The Midlothian quarry near Dallas, Texas, is probably the most efficient crushing operation in the world. Two excavator operators feed two crushing units that produce some 1,200 tons of limestone every hour. The owner, Zemer International Inc., is happy. With the addition of the second LT140 unit, the quarry now produces 1,200 t/h.

Eduardo Martínez, Vice President, Zemer, and Greg Venghaus, Metso Minerals

"We made a trip to Finland which really caused us to seriously consider this type of in-pit operation. We now feel very proud of our two Nordberg LT140s because we think this is the most efficient mobile in-pit operation not only in North America but possibly in the whole world," says Mr Kennedy Miller, the plant manager.

The first LT140 with LL mobile conveyors started production in 2000. Since then, the machine has produced over four million tons without problems. This machine has now been joined by a younger brother, also with LL mobile conveyors.

The two LT units crush approximately 280,000 tons every month. In this first stage, the material is crushed to minus 6 inches and in the second stage to 1-3 inches.

"We have a 7-year contract with a cement factory operated by Holcim. The reserves at this site will last for 85 years, so I look forward to seeing my grandchildren working here," comments Mr Eduardo Martínez, VP, Zemer.

Zemer is a Mexican company active in Mexico, the United States and Venezuela. In Mexico they have six sites, in Venezuela four, and in the US currently one, the Midlothian quarry. The company is owned by two families, the Martínez's and the Zepeda's. Its business idea is very simple:

The Midlothian is a huge operation. Although Eduardo Martínez of Zemer and Greg Venghaus of Metso Minerals know the quarry well, they still are impressed by its performance. The LT140 here is the first track-mounted crushing unit at the site.

Source:
Aggregates News 2, 2003