Positive displacement (PD) pumps move fluid by repeatedly closing a fixed volume and moving it mechanically through the system. Simply put, positive displacement pump is a pump that uses the change in volume within the pump cylinder to move fluid. The pumping action is cyclic and can be driven by pistons, screws, gears, rollers, diaphragms or vanes.
Positive displacement pump working principle
There are many types of positive displacement pump designs, but most can be divided into two categories: reciprocating and rotary.
Reciprocating positive displacement pumps
Reciprocating positive displacement pumps work by repeated back and forth motions (strokes) of the piston, plunger or diaphragm (see figure below). These cycles are called reciprocating.
In a piston pump, the first stroke of the piston creates a vacuum that opens the inlet valve, closes the outlet valve and draws fluid into the piston chamber (suction phase). When the piston motion is reversed, the inlet valve, now under pressure, closes and the outlet valve opens, allowing the fluid in the piston chamber to be expelled (compression phase). A bicycle pump is a simple example. Piston pumps can also be double acting, with inlet and outlet valves on either side of the piston. While one side of the piston is in the suction state, the other side is in the compression state. More complex radial versions are often used in industrial applications.
| Item | LONGSHUO LASER DISTANCE METER |
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