How Do Hydraulic Pumps Work?
Hydraulic pumps are indispensable in modern industry. Whenever you see machinery doing heavy lifting, hydraulic pumps are the driving force that enable those machines to function. By converting mechanical energy into hydraulic energy, they provide the superhuman strength required in many industrial applications.
How do they work?
While pneumatic systems operate by compressing air, hydraulic systems work differently — because liquids are incompressible. Instead of compressing fluid, hydraulic systems transmit energy by pressurizing fluid, allowing it to interact with actuators such as:
- Cylinders (for linear motion)
- Hydraulic motors (for rotational motion)
Inside a hydraulic pump, a mechanical action (typically driven by an electric motor or internal combustion engine) creates a low-pressure area (near vacuum) at the inlet port. This causes fluid to be drawn in from a reservoir.
Then, the pump moves this fluid to the outlet port, where it is sent into the hydraulic system. Resistance to flow within the system is what builds pressure. This pressurized fluid is what allows cylinders and motors to generate motion and force.
As Pascal's principle says :
"A change in pressure at any point in an enclosed incompressible fluid at rest is transmitted equally and undiminished to all points in all directions throughout the fluid, and the force due to the pressure acts at right angles to the enclosing walls."
Two main pump operating types
- Positive-displacement pumps
They work by displacing the fixed amount of fluid with each cycle. The flow rate is always constant and derives from pump design. Due to simple construction they are the most affordable option. Their core strength is the ability to generate very high amounts of pressure.
- Variable displacement pumps
A subtype of positive displacement pumps, they allow for variable flow rate depending on system demands or load requirements. This makes them highly flexible, and because of that, they are commonly used in hydraulic systems such as mobile machinery.
Most common pumps
Piston pump
A piston pump is a positive displacement device that uses a piston and a high-pressure seal to move liquids or gases. One of the key benefits of piston pumps is their flexibility, as they can function effectively at a wide range of pressures. They are also well-suited to handle thick liquids and particles.
In most piston pumps, a piston cup moves back and forth through an oscillating action. When the piston moves downward, pressure changes occur, causing the pump chambers to fill. As the piston moves upward, it expels the fluid from the pump.
These pumps are commonly used in applications requiring steady high pressure, such as in irrigation systems and fluid delivery.
Piston pumps come in two main varieties: axial and radial.
Gear pump
A gear pump is a type of positive displacement pump that uses gears to move fluids. These pumps operate by trapping a fixed volume of fluid between the gears and the pump housing and then pushing that fluid through the pump. Gear pumps are recognized for their straightforward design, durability, and ability to maintain a steady flow under varying pressures. There are two main types of gear pumps: external and internal.
External Gear Pumps: These have two meshing gears that rotate in opposite directions. The fluid is drawn into the space between the gears and the pump casing, where it is then transferred to the discharge side.
Internal Gear Pumps: In these pumps, one gear is inside another. The outer gear drives the fluid into the pump, while the inner gear helps move the fluid out. This design can handle higher pressures and is generally more efficient at moving thicker fluids.
Gear pumps are commonly used in applications where steady, high-pressure flow is needed, such as in hydraulic systems, lubrication systems, and chemical processing. They're particularly effective with viscous liquids, as their design allows them to maintain a consistent flow even with thick fluids.
Vane pump
Ideal for low-viscosity fluids, vane pumps operate on a simple principle. Inside a cylindrical cavity, there is a rotor with vanes attached. These vanes maintain contact with the cavity walls and create separate chambers. Due to a slight offset of the rotor, the chambers near the inlet are larger and shrink as the rotor turns, moving the chambers toward the outlet, resulting in fluid discharge.
High-pressure variants are commonly used in automobiles, such as in air conditioning systems and automatic transmissions. Mid-pressure versions are often found in coffee machines, soda dispensers, and similar devices.
Conclusion
Hydraulic pumps are the backbone of many modern mechanical systems, enabling precise control and immense power in a wide range of applications - from heavy industrial machinery to everyday appliances. By converting mechanical energy into pressurized hydraulic energy, these pumps allow for efficient movement, lifting, and force transmission.
Understanding the different types of hydraulic pumps - piston, gear, and vane - helps in selecting the right one based on pressure requirements, fluid characteristics, and system demands. Whether it's the high-pressure capability of piston pumps, the consistent flow of gear pumps, or the simplicity and versatility of vane pumps, each design plays a crucial role in powering today's technology-driven world.
As industries continue to advance, the demand for reliable, efficient, and powerful hydraulic systems will only grow, making hydraulic pumps an essential component in driving innovation and performance.
If you've decided that a gear pump is what you need, feel free to check out our selection - we offer a wide range of gear pumps manufactured by reputable companies such as HM Line and Galtech.
