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Cement Shipments Decrease in March Total shipments of portland and blended cement in the United States and Puerto Rico for March 2013 were about 5.8 million metric tons (Mt), ac‐ cording to the most recent USGS Mineral Industry Survey. This was nearly 3 percent less than ship‐ ments in March 2012. Shipments for the year through March were up slightly 15.4 Mt. The lead‐ ing portland cement producing states in March were Texas, California, Missouri, Florida and Ala‐ bama, in descending order. The leading consum‐ ing states (Texas, California, Florida, Louisiana and Arizona, in descending order) received 46 percent of the March total shipments. Clinker production totaled about 5.6 Mt in March, 4 percent more than the output in March 2012. Production for the year through March was 13.7 Mt, down slightly. The leading clinker‐ producing states in March were Texas, Missouri, California, Florida and Alabama, in descending order. Masonry cement shipments in March of about 164,000 metric tons (t) were up by al‐ most 3 percent from those of March 2012. Ship‐ ments for the year through March were 435,000 t, up by about 3 percent. The leading masonry cement‐consuming states were, in descending order, Florida, Texas, California, North Carolina and Georgia, and these received about 53 per‐ cent of March's total shipments. March 2013 imports of cement and clinker of about 443,000 t were about 3 percent more than those in March 2012. Imports for the year through March totaled 1.223 Mt, up by 12 percent. Siemens Multi-Drive System Powers Holcim Mill The Siemens Drive Technologies Division has developed a new drive system for a cement mill as part of a joint project with Gebr. Pfeiffer SE. With an overall power rating of 11,500 kW and producing 450 metric tph of cement, the vertical mill is the most powerful of its kind in the world today. The mill will be operated by the Brazilian cement producer Holcim, which will commission the plant as part of a project to expand the capacity of its Barroso works in the Brazilian state of Minas Gerais. The multi‐drive solution meets the demands of the cement industry for more availability, reliability and performance power. The modular and redundant drive system consists of six identical 1,920‐kW drive modules that drive the grinding table of the cement mill. Siemens is also supplying all components of the drive train: gear unit, coupling and oil supply system, as well as electric motors and frequency converters. A decisive advantage of this concept is that the drive units are mounted on carriages, thus enabling them to be replaced quickly whenever maintenance is required and ensuring the fastest possible resumption of mill opera‐ tion. The radial arrangement of the drive units around the grinding table bearings protects the drives against grinding forces. The frequency converter allows variable speed ad‐ justment and thus flexible adaptation of the milling process to suit the requirements of different input materials. This makes it possible to optimize, for example, throughput or energy efficiency. With this system configuration, even higher‐output drive modules can be installed for an overall 50 ROCKproducts • JULY 2013 power rating of up to 16,500 kW. Up till now, the mechani‐ cal engineering limit attainable by conventional plants was only 8,000 kW. "The multi‐drive solution developed by Siemens is another example of how we can offer significant benefits to our cus‐ tomers by combining innovative mechanical drive compo‐ nents with suitable electronic drive systems to create an integrated drive system. Thanks to the modular design of the drive train, a system can deliver previously unattain‐ able performance ratings and offer significantly more en‐ ergy efficiency and availability," said Dr. Bernhard Hoffmann, head of drive applications at Siemens' Mechani‐ cal Drives Business Unit. www.rockproducts.com