Rock Products

JUN 2013

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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CRUSHING BREAKING Knocking the Blockage Off HYDRAULIC BREAKER The Doosan DXB260H hydraulic breaker features two-speed control of breaker frequency for improved efficiency in demanding demolition and rock-breaking applications. Delivering up to 600 blows per minute, the 5,400-lb. DXB260H is designed for use with excavators in the 27 to 37-metric-ton weight range, specifically the Doosan DX300LC and DX350LC. Rated in the 8,000 ft.-lb. impact energy class, the DXB260H requires a hydraulic flow rate of between 39.5 and 63.5 gal./min. Doosan, 26 ROCKproducts • JUNE 2013 When working around crushing equipment, one of the safest places a person can be is in an operator's cab. When looking at what forces operators to leave their cab, the age‐ old practice of manually clearing material blockages from the crusher feed inlet stands at the forefront. The wide range of wheel loaders and exca‐ vators used to load material to all brands of tracked portable crushers can routinely de‐ liver oversized, stacked or misaligned mate‐ rial that clogs or bridges the inlet entrance to the crushing chamber that needs to be cleared. Blockage Means Stoppage Job‐site crushing projects can be brought to a halt due to this material bridging. Produc‐ tion is stopped while the crushing rotor and engine of the machinery must be shut down making it safe for personnel with tools to clear the bridged material. Typically, pry bars, slings and hydraulic or pneumatic hammers are utilized to free the bridged material so that production may re‐ sume. Common to this process is the poten‐ tial loss of hours of production per episode along with the loss of hundreds of tons of productivity, depending upon the severity. Safety of job site personnel should be of paramount concern in this situation, along with lost production. Efforts to avoid the safety concerns and manual labor involved in clearing this bridging can lead to further productivity woes. Loader operators often slow the feed of their crushers to 50‐75 percent of their "rated" capacity or spend an excessive amount of time pre‐breaking the material into smaller sizes in an effort to avoid re‐ peat bridging issues. Both methods signifi‐ cantly slow production output. Herein lies the motivation behind the idea to equip the Screen Machine Industries, 5256T and 4043T Impact Crushers with the capability to remotely raise and lower the entire crusher lid curtain while the machine is in service. The company's team of engineers designed a remote‐controlled pivoting arrangement between the cham‐ ber lid and the chamber housing to accom‐ plish this. Push-Button With the push of a button, the lifting lid of the chamber will raise and lower vertically relative to the housing opening without having to shut down the machine. The cur‐ tain relief system creates a temporary in‐ crease in height permitting material that has bridged or obstructed the crusher opening to pass freely through the chamber, preventing costly down times and lost pro‐ ductivity. It also helps alleviate the fear of material bridging and the need for exces‐ sive pre‐breaking of the material prior to crushing. This system has been a standard Screen Machine patented feature since 2007, which keeps production on task, on time and operators safely inside their cabs. Addi‐ tional labor costs and downtimes are effec‐ tively minimized while productivity is enhanced. Adding Up the Numbers A look inside the numbers reveals that due to the weight and speed of the rotor it takes approximately 20 minutes for the crusher to fully "wind down" to a complete stop when shut down. It is not uncommon

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