Particle measurements in ultra-pure water (UPW) systems play a pivotal role in maintaining the stringent standards required for high-end manufacturing processes. This post describes a comprehensive study conducted to understand the critical factors influencing the stabilization time of particle measurements in UPW systems, particularly focusing on particles 20 nm and above.
Characterization Study
The study employed an Ultra DI® 20 (UDI-20) Liquid Particle Counter to evaluate various factors affecting the stabilization time. The tested factors were categorized into non-invasive and invasive, depending on their impact on the system without or with the introduction of new components.
Non-Invasive Factors:
- Instrument Warm-up: The warm-up period was assessed. Although a temporary increase in particle counts occurred during warm-up, the system stabilized after approximately 10 minutes.
- Valve Actuation: Actuating a PTFE diaphragm valve resulted in a modest increase in particle counts, returning to baseline within 5 minutes.
- Disconnecting/Reconnecting Tubing: Introducing friction by disconnecting and reconnecting sample tubing caused a temporary rise in particle counts, with the system stabilizing within 20 minutes.
- Renewing Flare: Flaring a sample tube did not significantly impact particle counts, emphasizing the importance of correct connections.
Invasive Factors:
- Installing New Sample Tube: Replacing an existing 80 cm sample tube with a new one led to a prolonged increase in particle counts, taking 65-72 minutes for 95% clean-up.
- Flushing After Tube Installation: Flushing newly installed sample tubes reduced clean-up time significantly, emphasizing the effectiveness of proactive measures.
- Effect of Sample Tubing Length: Longer sample tubes correlated with longer clean-up times, reinforcing the significance of tubing length in particle stabilization.
- Installing New Valve: Introducing a new PFA diaphragm valve led to a substantial increase in particle counts, taking approximately 270 minutes for 95% clean-up.
Real-world Implications
High-end ultra-pure water systems, being more complex, may take months to stabilize due to invasive factors. The study underscores the importance of using high-sensitivity particle counters for accurate monitoring.
