Sieve calibration, Sieves, Sieve Recertification, Sieve Cleaners

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

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

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

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.

WAYS TO EXTEND USABLE SIEVE LIFE

Use an ultrasonic sieve cleaner

Use a vibratory sieve shaker

Buy higher quality sieves

589 Rappahannock Drive WhiteStone Va 22578

Tel (804) 435-5522 Toll Free (866) 244-1578 Fax (703) 991-7133

www.coffeelabequipment.com

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.

5) THIRD PARTY CERTIFICATION

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