Zane makes sure the crusher’s machined surfaces are ready for assembly.
We’ve worked on a lot of torn-up cone crushers for large rocks in our business and we see the same expensive problems crop up, time and again. Our technicians work on over a hundred different cone crushers every year, both in our shop and out in the field. I asked two of our more experienced techs, Bill and Dave, who have had a hand in the history of cone crushers to talk a bit about the most common problems they see. They started rattling off a bunch of things they have seen, but I will limit this list to ten items. Maybe one of their observations will help you keep your machine running another year, or ten.
As you will see, many of the issues are of the “domino variety”, which means that the original problem is not that bad in itself, but the consequences “down the line” are catastrophic for the machine and your wallet. Every one of these items will likely save you a few bucks in the short run, but then your run ends and you will need deep pockets to put things back together.
- Neglect your maintenance: you go one day without maintenance and you see no consequences. Soon enough you are encouraged to send the crew home early so you can save a few bucks on the time they would have spent on manufacturers recommended maintenance. Or worse, the crew is not even trained to look after the equipment, so they don’t even know what to look at, even if they were to do maintenance.
No maintenance means neglect to check on filters, which leads to a poor flow of lubricants, which will burn up a $50,000 bearing in a few minutes. A clogged air filter or breather can cause positive pressure to build up inside the bearing housing. This makes a seal pops out and then you have a sealing problem in a place that requires the head to be pulled for a proper repair. If you don’t fix the seal, the oil will spill out and dirt will get in and your problem gets more expensive each day.
- Poor housekeeping: it is ironic to think about housekeeping in a place that seems so full of dust and mud, but we see the destructive, costly results of things that are left to the wind. Electric and hydraulic cabinets are left open; they collect dust and moisture and the components inside fail prematurely. Rocks that fall around the crusher are allowed to build up and rub through hoses and electric wires. Filters are allowed to clog.
- Fail to check for wear: Every machine wears down. The question is “How much is too much?” To a certain point, it is economically feasible to repair crusher wear, but let it go too far and you get vibration and metal fatigue and a host of related problems that means it could be “cap ex time” when you have no capital expenditure budgeted.
- Shock loading with feed material: yes, the machine is built to crush, but when you dump a bunch of material in all at once, the head momentarily gets pushed down and squeezes out the thin film of oil that separates the spinning parts from the stationary parts, like at the thrust bushings. Before you know it, parts don’t fit together the way they are supposed to and you have a big, expensive paperweight on your hands.
- Run your wear liners thin: Manganese wear liners, aka “bowls” and “mantles”, can be expensive. And there is a temptation to run those liners until they all but fall out of the bottom of the crusher. It can be done, but it is a false economy. The cost of replacing manganese pales compared to repairing or replacing any of the parts that were left unprotected by the liners.
- Use the crusher for the wrong application: every tool has a limited range of use. A screwdriver is not a hammer but you need both in your toolbox. Crushers get abused and worn out prematurely by being used in applications they were not designed, nor dimensioned, to handle. If a crusher is made for a 4:1 reduction ratio, you are not doing yourself favors by trying to make it reduce more than that. And when you are considering changes to your plant, it’s a good idea to have your plant and components audited by an applications engineer who can make recommendations for your equipment and their use.
- Wrong closed side setting (CSS): The tighter you set the cone on your crusher, the finer it will crush—to a limit. Finding that limit is an art, going past that limit is easy and expensive. This is because a crusher will tend to “pancake” the material if you try to go beyond the reduction ratio the machine was designed for, which leads to “ring-bounce” in the crusher head, which tears up your seats, and is expensive to repair. The pieces that fall out tend to be shaped like oysters and the condition is called “oystering”.
- Compensating for errors by making mistakes: For example, once you experience something like “ring-bounce” (see #6), you might be tempted to simply jack up the pressure in your accumulators to keep the head down and mash the material through. It can be done—we have seen it countless times, but what you have done is compromised the tramp relief system and made it more difficult for “uncrushable materials” to pass through the crusher. Then, one day when you least need it, an old drill bit that someone lost 30 years ago makes its way into the crusher and… stops. It. Cold. Or blows out the accumulators, or cylinders, or snaps the countershaft. Even if nothing breaks, you now have a piece of metal in your crusher that is squeezed so hard it becomes a missile when someone goes to cut that piece out.
Another big set of well-intended mistakes is when crushers are altered to compensate for problems that develop as a result of any of the other points. We see shims, welds, wedges, rerouted hoses, chained-down heads, and a variety of other “solutions” that do nothing but defer and add to the expense of a proper repair or even make a repair impossible because of damage that is too far gone.
- Lopsided feed: you know how trees at the beach tend to grow crooked because the wind always pushes them from one side? Well, the one-sided feed will do something similar to your crusher’s cone. Your manganese will wear through in one spot, the main shaft is constantly side-loaded, your crushing chamber is not used efficiently and your product is made as well as it could be. The feed should be constant and even. A surge bin can be a good solution for intermittent feed, but open the gates slowly (see #3).
- Support the crusher unevenly: Uneven support can allow the crusher frame to flex or vibrate or cause uneven wear in the bearings because of the weight of the parts shifts to one side. The support might have been good when the crusher was installed, but supports can shift because of mechanical wear. Cribbing might settle because of water running through the plant over the years. Or frames might shift because they were placed when the ground was frozen and when spring comes, the frame settles and the crusher begins to fail prematurely.
There is more, of course, but this should give you the idea that cone crushers are fickle machines if you don’t treat them right. Using your operators’ manuals to check your equipment routinely and frequently is key to managing your production cost-per-ton. If you feel your personnel is not trained to perform the necessary maintenance, then schedule a meeting with Mellott Company or call 888-801-1410 for proper training, service, and auditing could save you loads of money in the long run.
Written by: Magnus Dahlgren, a member of the aggregates equipment industry since 1993.