Security sieve for sifting out foreign materials, dissolving of product lumps and fluidizing the product in pressure-tight operation, respectively pneumatic conveying systems. Safety screens can also be used for bag emptying stations to reduce the risk of contamination by pieces of paper, string, and other contaminants from the bagged material. Vibrating sieves are particularly suitable for fragile products such as semolina or sugar. The material is fed through the inlet piping. The filter material vibrates freely and therefore cleans itself automatically. Coarse material is discharged via a tailings container and the sieved product is conveyed to a collecting cone where it can be handled to the receiver cyclones.