Hello good people of the world! Today’s post deals with the User Requirements Specification (URS) for a Purified Water System. It may be RO/DI, Purified Water, or WFI, but it should probably have a URS. As with any URS, make sure requirements are specific, measurable, accurate, repeatable, and testable. Considerations specific to purified water systems include:

Process Requirements:

• Capacity – how much water is needed? What is peak load? Include number of users, use points, and usage priorities, as applicable
• Quality – what water quality does the system need to produce? Site USP, EP and other applicable standards

User Requirements:

• Consider available support utilities (incoming water, compressed air, steam, power, drainage, etc.) up front
• Know what your incoming water looks like. This will ideally include more than one sample on one day. Sample over time and look at variations in incoming water quality. Feed the Purified Water System with RO water if possible.
• Space layout where system will be installed – be sure to consider operator access for both normal operation and maintenance activities

Mechanical Requirements:

• What piping standard(s) must be met (material of construction, surface finish)
• User of sanitary components (valves, pumps, tri-clamp connections, etc.)
• Welding requirements
• Air break in floor drains to prevent contamination
• Piping slope requirements
• Piping dead-leg requirements
• System drainability
• Inline monitoring requirements

Electrical Requirements:

• NEMA, UL, etc. standards as applicable

Sanitization Requirements

• How will system be sanitized? Ozone? Heat? UV?

Automation Requirements:

• What automation hardware will be needed? PLC? HMI? 
• How will custom code be developed and documented? Software Design Specification (SDS)?
• How will the controller/HMI interface with existing plant automation? What does the network look like? What IP addresses should be used?
• How will data be stored? Existing historian?
• What other interfaces are required?
• 21 CFR Part 11 compliance, if applicable. How do you know if your system needs to comply with 21CFR11? Click here for tips.

Documentation Requirements

• As-built P&IDs
• Panel layout and electrical diagrams
• Isometric piping diagrams
• O&M manuals
• Documentation of piping leak testing
• Documentation of sanitary welds (weld logs, coupons, welder qualification, weld inspection, boroscope documentation)

Validation Requirements

• Validation Plan
• Equipment Qualification (IOQ, PQ)
• Ongoing monitoring

Safety/Ergonomic Requirements

• Pressure relief devices
• Considerations for ease of operation and maintenance
• Insulation of piping that may be hot
• Guarding of moving parts (e.g. pumps, motors)
• Required signage
• Height/accessibility requirements for sample valves

What else do you put in your URS?

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