Operators can put their crushers through considerable paces day after day. Different materials such as asphalt, shingles, concrete and even mystery materials can be fed through a crusher, and begin to erode the wear parts. There are simple ways to improve the useful lifespan of a wear part, including daily inspections and understanding which type of blow bar is best suited to crush different materials.
Knowing when to replace wear parts is more of an art than a science, say recyclers. There are too many variables involved to be able to know exactly when a wear part will need to be replaced. However, regular maintenance can make it easier to predict.
“We generally will run blow bars until they are about an inch from the rotor, then we will change them or flip them,” Joe Logan, president of Logan Aggregate Recycling Inc., Richmond, Va., explains. “We try to run all of our side curtain liners and chamber liners until we get every last bit of life out of them before we change them out. We certainly don’t want to wear through a liner to where you’re into the frame of the crusher, but you also don’t want to change a wear plate when there is 50 percent life left on it.”
Following the manufacturer guidelines and having a maintenance schedule for inspections can help determine a pattern for how many operating hours a given part may last. Neil Hise, owner and president of CEMCO, City of Industry, Calif., explains that learning when wear parts need to be changed simply takes experience, and he suggests imposing markers to indicate when parts will need to be changed.
“You may be inclined to place the part on a scale and measure how much potential life it has left, but a great deal of that is subjective because there may be deep grooves in one [portion] of the part and not in the other,” he says.
Ryan Newman, parts sales manager for KPI-JCI, Yankton, S.D., agrees there is no one formula for determining a wear part replacement schedule. “There is no blanket answer to this one. All must be determined based on the application. In some cases it might take a little trial and error in order to get things exactly right.”
When working outside, operators must sometimes contend with less than ideal weather conditions. Extreme heat can cause problems with materials such as asphalt shingles. High temperatures will cause them to become tacky and stick to the wear parts, say operators.
Cold weather can be fine to work in “as long as it’s dry and not cold enough to cause problems for your equipment,” Ron Brocco, operations manager for Independence Excavating Inc, Independence, Ohio, says. “In general, in the cold, that’s about 20 to 25 degrees.”
Routine maintenance is often the first thing most operators and yard supervisors point to when discussing improving the life of equipment.
“Daily routine maintenance is important to optimizing the wear life out of your wear parts in your crushers,” Brocco says. It also can keep cost to a minimum and reduce downtime brought on by complicated repairs. When maintaining wear parts, there are important things to look for that go beyond a daily greasing.”
Logan agrees, “With routine maintenance, most people think of changing the engine oil or greasing the bearings—that kind of thing—but our maintenance every day involves opening up the crusher and cleaning out any material buildup in there”
Brocco says sometimes material can build up in the corners or the impactor box of the crushing chamber. “As that builds up, it can wear into the corners of your rotor or your blow bar,” he says. “We’ve found by just opening up the crusher everyday and cleaning out any material buildup, it has really made a big difference for us.”
Brocco says knowing the correct speed at which to run an impact crusher is paramount in optimizing wear parts. He also suggests operators understand how the chemistry of the wear parts used will affect production and wear costs.
Logan also emphasizes speed. “We try to pay attention to things like the speed of the rotor and the crushing gap setting, depending on the material you are making,” he says. “If you are running the rotor too fast, the material will just be grinding on the bars of the chamber, and if you run it too slow, you run the risk of clogging it up.”
Logan explains there is a primary and a secondary curtain on the crusher. He has a general rule of two to one.
“When crushing concrete, it would be set to the primary curtain at five inches and the secondary at two-and-a-half inches,” Logan says. “This way you get two stages of reduction.”
If the operator doesn’t check those three settings on a regular basis to make sure they are where they are supposed to be, “You can start to have problems,” Logan warns.
Understanding how the manufacturer designed the machine and configuring it based on the material you are going to produce is important for long wear part life. Logan says he has seen problems occur when operators do not check these configurations consistently.
“The biggest thing that we have seen is if an operator is not checking [the configurations] on a regular basis and the bars wear down into the rotors,” Logan says. He adds that both of the crushers used at Logan Aggregate Recycling have four-row rotors “so we run two long bars and two short bars (or dummy bars) that are basically just there to fill the gaps.”
Logan says if all four bars were the same length, the material could not penetrate the path of the rotor. “So, I run it two up and two down to get that interruption where material can fall in.”
If the operator lets the bars wear to a point where they are all the same length, Logan says there will be no interruption and material will just ride on top of the rotor and never falls down. “Or, all four bars can wear down into the rotor [and wear] down into the rotor itself, which can be extremely expensive,” he adds.
Concrete and aggregates processors agree that the manufacturer can be a great resource when trying to understand a crusher. “Most manufacturers are eager to share with purchasers their concepts behind the design of their crushers. Understanding why your plant was designed the way it is very important for your operators,” Brocco says.
One of the most effective things an operator can do to extend wear parts is be aware of the differences between materials such as asphalt and concrete. Wear parts that will have a long life crushing concrete are not necessarily the same ones that will do well crushing asphalt.
Brocco says, “The wear factor with concrete and asphalt is largely related to the aggregate used in making the concrete or asphalt. Wear costs also are directly related to the size of the material that you wish to produce.”
By using different wear parts for different materials, operators can prevent breakage and extend life to some extent. However, blow bars used to crush concrete may have a shorter lifespan because they need to be softer to avoid shattering when coming in contact with certain materials.
Newman explains, “Wear parts can be misapplied also. For instance, a high chrome wear part may be introduced into an application where a low chrome would be better suited. In this type of situation, you may see the wear part fail prematurely rather than wearing out.”
Increasing the chrome content increases the wear parts resistance to wear. However, brittleness will increase as well, Newman says. Ceramic inserts in wear parts slow wear without increasing the brittleness.
Logan says his team typically gets about twice as much wear out of blow bars when crushing asphalt compared to processing concrete material.
Hise says, “Manufacturer recommendations are a valid starting point for taking care of crushers, but ultimately it is best to get in there and learn about the machine and its parts.”
The author is assistant editor of Construction and Demolition Recycling and can be contacted at email@example.com.