AVOID WATER UNDER THE BRIDGE
Problems associated with contaminated product and out-of-limit processes drive up manufacturing costs and wreak havoc with such elusive notions as competitive advantage and profitability. The longer the time between the onset and detection of contamination or loss of process control, the higher the costs and the more extensive the damage to the company. This is especially true with high volume production where a significant amount of work in process (WIP) may require rework or become scrap. Manufacturers can avoid high costs by detecting out of spec situations as soon as possible. It is even better if changes in process parameters that can cause contamination are detected before unacceptable contamination occurs.
“SEND IT TO THE LAB”—THEN WAIT
An array of analytical methods can be used to detect and speciate surface contamination and to characterize attributes of processes. Many involve “sending a sample to the lab.” Whether the lab is across the hall, across town, or across the country, valuable time is lost waiting for results. There are many quicker, even if less precise, methods of determining that the process is outside of control parameters. Such methods should be thought of as complementing rather than replacing laboratory tests. Lab analysis is invaluable to pin down the specifics of contamination culprits and should remain in any troubleshooting or long-term process maintenance program.
For in-process monitoring, automated or manual tests can be performed in-situ on the production floor. These tests may be continuous monitoring of key parameters or periodic “grab samples” of product or process fluids/parameters that can be quickly analyzed and the results acted on in an expeditious manner.
WHAT CAN BE MONITORED IN-PROCESS?
In-process monitoring can characterize the process environment. Examples include the surrounding air, process materials and chemicals, the functionality of the critical cleaning processes, and product surfaces. During receiving inspection, for example, it may be desirous to quickly test the particle count or pH of incoming process chemicals or scan the surface of a product received from a supply chain sub-vendor to verify that surfaces are clean and that coatings and finishes have the appropriate qualities and attributes.
During assembly, monitoring of process chemicals, including water, can signal the need for bath modification or change-out. Premature cleaning bath degradation might also signal that an upstream process is not in control. For example, a rapid change in conductivity in a cleaning tank might be caused by overly contaminated product being introduced or it could signal a need to change water purification media.
Examples of fluid monitoring techniques include:
- Liquid particle counting
- pH monitoring
- conductivity measurement
- temperature measurement
- flow rate determination
- turbidity measurement
- ultrasonic cavitation metrics
Surface monitoring techniques include:
- Visual observation, with or without magnification (Figure 1)
- Portable Fourier Transform (FTIR) spectrometers
- Hand-held X-Ray Fluorescence (XRF) scanners
- Optically Stimulated Electron Emission (OSEE)
- Contact angle measurement
- Ion Mobility Spectroscopy (IMS)
In Part 2 of this series, we will expand on some of these monitoring techniques, including both their strengths and weaknesses.
Barbara Kanegsberg and Ed Kanegsberg, “the Cleaning Lady and the Rocket Scientist,” are independent consultants in critical and precision cleaning, surface preparation, and contamination control. They are the editors of The Handbook for Critical Cleaning, CRC Press. Contact them at BFK Solutions LLC., 310-459-3614; email@example.com; www.bfksolutions.com.