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Buying a Sieve Shaker (6 replies)
This is a real service providing some commentary around sizing of samples using sieves. Many people assume this testing is so simple that it cannot be done incorrectly!
I would also encourage people to consider the quality of the sieves used at their internal labs or the external labs they are using. The section of your website referring to calibration samples provides some insight into this.
http://www.cscscientific.us/Particle-Size-Analysis/Calibration-Samples
The sieves do not last forever & the variability inherent to woven or other materials can be an appreciable fraction of the supposed mesh / micron size openings. There are some good papers and guides available covering this.
Sample preparation using riffles and use of correct sample sizes are key parts of this.
Excellent; It is good that a basic task of sieving is brought on to the table;usually the total task of sampling followed by sieving is considered non technical and is carried out by persons with no knowledge of basic things like why it is being done,how it has to be done and the effect of any wrong doings on the interpretations which follow..I hope mineral engns give more importance to this.
The basics Mineral Processing starts here. Sampling and sizing are the key parameters to establish a process flow sheet / unit operation/ improving the process itself. Simply placing samples in sieves and plotting for retained or passing is the only out put one sees.
Nice to see and start the basics
It's important that some known "standard" samples be retained, both for checking any new shakers brought into the picture and for testing any new sieves that are brought into the deck. Consistency in equipment and procedures is the only way to get consistent, repeatable results.
Once at a plant where I worked as a young metallurgist, new sieves were brought into the lab for checking the final grind of concentrate, a major control point in an iron ore plant feeding a pelletizer. They were not checked against a standard sample. After a drop off in production was noted, it was traced back to the new sieves having slightly smaller holes, pushing the measurements of % passing that size to the coarser side. The feed rate to the plant was slowed down to maintain the measured grind. It took a lot of metallurgical detective work to find this and get the plant concentrate grind and productivity back in control.
A good idea is to always check new sieves. We use a scaled microsope and it is not uncommon for seives to be incorrect, even from suppliers of quality seives.
Also, I have seen lots of errors in sieve sizing and other methods of sizing and generally comes from people who may not completely understand what they are doing, but sometimes from people you would expect to know better. A lot of people don't even think that the sizing results they get may be incorrect
cheers!
The selection and purchase of a quality Sieve Shaker may seem trivial but it not.
One of the ways to check your sievers is to use calibrated microspheres. These give the results of the check in terms of mean aperture. That gives you two things. First it is a base reference for later checking of wear. Second it is a measure of how close the performance of the sieve is to the stated aperture size.
http://www.cscscientific.com/csc-cientific-blog/what-so-special-about-picking-a-sieve-shaker
http://www.mep.net.au/wpmep/wp-content/uploads/2013/07/MEP_expert_guide_sieving_en.pdf
The microscope approach is tedious. The sphere approach is easy and quick.