFI at ≥ 85°C stored in SS316L jacketed tank
- Recirculation loop maintains ≥ 1.2 m/s velocity
- Equipped with:
- Flow, temperature, pressure, conductivity sensors
- Provision for TOC analyzer
- Conductivity-controlled diversion:
- If >1.2 µS/cm → water diverted to drain
Sterilization
- Temperature: 121°C (Pure Steam)
- Automatic cycle with monitoring
- Includes tank and loop sterilization
Key Design Features
- SS316L contact parts
- Electro-polished surface (Ra ≤ 0.4 µm)
- Orbital TIG welding
- Zero dead-leg valves
- Slope: 1:100 (drainability)
6. TECHNICAL SPECIFICATIONS
6.1 Equipment
WFI Storage Tank
- Capacity: 1500 L
- Type: Vertical, Jacketed, Insulated
- MOC: SS316L (contact), SS304 (external)
- Finish: Ra ≤ 0.4 µm
Distribution Pump
- Capacity: 2.6 m³/hr
- Make: Fristam
- Qty: 2 (1W + 1 Standby)
Control Panel
- PLC: Siemens S7-1200
- HMI: Siemens KTP-900
- VFD: Siemens SINAMICS V20
6.2 Instruments
- Level Transmitter (Capacitance type)
- Pressure Gauges
- Conductivity Analyzer
- Flow Transmitter (Vortex type)
- Temperature Sensors (PT100)
6.3 Valves
- Diaphragm Valves (Manual & Actuated)
- Ball Valves
- Sampling Valves
- Steam Traps
- Flow Diverter Valve (FDV)
- Safety Valves
6.4 Piping
- Material: SS316L
- Finish: Electro-polished
- Insulation: Armflex with cladding
7. WELDING & CLEANING
- Orbital TIG welding
- Argon purging (99.9%)
- Inspection:
- 10% orbital welds
- 100% manual welds
- Passivation: As per ASTM A967
- Slope verification: ≥ 1:100
- Hydro/Pneumatic testing conducted
8. CONTROL PANEL DESCRIPTION
- PLC-based automation
- IP54/55 enclosure
- Fully automated operations
- Password-controlled access (4 levels)
9. DOCUMENTATION
Includes:
- P&ID
- GA Drawings
- IQ/OQ documents
- Calibration certificates
- Welding records
- Manuals
10. INTERLOCKS & CONTROL LOGIC
Critical Controls
- Low level → Pump trip
- High conductivity → Drain diversion
- Low velocity → VFD correction
- High temp deviation → Steam control
- Emergency stop → System shutdown
11. CRITICAL SAFETY REQUIREMENTS
- Continuous circulation at ≥85°C
- Periodic sterilization mandatory
- Monitoring of critical parameters
12. SAFETY FEATURES
- Safety valves
- Insulated equipment
- Emergency stop
- Phase failure protection
- 24V instrumentation
13. UTILITIES REQUIRED
| Utility | Requirement |
|---|---|
| Power | 415V, 3-phase |
| Plant Steam | 230 kg/hr |
| Pure Steam | 130 kg/hr |
| Air | 6–8 kg/cm² |
14. ENCLOSURES
- P&ID
- Tank Drawings
15. REVISION HISTORY
16. ABBREVIATIONS
17. SUMMARY
The WFI Storage and Distribution System is designed to meet USP standards and user requirements for pharmaceutical-grade water. The system ensures:
- Continuous circulation
- Temperature control
- Microbial control
- Automated monitoring
All components are selected to maintain hygienic conditions and ensure compliance with cGMP guidelines.
CONCLUSION
The design of the WFI Storage & Distribution System is adequate, compliant, and suitable for its intended application. It fulfills:
- User Requirement Specifications (URS)
- Regulatory requirements (USP, cGMP)
- Operational and safety standards
The system is therefore recommended for installation and further qualification (IQ/OQ/PQ).