Loop Design Modification in PW/ WFI Systems

In response to the client’s requirements for enhancing WFI and PW distribution systems, we deliver comprehensive solutions that combine premium materials with precision orbital welding. Our services cover weld inspections using borescopes, surface passivation for corrosion protection, and full documentation and validation packages in accordance with GMP standards.

Loop Design in Purified Water (PW) and Water for Injection (WFI) systems is a critical aspect of pharmaceutical water infrastructure. A well-designed loop ensures continuous circulation, microbial control, and uniform water quality, while meeting regulatory requirements like ASME BPE and FDA. Key aspects include:

1- Valve Selection and Placement:

• Choosing hygienic valves (e.g., diaphragm valves) to prevent dead legs.

• Strategic placement of block valves, sampling ports, and drain points to facilitate maintenance and validation.

2- Flow Velocity and Branch Design:

• Maintaining a minimum flow velocity (usually ≥1.0 m/s) to prevent stagnation and biofilm formation.

• Limiting branch length to avoid zones where water can remain stagnant (max 1.5D per ASME BPE).

• Proper outlet angles (preferably 45°–60°) to ensure effective drainage.

3- Temperature Control:

• WFI loops are typically maintained at 80–85°C to inhibit microbial growth.

• Incorporating point-of-use cooling for sensitive equipment (20–25°C) without creating dead zones.

• Using heat exchangers or integrated coolers to stabilize water temperature despite seasonal variations.

4- Piping Materials and Surface Finish:

• Using 316L stainless steel with low sulfur content.

• Polishing and electropolishing to achieve smooth surfaces (Ra ≤ 0.4 µm) to reduce biofilm attachment.

• Passivation after installation or maintenance to restore the protective chromium oxide layer.

5- Loop Configuration and Redundancy:

• Designing symmetrical loops for even flow distribution.

• Providing parallel paths or redundant loops for critical areas to maintain continuous operation during maintenance.

• Avoiding sharp bends or complex fittings that can trap water or compromise cleanability.

6- Monitoring and Validation:

• Installing sampling points, flow meters, and conductivity sensors for continuous monitoring.

• Performing regular microbiological and TOC testing to verify system integrity.

• Documenting all changes and modifications to ensure compliance with GMP standards.

Benefits of an optimized loop design:

• Continuous, uniform delivery of high-quality PW/WFI.

• Minimization of microbial risk and biofilm formation.

• Improved operational efficiency and reduced energy consumption.

• Easier maintenance, validation, and regulatory compliance.