How to calibrate a sieve?
pl. let us know are u talking for calibration of sieve aperture or the performance of sieve
Please let me know the calibration of both aperture size and performance?
and mention other calibrations for sieve other than these two?
There are two common recognized ways to calibrate test sieves:
1. Conduct calibration tests using glass spheres. 2. Physically examine each sieve using microscopic projection.
Both methods are accurate; but complex and difficult. We can set out to develop an alternative to calibrate working test sieves.
AN EASY AND INEXPENSIVE CALIBRATION PROCEDURE.
Use certified test sieves. A certified test sieve is one that complies with a national or international standard. An American Society for Testing & Materials (ASTM) certification assures that the sieve openings are within the plus or minus tolerance allowed in ASTM E-11-95. A master set of sieves is needed as the standard against which working sieves are checked. The two types of certified sieves
commonly used for master sets are certified and certified mid-point;
Normally the mid-point set is used. Mid-point sieves are certified that the openings fall in the middle of the ASTM E-11-95 specification. Mid-point sieves provide a solid foundation for a dependable sieve calibration system. Although not recommended, a new set of calibrated sieves could be used. The sieves from a master set should only be used to calibrate working sieves. These should never be used in regular sieving operations and then reused in a master set. If a sieve from a master set is used in an operational test, it should be marked as a working sieve and a replacement purchased for the master set. Great care should be taken when handling and cleaning the master set of sieves. The master set is the standard, and the most important part of this calibration process.
If you have more than one working stack of test sieves, it is important that the individual sieves in a stack be used together. One of the most effective ways to ensure stack trueness is to keep a record of
the serial numbers of each sieve in each working stack. Another way is to mark each sieve with a stack identification. These techniques will assure that you have a valid calibration tracking procedure. This will
eliminate corruption of the results that would occur if the individual sieves in a stack were switched at the time of calibration. One sieve from another stack will corrupt your results.
Glass spheres or calibrated samples are available. If customers or other product specifications call for other methods such as calibrated production material samples, it is recommended that the material used for calibrating be from a representative sample of the product being tested in your operations. This provides a calibration basis that translates easily to operation procedures. The first step in preparing the material for a calibration standard is to split a sample into quarters. Use either a manual or mechanical device. A hand sample divider that splits samples into quarters will work fine
The results of processing a part of the calibration sample through the master stack will be compared to the results of processing a second part of the calibration sample through the working stack. This
comparison is the means to identify the need to replace working sieves that are out of tolerance because of wear or breakage, which will distort operating results. The steps that will assure effective calibration data are:
- Split the sample into four representative samples.
- Weigh and record the four representative samples.
- Place the master set of sieves on the sieve shaker. Use one quarter of the sample that was split and run a test. It is important that the same shaker and the same settings are used for all calibration tests. It
is recommended that the same person run all of the calibrating tests.
- Record the weight retained in each sieve. It is easier to compare the results if they are calculated to percent retained.
- Place a working set of sieves on your sieve shaker. Use one quarter of the sample, and run a test. Note: it is critical that the same shaker and settings are used as in the test that used the master set.
- Record the weight retained in each sieve and convert to the percent retained.
- Compare the results from the master set of sieves with the results of the working set.
- Record the difference retained in each sieve of the working set vs the same sieve in the master set.
This difference is the allowable curve. Keep these records on file for future reference. You will use the
same curve every time you calibrate.
This last step completes the establishment of a calibration standard. The next procedure deals with the actual calibration of the working sieves.
Once the calibration steps have been completed and the calculations finished, the evaluation of the working set needs to be done.
Compare the difference of the allowable curve established with the difference in the calibration test. If your results are not within the tolerances you have specified, the out-of-tolerance sieves should be identified and replaced with new calibrated sieves. To make this testing procedure produce traceable and practical product quality standards, it is recommended that:
-------- Frequency of performing calibration checks on working sieves be established and implemented;
--------- Based upon the frequency of calibration checks, a replacement schedule should be established for the master sieves.
The frequency of performing these tests and replacements should be based upon operational test schedules, sieve maintenance procedures, the characteristics of the material tested and the tolerances for acceptable quality standards.
What is a Mid-Point Sieve?
The Endecotts’ inspection process for sieves
The inspection process for all Endecotts certified sieves is stringent to ensure only World Class Quality
Sieves are produced. Every roll of wire cloth received by Endecotts is given an initial visual inspection. The cloth is stretched out over a back lit table and inspected for defects in the weave. Then, the
accepted cloth is cut into three, eight and twelve inch squares and goes through a more thorough visual inspection using an optical comparitor. Next, the frame, skirt, and fillet are added to the mesh squares that pass the optical examination. Once the sieve is constructed, its inner and outer diameters are inspected against traceable gauges. If the sieve passes inspection, it returns to the optical comparitor again. The comparitor prints a sieve certificate or rejection form after it has finished scanning the sieve. During the final inspection, up to 30% of the sieves are rejected and destroyed by Endecotts.
The Endecotts’ inspection for Mid-Point Sieves
The increasing demand for more precise and accurate sieve analyses led Endecotts to develop a method to select a premium quality 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, providing precise and accurate testing.
ASTM E11 MIDPOINT
Y , +Y 0.0400 0.0280
+Z 1.0800 0.7560
+X 1.1350 0.0000
%Z 5.0% 3.5%
Y : Permissible variation of average opening from standard sieve designation (standard deviation allowed for aperture size)
X : Value of maximum individual opening
Z : Value of intermediate tolerance
How are Mid-Point Sieves Used?
Endecotts Mid-Point sieves were developed in order to meet the rising demand for precision and accuracy when using matched sets and also for an easy calibration technique for working test sieves.
Many of our customers demand precise particle size analyses that even certified sieves cannot provide. The mesh used when manufacturing Mid-Point sieves have aperture sizes in the middle of ASTM E-11
tolerance range specifications. The reduced tolerance range used during Mid-Point sieve production ensures consistent and accurate results.
Calibration of your Working Test Sieves
When we developed the calibration procedure using Mid-Point sieves, our goal was to provide an easy and inexpensive way to calibrate working test sieves.
Matched Sieve Sets
Many of our customers have found they prefer using Mid-Point sieves in place of traditional Matched Sets for two reasons: the availability of Mid-Point sieves and the reliability of the results that are provided
using Mid-Points. A Matched Set is obtained using all Mid-Point sieves for a designated stack. Because all Mid-Point sieves are certified and inspected to the same range of tolerances, not by using a sample standard, results are accurate and precise for every stack of sieves you use. Mid-Point sieves are also readily available, so you will not have to wait for a replacement sieve.
Note - The crude method is to verify the aperture size & no. of aperture is by tracing the area of 1 x 1 inch and measure the dimensions of apertures and no.