Screw pump is a single-screw transfer pump. Its main working parts include the screw of eccentric helicoid(called rotor) and the screw bush with a double-line helicoid on its inner surface(called stator). Its working principle goes like this: when the electric motor drives the pump shaft t rotate, the screw rotates around its own axes on one hand and rolls along the inner surface of the bush on the other, thus forming a seal cavity in the pump. When the screw rotates a cycle, the liquids in the seal cavity will advance a screw pitch forward. With the continuous drive of the screw, the liquids will press from a seal cavity to another cavity in a spiral manner until it is pressed out of the pump body finally. Screw pump is a new type of machinery for the liquid transfer. It boasts such advantages as simple structure, safe and reliable operation, easy maintenance, continuous and uniform liquid discharge and stable pressure. The metal parts contacting materials of our underflow pump all adopt top-grade stainless acid-proof steel and the shaft material is 2Cr13. The bush adopts nontoxic rubber with no peculiar smell. Its working temperature can reach up to 100 degree celsius. It can be used for the transfer of corrosive media like foodstuff slurry, solution or suspension containing solid grains or rubber blocks with a viscosity of 10000Pa.S. It is widely applied in such industrial sectors as food, metallurgy, construction, pharmacy and chemical industry etc.