Sieve calibration, Sieves, Sieve Recertification, Sieve Cleaners

CALIBRATING TEST SIEVES

RECOMMENDED SIEVE RECERTIFICATION SCHEDULE

Aperture 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

QUESTION: Although a sieve may come from the factory with assurances of compliance, how long after use is it still considered calibrated?

Depends on use

TYPE OF SIEVE MATERIAL

TYPE OF SIEVE SHAKER USED

NUMBER OF TESTS

SAMPLE CHARACTERISITICS

(Many states now require laboratories to calibrate their sieves every 6 months to remain certified)

ANSWER:

1) MICROSCOPY

Primary Method-Directly traceable. Use of a caliper to calibrate all or a minimum of 30

apertures on a sieve is labor intensive

2) DEDICATED IMAGE ANALYSIS

Dedicated image analysis has made huge strides recently, due to software development.

NOTE: Recent innovations have brought this technology to the forefront. Costs have

been reduced and operational macros have virtually eliminated operator training

New image analysis software can be programmed for sieve calibration functions, using digital camera technology

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) at an average cost of $80 per sieve per test. They can 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

4) PERFORMANCE TESTING USING A MASTER STACK OF SIEVES (ASTM E 2427) NEW IN 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.

5 THIRD PARTY CERTIFICATION

Third party certification is always an option at a cost of about $70 to $90 per sieve

WAYS TO EXTEND USABLE SIEVE LIFE