Hydraulic pumps are essential machines that convert mechanical energy into fluid power by moving fluid through a hydraulic system. Their operation can be understood through two key functions.
First, the mechanical action of the pump creates negative pressure at its inlet, enabling atmospheric pressure to draw liquid from the reservoir into the pump’s inlet line.
Second, this action pushes the liquid through the pump, to the pump outlet, and into the hydraulic system.
Let’s take a deep dive into the basics of how they work and the different types.
The Basics of Hydraulic Pumps
In practice, the hydraulic pump generates continuous flow and forces fluid through an attached system and into a hydraulic actuator, where pressure builds as the fluid encounters resistance from an attached load.
This pressure is then converted into mechanical energy by the actuator, pressurizing the fluid on the opposite side of the piston, which is subsequently returned to the reservoir or pump.
It’s important to note that the pump itself does not generate pressure but rather facilitates fluid movement, which is crucial for creating pressure due to resistance in the system.
To ensure the hydraulic circuit maintains the correct pressure, a pressure-regulating valve is necessary. When the system pressure reaches a specified level, this valve opens to allow fluid to pass.
Classification of Hydraulic Pumps
Hydraulic pumps can be classified into two main categories:
- Positive displacement pumps
- Non-positive displacement pumps
The majority of pumps utilized in hydraulic systems are positive displacement types, which are prevalent in automation applications.
Non-positive displacement pumps deliver a continuous flow, but their main limitation is that their output fluctuates significantly with changes in pressure, as they lack a reliable positive internal seal to prevent slippage.
For instance, if the output port of a non-positive displacement pump is blocked, the pressure will increase while the output drops to zero, meaning that even though the pumping mechanism continues to operate, flow ceases due to internal slippage. Common examples of non-positive displacement pumps include centrifugal and propeller pumps.
On the other hand, positive-displacement pumps experience minimal slippage compared to their flow output. If their output port is blocked, the pressure can rise rapidly to a level that may cause the pump’s components to fail or the motor to stall.
Positive-displacement pumps are the most widely used and come in various forms, including reciprocating, rotary, gear, screw, lobe, vane, and piston pumps.
Shop a Variety of Hydraulic Pumps
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Check MISUMI’s lineup and experience the convenience of our hydraulic equipment selection here.
