Get to know your gear pumps

What is a gear pump?

Gear pumps are a very important element in the hydraulic circuit. Its function is to transform mechanical energy, transmitted by a motor, into hydraulic energy. And this is achieved in two phases, the suction phase and the compression phase.

These pumps are normally made of aluminium alloy or cast iron and, as the name suggests, transmit their power through two gears. One named driver and the other driven

How does a gear pump work?


1. Pump body

2. Supply hole

3. Outlet hole

4. Driving pinion (motor)

5. Driven pinion C.- Holes in which the enclosed oil is dragged



A gear pump has, as we have seen, 2 gears. The one that acts as a driving gear (4), will be connected to a motor that will be the one that transmits the mechanical energy to us. On the other hand, we will have the other gear called the driven pinion (5). The oil enters by aspiration, moves thanks to the pinions on the sides of the chamber and leaves through the pressure hole.

Gear pumps have two phases, suction and compression. The suction phase is achieved because the pump generates a vacuum that causes the oil to flow into the pump from the tank by depression. Once there, the oil fills the holes in the pinions between tooth and tooth (C).

The oil travels on these teeth through the outside of the chamber, as indicated by the arrow, until it reaches the area of ​​the outlet hole (Pressure, 3). There, when the teeth of both pinions meet, the oil that was inside is expelled. Then due to the incessant flow of oil, it is expelled by pressure (3), ending the compression phase.

Data of interest:

– It is advisable to help the pump with a gravity-based installation. For this, the pump must be below the tank in terms of head levels. In this way the oil will be easier to feed the pump due to gravity.

– The Pump itself does not generate pressure . The pressure is produced when there is a choke in the circuit or some element offers some resistance such as a cylinder or an engine.

How to know which hydraulic gear pump to buy or mount?

When buying a hydraulic gear pump, the best offer is to buy the right one to avoid modifications and above all to avoid major breakdowns. That is why we are going to show you what are the tricks and aspects that you must take into account when choosing the pump.

The most important aspects that you must take into account in a gear pump replacement are: Pump displacement, Cover, Shaft, Connections and Rotation. You can provide us with the reference of the pump that you have mounted and our professionals will offer you an equal or equivalent pump. If, on the contrary, it is a new installation, our technical office will make the necessary calculations to be able to carry out your application in the most reliable and safe way.

Hydraulic Gear Pump Displacement Types

The pumps can be of group 1, 2 or 3. Within each of these groups there are several displacements. Those of group 1 usually oscillate between 1 and 10 cm3. While those of group 2 usually go between 4 and 26 cm3. And finally, those in group 3 are usually between 19 and 62 cm3.

Types of Hydraulic Gear Pump Covers

Next, we leave you the most common tapas. These covers will be in charge of joining the pump with the motor.

Hydraulic Gear Pump Shaft Types

The shaft is the element of the pump that will make contact with the motor and through which the pump will receive mechanical energy. These shafts are the most common and used in gear pumps:

Types of Flange Connections for Hydraulic Gear Pumps

This element is the one that will determine in which way we are going to connect the hydraulic pipes with the pump. Having these main connections:

Swing Types for Hydraulic Gear Pumps

The gear pumps have as a general rule left or right rotation and are very easy to interchange if necessary, although there are also reversible ones.

If you want to find out more information visit the Hynesur website and get in contact with them today!

Source: Hynesur

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