Twin Shaft Mixer Delivers for Cement Manufacturer

Twin City Concrete, a cement manufacturing company in Minnesota, looked to Scott Equipment Company, Inc. for answers and results for a mixing application. George Basset of Twin City Concrete was preparing to upgrade the entire system and was searching for a mixer that would provide “quality and speed”.

Previously, Twin City Concrete was first blending sand, portland cement, and lime, pneumatically conveying the mix to bins from which the mix was then dispersed into baggers. “We were having a lot of trouble with segregation,” says Basset. “In this industry, it is crucial to have the most consistent mix possible. If the product is not accurately mixed, the ingredient amounts vary per bag and numerous problems may result from too much or too little cement in the mortar. If the mortar is stronger than the block, the block will crack if there is any shifting or settling of the walls. If too little cement is in the mix, the mortar may crumble.”

Another concern of Basset’s was to achieve an efficient mix when pigments are added to the mortar. If the pigments are not properly dispersed, the mortar color will not be consistent throughout the job.

After considerable testing, Twin City Concrete chose the Scott 66 x 66 in. twin shaft batch mixer, which Scott began manufacturing in the early 1990s. The design features of this mixer include two counter-rotating agitators that consist of a combination of paddles and ribbon flighting. In a twin shaft mixer, mix times can be reduced anywhere from 40–50% compared to a single shaft mixer, and the minimum batch size that can be efficiently mixed can go as low as 10% of the full-rated capacity. The twin shaft mixer easily accommodates retrofits, while increasing mixing capacity in height-restricted areas. This mixer takes up less vertical height than a comparably sized single rotor mixer.

Twin City Concrete’s upgraded production system begins by weighing sand in the twin shaft mixer, then pneumatically conveying the portland cement and lime into the mixer. Basset says the Scott mixer achieves an accurate mix in 30–45 seconds, with a batch size of 3200 lb and a coefficient of variation under 3, well within the required parameters. The batch is then discharged from the mixer by a double drop bottom gate into a hopper where the product is then bagged. The twin shaft mixer is also available with other gate options, and can be constructed in carbon steel, 304, or 316 stainless steel, as well as sanitary finishes to meet USDA, FDA, or 3A Dairy requirements.

Scott Equipment Co. (New Prague, MN) is a leading manufacturer of custom processing equipment for the agricultural and industrial markets. Scott designs and manufactures batch and continuous mixers and blenders, coolers for ground material, and size reduction equipment. It also manufactures the patented AST drying system, air/product separation equipment, and square bolted storage bins. For more information, call 800-264-9519 or visit www.scottequipment.com.