It's generally pretty obvious when a blow bar breaks because it throws the rotor out of balance. "But you might not notice it if just a small piece of the blow bar breaks away, such as at the extreme end. If this happens, the rotor can be damaged by incoming material hitting the rotor instead of the blow bar," Weber says. "That's why it's important to check inside the crusher at the start of every shift."
Weber Sand & Gravel uses two blow bars out of the possible four for crushing. "We've found that using two bars in a four-bar rotor gives us the combination of production efficiency and cost effectiveness that we need for our type of operation," says Weber.
Due to the speed of the rotor, the high bars impact the incoming material to be crushed, and very little hits the low bars. "When the high bars wear down to about the level of the low bars, we remove the most worn set and install new high blow bars. The worn-down bars now act as the dummies," Weber explains.
Another important wear part is the side liner. As a rule, Weber Sand & Gravel turns side liners inside the "rotor zone" at about 50,000 to 75,000 tons. "As the rotor spins, it creates a circular wear pattern on the two side walls caused by crushed material getting between the wall and side of the rotor," Weber notes. "The wear pattern usually is such that you can unbolt the plates, turn them 90° to 180° and keep using them, rather than replace them at that time. The wear plates outside the rotor zone will last longer and sometimes can be switched with rotor zone plates to get longer life from the whole set."
Each of the company's impact crushers utilizes four interchangeable aprons. This allows fewer spare aprons to be stocked and helps keep the parts inventory lower.
Like Cherrington, Weber cautions against over greasing. "It's wasteful and can cause harm if you over-grease the bearings anywhere on your plant. It causes them to overheat and wear out faster," he states. "We give all bearings (except the impactor) two to three pumps of grease in mid-March when we begin our crushing season, and again in mid-September. We grease the impactor every 40 hours."
In some cases, you can reduce downtime by custom designing certain aspects of the plant. "For example, I had Grasan engineer the crushing and screening plants with quick-disconnect pins instead of bolts for almost anything we have to dismantle or take off for over-the-road travel," says Weber. "That saves a lot of time and hassle. It takes longer to work with bolts. The threads get worn after a while so the bolts need to be replaced, and it's easy to lose a nut or washer. The pins are quick, simple and chained to the equipment so you won't lose them."
Information for this article was provided by Grasan.