Product feature: Sanland range
Screening and crushing equipment from Sanland
As concrete plants get busier, the smaller end of crushed material gets scarce and presents opportunities for aggregate producers. With natural sand sources getting harder to find, and even harder to obtain permissions to extract the resource, how does one make money from making sand these days?
Like all crushing, it starts with what have you got: how big is it, how hard, how ‘clean’, and importantly, how abrasive is it?
Machinery that can crush material down to sand will nearly always be used in closed-circuit with a screen. A recirculating load should not be seen as a waste of movement but instead a necessary part of ensuring the lowest amount of energy and wear-cost is applied to get the correct-sized sand required.
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Kumbee hammermill can efficiently process larger-sized feed material
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Some mills make sand in one pass; these mainly work in lime and softer stone where a ‘grid’ is made under the crushing hammers and won’t allow the material to pass until it’s below the required size. In harder rock, this approach would be overly expensive in wear costs when compared with accepting a recirculating load from a screen.
In New Zealand, the work is mostly done with impactors, hammermills, and vertical shaft impact crushers (VSIs). Some cone crushers can do the work and can be an option with modified liners but mostly, impact machinery is used.
Impactors and hammermills have benefitted hugely from advances at the foundry and have made quarries that previously would never have considered these machines—an economic success.
The Kumbee hammermill that Sanland Equipment makes is an example of this. Many quarry operators may remember using one in the 1990s and they were expensive, but those old machines have benefitted from new metallurgy processes, in much the same way as the expensive mobile machines have improved with new technology.
VSIs are common in sand making; they generally take a small feed and can crush it by throwing it against a rock shelf to break it. The smaller feed size can be an advantage or disadvantage, depending on what the raw product is.
In the South Island, with its loose alluvial deposits, VSIs can be a great way of reducing unsaleable pea metal, as the small size of the raw product won’t process as efficiently in a hammermill or fixed hammer impactor.
This differs in the North Island with raw feed being more suited to a Kumbee hammermill or fixed hammer impactor; these machines are able to efficiently process larger-sized feed material.
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VSIs can be a great way of reducing unsaleable pea metal
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The ‘Barmac’ style of rock-on-rock crushing was developed in New Zealand, and this country has favoured it almost exclusively. There’s good argument that operators should be reviewing this method, given the high level of ultra-fines (under 300 micron) this type of crushing produces.
The smaller fraction is often unpopular with ready-mix concrete producers and may result in the need to wash the sand. The older-style anvil set-up in a VSI produces much less fines and gives output at the same level with around 33% less power used.
Sanland says their team can advise anyone considering producing sand on all the above processes and they know how to make it work efficiently and cost-effectively.
For more information, contact Sanland on 09 296 9488 or visit sanlandequipment.co.nz
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