Headquartered in Watsonville, Calif. near Monterey Bay, Graniterock is a family-owned company formed in 1900 by MIT trained engineer Arthur Wilson, who along with his business partner formed the company to supply material to the Southern Pacific Railroad. awesomeearthmovers.com

The quarry is situated just 20 miles from Graniterock’s headquarters and sits in the picturesque hills of Aromas. Named after Arthur, the A.R. Wilson quarry sits on top of the San Andreas Fault, extends over 2,000 acres and currently produces about 5 million tonnes of material per year, most of which is used on construction projects throughout Northern California. Its annual output makes the A.R. Wilson Quarry one of the largest in the western U.S.

The Wilson Quarry produces a wide variety of products, from general aggregates to rail ballast, with materials leaving the site 24-7 thanks to an automated weighing and ticketing system. Current output from the site is around the 5-million-ton mark with reserves available for another 100 years of rock production!

To effectively produce this volume of material, the quarry has invested in some of the largest kit around. Traditionally, a static crushing plant was utilised, but with demand increasing and repairs on the existing plant taking over, the decision was made in the 1980s to invest in mobile crushing operations. The requirement to increase production and reduce downtime and increasing repair bill was a major factor in looking for alternative processing solutions. With material being hauled from an constantly enlarging pit, the flexibility of a mobile crushing solution was becoming more and more attractive.

At the time, huge production crushers were few and far between, especially when it came to adding in the mobile factor. Following searches across the U.S. and beyond, the answer to Graniterock’s search came from the German engineering masters, Thyssen Krupp. Krupp, a well-known brand in Europe had already produced several large crushing plants. However, the monster crusher they supplied to Graniterock topped them all. Dubbed “The Krupp” by Graniterock employees, the crusher is said to be the largest mobile crushing plant in the world with an operating weight of approximately 750 tons and an appetite of 3,000 tons per hour of hard rock granite.

“THE LARGEST MOBILE CRUSHING PLANT IN THE WORLD.”

The granite is removed from the ground with traditional drill and blast methods. From there, tradition goes out the window with the quarry employing a pair of D11T dozers to push the granite toward the Krupp.

As the Krupp is mobile and the blast moves around the quarry, the crusher is ideally located within 50 feet of the face where material is pushed over. Whilst we say the crusher is mobile, only very short movements are seen as ideal. Due to its bulk, the Krupp isn’t going to break any speed records.

While many quarries operate either a 12-hour day shift or work 24 hours producing material, Graniterock only runs the Krupp for 10-12 hours, starting at 6pm, as the electric power demand from the machine sadly makes it cost prohibitive to run during peak tariff times. Such is the voracious appetite of the Krupp that during this night shift a pair of Caterpillar 992K wheeled loaders simultaneously load the giant hopper of the crusher. The two wheeled loaders work tirelessly throughout their shift to keep the hopper filled, allowing the Krupp to meet production targets. Processed material is fed directly from the crusher to a conveyor system, which carries the material up to the secondary crushing plant and screening equipment before it is stocked and ready for dispatch.

To keep the Krupp crushing rock at full capacity, Graniterock invests in proper maintenance with regular servicing and replacement of parts to ensure a long lifespan. A full-time maintenance team is dedicated to the Krupp’s wellbeing to ensure the behemoth remains as productive as ever.

To ensure material is crushed in a steady and effective manner, the material is loaded into the ground level hopper with a wide belt moving the material into the huge jaw crusher. The blast pattern at the quarry ensures the material remains smaller than the 1m bridging width of the jaws. Steadily grinding out granite 10 inches and smaller, the material is separated at the secondary plant where it’s screened and re-crushed should a smaller size be required. No material is wasted with the fines produced being sent through a wash plant followed by a plate press, allowing both the material and water used in the process to be recovered.

The Krupp currently operates at 120 feet below sea level. During the last stand-down, the maintenance crew relocated the crusher along with additional conveyor belts and associated power cabling in just three days, allowing production to resume in record time.

With over 25 years of material within easy reach of the CAT loaders, the Krupp will spend the foreseeable future in this location. “We will work a portion of the quarry moving the crusher short distances to accommodate our changing working areas. When we moved to this location, we used an outside haulage company with a pedigree of moving heavy equipment in the mining and quarrying industry. Placing the Krupp on a pair of self-propelled modular trailers, we were able to haul it safely to its new location.”

Looking at the crusher from the top of the high wall does not do it justice. It is only when you get up close that you realise it’s being attended to by a pair of 100t class wheeled loaders that the size really becomes apparent.

“WHILST GRANITEROCK IS TAKING EVERY STEP TO ENSURE THE KRUPP STAYS THE COURSE, IF IT WENT WRONG, WHAT WOULD THEY TURN TO?”

“The build quality of the machine is second to none. We do undertake some strengthening and rebuilding of the basic machine on a regular basis to ensure it retains its formidable integrity. We do realise, however, that time will come when the Krupp needs to be replaced. At this time, we are keeping an eye on the markets to see what innovations are being made and how they could adapt to our operation in the future.”