RECOMMENDED SIEVE RECERTIFICATION SCHEDULE
5 inches to .25 inches 80 uses or 36 months
US No. 1/2 to US No. 12 70 uses or 30 months
US No. 14 to US No. 40 60 uses or 24 months
US No. 45 to US No. 140 50 uses or 18 months
US No. 170 to US No. 325 35 uses or 12 months
US No. 400 to US No. 635 20 uses or 6 months
RECALIBRATING TEST SIEVES
Although a sieve may come from the factory with assurances of compliance, how long after use, is it still considered calibrated?
Primary Method-Directly traceable.
Use of a caliper to calibrate all or a minimum of 30 apertures on a sieve is labor intensive
Recent innovations have brought this technology to the forefront. Costs have
been reduced and operational macros have virtually eliminated operator training.
3) CALIBRATION STANDARDS
WIDE DISTRIBUTION CRUSHED QUARTZ
Irregular shape of crushed quartz powder leads to confusion in
exact parameter required to pass sieve apertures.
PRECISION SODA-LIME GLASS MICROSPHERES
Glass microspheres are certified using electroformed sieves,
and measure the minimum mean aperture size,
(Dimension that retains spherical particles)
They can generally only be used once however,
because some damage is presumed to occur during the calibration test.
These glass microspheres calibrate
close to 80% of the sieving medium
WAYS TO EXTEND USABLE SIEVE LIFE
- Use an ultrasonic sieve cleaner
METHODS OF CALIBRATING SIEVES
"Without an active sieve re-certification program in place, you're simply guessing."
CALIBRATING LABORATORY TEST SIEVES
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MOISTURE, PARTICLE CHARACTERIZATION, COLOR, AND SAMPLING
The chart on the right gives some basic guidelines for sieve calibration, but there are a few factors to take in to consideration.
Depending on the type of sieve shaker used, the samples characteristics, ie... sand, powder etc...and sieve construction, the frequency would be different.
4) PERFORMANCE TESTING USING A MASTER STACK OF SIEVES (ASTM E 2427) Introduced 2006
Midpoint sieves (30% reduced tolerance), precision electroformed sieves, or Certified Sieves
(Furnished with a detailed calibration certificate) may all be used as a master sieve stack,
to compare results to a working stack of sieves, using a representative sample.
This can be a very cost effective method of calibrating working sieves.
Sample degradation can be a concern.
Third party certification is always an option at a cost of about $70 to $90 per sieve
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