Screw pump is a positive displacement pump which employs one or multiple screws to move fluids from one point to another. Its operation is similar to that of gear pumps.
The diagram below is the simple single screw pump setup
It has 2 screw spindles, one of which is a driving gear and the other the driven gear. The gears drive the shafts. The inlet for the fluid is always located at the bottom and the outlet at the upper part of the pump.
The fluid enters from the inlet at the bottom of the pump. The driver and the driven screw rotate in opposite directions, which builds up a suction pressure at the lower part of the pump. This pressure drives the fluid upwards. The fluid crosses the small clearance between the two screws and experiences a centrifugal force. The combination of suction pressure and centrifugal forces the fluid up and out of the pump.