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Knocking the Blockage Off


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 excavators used to load material to all brands of tracked portable crushers can routinely deliver oversized, stacked or misaligned material 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. Production 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 resume. Common to this process is the potential 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 repeat bridging issues. Both methods significantly 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 chamber lid and the chamber housing to accomplish 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 curtain relief system creates a temporary increase in height permitting material that has bridged or obstructed the crusher opening to pass freely through the chamber, preventing costly down times and lost productivity. It also helps alleviate the fear of material bridging and the need for excessive 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. Additional labor costs and downtimes are effectively 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 for it to then take 40 minutes or more to clear a jam within the crushing chamber. That is one hour of downtime for each blockage occurrence.

For simplicity sake, let’s assume you were crushing limestone at a rate of 600 tph and selling your crushed material for $10 per ton. Your company can lose $6,000 per each episode. Even if this happens just 2-3 times daily, you would be left with only 5-6 hours of actual productive work in an eight hour day, losing $6,000-$18,000 or more on a daily basis.

By utilizing the SMI system, most blockages can clear themselves with the push of a button in the time it takes the loader operator to grab another bucket full of material to be crushed.

Screen Machine Industries, www.screenmachine.com