“Before we changed over, we could crush about 500,000 tons per year with our own static plant,” he explains. Subcontractors’ machines were hired in to bulk up production. Now, we’re extracting our production target of nearly 1 millions tons per annum using just one machine, the MR 172.”

Admittedly, on paper the MR 172 is a higher-capacity unit than the stationary unit it replaced — so it should deliver more, Byrne points out. “Nevertheless, the extra throughput is not just down to the size of the machine,” he says. “The whole system is better balanced now, and we have more control of our stockpiles.”

Impact versus jaw

Byrne says his operation chose an impact crusher rather than a jaw-type machine because the area in which the quarry is located is predominantly limestone — much less abrasive rock. An impact crusher is better suited to this softer-type material, he says.

The Kleemann 172 can average 450 tons per hour. Two-Mile-Ditch Quarry now crushes about 4,000 tons per day.

“We typically crush more than 4,000 tons per day,” Byrne adds. “That’s on a nine-hour shift. We generally average about 450 tons per hour. And because the capacity of the primary crusher determines the performance of the entire quarry, the MR 172 plays a critical role.”

To simplify logistics and service backup, Roadstone opted for matching Kleemann screening equipment when installing the crusher. This enables Roadstone to crush at the face as well as carry out secondary processing there.

Internal haulage and re-handling are kept to a minimum because so much processing takes place at the blast site. In some cases, ready-for-sale products are being taken directly from a machine that works at the rock face, meaning it doesn’t have to be reloaded elsewhere on the site.

“Our Kleemann MR 172 is set up to crush down to six inches or smaller,” Byrne says. “The crusher’s own pre-screener removes blast fines in either 3-inch to zero or 1-3/4-inches to zero sizes. This is sold off-site or taken for further processing, depending on demand.”

The screener, which works in tandem with the MR 172 impact crusher, takes the 6-inch to zero rock and splits it up into three different sizes. These include 1-1/2 inch to-zero (state-spec road base), 3-inch clean stone, and larger 6-inch clean stone.

Because so much processing takes place at the blast site, internal haulage and re-handling are kept to a minimum, Byrne says. “For example, in some cases we’re taking ready-for-sale products from a machine that works at the rock face,” he says. “That means it doesn’t have to be re-loaded elsewhere on site.”

Jim Breen is a freelance writer based in Ireland 
and wrote this article on behalf of Kleemann/McHale. Breen writes for several machinery and equipment publications in the agricultural, forestry, and plant/construction sectors.