Re: Non Segregated Stock Piles
Dear Mr. George Baker,
I am not very sure, but it seems you are referring to size segregation during formation of the stockpile, i.e. bigger size will roll down towards the base and smaller size tends to remain at upper level. Regarding stockpile formation by stacker or stacker-cum-reclaimer, there are well-defined methods by which this phenomenon can be minimized to bare minimum level. For example, if you make stockpile by windrow method, then, at a time you are forming a small segment of stockpile, which is, say 1 to 1.5 m height. In this segment, there would be segregation but it would be very much localised. The complete stockpile is formed by series of such rows formed one over the other, so in a total cross section of stockpile, the affect of segregation will be minimized, i.e. the reclaiming occurring at any point will immediately reclaiming fines as well as coarse material. So, the end result, minimizes the adverse affect due to size segregation.
There are also other methods by which this problem can be reduced.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Advisor / Consultant for Bulk Material Handling System & Issues.
Email : parimul@pn2.vsnl.net.in
Tel.: 0091 (0)20 25882916 ■
Re: Non Segregated Stock Piles
Hello,
There are few factors involved with segregation. By admitting there is a particle size spectrum and recognising that the bigger bits will roll down a slope: then to eliminate segregation we must lay down material in layer depths with the same order of magnitude as the largest particle. Further recognising that such a lay up method is impratical in terms of cost, complexity, excessive machine movement and dust generation we have to accept a fair degree of segregation in stockpiling activities. (The opener refers to sand and aggregates stockpiling). It is all very well to talk about depositing thinner layers but the machine discharge must move faster to spread at the desired tonnage; and all the time. This pushes up the drive power consumptions and complexity of the machines. Downtime creeps in.
When stacking in wet regions there is a likelihood that undesireable rainwater is retained within reduced bed heights, particularly in windrow stacking. In Malaya there was a fairly recent case where accumulated rainwater would have shoved the power station coal well out of spec if the material had been windrow stacked.
As a (sometimes) tipper truck driver I have been forced to recognise that there is no finer way to load aggregates than with a front end loader. Further if the material is drier the dry bulk content is higher and the transport operation becomes more profitable. Water drains out along the road and besides the environmental impact the quarryman, or his customer, pays to transport this extra moisture for the full journey.
So if you are loading with a shovel, blend with the darling machine and forget anything fancy at the stacker end. If you are loading from an overhead conveyor; don't. ■
John Gateley johngateley@hotmail.com www.the-credible-bulk.com
Thankyou For The Helpful Info
Appreciated, as usual, George ■
Non-Segregted Stockpiles
Quality control of cement concrete for high-end applications requires that aggregates of specified particle size distribution (and not just the top size specification) be used. A consistent particle size of aggregates from several quarries can be achieved if they are homogenized through systematically layering over a stockpile. This becomes even more critical when using coals of different calorific value and sulfur contents.
However, an alternate to layering over a stockpile is "dynamic blending" which involves drawing preset proportions of materials from different stockpiles and blending them during conveying.
Thanks,
Vas ■
Stockpile Segregation
The simplest method is to screen the product and then seperate and stockpile the product by size. The various sizes can than be combined on a conveyor belt to a particular recipe.
An alternate method if you have a long linear stockpile, would ne to select a reclaimer that reclaims the full pile cross section such as a wheel on bridge or bridge scraper reclaimer. These reclaimers are not sensitive to pile segregation and you get a uniform product. For an even better blend, you can use these reclaimers in conjunction with windrow stacking.
If you would like some photos or an article send your email address to frank@loefflerengineering.com. ■
Non Segregated Stock Piles
I would enjoy a discussion on the theory of SEGREGATED AND NON SEGREGATED stock piles........specifically in aggregate process systems (sand and gravel).
Some people do not feel the use of fancy stinger design or telescopic conveyors are a necessity.......to create non segregated stockpiles and others do.
SOME operators prefer to just blend the coarse materials that runs off the edges of their CONICAL STOCKPILES back together with the fines with a front end wheel loader prior to loading.
others.........
prefer the use of SPINNER TYPE pulleys at the top or HEAD END of their stacking conveyors.....to BLEND? Prior to stockpiling?
others.......
DO see and agree with the concept of TELESCOPIC manually or PLC controlled STACKERS........that build a stockpile in layers in a pre-defined radially traversing height, stockpile RADIUS and stockpile TONNAGE FOOTPRINT. These units stack in lower heights,,,,,,,,avoiding coarse running off of the fines........laying down full radial piles......uniformly and BLENDED...or NON SEGREGATED.........and substantially reducing operating costs due to non use of WHEEL LOADERS.....to blend and transport.
OPINIONS would be welcomed.
Regards, George Baker ■