Water For Injection Optimization
The Problem:
While supporting the operational and performance qualification of a new Vapor Compression Water for Injection system our specialists were asked to investigate severe water hammer observed during intermittent conditions
Additionally at this time PTS had been tasked to assist with system tuning and optimize the system to minimize still start-stop events & improve overall quality of WFI distillate
Oscillations in WFI supply piping were detrimental to both these goals as well as risking system damage after prolonged use
Partnering with client subject matter experts, our team determined a lack of backpressure at the end of the fill line was causing the line to become partially filled - and refilled rapidly causing a form of water hammer to shock the system
The water hammer induced pressure oscillations propagated to the WFI still itself causing issues with local control loops
The Solution
Utilizing the GEMÜ 1441 cPos-X, an intelligent, digital electro-pneumatic positioner, PTS automated two existing manual valves. This allowed for the deployment of variable backpressure control to maintain adequate back pressure control regardless of still output or a tank being down for service
Additionally this control allowed for active control of the difference in level between the two tanks allowing the system to send water to the tank that needed it most. This allowed the still to remain active longer reducing waste associated with starts and stops as well as improving the availability of this critical utility.
Challenges
Due to the WFI stills ability sensitivity to changes like back pressure and variable production rates all conditions needed to be tuned together to ensure smooth operation.
At the time of implementation this system was in the qualification process and in use. PTS partnered with end user quality professionals to derive and execute a plan to commission, validate, and return the system to service without impacting operations.
Results & Performance
Following commissioning & tuning of the new back pressure control system , the new 1441 Positioners coupled with the PTS derived control strategy, were able to eliminate the previously observed water hammer. Additionally the consistent backpressure improved operation of local control loops on the WFI still improving distillate quality & still operation overall. The active level control allowed for further adjustment on still sequencing setpoints allowing the team to minimize wasteful start and stop operations of the still saving both water, electricity, and steam.
