In 2011 "Powder-Bulk Solids" published an article 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 problems outlined in the article are still dogging todays QC Managers
Yes Harry, there is a Santa Claus. Or, more specifically, there really is a Holy Grail for ensuring consistent particle size analysis.
If you’ve been following along, you know it was proven by Pequeño and his family of 150 micron particles who tried to bust our friend Harry’s quality control by attempting to slip through the mesh in Harry’s test sieves and defeat sieve certification.
If you missed this drama, check out previous posts in the Holy Grail series here:
And finally check out our eBook here: Free eBook
Now that we have indeed confirmed that, yes, sieve calibration really is the Holy Grail that sieve testers have been looking for, let’s get to work and dive a little deeper. Let’s examine some methods of sieve calibration.
Topics: Pequeño, Calibration, Particle Size Analysis, Sieve Calibration, Sieve Certification, Sieve Testing, Sieves, Sieving Process, du Nouy tensiometer, sieve mesh, particle sieze testing, sieve stack, Sieve Quality
You may remember Pequeño and his family of very small 150 micron (150µ) particles being very determined to defeat sieve certification.
Adventures of Pequeño
This is another Adventure of Pequeño: The 150 Micron Particle, I wonder why I get myself into these fantasies. However, once I start I feel constrained to press on.
In an earlier encounter, our little friend Pequeño, was on a determined quest to make it through sieves -- particularly those through which were said be too small for him 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.
Holy grail and Sieve Calibration
- 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 our business, we use the word “sieve” to describe a piece of equipment that separates different sized particles using a woven wire screen. To others, “sieve” can mean something very different.
Do You Re-Certify? Compare with a Master Stack? Check with Calibration Samples?
What Does Recertification Give?
The ASTM E-11 committee has done a great job of establishing three levels of testing. These levels show the probability of a sieve’s mesh to be within the permissible variations. These variations relate to the size of openings in wire-cloth used for test sieves.Read More
Topics: Sieve Shakers, Mid-Point Sieves, ASTM, Particle Size Analysis, Sieve Calibration, Sieve Certification, Sieve Testing, Sieving Process, Quiet sieve shakers, RoTap, sieving, test sieve equipment, sieve mesh
For several years, people in the test sieving business have been grousing about the difficulty of making sure that a test sieve certification is what they need. Anyone who is working with close tolerances in the smaller particle sizes, like 300 microns and smaller, have serious issues in matching results from test sieve to test sieve.Read More
The relative value of a sieve certification process vs a sieve calibration has perplexed me for a long time.