You may remember Pequeño and his family of very small 150 micron (150µ) particles being very determined to defeat sieve certification.
CSC Scientific Blog
We continue to search for answers to the question "Is Sieve Calibration Really the Holy Grail?" As promised,we present Episode III of the Pequeño saga. You may remember him as a very small (150-micron) particle with many similar-sized family members who are determined to defeat sieve certification.
Is Sieve Calibration Really the Holy Grail? Part II: Inside a Sieve Test
As I start on this second installment of The Adventures of Pequeño: The 150 Micron Particle, I wonder why I get myself into these serial onslaughts. However, a promise is a promise, so I shall press on.
You will recall from Part I: Sieve Certification, our little friend Pequeño, a particle on a determined quest to make it through sieves -- particularly those through which he should be too large to pass. In this scenario, Pequeño along with some of his family and friends -- all small particles about 150 microns in size -- are on their way to a sieve test.
- Is your concrete going to be strong enough?
Will you chocolates taste right?
Will your washing powder flow and dissolve as advertised?
Is there dangerous residue in your pill stock?
Will the “frack sand” keep the fractures open?
Is my salt of the correct grade?
If these are not correct, serious consequences could result (e.g. spoiled product, returned batches, rework or scrap).
In April, we published an article in "Powder-Bulk Solids" comparing certification process veracity with a sieve calibration process using calibrated glass microspheres (or beads). The certification process merely indicates that a sieve mesh conforms to a standard that has a wide tolerance regarding mesh openings. It is performed on a small number of openings. On the other hand, calibration using the calibrated beads results in a number representing the mean opening -- a result generated by actually performing a test encompassing at least 80% of the mesh openings.
The primary purpose of a sieve shaker is to provide motion to a sample in a test sieve.
An effective sieve shaker creates a motion that presents all the particles to all of the sieve openings and assists particles in passing through. This requires both rotary and vertical motion.
This process seems simple enough, but let's not be taken in.
When I tell people at cocktail parties that we specialize in Particle-Size Analysis. I usually get a polite response of ------ “OH !!,” which translates to “So who cares?”
The relative value of a sieve certification process vs a sieve calibration has perplexed me for a long time.
I have often ranted about the limited range of ASTM 11 sieve mesh standards as it relates to individual sieve certification. We at CSC have tried to help clearly distinguish between different levels of inspection and/or degrees of conformity. We outlined three levels of sieve certification. These are working sieves, mesh certified sieves and mid point sieves. There are summary definitions of these categories on the CSC Web site.
In one of my more contemplative moments, I thought a bit of history about particle size analysis would be of interest. So let’s see Who Cares About Sieve Testing.