To Mark Krause, operations manager with River Aggregates, increasing crushing efficiency might necessitate a shorter-term view of the operational life of crushers, although some adjustments can be made to extend their lives and maximize their throughput.
“We’re asking a lot more out of our equipment,” he said. “We’re asking it to be more efficient, and we’re asking smaller packages to do more. Do we keep in mind that when we do that, we’re more than likely shortening the life expectancy of that equipment? For instance, we probably expect a cone crusher to last 25 to 40 years. Today’s new cone crushers are probably 10- to 15-year machines. There’s nothing wrong with that – it’s just a different mind-set.”
Krause says he is spending less up front because he is buying a package that’s more efficient, but it might not last as long as the old one.
“The other thing about crushers is, whether it’s a primary or secondary impactor, make sure you’re using modern technology for wear parts,” Krause said. “There’s been a lot of work done in the past few years on ceramic and carbide-embedded wear parts. The longer you can let those parts run, the more efficiently that crusher is going to run.”
Increasing the speed or replacing the liner are other simple operational changes. Ensuring that the crusher’s surge point remains full also costs less than purchasing a new crusher.
“If you’re going to get the most out of any tool, you need to keep it full,” said Krause. “Spend the money on the surge point and see if you get your desired outcome that way; if you don’t, you can worry about buying a new crusher. But you’ve already spent the money that you’re going to have to spend on a new surge point anyway.”
Krause says that adding a surge bin is a low-cost way to keep the surge point full. “They’re not big bins – maybe 40 to 50 tons. Some operators might use a 20- to 25-ton bin and a belt or vibratory feeder.” The entire cost is probably around $50,000, he estimated. “Sometimes you’ll find that you can’t put the bin above the crusher, so you need to locate it a conveyor length away.”
Screening Helping Crushing
While maximizing the efficiency of crushing operations will definitely help plant productivity, improving screening efficiency can also make a big impact on plant throughput in most operations. “There are a lot of screens that were installed 10 years ago for certain applications; the application has changed, but they haven’t gone in and changed the mechanical setup of the machine,” Krause said. “They're still using the same speed, same stroke, same everything.”
Changing speed is easy, but adjusting the stroke is more difficult. “We have to be cautious that we don’t go outside the bounds of what the manufacturer suggests the screen can do. You can’t have high speed and high stroke together or you might end up destroying the screen.” Newer machines make it easier to add weights, allowing producers to adjust to different material often.
Krause says the media has changed dramatically in the world of screening. “There are all types of live wire screen deck today that incorporate rubber and wire or urethane and wire in combination on a deck where, traditionally, we once used wire cloth. Then rubber decks and urethane decks came along: rubber for dry applications, urethane for wet applications,” he said.
“Washing has been so misunderstood,” Krause said. “We’re inefficient for two reasons. One is the concept that more water is more efficient. Then, it’s a lack of understanding that there is new technology – for example, dewatering screens, different pumps, different additives such as flocculants, that can greatly reduce the cost of the washing operation.”
To Krause, high water use in washing creates two types of costs. “Whatever water you put in, you’ve got to take out and treat,” he said. “Secondly, we see a lot of waste because water tends to carry particles with it and particles that you wish to retain – your sand – are now going somewhere you don’t want them to go. There’s a cost to going in there and reclaiming that. If that sits in the bottom of the pond, at some point, you’ve got to clean out your pond.”