Resources
Boliden Mineral AB, www.boliden.se
Metso Minerals Industries Inc., www.metso.com
Twiflex Ltd., http://www.twiflex.com/

Metso Minerals Industries Inc., Helsinki, Finland, just replaced five grinding mills at a Swedish copper mine with two of the largest mills commercially available. Each of the 22.5-MW mills uses wraparound motors and measures 38 ft in diameter and 45-ft long. Together, they can grind about 2,025 tons per hour. But these large machines need powerful brakes. So Metso engineers chose Twiflex VMS-SP caliper brakes with pedestals, and eight will be installed on each mill. The brakes will hold the mills during maintenance and stop them in emergencies. They will also allow inching or creeping in case of bearing lubrication problems or power failures. Each mill will have brakes that generate 38 Nm of braking torque acting on a 1.297-m flange diameter. Each caliper weighs 1.85 tons and delivers 940 kN of clamping force. The brakes can stop one of the new mills in under 2 sec. md

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