After Youngquist Brothers Rock built its first limestone operation in 1995 and then sold it in 1997, Tim and Harvey Youngquist wanted to build something bigger and better. Their criterion: energy efficiency, massive inventory and freedom from haul trucks. They reached their goals with help from internal and external engineering teams and an in-house machine shop built for the company's well-drilling operation. And it only took from February 2003 to November 2003 to build it from the ground up.

Based in Fort Myers, Fla., Youngquist Brothers' well drilling was founded in the early 1970s and grew into one of the largest operation in the United States. One of its assets was an ISO9000-certified machine shop where it could supply its own parts and maintenance. “Down here in Florida, there is no support for a drilling operation,” says General Manager Ed Callahan.

That shop proved valuable when Youngquist Brothers decided to build an aggregate mining operation. It allowed the Youngquist team to build a track-mounted primary plant in house and manufacture thousands of feet of transfer conveyor to move sand and limestone. Their base rock plant, a secondary plant built around a Boringer Impact Crusher and a Deister grizzly screen, produces 1,000 tons per hour. And the sand plant with two sets of six cyclones and seven dewatering screens can produce 1,200 tons per hour. All together the plant has the ability to produce 12 million tons of finished material each year.

The behemoth primary plant was designed not only for efficiency and production capacity, but for mobility.

The 500,000-pound machine was built around a Metso C160 jaw that crushes as much as 3,000 tons per hour. It is fed by a Deister variable-speed pan feeder. Material is screened to 6 inches through a Deister grizzly. Callahan says the primary's framework, the operator station, the walkways and the conveyors were all built and designed in house. “It's definitely a Youngquist Brothers' crusher (plant),” Callahan says. “We built it in three pieces and brought it out here and then welded it back together.”

The dimensions of the assembled machine are 35 feet tall, 85 feet long and 25 feet wide. Yet all this steel had to move. The 25-foot tracks were pulled from a Demag H241 mining shovel that Project Manager Marvin Igo bought used from an operation in Canada. The Youngquist Brothers' team welded the tracks on sideways instead of a traditional straight assembly. This allows the primary plant to travel parallel to the conveyor; both plant and conveyor are between the spoil pile and the lake.

Production at the site starts with Youngquist's in-house blasters. The blasted material is collected by a 4-million-pound Bucyrus Erie 1260 dragline. It piles material along the length of the lake with a 44-cubic-yard bucket, which is an upgrade from a 33-cubic-yard bucket. The spoil pile then air dries for about two months. An electric-powered Liebherr 994 backhoe with a 20-cubic-yard bucket feeds the dried material to the portable primary plant.

As the material is consumed, the crusher creeps along the length of the pile. On average, it moves 40 to 50 feet during a 10-hour shift, five days a week. The primary plant is controlled from the ground by a Hetronic industrial remote control. “It's like one of the world's largest remote control toys,” Callahan says.

This toy is propelled by several electric motors. A 250-hp motor for the hydraulic system runs whenever the machine is in motion and shuts down as soon as it stops. A 300-hp motor operates the jaw crusher. A 75-hp motor operates the pan feeder, and a 50-hp motor controls the grizzly. Another 60-hp motor controls the smaller hydraulic systems, Callahan says. “There's no sense in running the big motor if we just have small hydraulic loads.”

One operator in the primary plant's control room controls the entire base-rock plant, main plant and sand plant. The primary is connected to the rest of the plant via a wireless link using Alvarion 900-MHz ethernet radios.

From the primary plant, a series of conveyors moves the material to various finishing stations. From C-0, the customized conveyor coming off the mobile primary plant, material is fed onto C-1 through a tripping car. The tripping car connects the two belts and provides a larger target for C-0, just like a movable hopper. C-1, a series of linked conveyors that stretches as far as 4,800 feet, carries that material north to C-2 as the crusher creeps south. All conveyors use Georgia Duck belts.

Once the entire length of the spoil pile runs through the primary crusher, the crew packs up and moves the entire primary plant and connecting conveyors to the other end of the lake. The dragline is moved to build a new pile on the side of the lake vacated by the primary plant. This happens about every five months, and every piece of conveyor can be moved and realigned in about three days, Igo says.

The C-1 conveyors were built for mobility in the company's machine shop. A structural analysis by Templar Technologies, a New Jersey engineering firm, helped keep the steel to a minimum, Callahan says. The conveyor framework was assembled into 40-foot segments, small enough to be galvanized at another shop. Those segments were later connected into 120-foot-long sections.

Each section has a steering axle from trucks found in a salvage yard. When it's time to move, they put a man on each wheel and snake it across to the other side with a backhoe that connects to the end of the conveyor with a ball receiver.

C-1 connects to C-2, which runs 3,100 feet up to the 500-ton surge bin. Callahan says the upper portion of that conveyor and the rest of the plant that follows, with the exception of the sand plant and radial stackers, was built by Process Machinery.

Project Manager for Process Machinery Gary Schley says Youngquist Brothers provided all of its own equipment and sized everything. The Youngquist team also received engineering advice from Rockwell Automation.

“It was a very large project,” Schley says. The Deister pan feeders in Tower One were sized for about 2,000 tons per hour with room to grow. “(Now) they probably have 2,500 tons per hour up the belt.”

The initial separation in Tower One begins on a 10- × 24-foot scalping screen. Anything larger than 1¼ inch is fed to two Metso Nordberg HP500 cone crushers for secondary crushing. And material requiring further reduction goes to another HP500 for tertiary crushing.

All of the rock that is of proper size is conveyed to the top of the finishing tower, Tower Two, where it is divided by a pant-leg chute and equally distributed across two Deister 8- × 24-foot triple-deck finishing screens. Fingers below the screen allow Youngquist Brothers to direct the final products to the appropriate piles. Callahan says the material circulated to Tower Two simultaneously makes stone size numbers 5 (1 to ½ inch), 89 (⅜ inch to 1.18 mm) and 57 (1 inch to 4.75 mm).

From the bottom of Tower One, number 3 (2 to 1 inch) and number 4 (1½ to ⅜ inch) stone bypasses the crusher and is conveyed straight to the stockpiles. “It's just a naturally occurring stone, and depending on the screen sizes, we can make it right off the tower,” Callahan says.

To wash the remaining stone, lake water is pumped 1,700 feet underground and up 40 feet with a 600-hp pump. The wash screen, which came premounted from Deister, has two manifolds, one on each side. Two manifolds were needed to thoroughly wash the material. Igo says they are running 12,000 gallons per minute from the turbine dock to spray all four decks.

The slurry collects in the retention sumps of the scalping and intermediate screens in Tower One. An ultrasonic level detector helps keep the water level as high as possible. The slurry is not permitted to fall to the ground, so the pump can rely on the force of gravity rather than horsepower.

“We minimized the horsepower requirements of the main sump pump by utilizing the potential energy of the water,” Callahan says. “We probably need half as much horsepower to pump the water over to the top of the sand plant compared to conventional sump designs.”

The sand plant was built by Art Iron Works. From the top of the plant, the slurry goes through a bank of dewatering cyclones. Fines smaller than 150 mesh float over and into another set of cyclones for fines recovery as small as 350 mesh. This fine fraction sand is dewatered on two dewatering screens before being discharged onto a conveyor belt.

Underflow from the cyclones dumps into six hydrosizers where the material is separated by density and cut at 50 mesh. The coarse sand discharges from the bottom of the hydrosizer onto three dewatering screens. Overflow of the hydrosizer goes into another manifold and is later sent through six cyclones for additional separation of a medium coarse sand. Two more dewatering screens are used before the medium fraction sand is put on a conveyor. About 5% of the material is sent back to the lake as waste.

“All three sand fractions are recipe blended back together to customer-specific blends,” Callahan says. The most common recipes are 131 sand that is 100% coarse and 40% medium, as well as gunnite sand that is 100% coarse and 60% medium.

Another design goal of Youngquist was large stockpiles to avoid turning trucks away at the gate or going into panic mode if something broke. The radial stackers were built by the Texas company Carpco. They were delivered in pieces that Youngquist Brothers assembled. Everything is stockpiled from 70 feet off of seven 100-foot radial stackers that can make 150,000-ton stockpiles. Callahan says, although it was a concern, the height of the stackers has not created any segregation issues.

The stackers are free standing on concrete pedestals with counter weights on the back. Callahan says it is a perfectly balanced system that rotates up to 300 degrees on a Rotec bearing with only 4 hp.

The massive stockpiles feed a growing market that Callahan says is booming. And he estimates the site has 40 years of permitted reserves to feed the market. He says that the plant will have no problem absorbing the demand as the market grows.

And the design goals achieved on this project will help assure that Youngquist Brothers Rock never skips a beat. The stockpiles will keep the customers satisfied, the galvanized steel will fair the weather and the thousands of feet of conveyor should keep material flowing without the burden of haul trucks.

Quality Control Manager Robert Pawlecki says the company's in-house machine shop built the plant ahead of schedule and under budget.

“We probably saved a year with just the engineering alone,” Pawlecki says. “We actually were making product while we were still building the plant.

“We have a $5 million sand plant out there that can classify sand all the way down to 270 to 325 mesh,” Pawlecki says. “It would have been more than that if we hadn't done a lot of the work ourselves.”

It's Electric

From the lake to the stockpile, Youngquist Brothers' aggregate operation is 100% electric.

“The cost per ton is much lower using electricity than relying on an overabundance of diesel engines,” says General Manager Ed Callahan. The electric-powered conveyors have eliminated the need for haul trucks that require fuel, drivers and maintenance. He says it would take at least five haul trucks to maintain the current production level.

However, the amount of electric motors throughout the plant has made Youngquist Brothers the largest electric consumer in Lee County Florida, more than all of the hospitals combined and the airport. And during peak hours, the demand for electricity would be pushed beyond the utility company's capacity. Like many operators, Youngquist Brothers had to compromise with the electric company.

To prevent a massive drain on the county's power supply, the electric company and Youngquist Brothers created a user agreement. It provides a discounted rate during off-peak hours, limiting operations mostly to night and leaving maintenance and blasting routines for the day. With the amount of electricity it takes to produce 300,000 tons each month, this agreement saves Youngquist Brothers more than $46,000. And it assures that all of the Lee County residents have an ample power supply.

There also are the obvious environmental benefits for the plant as the company's reliance on electricity eliminates the need for fuel farms, and the plumes of black smoke from haul trucks.

Major Equipment Reference

Primary Plant:

• Metso C160 jaw crusher
• Deister pan feeder and grizzly feeder

Tower One:

• 6 FMC Syntron pan feeders
• 3 Metso Nordberg HP500 cone crushers
• Deister 10- × 24-foot scalping screen
• Deister 8- × 24-foot intermediate wash screen

Tower Two:

• Boringer impact crusher
• 2 Deister 8- × 24-foot triple-deck finishing screens

Sand Plant:

• 6 LPT 10- × 10-foot Hydrosizers
• 9 LPT cyclones
• Deister 6- × 12-foot cyclone
• 14 Krebbs Gmax cyclones

Other:

• Liebherr 944 backhoe
• Bucyrus Erie 1260 dragline
• 7 Volvo 220 wheel loaders with Loadrite bucket scales
• Emery Winslow Genesis 100-ton 11- × 80-foot truck scales
• Engineering Software Products plant automation
• Allen Bradley IntelliCenter motor control centers
• Georgia Duck conveyor belts
• Continental CEMA D idlers
• Dodge Quantas and Cyclone gearboxes