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AGGREGATES & QUARRIES

IMPROVEMENTS INCREASE SAFETY ON AND AROUND JAW CRUSHERS By Lee Toop, Associate Editor

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ggregate production, when you get right down to it, is a simple process: large rocks are bashed against large pieces of iron to make them smaller rocks repeatedly until they’re the size that a customer might want. That’s a bit of an oversimplification, but it captures the concept fairly well. It also illustrates why workers in quarries who are around the machines that do all that bashing are always keenly aware of safety. They want to know that when there are issues with how their crushers work, they can sort them out without putting themselves into an area of potential danger or damaging their machine. Primary crushers that handle the largest rocks on a jobsite are an especially challenging machine to manage when it comes to safety, but Telsmith has worked on adding features to its Hydra-Jaw crusher line that bring more safety to its large machines and the sites they work on. The Hydra-Jaw primary crushers have been on the market for some time, but the company introduced a number of new additions at bauma this past spring. These include updating the hydraulic system, modifying controls and several other changes. Josh Terry, a Telsmith product engineer, said some of the changes are designed to help get the machine back up and running when problems occur – without putting the operator in potential danger. “If you have a power interruption with a full chamber of rock, or you get a rock jammed, in the past you would have to clear out that crushing chamber before you could restart the crusher. You can’t start a jaw crusher with a full chamber or the belts are going to burn out, you’re going to overamp the motor,” Terry related. “Going way back, you heard stories about dynamite, or you would have 28

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to get chains in there and get an excavator to try and lift individual chunks out. You’d have people walking around a crushing chamber full of rock trying to rig up rocks that are hard to rig because they’re stacked up.” In other cases, workers would use long bars, standing at the top of the crusher to try and move rock around inside the chamber, Terry said.

Hydraulic chamber clearing

Needless to say, those practices are less than ideal. Telsmith has added a unique hydraulic chamber clearing system that keeps workers away from the machine while getting the crusher back to work quickly. “Using the hydraulic clearing system, you can open and close the crusher, and break out all the rocks that are in the chamber,” Terry described. “It’s not going to be as fast as what the crusher would normally do processing rocks, but in 20 minutes or a half-hour you can have it completely empty and ready to run again – and that’s worstcase. The best case is that you just have something bridged across the crusher opening. . . a lot of times what you can do is just open up the crusher and get that rock started into the chamber, then go back to your usual settings.” Along with worker safety, the chamber clearing system protects the toggle, which can be damaged if the crusher winds up overloaded. “In a traditional jaw crusher, the toggle can either break or bend, or in a worst-case scenario it will lock up, stall and you need to find a way to release some of that tension,” Terry described. “Having a hydraulic cylinder in there means you can safely let that tension out.” Hydraulics also make it much easier to make pressure setting changes, Terry noted; rather than adding

or subtracting shims, a time-consuming process, the process is as easy as pushing a button. “Sometimes that means a crusher doesn’t get adjusted as often as it should, because it’s going to take some time out of someone’s shift to make that small change. So, they run it at a less than optimal setting,” Terry said. “With the hydraulic system, it’s a change you can do frequently.” To handle the additional work, the hydraulic system has been updated; what started as a gear pump system to make adjustments has been improved to meet those greater power needs. “The new unit is a piston pump system with a pressure compensated pump continuously running; it’s a 5,000 psi system to match the cylinder a little better,” Terry described. “What that means is that if you get a bunch of really hard rock jammed in the chamber and you need a little more force to clear it without stalling, there’s more capacity to do so.” The Hydra-Jaw crushers have received updates in other areas as well. Terry noted that the control systems have been updated, taking advantage of a new programmable logic control (PLC) unit that allows for monitoring of various conditions on the machine. A new touchscreen also helps make the crusher easier to operate, he added. “You don’t want to have to push a bunch of buttons and navigate a lot of different menus; the touchscreen menus are pretty intuitive,” Terry noted. With a lighter weight than other crushers, the Hydra-Jaw has drawn interest from quarry operators as a component in their wheeled portable plants, along with its more traditional stationary primary crushing role. “We do have some big primary stations we’re still selling. . . we focus on the bigger wheeled portable systems, though. People want to move it around the pit a little easier – that is an advantage,” Terry said. HEG

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Heavy Equipment Guide July/August 2019, Volume 34, Number 7  

Heavy Equipment Guide July/August 2019, Volume 34, Number 7  

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