Luck Stone Sees As Low As 7% Moisture with McLanahan Fine Material Screw Washer and Dewatering Screen

Case Studies

Luck Stone is the largest privately held, family owned and operated producer of crushed stone, sand and gravel in the United States. Their 28 sites across Virginia, Maryland, Georgia and the Carolinas provide consistent, quality aggregate materials that serve as the foundation of roads, bridges and buildings. 

At each new site Luck Stone develops, they extend their core operating principles of economic development, environmentally sound practices and values based leadership. They are committed to being a good neighbor and providing a positive impact on the communities in which they operate.


Challenge

In 2002, Luck Stone purchased their Bull Run Plant in Chantilly, Va., to serve the growing Northern Virginia market. Started in the 1950s, the quarry was a low-volume, eight to 10-conveyor operation when Luck Stone began expansion efforts to meet the market demands. They moved a road to access more reserves and grew the site to approximately 70 conveyors that transport traprock from the quarry through the crushing and wet processing plants to the stockpiles.

The expansion efforts also included upgrading their asphalt sand processing plant to increase production.

“The main driver for the expansion of the sand plant here was just the demand in the market for sand products that needed to be clean,” said Craig Wiant, assistant plant manager at the Bull Run site. “At those volumes, we can’t afford to make a pile and let it decant before we sell it, so we really needed to be able to make it on the fly, ready to ship.”

The Bull Run Plant has a lot of stock turnover, so their sand needs to be ready to ship. They wanted a solution that would put the product on the ground as dry as possible.

“It’s really critical to us to have a lot of sand-making capacity but also to have a lot of sand on the ground that’s ready to sell,” shared Wiant.

Solution

As part of the expansion of their sand plant, Luck Stone replaced a much smaller sand screw with two McLanahan twin 44” x 33’ Fine Material Screw Washers to more effectively remove fines from their asphalt sand.

Luck Stone also wanted to include dewatering capabilities in their new wash plant, something they didn’t have in the old plant. Dewatering Screens have been proven to produce final products that are at least 10% drier than Fine Material Screw Washers. When the two are used together, they provide a greater level of dewatering. Luck Stone followed each Fine Material Screw Washer with a McLanahan VD18 Dewatering Screen for additional moisture removal before stockpiling.

“The screw classifiers clean the material so it’s within our customer specs and above,” Wiant said. “Then, the addition of the dewatering screens allows us to produce the product at a moisture content that’s ready to ship.”

To keep valuable solids in closed circuit, the screen throughs collect in low-profile sumps underneath the Dewatering Screens and are pumped back to the screw feed via McLanahan Slurry Pumps.

Results

The McLanahan Fine Material Screw Washers and Dewatering Screens help Luck Stone produce a clean, drip-free asphalt sand for their customers.

“Our customers really want to see the percent passing the 200 mesh at a 2 or less, especially for asphalt mixes,” said Wiant. “We can typically put it in the pile at about 1.5% passing the 200.”

Not only does the McLanahan equipment help Luck Stone meet the strict specifications required of their final product, it also allows them to produce a drier sand. The moisture content of the sand coming off the Dewatering Screen is as low as 7%.

“Depending on weather and setup, we usually see somewhere between 7 and 9% moisture coming off,” explained Wiant. “It allows us to sell our material much quicker, so it doesn’t have to sit in the pile and decant. It’s pretty much ready for sale as it comes off the stacker.”

Wiant said they’ve been really happy with the McLanahan systems at the Bull Run Plant.

“The McLanahan screws and dewatering screens have been incredibly reliable,” Wiant said, “so our quality has been great. They provide a really clean product, which is what our customers demand, and they’ve been reliable since we put them in.”

With the increase in infrastructure projects in Northern Virginia, the McLanahan Fine Material Screw Washers and Dewatering Screens will continue to help Luck Stone meet the needs of their customers.

“Being able to provide a clean sand at low moisture to our customers allows them to build projects with the longevity to serve the surrounding community,” said Wiant.