Screw pump is also called as Progressive Cavity Pump. A screw pump is a type of rotary pump which is equipped with rotor and stator. The rotor and stator is combined together and rotate within a cylindrical cavity or liner. The fluid or transfer medium enters from the suction side of the screw pump and moves linearly along these intermeshing screws / rotors to the discharge side of the pump.
Screw pump is a popular feeding pump type for centrifuge, no matter for decanter centrifuge, 3-phase centrifuge, or disc centrifuge. Besides screw pump, submersible slurry pump and sand pump are also been used a centrifuge feeding pump. But as submersible slurry pump and sand pump are both a kind of centrifugal force pump, they are not as good as screw pump to feed for decanter centrifuge.
Decanter centrifuge is a high speed rotating device. There will be many self-protection function for safety and also for protect the device. A major self-protection application is over-load protection. It means in case the centrifuge feeding is over load, the centrifuge will be stopped to avoid damaging bearings or damaging rotating component. In this case, the feeding screw pump must be capable to adjust the feeding flow. There are mainly 2 ways to control the feeding screw pump input flow rate:
1) If fixed speed screw pump is used to feed for decanter centrifuge, a VFD control panel is requested to adjust the feeding flow rate to avoid over load, and to reach the better separation performance.
2) If manual adjustable speed screw pump is used as decanter centrifuge feeding screw pump. Fix speed control panel can be used for the pump for start and stop.
Furthermore, as the decanter centrifuge has self-protection function in case of overload. To avoid damage the centrifuge, there must be an inter-lock connection between the centrifuge control and the feeding pump control. In case the centrifuge is stopped, feeding pump can be stopped immediately. And the screw pump cannot be started until the decanter centrifuge is running stably.