Optimizing a load of sand and gravel on a trial-and-error basis can be a time-consuming – and costly – endeavor.

At the Punta Gorda, Fla., mine of Coral Rock, Inc., drivers with overweight loads “would have to go back, open their tailgate, dump a little bit on the pile, then close the tailgate and come up to the scale house again to get reweighed,” says Bob Milhous, Coral Rock’s executive sales and logistics manager. “This took about 10 minutes per round trip, and sometimes they would have to go around four times before they got it right.”

Such inefficiencies ended at the Punta Gorda mine in 1989, when Coral Rock, Inc., installed a Lightning Loader manufactured by Petersen Industries, Inc., of Lake Wales, Fla. Now, optimizing a truckload at the mine’s scale house takes just a minute or two, Milhous says.

Load optimization is a goal that sand and gravel miners share with the truckers who haul these materials. Sand and gravel are sold by weight. If a truck is underloaded, the mine sells less, and the driver makes less money per trip. If a truck is overloaded or if the load is improperly distributed, the driver risks being cited and fined by local law enforcement authorities. And, if a truck exceeding state requirements is involved in an accident, the mine where the truck received its load will share liability with the driver and the truck’s owner.

Modern front-end loaders can measure their payload’s weight while filling a truck, but can’t calculate the distribution of that weight across the truck’s axles. Some dump trucks with air suspension have load cells that indicate weight, but even if a driver knows he is overloaded, he still must do something about it.

The Lightning Loader optimizes loads at the scale house by adding material to an underweight truck from a nearby reserve pile, or by transferring excess material from an overweight truck to the reserve pile. The machine is a knuckleboom grapple loader, a first cousin to the truck-mounted grapples used to pick up bulky trash and yard waste.

The grapple loader stands on a pedestal that supports a rotating head, from which extends a boom with a bucket mounted at its far end. The operator controls the loader from within the scale house. From there, he watches the scale, ensuring the precise weight. Flexible controls allow the operator to add or remove as little as 20 pounds of material at a time from a truck. The process takes just 65 seconds on average, expanding a mine’s potential sales volume by allowing many more trucks per hour to move across the scale.

Adaptation for aggregates

The Lightning Loader evolved from a device that Petersen Industries’ founder, John E. Petersen, developed in 1958 for bulk handling of oranges in Florida’s citrus groves.