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Crushing do’s and don’ts

By and |  January 4, 2016

The simplest details make a huge difference when crushing, says Stephen Dobler, Sandvik Construction‘s business line manager for crushing and screening in Canada.

“I think everyone has a good grasp on how they should be feeding a crusher,” Dobler says. “But every operation has certain priorities, and sometimes these things fall on the backburner because they don’t seem to have an immediate impact. Still, a lot of these basic things will have an impact on your operation.”

Dobler shared some takeaways with Pit & Quarry that aggregate producers can apply to their own crushing operations. Here are Dobler’s do’s and don’ts:

Do: Realize that the quality of your rock may change the deeper you move into your reserves.

“The quality of the rock will affect operating costs,” Dobler says. “If an operation isn’t double-checking work indexes and abrasion indexes, they can get caught by surprise when wear parts wear out faster.”

Producers typically take core samples before quarry operations begin, but testing should never stop because initial core drilling was done.

“Just because some core sampling was done doesn’t mean you have a real indication of what’s really there,” Dobler says.

Do: Involve all stakeholders when selecting crushing equipment.

If a parent buys a child a gift for Christmas but the gift is not what the child wanted, the child will likely throw it in a closet and not use it, according to Dobler.

“But if you buy your son a gift he wanted for Christmas, he’ll probably use it for a long time,” he says.

The same logic applies to crushing equipment, Dobler adds.

“Involve all stakeholders, but also involve operations, maintenance, engineering,” he says. “You get a much better buy-in from them. They’re going to do the best they can when they’ve got a vested interest.”

Do: Consider where you put your crushing plant.

Place the crusher where it makes most sense, Dobler says. Also, consider if a portable setup is the way to go and what type of crusher matches your rock’s needs.

You could be anywhere from operating costs that are two to three times higher with an impact crusher versus a cone crusher, assuming you’re in low abrasion rock,” he says. “And that’s just on the wear parts alone.”

Do: Design conveyors as wide and as slow as possible to improve the lifecycle and reduce operating costs.

This reduces the need for rock boxes and deflectors, says Dobler, who recommends producers only use rock boxes and deflectors if they absolutely must.

“A rock box or a deflector is something you install at a transition point between two things,” Dobler says. “They’re a means to essentially slow down material and redirect it.”

So rather than run narrower conveyor belts that operate at higher speeds, Dobler recommends employing wider belts that run at slower speeds. This approach generally offers much better material flow, he says.

“Then, you don’t need more complicated rock boxes or deflector systems,” Dobler says. “Transition points are simplified. By definition, you will have much simpler transfer points within the plant and there will be less wear on it.”

Don’t: Stack conveyors on top of one other.

If producers do this, they’ll leave little to no access for maintenance crews.

“Producers always try to save costs by setting up nice and tight, but quarries and mines typically have equipment that needs maintenance,” Dobler says. “You’re always going to be replacing parts and wear parts. We always recommend having equipment set up in a way that it’s easy to get to these areas.”

Don’t: Feed material at an angle or change the feed direction ahead of equipment.

As an example, material that’s flowing toward a screen box should be directed to it in a straight line, Dobler says.

“You want the conveyor to discharge parallel to the flow of the material going down the screen,” he says.

Material should enter a crushing chamber in the same fashion. If material is suddenly diverted on a conveyor belt at a sharp angle, producers may shift the balance of material entering the crusher.

“In a crusher, the crushing chamber is going around in a circle and the crusher is closing up in one location,” Dobler says. “Once you have segregation in that chamber, one side is coarse and the other is fine. Over time your components will feel that, and they will fail.”

The same logic applies to impact crushers, Dobler adds.

“With all of the coarse material on one side and all of the fine on the other, wear parts will wear faster on one side and not as fast on the other,” he says.

Do: Keep detailed records of equipment maintenance and check data trends to extend equipment life.

Take a concept as simple as bearing vibrations. If producers regularly measure bearing vibration on any bearing assembly and note changes, Dobler says they should be able to predict when that assembly has reached its limit.

“The same thing applies to a bushing in the crusher,” he says. “If you’re measuring the plate between the crusher and doing it over time, you can see the change. You’ll know what the limit is and be able to know when you hit the limit.”

Operations will be more efficient when producers can forecast such changes, too.

“The idea is to predict when you’re going to need a new component rather than undertake one certain maintenance task,” Dobler says. “It’s like you’re going in to change a liner on a crusher, and you see a dust shield that’s worn out and needs replaced. The option is to wait a day for the part to come, but then you’re doing two long interventions instead of one short intervention.”

About the Author:

Megan Smalley is the associate editor of Pit & Quarry. Contact her at msmalley@northcoastmedia.net or 216-363-7930.

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