Press and Shredder Combination
March 13, 2007 ISSUE #185
An unusual feature of the Vincent Series TSP twin screw presses has come to have important application possibilities. The screws of the Vincent twin screw presses, like all Vincent press screws, feature the interrupted flight design. This means that there are places on the shaft of the screw where there is no helicoid flighting. The flights after each of these gaps constitute an additional compression stage in the press.
Stationary resistor teeth project through the screen of the press into the gaps where the flights are missing. The screws used in the twin screw presses have seven such compression stages, so there are fourteen teeth, seven on the top and seven on the bottom. However, since there are two screws in each press, a total of twenty-eight teeth are employed in Series TSP machines.
There is a tendency for the teeth to shred material that is being dewatered in the press. This effect is multiplied in twin screw presses because the two screws overlap each other. This creates especially aggressive tearing action within the press.
The shredding effect of the twin screw presses was noted with the initial prototype. Any time material, even previously shredded material, was admitted to the press, the cake was noted to consist of smaller sized particles.
This characteristic was put to test with material from the Del Monte sweet corn cannery in Sleepy Eye, Minnesota. Corn husks and cobs were fed, un-shredded, into a Model TSP-6 press. It was readily apparent that the final press cake was made up of smaller particles than the same material that was shredded in 75 hp shredders (prior to being dewatered in the Model KP-30 press at the same location).
Following this success, a Model TSP-12 was installed at the Birds Eye sweet corn cannery in Waseca, Minnesota. The drive was changed to obtain more than triple the brochure screw rpm (52 rpm); the motor horsepower was doubled from 30 to 60 hp. The results were huge throughput capacity. More importantly, the resulting press cake was shredded to acceptable particle sizes without the use of a hammer mill.
Since then additional testing has been conducted. Notable success was found feeding un-shredded produce waste and salmon fish waste into twin screw presses. In both cases, excellent shredding was achieved inside the press.
The potential to eliminate the need for a shredder is exciting. Eliminating the shredder obviously reduces capital investment and future maintenance needs. In addition, the high decibel level associated with the shredder is eliminated, as is a significant motor electrical energy requirement.
The improved feeding characteristics of twin screw presses over single screw presses are one more plus in the equation. Large items like whole melons and cabbage heads feed through the press without difficulty.