FSFG series of closed type pellet grading sifter, independently developed by our company, is a more efficient plane-rotary sifter with the following main characteristics: sieve box located inside sieve body, compact structure, perfect sealing and no leakage. An enlarged sieve box with a large flow rate is installed in the sieve case. Its screening area is 30% larger than those of the conventional sifter. The sieve box is detachable in structure, reasonable stress as well as a  longer service life.