Red rock meets its match

By |  October 29, 2013

A California producer finds a cost-effective way to process hard, abrasive material.

Edited By Kevin Yanik

Three men. Working all day. On a single job.

That’s typically the scenario that unfolds at Porterville Rock & Recycle, an aggregate producer based in Porterville, Calif., when a primary screen must be replaced. Replacing screens is a labor-intensive task, but it’s one that’s necessary for the operation to remain productive. The less often the operation has to change out screens, the better.

Still, considering Porterville Rock recently began mining metabasalt, a notoriously hard granite and red rock which owner Mitch Brown describes as harder and more abrasive than anything his business has processed in his time, the operation was forced to replace screens more often than he preferred.

The upside of the red rock is it’s a high in-demand material, Brown says – at least in California, where Porterville Rock competes locally against four other producers.

“It’s such a good rock that it meets new [California Department of Transportation] regulations,” Brown says. “It goes into concrete products. It goes into asphalt products and any road-building material – that’s really its main use. It meets the rock spec for railroads. It’s a great riprap source. I haven’t found anything it won’t work for right now.”

The red rock has a downside, though: It beats the heck out of equipment, including Porterville Rock’s screens. Considering this factor, as well as the fact that Porterville Rock has 100 million tons of red rock remaining in its deposit at its Wilcox mine, Brown sought solutions to extend the lifespan of his screens.

Looking for answers

Initially, Porterville Rock ran several screening tests to determine which screens would suit its red rock best. The screens Brown’s crew installed originally in one screen box were a top-deck wire-cloth screen with a 2-in. opening and 3/8-in. double wire; a middle-deck wire-cloth screen with urethane strips and both 1 1/8-in. and 1 1/16-in. openings; and a bottom-deck, wire-cloth screen with a square-opening design that featured 1/2-in. and 3/8-in. openings. The bottom-deck screens were Unified Screening & Crushing manufactured.

The original upper-deck screens were no matches for Porterville Rock’s red rock, Brown says. They lasted just three weeks. The top- and middle-deck screens wore out much too soon and needed premature change-out, he says.

Once Brown realized he didn’t have a usable system for the red rock, one of his next moves was to phone Ray Sailer, general manager of Unified Screening in California.

“We listen to the people who come in and try new products all the time,” Brown says. “It’s labor intensive when you have to start changing out screens and cone liners all the time. When you start doing that, you have to find longer-lasting products to save on some of the labor.”

Sailer visited the Wilcox site and observed the operation, recommending a start on the middle deck with a diamond-type, 1 1/8-in. opening and three-gauge Tufflex wire. For the bottom deck, Sailer recommended keeping the square-opening Unified screens.

According to Unified, its SuperFlow screens sport a hybrid design that features a combination of Tufflex wire and polyurethane. The combination is designed to deliver greater flexibility, longer life and accurate sizing. The Tufflex wire is specifically durable against abrasive material such as Porterville Rock’s red rock, and Unified’s SuperFlow concept is designed to handle damp and sticky material with vibrating wires that reduce binding.

In addition to making suggestions for Porterville Rock’s middle and bottom decks, Sailer made recommendations for the operation’s top deck. Rather than use the wire-cloth screen with the 2-in. opening and 3/8-in. double wire, Sailer suggested trying another screen with a 2-in. opening yet one with 1/2-in.-diameter wire. Porterville Rock made the switch, and Unified replaced the feed end with its rubber impact screen.

Put to the test

With the new setup, Porterville Rock embarked on a series of tests to prove the validity of the system. SuperFlow screens were tested in a 6-ft. x 16-ft. screen box with four 6-ft. x 4-ft. sections – impact end, secondary screen, a third screen and the discharge screen section.

Test product ran on both the top and middle screen decks with maximum production scheduled. According to Brown, the plant passed 200 to 250 tph through the screens on an eight-hour-per-day schedule.

Compared with one previous setup, Brown found the new system yielded longer-lasting screens. Porterville Rock was forced into a change-out just three weeks into using a previous screen set. The system Sailer recommended lasted three months, according to Brown.

“The SuperFlow screens outlast any previous product we have used,” says Brown, who adds that he tried testing as many as four types of wire. “With the material wearing longer, we’ve had a cost-savings benefit due to the longevity of the screens. In today’s economy, it helps to have a dependable product that can improve your bottom line.”

The mining site where Porterville Rock & Recycle currently sits was reduced to a concrete-bagging plant at one point, but owner Mitch Brown acquired it in the 1990s, got the land permitted and fired the plant back up.

More recently, after nine years of trying, Brown received a hard rock quarry permit to mine the red rock available to Porterville Rock. In terms of quality, the red rock is two to three times better than the sand and gravel the operation produces, Brown says.

Porterville also recycles concrete and asphalt, so it’s responsible for processing a variety of materials. But crushing those different materials is no easy task.

“The challenge is that each one of them runs at a different rate,” Brown says. “You have to set crushers at a different setting. Your hauling equipment changes, your loading equipment changes and the place where you put it each time is different. It just takes adjustments every time you change materials.”

As Brown puts it, every action has a reaction. And not every reaction is a positive result. Still, having a variety of materials at its disposal helps to make Porterville Rock competitive in a market that primarily includes two cities: Porterville and Tulare, Calif.

“We’re in a small farming community here in Porterville,” Brown says. “There’s not much of a market here.”

In 2009, Brown says Porterville Rock produced 625,000 tons. The operation was reduced to 325,000 tons in 2012, leaving Brown with tough decisions to make for his 100-acre site.

“We’re faced with the challenge of going to half the face and still using the same amount of people,” Brown says. “What do you do with your [employees] the other four hours of the day now? That’s been a big challenge for us figuring out how to be productive.”

Porterville Rock overcame one daunting challenge, though: how to screen that hard, abrasive red rock.

Take Note
The original upper-deck screens were no match for Porterville Rock’s red rock. They lasted just three weeks.

Porterville Rock’s key equipment
■ 42-in. x 48-in. jaw crusher from Telsmith
■ WF 400 cone crusher from Omnicone
■ 6-ft. x 20-ft. screen from Terex
■ Tertiary cone crusher with a 4 1/4-ft. short head cone from Symons
■ 5-ft. x 16-ft. three-deck screen
■ 5-ft. x 16-ft. wash plant screen
■ Unified’s Superflow screens

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