California Firm Combs Mojave for Colored Rocks

Mon August 21, 2006
Aggregate Equipment Guide

Nestled in the Southwestern part of the United States, in the blistering heat of the Mojave Desert, is BruBaker-Mann Inc., one of California’s colored rock producers.

BruBaker-Mann Inc. offers a large selection of natural rock colors including gold, green, white, pink, wine red and lilac; much of which is used by landscapers and homeowners for decorative purposes. These colors come from eight different quarry areas located throughout the Mojave Desert.

The material is blasted at the quarries and transported to BruBaker’s Barstow location, where it is crushed and screened. BruBaker’s Marble White quarry is approximately 55 mi. to the northwest, the Surf Green quarry is 35 mi. to the east, and the other quarries are scattered approximately 5 mi. from Barstow.

William Mann, together with his cousin Ronald BruBaker, founded the company in 1950 for the purpose of producing colored rock. Their interest in quarrying stems from their early Boy Scout expeditions to abandoned mines in the Mojave Desert.

After blasting the rock face both Mann and BruBaker transported the material to the mill in Barstow, where it was crushed and screened. The original mill consisted of a crusher from the early 1900s, a wooden screen, and a dilapidated bucket elevator. The finished product went into sugar sacks.

As demand for the colored rock grew, and they sought to offer high quality rock in a wider range of sizes, Mann and BruBaker constructed their own stationary crushing plant from scrap metal. This device eased exhausting physical labor and produced higher quality rock products at high production rates.

By the late ’90s, the stationary crushing plant had been exhausted. Rather than dismantling, moving and reassembling their existing plant, Julie Mann, William’s successor and now president of BruBaker-Mann Inc., decided to adopt a clean-sheet approach and invest in new mobile crushing and screening technology. Julie decided to meet with a technical field consultant from Extec Inc.

Mann discussed with Mike McCann the size and type of units to purchase so they would match the production requirements and working conditions of the Barstow quarry.

“Our fifty year old stationary crusher by itself wasn’t giving us the production necessary to meet all our needs and the needs of the market,” she said. “Extec Inc. was a big help, showing us how to use the right jaw crusher and screening plant to improve and speed up our production and get a much wider range of crushed/screened products at less cost.”

During a demanding selection process, Extec worked closely with the company to identify the duties required from the chosen mobile screener and crusher. The factors considered as vital regarding the selection of crushing and screening equipment were:

• The quality of service provided;

• Serviceability of the crushers/screeners;

• Parts availability; and

• Crusher/screener reliability/productivity.

Extec Inc. matched the machinery to the tasks and to BruBaker’s required specifications. The screening and crushing plants selected were the Extec C-12 jaw crusher and S-5 Doublescreen. The user-friendliness and production rates of the Extec S-5 and C-12 were major components in the purchasing decision.

“In the end it was the simplicity of the crushing and screening operation and the terrific production capability of both machines that confirmed our purchase,” said Mann. “Both machines can be easily propelled around site providing an operator-friendly system that enables us to make quick and easy adjustments.”

The C-12 was chosen as the first step of BruBaker’s quarrying process, which begins when the overburden is removed.

Once a suitable “face” has been established, a selected blast site in the quarry area is drilled to create multiple bore holes and filled with explosive materials.

The C-12 is maneuvered to any position by an excavator or loader at the quarry face, where recently blasted colored rock is piled to the floor.

Colored rock boulders approximately 18 in. (45.7 cm) in size are fed directly from an excavator to the jaw crusher, where the vibratory feeder transfers the material towards the C-12’s 50-by-30 in. (127 by 76.2 cm) jaw crushing plant.

As the rock advances downward into the crushing chamber, it is crushed between the wear plates and deposited onto the main conveyor.

Each rock is crushed an average of 2 to 2.5 times, as it passes through the jaw with a reduction ratio of approximately 6-to-1.

The Extec C-12 jaw crusher has a feed opening of 50 by 30 in., encompassing such features as a vibratory feeder, with automatic control to regulate the feed into the crusher; a hydraulic adjustment system, to regulate the product size to be crushed, reverse crushing action to assist in clearing blockages and a high crushing speed.

Crushed rock is then fed from the C-12 to the Extec S-5 Doublescreen, which separates the rock into 1 in. (2.5 cm), .75 in. (1.9 cm), and .125 in. (.318 cm) sizes.

The S-5 Doublescreen is a self-contained tracked machine built to withstand the rigorous conditions of BruBaker’s quarry.

The S-5 uses a diesel engine to provide the power to the hydraulic power pack to generate electricity for the electrical systems of the machine. The tracks, hopper, conveyors and all working parts of the machine are hydraulically driven.

Screening is undertaken by throw back onto the screen box with sorting taking place by size and product shape. Colored rock is loaded into the hopper where material falls onto the conveyor, it is then fed onto the main conveyor where at the top it is transferred onto the screenbox.

The material passes over a series of screen meshes which separates the limestone into three grades. The larger and medium grades are separated onto the side conveyors leaving the fines to travel up the tail conveyor. Each grade of rock then falls onto three separate stockpiles around the machine.

The Doublescreen box assembly represents innovation in mobile screening systems as it resolves the conflicting principles previously associated with providing a larger screening area on mobile plant. Traditional solutions have been a compromise of strength over mobility due to the battle over increasing weight or lessening structural durability. The Doublescreen avoids this compromise through the use of two screen boxes.

Based on many years of experience within the mineral extraction and construction industries, the Doublescreen box allows for more than 20 easily adjustable screening angles, according to the manufacturer. Screening efficiency is maximized as material flow is directed by the angle of the screen box resulting in:

• A steep angle for the primary screen box ensures that the majority of the material is processed in the initial impact area;

• The majority of the undersize is removed during initial impact;

• Only near size material passes to the secondary screen box. This may be set flat enough to ensure any remaining material is screened efficiently;

• Clean gradings, at very high output, are produced as material is exposed to large screening area.

As a result of the new, mobile crushing and screening systems, BruBaker-Mann realized the following benefits:

• Improved product cycle times;

• Ensured stockpile quality using a three way split machine instead of the stationary crushing plant, preventing the compaction or contamination typically seen when using stationary plant to build stockpiles;

• Increased stockpile volumes. The Extec Screening systems can build a larger volume stockpile in a given space thereby maximizing efficiency on a smaller site.

• Minimized truck/haulage use.

“Since our investment in mobile technology, the haulage trucks are only required during the day shift when the Extecs are producing material,” said Mann. “With truck and haulage costs cut by almost a half, we soon benefited from the savings on labor, fuel and maintenance.”

With its new crushing and screening technology, together with an expanding range of products and services, Brubaker-Mann Inc. is now well-positioned to meet the challenges of the future, according to the company.

Yet despite employing some of the latest technology available, Brubaker will still have managed to maintain its reputation for providing customers with the “personal touch” which has been the company’s hallmark for more than 50 years.

For more information, visit www.extec.eu.