There’s no point in cleaning something if you can’t be sure how clean it is when you’re done. That’s why every facility needs a cleaning validation program.
As you’ve followed our blog, you’ve seen blog posts on how to handle meeting a specific cleanliness standard. Almost every method we presented is employed after the cleaning process is finished, or at least, after the part is removed from the ultrasonic cleaner. That makes sense, of course; why try to measure cleanliness when the cleaning isn’t finished?
There are actually some good reasons to do so, and a method specifically designed to evaluate cleaning effectiveness during the process. It’s called In Situ Particle Monitoring (ISPM), and it might help you make your cleaning process better.
How It Works
To use ISPM, you’ll need to sample the liquid medium in your ultrasonic cleaner. This should be done by taking a sample from the filtration loop, upstream of the filter. Sampling should take place while components are being cleaned. You’ll usually want to take a single sample, but as we’ll see there can be benefits to sampling multiple times in the same cycle.
Once you have the sample of the cleaning medium, the size and amount of contaminant particles in the medium should be verified. If the usual particle size is easily visible to the naked eye, this can be done with simple visual inspection after passing the liquid through a filtration medium. It’s best to use a lightly-colored or white filtration medium for contrast, and to ensure that the contaminants are spread over a certain measured area (for the sake of consistency) each time you test.
Smaller particle sizes can be counted with low or high-power microscopy, or other validation methods.
What Can We Find Out?
ISPM is simple, and can help an operator evaluate cleaners and processes by allowing an apples to apples comparison.
IPSM can be used to perform A/B testing on the effectiveness of certain detergents or formulations. For example, one can evaluate how quickly and effectively a specific formulation is in relation to another that is cleaning the same objects. This is especially effective if the target objects are sample plates with identical contamination.
IPSM can also be used to evaluate cleaning processes. Samples can be compared in order to determine how well and how quickly ultrasonic cleaning is removing contaminants if a change in frequency, procedure or tank arrangement is being considered.
By evaluating several samples taken during the cycle, you can graph a profile of when the most cleaning is taking place and how effective it is. It may seem that the amount of particles in the medium would just continue to climb, but remember that the filtration system is removing some portion of the particles as the process continues. You’ll usually see a spike at the beginning of the cleaning process, with other particles coming off steadily over time. This can be used to optimize your cleaning time.
Lastly, ISPM can help you monitor the condition of cleaning baths and your filtration systems. Regular checks are simple, and sudden increases in particle count will let you know changes need to be made.
ISPM isn’t as precise as some post-cleaning validation methods and lacks the gee-whiz factor of methods like Surface Ultraviolet Fluorescence, but it provides ultrasonic operators with information they can’t obtain after the cleaning cycle is finished. That makes it a tool to consider as you seek to make the single best industrial cleaning method, ultrasonic cleaning, work even more efficiently for your particular operation.