Pit stop for paper bags

By Werner Schandor - What does industry-scale cement bag filling have in common with a pit stop in Formula 1? Filling a 25kg paper bag with cement in the factory takes about three seconds, about as long as a pit stop. But packaging and paper manufacturer Mondi reckons this is too long. They asked TU Graz to study the material flow that is at work in this process. One of the deliverables is a simulation model for material transport trough paper so that the knowledge of the "paper bags" can also be applied to other packaging applications. Of course, the test piece on the rig is not conventional paper but so-called sack kraft paper designed to resist the filling pressure it is exposed to, for example in a cement filling line, without bursting. When a bag is filled with cement, up to 80 percent air is blown into the bag. This air can escape through pores on the paper's surface.