Sieves

The Sieve and its Use

A sieve is a device used to separate solids based on size. Sieves have been in use since ancient times- the first recorded usage was in Egypt, over 5,000 years ago.

Sieves are used for a variety of applications, including Sieves are widely used to evaluate the uniformity of granular material, as well as measure particle size in powder form. Sieves are used in research and development, environmental monitoring, and quality control. Specific applications include sieving soil samples in the construction industry, separating particles in chemical and pharmaceutical processes and measuring the particle size distribution in food production.

Our range of sieves are in the category of laboratory and quality control test sieves.

Sieve Components

 Sieves are constructed of a frame, mesh material, and clamping device. The frames can be made of brass, Stainless Steel or acrylic. Standard frames are round and come in diameters of 3 inch, 8 inch, 12 inch diameters (also available in metric equivalents). Options of full height and 1/2 height and are available as deep water wash sieves.

The mesh material can consist of woven wire mesh, perforated plate or electroformed material.

• Aperture sizes for woven wire mesh range from 100mm to 20 microns. 
• Perforated plate is made to order and has an effective range of 125 to 1 millimeter round hole and 125 to 4mm with square holes (a special versions for grain and coffee are available for grain and coffee testing.
• Electrofomed sieves range in  aperture size form 5 Micron to 200 Micron

Sieve Standards

ASTM and ISO have set standards for mesh designations, inspection criteria and acceptable tolerances.These are defined for ASTM in a the table USA Standard Sieve Specification.  

.You may notice that the acceptable variation in  mesh hole size becomes a larger portion to the nominal size as the holes become smaller.  Because of these wide variations the certification of  as sieve should  be viewed as only an insurance policy - assurance that a sieve's mesh is within a required specification. It is not a valuable predictor of a sieve's performance.

Three Sieve Inspection Levels

The acceptable variations in the apertures of wire mesh sieves is stated in the basic ASTM Document.  Three level of validation have been established.

• Compliance. - Mesh is examined before it is assembled into a frame.  The  openings to be mesasured are stated per 100 square feet of mesh.
• Inspection - Mesh is examined after it is assembled into a frame.  The number of apertures is stated sieve.
• Calibration - As with inspection the mesh is examined after assembly.  The number of aperture is approximately twice the number for the inspection sieve.
• A special sieve category is the Mid-point Sieve.  MidPoint Sieves are manufactured to tolerances that have been reduced by 30%, in comparison to ASTM E-11 specifications. This results in sieves that fall in the middle of the ASTM E-11 tolerance range.

The Ultimate in Narrowing the Tolerance Gap. - Sieve Calibration

Sieve Calibration using calibrated spheres relate to a sieves performance. 
The development of microspheres with tolerances as tight as +/- 0.5 microns in diameter has made possible a new way of thinking about sieve certification and calibration.

Rather than simply an assurance that a sieve conforms to the construction and tolerance parameters set by stands organization such as ASTM and ISO, calibration using micro spheres provides a measure of operational performance.

How Does This Sieve Calibration Technique Work

To calibrate a sieve,the complete contents of a single dose bottle of microspheres of a specified size is poured onto the sieve surface and shaken for about 1 minute. As standards are spherical they have a very high sieving rate that is independent of the shaking method. Therefore manual shaking, mechanical or electromechanical action, Airjet and sonic sieving all give the same results. 

The percentage of the microspheres passing is then used to determine the aperture size from the calibration graph on the Certificate of Analysis. Because the size distributions are so narrow.  Variations as 5% in the percentage passing. For example with a 63 micron sieve, the mean aperture difference is about 1 micron, making the technique highly accurate. 

Watch this Video - How to run a Sieve calibration.

Sieve Calibration Conclusions

The introduction of narrow particle size distribution standards has at last brought sieve calibration directly into the laboratories using the sieves and answers the demand for routine inspection by regulatory bodies. This novel approach to sieve calibration fulfils all of the requirements of the quality control laboratory by delivering simplicity, speed, accuracy and above all, NIST traceability to the International unit of length.