Pumps and compressor are the primary sources of flow in liquid power system. Maximum system hourse power is controlled by the size of these components along with the system flow.
The following hydraulic formula illustrates a relationship between Horsepower, Pressure, and Flow. Hydraulic Horsepower = GPM x PSI x .000583 The three basic types of pumps are the Gear, Piston, and Vane designs.
HYDRAULIC PUMPS AND POSITIVE DISPLACEMENT In its most basic sense, positive displacement means what you take in you put out. In other words, for each revolution of a hydraulic pump of this type, a specific quantity of fluid is produced relating to the displacement of the pump.
Pumps and Compressors Before we go any further it should be pointed out that no matter what design of pump or compressor is being discussed, all pumps produce flow the same way. Pumps and compressors produce flow by creating a “pressure differential.” Fluids always flow from a higher pressure to a lower pressure. By using the increasing pump volume at the inlet, the pump (or compressor) creates a region of decreasing inlet pressure (vacuum). This causes the higher reservoir pressure (atmospheric) to push the fluid to the lower pressure inlet area. An example would be a person drinking water through a straw. One sucks, creating a lower pressure (vacuum) inside the mouth, and the higher (atmospheric) pressure on the liquid surface pushes it up the straw. The fluid is trapped inside the pump, and it is carried to the outlet where the volume is decreased and pressure increased. Fluid will take the path of least resistance, which is out the device outlet.