Screw pumps are rotary, positive displacement pumps that can have one or more screws to transfer high or low viscosity fluids along an axis. A classic example of screw pumps is the Archimedes screw pump that is still used in irrigation and agricultural applications.
Although progressive cavity pumps can be referred to as a single screw pumps, typically screw pumps have two or more intermeshing screws rotating axially clockwise or counterclockwise. Each screw thread is matched to carry a specific volume of fluid. Like gear pumps, screw pumps may include a stationary screw with a rotating screw or screws. Fluid is transferred through successive contact between the housing and the screw flights from one thread to the next. Geometries can vary. Screw pumps provide a specific volume with each cycle and can be dependable in metering applications.
The geometries of the single or multiple screws and the drive speed will affect the pumping action required. The capacity of screw pumps can be calculated based on the dimensions of the pump, the dimensions of the surface of the screws, and the rotational speed of the rotor since a specific volume is transferred with each revolution. In applications where multiple rotors are used, the load is divided between a number of rotating screws. The casing acts as the stator when two or more rotors are used. Based upon the needs of the application, timed or untimed rotors may be chosen. Untimed rotors are simpler in design.
The combination of factors relating to the drive speed, flow, and the characteristics of the fluid transferred may affect the flow rate and volume fed through each cavity. In water and wastewater treatment applications, a less viscous solution will require a lower power drive compared to untreated sewage, excess sludge, or concentrated slurries, which may require a higher power motor. The viscosity of the fluid transferred and the lift required may affect the speed and power required. Indicators of pump malfunction include decrease in flow rate or increased noise. The efficiency of screw pumps requires that each rotor turns at a rate that allows each cavity to fill completely in order to work at full capacity.
Related Products & Services
Booster pumps are used in applications where the normal system pressure is low and needs to be increased.
Centrifugal pumps consist of a set of rotating vanes, enclosed within a housing or casing, that are used to impart energy to a fluid through centrifugal force.
Condensate pumps are used to collect and transport condensate back into a steam system for reheating and reuse, or to remove unwanted condensate from an HVAC or appliance collection pan.
Diaphragm pumps use a diaphragm that moves back and forth to transport liquids from one place to another.
Drum pumps are used to transfer materials from a container into a process or other container. They may be electrically, hydraulically, or pneumatically powered depending on the working environment or application.
Liquid Handling Pumps
Industrial liquid handling pumps are classified in many different ways, and are distinguished by the media pumped and the fluid motive mechanism (dynamic or displacement).
Metering pumps are positive displacement pumps designed to dispense precise amounts of fluids and measured flow control.